December 2008 Archives

The subject of our natural environment -- its well being versus its degredation, the
sustainability of its resources versus their exhaustion, the changes wrought on the
environment by natural forces and by man's activities, the effects those changes are having on
us and on the millions of non-human creatures with whom we share this planet -- these and
myriad similar issues arrived in the public consciousness in 2008.
It's our prediction that environmental issues will become increasingly important.
Wangari Maathai, the recipient of the 2004 Nobel Peace Prize, once said, "One of the
disadvantages of environmental degradation is that it's a very, very slow process and that, quite
often, the generation that destroys the environment is not the one that pays the price."
It has also been said that we are the stewards of the Earth because, of all the Earth's
creatures, only we are truly aware of the environmental consequences of our actions, and
only we can alter our actions accordingly. If an intelligent being from another world
were to visit the Earth, could we say to him with pride: "This is our beautiful planet. Come
see what we have done with it."
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
What is the most number of consecutive days of measurable snow we have ever had in
Chicago?
Paul Sarewich, Chicago
Dear Paul,
The answer is nine days, from January 29 through February 6 of 1902. That's the result
of a computer search of Chicago's daily snowfall records from the winter season of
1884-85 to the present. Measurable snow is defined as 0.1 inch or more, and every day
in that nine-day period nearly 107 years ago received at least that much. "Nine
consecutive days of snow" conjures up an image of a city paralyzed by an unrelenting
nine-day snowstorm, but don't let the statistics deceive you. In this instance, all that
occurred were periods of light snow and snow flurries. Daily snow totals Jan. 9, 1902,
onward were (in inches): 0.2, 0.6, 1.0, 0.1, 0.8, 0.2, 0.6, 0.3 and 1.2 for a nine-day total
of only 5.0 inches. The highest temperature through the period was 27 degrees, so the
snow did not melt.

Computer models indicate the trend of Chicago temperatures over the next seven days is
downward, though viciously low readings are not anticipated, at least when judged by the
standards of late December and early January. The city's temperatures will struggle to
reach the lower 20s this afternoon. Chicago's high temperature on Tuesday -- 40 degrees --
was hardly a "mild" reading, but it's likely that area residents will not experience that
relative warmth again during the next two weeks.
STORM TRACK TO REMAIN NORTH
Chicago's weather through the weekend is to be dominated by a progression of rapidly
moving, moisture-starved and relatively weak weather disturbances. Three low-pressure
systems are anticipated, each pushing from the northern Rockies toward Lake Superior and
eastward to New England -- and each accompanied by a surge of light snow along that path.
Chicago, well to the south of the primary track, will see only light snow.
PATTERN CHANGES NEXT WEEK
The possibility of a major snowstorm looms for Chicago on Tuesday and Jan. 6.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
Recently your forecast said,"A frigid start to the day as temperatures begin in the single
digits," but then you show the low temperature as 18 degrees. My thermometer showed
8 degrees! How do you figure the low temperature?
Peggy Gudbrandsen

Dear Peggy,
We always present temperatures on this weather page in chronological order. The
expected high temperature on a given day appears first, followed by the expected low
temperature during the following nighttime period.

The situation that you described, "A frigid start to the day ...," refers to early-morning
temperatures expected before that day's forecast afternoon high temperature. The low
temperature is the predicted minimum temperature during the following night.
Minimum temperatures usually occur in the early morning, approximately at daybreak,
of the next calendar day.

After tickling the 40-degree mark in the afternoon (a reading 10 degrees above the day's
normal high), area temperatures head downward with the arrival of arctic air, gusty
northwest winds and snow flurries Tuesday night. It won't be horribly cold by late-December
standards -- over- night lows are pegged only into the single digits in the outlying areas
-- but subzero windchills will be the rule.
Looking ahead, computer models suggest a moderately cold weather regime for several
days. Moisture-starved disturbances, each with a bit of snow, zip west-to-east across the
region at 48-hour intervals.
RECORD SNOWS BLANKET
PACIFIC NORTHWEST
While Chicagoans and Midwesterners have been coping with their own winter weather
problems, residents of Oregon and Washington have had it a great deal worse.
Snowfall has reached record or near-record levels in 30 of Washington's 39 counties. As
of Monday, Spokane, Wash., has logged 59.7 inches of snow since Dec. 1, a December record.
Pendleton, Ore., has had 32.5 inches versus a normal of 4.8 inches.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
With all the snow and cold we are getting, how can the advocates of global warming
justify their arguments?
Paul Nadick, Round Lake, Ill.
Dear Paul,
Actually, no justification is necessary because the trend of global temperatures speaks
for itself. Since the end of the last glacial maximum about 15,000 years ago, global
temperatures have risen approximately 11 degrees. The rate of warming accelerated
greatly with the onset of the Industrial Revolution, and the Earth's average surface
temperature has risen, conservatively, about 1.5 degrees since the mid 1800s.

The grand sweep of global temperatures is upward, but many factors -- some
understood, some not -- can temporarily reverse the rising trend. For example, global
temperatures declined from the 1940s through the 1970s. It is a probably a mistake to
interpret a harsh winter as a permanent reversal of the trend of rising global
temperatures.

Chicagoans reeling from a series of disruptive December storms will welcome this week's
transition to a progression of less intense and less extreme -- though equally fast-paced
-- weather systems.
Swollen area rivers will have a chance to drain, though substantially subfreezing
temperatures by midweek may retard the process.
The forecast indicates that three of the upcoming seven days are to be absolutely
precipitation-free. Contrast that with a total of only four dry days in the preceding four
weeks of December in Chicago.
MILD THROUGH TUESDAY, THEN COLDER
Temperatures Monday bounce into the 40s under a mainly sunny sky, but many will find it
unpleasantly windy. Southwest winds gusting well above 30 m.p.h. will create an afternoon
"feels like" temperature of 30 degrees despite an actual reading about 15 degrees above
the daily normal high of 31.
Relatively mild readings carry into Tuesday, but sharply lower temperatures and a little
light snow arrive late Tuesday. That sets the stage for subnormal temperatures that
persist through year's end.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
What is the usual range of temperatures necessary for it to snow?
Beola Lenard, Bettie S., Patricia L., Evergreen Park
Dear Beola, Bettie and Patricia,
Ice crystals (that eventually clump into snowflakes) form in clouds only
when water vapor condenses in a below-freezing temperature environment.
Condensation in above-freezing temperatures results in water droplets and,
ultimately, rain. Air temperatures at ground level are sometimes a little
above freezing (but rarely above 40 degrees) when it is snowing because
snowflakes, falling from subfreezing air above, do not have time to melt
before they make it to the ground.
There really is no lower temperature limit at which snow can occur, though
Chicago's biggest snowstorms usually occur with readings in the 20s. Nearly
an inch of snow was measured at O'Hare Airport on Jan. 10, 1982, with the
temperature around 15 degrees below zero.

Thanks to Robert Munger of northwest suburban Hampshire for passing along this photo of flooding caused by the rapid snowmelt coupled with heavy rainfall.

Photo by Robert Munger

Posted by Steve Kahn WGN Weather Center

Chicago weather records fell like dominoes Saturday as one of the most bizarre three-day
periods of weather in the city's history came to an end. Since Christmas morning, the
city has weathered severe cold, an ice storm, dense fog, heavy rain, rapid snowmelt, urban
and river flooding, high winds, severe thunderstorms and record warmth. Saturday's high
of 61 degrees at O'Hare tied a 1982 record and the 1.73 inches of rain broke the 1.57-inch
benchmark set in 1942. The heavy rainfall, coupled with the 2 inches of water released
from the rapid snowmelt, not only sent area rivers and streams into flood but caused
flooding of roads and basements throughout the area. The heavy weekend rainfall pushed
Chicago's annual precipitation total above the 50 inch mark for the first time in history.
The city's current (1971-2000) normal annual precipitation total is 36.27 inches.
CALMER WEATHER AHEAD
Temperatures were plunging by late Saturday evening as colder air returned, courtesy of
strong west winds. The year's final days promise to be uneventful with temperatures near
or above normal. The city's next encounter with significant snow should hold off until
New year's night when a "clipper" system could bring some accumulating snow.
--By Steve Kahn, WGN Weather Center Meteorologist

Dear Tom,
How can it rain at 26 degrees?
Jim O’Shea, Oak Lawn
Dear Jim,
The form in which precipitation reaches the ground is not determined by the surface
temperature, but by the temperature profile from the ground to cloud-level. Most winter
precipitation begins as snow. If it encounters a deep enough layer of above-freezing air as
it falls to Earth, it melts and becomes rain. The rain then refreezes when it makes contact
with the below-freezing ground and the result is a glaze-producing freezing rain. If the
rain falls through a thick enough layer of belowfreezing air before it hits the ground, it
refreezes into ice pellets (sleet). Forecasting winter precipitation types is difficult,
especially in the Chicago area, a region that is frequently close to the dividing line
between rain and snow.

A foggy day after Christmas Eve

Thanks to Janice Goldman of Chicago for sending us these pictures of fog-shrouded Chicago Friday evening. The dense fog was caused by warm, moist air being chilled to its condensation point as it passed over the cold, snow covered ground. Dense fog was prevalent across much of the Midwest playing havoc with air travel, totally shutting down Chicago's Midway Airport..

Photos by Janice Goldman

Winter weather systems typically show both warm and cold faces, and the powerful storm
system sweeping across the Midwest today is no different.
This time around, though, Chicago finds itself on the warm side of the storm. That means
rain, and plenty of it today -- perhaps as much as 2 inches. Melting snow will
contribute the equivalent of an additional rainstorm. Widespread flooding will be the result of
all that water.

"ZERO-ZERO" FOG
The perfect recipe for pea-soup fog: mild, moist air and snow cover. Those ingredients
came together across northern Illinois Friday night and are persisting Saturday morning.
The result: Fog so dense that both vertical and horizontal visibilities in the area were
reduced occasionally to less than 100 feet. It is a "zero-zero" situation.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
Another active hurricane season has ended. As you have said many times,
hurricanes are fueled by warm, moist air, so why can't they be stopped by
chilling the eye with ice?
Matthew Sabin
Dear Matthew,
Dr. Chris Lansdea, Director of the National Hurricane Center's Research
Division, has written extensively on the subject of hurricane modification.
He states categorically that "... Hurricane modification by any means is an
exercise in futility and impracticality. Consider the scale of what we are
talking about. The critical region in the hurricane for energy transfer is
under or near the eye wall," an area of about 2,000 square miles. Allowing
for storm movement and uncertainty in its track, the "cool patch" expands to
31,000 square miles. That's 55 percent of the area of Illinois, and it is
simply impossible to chill such a huge area.

The factors that contribute to wintertime river flooding in the Chicago area -- heavy
rainfall, surging temperatures, rapidly melting snow cover and ice-choked rivers -- are
falling into place.
The Chicago National Weather Service has issued a flash flood watch for metropolitan
Chicago from late Friday night through Saturday night, and advises that "major to record
flooding [is] expected this weekend." Computer models suggest that 1 to 3 inches of rain
will fall across the area by Sunday morning -- 1-inch totals most likely toward Rockford and
3-inch totals across southern sections and northwest Indiana.
A period of freezing rain, sleet and hazardously icy conditions is likely early Friday
before temperatures climb above freezing. Warming that continues into Saturday carries
temperatures into the 50s.
ACTIVE THUNDERSTORMS A POSSIBILITY
The interaction between 80-m.p.h. winds aloft and mild, moisture-laden, unstable air
drawn north from the Gulf of Mexico provides a favorable environment for thunderstorms.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
I am a retired forecaster from the old Springfield, Ill., National Weather
Service office. Who originated the term, "Alberta clipper," and when?
Fred Snowden, Springfield, Ill.
Dear Fred,
"Alberta clipper" is a colorful term that appeared in meteorological jargon
in the early 1970s, courtesy of Rheinhart Harms. At that time, Harms was the
Meteorologist-in-Charge of the Milwaukee, Wis., Weather Bureau office, and
he authored a research paper titled, "Snow Forecasting for Southeastern
Wisconsin" in 1970.
Harms noted that a distinctive class of snow-producing low pressure systems
originated in or near Alberta Province, Canada, and moved rapidly southeast
across the Midwest, producing a belt of low water-content snow. He called
those storms "Alberta clippers," and staff members of the Milwaukee weather
office began using the term in the early 1970s.

Holiday snow bunting
Thanks to Nancy, Ginny and Chuck Berg former Chicagoans now lliving in Tonka Bay, Minnesota for sharing this unusual shot of snow draped like bunting across the deck to the home.

Posted by Steve Kahn WGN Weather Center

Chicagoans, made weary by the frequent bouts of harsh weather that have characterized
this young winter season, are about to experience yet another vigorous atmospheric event.
This time around, though, it's to be a surprise on the mild side. Thursday's frigid
readings, biting winds and subzero windchill temperatures yield quickly to comparatively mild
air, clouds, fog and rain that arrives Friday and continues into Saturday. A period of
early ice may precede Friday's rain.

WEEKEND FLOOD THREAT
Temperatures in the 40s, rapid snow melt and potentially heavy rain, even a few
thunderstorms, suggests the threat of flooding on area rivers this weekend.

TSUNAMI REMEMBRANCE
And lest we forget, Christmastime marks the fourth anniversary of a staggering natural
catastrophe: The Indian Ocean earthquake and resultant tsunami that claimed 230,000 lives
in coastal areas around the ocean basin. Residents in affected areas there are still
struggling to put their lives back together.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
Of the ten snowiest winters in Chicago history, how many had a white Christmas?
-Lt. Pat Byrne, Hoffman Estates, Ill.
Dear Pat,
A snowy winter in Chicago does not guarantee a white Christmas (at least one inch of
snow on the ground), but it does increase the odds. Historically, only four Christmases
in 10 have met the one-inch criterion

But Chicago weather historian Frank Wachowski found that six of the city's 10 snowiest
winters had white Christmases. Last winter was Chicago's eighth snowiest with 60.3
inches, yet the ground was bare on Christmas morning.

Chicago's snowiest winter (1978-79 with 89.7 inches) and the city's least-snowy winter
(1920-21 with 9.8 inches), barely qualified, each with only a one-inch Christmas
morning snow cover.

A treacherous mix of snow, sleet and freezing rain that has Chicagoans slipping and
sliding changes over to a final round of snow Wednesday, and several inches may accumulate by
the evening. Temperatures plunge toward zero degrees overnight as a surge of arctic air
sweeps into the city, but the new chill will be brief. Another vigorous storm system
arrives Friday, accompanied by thawing temperatures, fog, copious moisture and heavy rain.
Rapid snowmelt and rain raise the possibility of flooding by Saturday. Christmas Eve in
1983: high minus 11 degrees, low minus 25.
2008: CHICAGO'S WETTEST YEAR EVER?
Following excessive rain and record flooding across the metropolitan area during the
summer and autumn, 2008 year-to-date precipitation as of 7 p.m. Tuesday stood only 0.66
inches short of an annual record. Heavy rain expected Friday and Saturday virtually assures
a new record.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Mr. Skilling,
Io, one of Jupiter's moons, has volcanoes but my friend Terry says I am wrong and he
won't listen to me. He says only Earth has volcanoes.
Robert Klyn, age 10
Dear Robert,
Your information is correct and we here in the WGN weather center congratulate you on
your knowledge of astrogeology.

Astronomers believe Io is the most volcanic body in the Solar System. Io revolves so
close to Jupiter (the largest planet in the Solar System) that Jupiter's powerful
gravitational field causes Io to bend and flex, heating its interior much like a paper clip
heats up when it is repeatedly flexed. That heat fuels massive volcanic eruptions on Io's
surface. NASA's Galileo spacecraft captured many high-resolution images of Io's
volcanoes in 1999 and 2000, and indicated lava at temperatures well above 2,600
degrees.

Earth's hottest lava: about 2,240 degrees.

How cold was it at last night's Bears game?

Rick Bardahl from Downers Grove has icy proof of just how cold it was at last night Bears-Packers game. His beverage froze solid shortly after he opened it.

Photo by Rick Bardahl

Posted by Steve Kahn WGN Weather Center

Sharing winter weather woes- Winter blasts Walla Walla

Chicagoans are not alone in experiencing severe winter weather this month. Our thanks go out to ex-Chicagoan Dick Swenson now living in Walla Walla Washington. That area has been hard-hit by snow and cold and now boasts a very unusual snow depth of about 20 inches.

Photos by Dick Swenson

Posted by Steve Kahn WGN Weather Center

The arctic wastelands of northeast Illinois

Regualr weather page contributor pilot Anson Mount was kind enough to share these pictures that he took during Sunday's near blizzard conditions. The pictures were taken on a drive from Mundelein to the Waukegan airport. Anson reported that many roads were drifted shut and even some snow plows were stuck.

Photos by Anson Mount

It's not often that Chicagoans shiver through a December afternoon with temperatures in
the single digits, but that's what happened Monday. The afternoon temperature struggled
to reach 4 degrees on the city's official thermometer at O'Hare International Airport.
That was the coldest December day since 1989, when the high was just 3 degrees on Dec. 22.
Since records began here in 1870, only 19 December days out of a possible 4,300 have
logged afternoon readings of 4 degrees or lower. Monday was the 20th. The chill eases today,
but the price to be paid is yet more snow in a snowy December that has already seen
three times the normal month-to-date snowfall of 5.7 inches.

CHICAGOANS SHIVER IN THE ICE BOX FOR 29 CONSECUTIVE HOURS
Beginning at 5 a.m. Sunday, and continuing through 10 a.m. Monday morning, the city
was in the grip of a brutal stretch of sub-zero temps. Windchills bottomed out at 33
degrees below zero at 10 a.m. Sunday.

CLOSING IN ON THE WETTEST YEAR
As of Monday, 2008's year-to-date precipitation of 48.56 inches is just 0.79 inches shy
of the 49.35-inch record set in 1983.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
Why do lowest average temperatures of the year occur in the weeks after the winter
solstice? It would seem to make sense that the most extreme temperatures would occur
when the sun is at its lowest angle in the sky.
Tim Arvidson

Dear Tim,
Chicago's normal high on Dec. 21 (the winter solstice) is 33 degrees; on Jan. 15, 29
degrees. On average, the winter's lowest temperatures occur about three weeks after
the winter solstice, and there are three good reasons why. First, the Earth's surface goes
on losing more heat than it gains long after the solstice. Second, the far north (the
source of our coldest air) receives no heat from the sun into mid January, and
temperatures there are still falling. Finally, the average continental snow field continues
to expand into early February. Snow surfaces effectively radiate heat into space and
generate cold air masses.

Northeast Illinois was hit with bone-chilling cold and blizzard conditions Sunday.
Howling west winds gusting more than 40 m.p.h. and subzero temperatures gave life-threatening
windchills of 20 to 40 degrees below zero. In open or rural areas, the winds picked up
and blew the 1 to 2 inches of Saturday's snow, cutting visibilities to near zero and icing
over portions of many north-south roadways. Windchills around 20 degrees below zero
Monday morning will gradually "moderate" to near zero in the afternoon as readings slowly rise
and winds decrease.
NEXT WINTER STORM ON THE WAY
Developing in the Texas Panhandle, low pressure is forecast to move northeast with
leading-edge snows possibly reaching this area Monday night. As the storm approaches, several
inches of heavy accumulating snow are possible over northern Illinois Tuesday.
WHITE CHRISTMAS LIKELY FOR THE AREA
The snow-bearing system should move east Wednesday with a fresh snow cover in place over
Chicago. While Christmas Day will be partly sunny here, a new rain/snow system may
arrive later Thursday night.
--By Paul Dailey, WGN Weather Center Meteorologist

Dear Tom,
I've seen neighborhood children eating snow. Is that safe?
James Anderson
Dear James,
It's not a good idea because snow contains potentially harmful airborne
pollutants. It's not that snow is immediately toxic, but it can contain
chemicals that you don't want to put into your body.
Here are the opinions of two experts. University of Toronto environmental
chemist Dr. Frank Wania reports that the atmosphere is exceedingly efficient
at transporting pollutants -- so efficient, in fact, that industrial
pollutants released into the atmosphere in India could be found in snow in
northern Canada only five days later. Argonne National Laboratory's Dr. Jeff
Gaffney is more specific. He says snowflakes can contain anything that
floats in the air: the chemicals that fall in acid rain, bacteria, sulfates,
nitrates and even lead from areas in the world that still burn leaded
gasoline.

Winter comes to Palm Desert California

Thanks to Jack and Carol Uhern formerly of Streator, Illinois who moved to California more than 50 years ago for sharing these pictures of snow in the California desert. This snow was a product of the same storm that brought all the snow, sleet and freezing rain to the Chicago area Thursday night and Friday. Snow from this storm was also reported in the higher elevations near Phoenix and in Las Vegas.

Photos by Jack and Carol Uhern

Steve Kahn WGN Weather Center

Frightful weather in Wauconda

Thanks to Eric Repking from Wauconda for this picture of today's blowing snow taken from his backyard near Lake Napa Suwe. Eric comments that trying to keep plowed areas snow free has been a losing battle.

Photo by Eric Repking

Steve Kahn WGN Weather Center

Casualty of the storm:The power of ice

This photo supplied by Jayne Fair-Walton of Matteson is a testament to the power of ice. The weight of the glaze deposited in the Thursday night/Friday morning ice storm was enough to topple this tree in her back yard.

Photo by Jayne Fair-Walton

Steve Kahn WGN Weather Center

The Winter Solstice occurs at 6:04 a.m., making this the shortest day of the year in Chicago, and it will be by far the coldest this winter. With temps in the single digits and winds gusting at times in excess of 40 m.p.h., dangerous wind chills -20 to -25 degrees will hold over the area today and tonight. Frostbite and hypothermia are a very real threat unless proper precautions are taken. The frigid high pressure air mass will begin to weaken Monday night.

TEMPERATURES MODERATE MIDWEEK
By Wednesday, temperatures are to reach more seasonable levels (Normal high: 33°). Even so, there is a good chance Chicago's snow cover will persist through Christmas.

Dear Tom,
What is the most unusual question that you have ever answered?
-Jim Oosner
Dear Jim,
This one from Dave Nelson in Evanston stands out: While enjoying a bright blue sky the
other day with puffy white cumulus clouds, I wondered: Am I looking at a sky and cloud
scape that a dinosaur might have observed 100 million years ago? The reply: Dinosaurs
lived from 245 million to 65 million years ago, and the same kinds of cumulus clouds
that you observe in our present-day summer sky assuredly populated the dinosaurs’
sky as well. The laws of atmospheric physics are immutable. Even assuming the
gaseous composition of the Earth's atmosphere was somewhat different during the age
of the dinosaurs, the nature of water vapor and the atmospheric processes that produce
cumulus clouds have not changed with time.

This remarkable set of photos from Larry Jahn of Macomb, Ill., certainly lays out the
scope of the ice storm which struck a wide swath of Illinois and Indiana. Larry reports power
outages were widespread and that trees were down all over town and throughout the
county there. The storm, he reports, was the worst he's seen in 40 years there! MANY
THANKS for sharing these images with us, Larry! Please stay safe!
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Photos courtesy of Larry Jahn, Macomb, Illinois

Winter-weary Chicago-area residents, witnesses to two winter storms in the past week and
to the 13th snowiest open to a cold season since 1884, are headed for another wintry
meteorological blow in the coming 24 hours.
Brutally cold air is on the move and is to pour into the area Sunday and Monday. After
lake-enhanced flurries from extensive clouds Saturday, a period of light snow with
possible 1-2 inch accumulations Saturday night is to be followed by the onset of howling
west/northwest winds expected to gust to 30-40 m.p.h.
Temperatures dive into the single digits before daybreak Sunday and are unlikely to
recover as Canadian high pressure keeps the chill coming. Windchills are to be dangerous --
even before the sun rises Sunday and then well into Sunday night and Monday morning --
dipping into the minus-15-to-minus-25-degree range.
CHICAGO'S HAD ONLY THREE EARLIER SUBZERO LOWS OVER PAST 20 YEARS
The predicted low Monday morning of 7 degrees below zero arrives nearly two weeks early.
What's more, only three of the past 20 years recorded the season's first subzero reading
any earlier.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
When people claim, "Back in my time, the winters were more severe," it is
usually a case of the weather being exaggerated in their memories. Well, I
grew up in the 1980s and winters were more severe then, but a neighbor who
moved here from Seattle thinks I'm wrong when I say I can remember many days
with temperatures 20 below zero. Help me convince him.
John Potempka, Chicago
Dear John,
You are absolutely correct. A computer sweep of the entire data set of
Chicago's official temperatures from Nov. 1, 1870, to the present supports
your recollections. In that period, Chicago recorded 15 days on which the
minimum temperature sank to 20 degrees below zero or lower. Five of those
days occurred before 1900 and nine of them in the winters from 1982 through
1985. The most recent occurrence was 21 below on Jan. 18, 1994.

Thanks for joining us for this Friday edition of Before the Forecast! After last night's snow/ice storm dumped as much as 2-5 inches of slushy snow and sleet in the downtown area, today was much more quiet. However, we are preparing for our second of three winter storms Saturday night. To hear more about this wintry weather, Tom Skilling has all the details on Tonight's Before the Forecast. Thanks to our weather interns Andrei Evbuoma and Jim Anderson, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Chicago Tribune photographer John Smierciak was kind enough to share these great photos of the ice storm near his home in St. John, Ind. Thanks John!
—WGN-TV Weather Center

Photos courtesy of The Chicago Tribune's John Smierciak, St. John, Ind.

Here's a look at the snow in Bear Lake in Michigan, courtesy of John Gehr. Thanks John!
—WGN-TV Weather Center

Photos courtesy of John Gehr

Here are more amazing photos from the ice storm, this time from Whiting, Ind.
—WGN-TV Weather Center

Photos courtesy of Carolyn Szepanski, Whiting, Ind.

Icy Demotte Indiana
Overnight freezing rain turned the landscape in Demotte in northwest Indiana into a winter wonderland. Unfortunately many residents in areas hard-hit by ice south of Chicago in Illinois and Indiana are without power and much tree damage has occurred.

Photos by Bonnie Sparks

Ice encases Peotone

Freezing rain left a coating of ice across Chicago's southern suburbs and much of central Illinois overnight. Many residents have lost power and there have been many reports of tree damage from the weight of the ice. Thanks to Sharon Schreiber of Peotone for sharing these pictures with us.

Photos by Sharon Schreiber

The storm pounding the Chicago area as Friday dawns arrives with quite a history. Its
uncharacteristically heavy early-season snows in the mountains near Los Angeles, San Diego
and Phoenix, and its production of the biggest snow in Las Vegas in nearly three decades
were early warnings the system was packing quite a punch.
A potent collection of meteorological ingredients is in place -- including the arrival
of a rare pocket of 180 m.p.h. jet stream winds that is vigorously lifting the air. The
feature has contributed to overnight thunderstorms that may continue into Friday evening,
producing especially heavy snowfall over the northern half of the Chicago area. It's the
second time this week a critical commuting period has been seriously impacted by the
weather. Accumulations are to vary widely -- 1 to 6 inches from Interstate Highway 80 north to
I-88 and 6 to 14 inches to the north, with the heaviest amounts in the counties along
With 13.9 inches of snow already down, this season ranks among the top 13 percent of the
snowiest cold-season opens -- before the expected 6-plus inches of snow from the
current storm is factored in.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
Where would you have to go in the United States to be absolutely sure of a
white Christmas?
Kenneth Gutman
Dear Kenneth,
"Absolutely sure" is a powerful term, and with that in mind, Canadian
meteorologist Dr. George Kimble has written, with some hyperbole, "The
regrettable truth of the matter is that over fully three-quarters of the
United States of America the odds on your waking up to a white Christmas are
so long as to be incapable of calculation."
Historically, Chicagoans can expect at least one inch of snow on the ground
on Christmas morning on four Christmases out of 10. Elsewhere in the lower
48 states, a 100 percent certainty of snow-covered ground on Dec. 25 exists
only on our western mountains, on a few of the Appalachian peaks (such as
Mount Washington) in New England, and in the Lake Superior snow belt of
northern Wisconsin and Upper Michigan.

Forces are coming together this evening that threatens to bring a major winter storm to
the Midwest and the Chicago area. A stunningly strong 180 m.p.h. band of jet
stream-level winds is helping generate this intense storm. This is the same system that
brought Las Vegas is biggest snowfall since 1979 and will have copious moisture to
feed it.

This evening radars are beginning to light up with returns as the storm assembles
across the Midwest. Freezing rain has developed in the St. Louis area and is being
reported in the extreme southern portion of the state. Clouds in the Chicago area
should lower and thicken this evening with precipitation expected to begin reaching the
ground in the far southwest portions of the metropolitan area by 7 or 8 p.m. and across
the rest of the area between 9 p.m. and midnight.

Significant accumulations of snow and ice are expected across the Chicago area.
Precipitation is to overspread the Chicago area from southwest to northeast late
tonight—then fall steadily, and at times heavily----through mid-morning Friday.
Strong vertical motion generated by the storm will produce thunder and lightning and
these strong updrafts will produce bursts of heavy precipitation. During thundersnow,
snow accumulation rates can exceed 2 to 3 inches per hour.

The system may seriously impact Friday morning’s rush hour. A cocktail of
precipitation is to affect the area with heavy snow and sleet north of I-80 and snow and
sleet changing to freezing rain and threatening serious ice accumulations to the south
from Pontiac and Kankakee to Rensselaer, Indiana. Local accumulations of around a
foot are possible in counties adjoining the Illinois/Wisconsin line before precipitation
winds down to sporadic flurries or snow showers later Friday morning and
afternoon---tapering off quickly to 1-5” south of I-80.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
--Steve Kahn, WGN Weather Center Meteorologist

Unfortunately, due to the breaking weather situation in Chicago, Tom will not be
available for tonight's Before the Forecast video.

But have no fear weather watchers: Tom is hard at work in the WGN Weather Center
along with the entire WGN, CLTV and Chicago Tribune weather page staff, closely
watching the incoming storm.

For complete weather information, tune in to WGN News at 9 p.m. and wgntv.com
for Tom Skilling's full and 7-day forecasts. We'll also be updating our blog as
conditions warrant.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Tons of snow in the Keweenaw Peninsula

Thanks to Tony Rocco for sharing pictures of the deep snow on Upper Michigan's Keweenaw Peninsula

Photos by Tony Rocco

Snowy Las Vegas
Snowy palm trees bring just the right Christmas to Las Vegas as the desert city was hit by its biggest snow storm since 1979. Thanks to former Chicagoans Jennifer and Jeff Thies (who moved to Las Vegas to get away from the snow) for sharing these photos.

Photos by Jennifer and Jeff Thies

Chicago's 7th snowiest December in 124 years is about to get even snowier. The second
major winter storm in a week -- this one wetter and stronger -- hits with thunder Thursday
night and Friday morning. Its track will dictate how the cocktail of precipitation it
produces is distributed across the area. Current indications point toward major snow and
sleet accumulations roughly north of Interstate Highway 80 with serious icing -- capable of
snapping power lines and downing branches -- being a problem late Thursday night in the
south. Computer models and various snowfall forecast techniques suggest the storm's 12 to
14 hours of steady precipitation will reach the city between 8 p.m. and midnight.
Estimates of the storm's water equivalent precipitation range from 0.86 inches to 1.75 inches
-- three to six times the moisture generated by Tuesday's system. That could translate to
6 to 14 inches of snow over parts of the metro area -- especially north -- into
Wisconsin. The presence of t-storms may lead to bursts of heavy precipitation.
RARE SNOW SOCKS LAS VEGAS
Two to 6 inches of snow hit Las Vegas Wednesday. The last time that much snow fell there
was in 1979 when 7.9 inches fell.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
I know that sometimes the smaller Great Lakes like Erie freeze over
completely, but has that ever happened to Michigan, Superior or Huron?
Ed Berling, Lockport
Dear Ed,
Environment Canada and the U.S. National Oceanic and Atmospheric
Administration monitor ice development on the Great Lakes during the winter.
Their data indicate that three of the Great Lakes (Superior, Huron and Erie)
have totally frozen over in a few of the very harshest winters since 1900,
but Michigan and Ontario have never achieved complete ice coverage.
Ice development usually begins on all five lakes in January and attains its
maximum extent in late February or early March. Ice covered 90 to 95 percent
of Lakes Michigan and Ontario in the severe winters of 1903-04, 1976-77 and
1978-79, the maximum coverage ever reported for those lakes.

No one captures a news event through pictures quite like our friend and
Chicago Tribune photographer John Smierciak. Check out these shots from
John of Tuesday's nightmarish Chicago rush hour snowstorm. THANKS John!
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

John adds the following description:
Eastbound traffic on I-80 near New Lenox, Ill., comes to a standstill
numerous times as the roads got worse in the mid-December snowstorm. A
trip from Channahon to Lansing, Ill., that usually takes 30 minutes,
took four hours.

John adds the following description:
As the snow came down in the early afternoon on westbound I-80 near
Joliet, Ill., traffic slowed to a crawl. A trip from Tinley Park to
Joliet, Ill., took an hour and a half.

Photos courtesy of John Smierciak, Chicago Tribune

Randy White recently moved from Chicago to Kingman, Ariz., (about an hour's drive
southeast of Las Vegas) in October to escape winter. He took these pictures from his
front yard Wednesday afternoon.
--By Paul Dailey, WGN Weather Center Meteorologist

Photos courtesy of Randy White

Jayne Ciasto caught a hawk in the middle of breakfast Wednesday morning near the
intersection of Foster and Winona in Chicago.
--By Paul Dailey, WGN Weather Center Meteorologist

Photo courtesy of Jayne Ciasto

Thanks for joining us for this Wednesday edition of Before the Forecast! After yesterdays snow storm, we got a break today with a mix of sun and clouds. However, there is yet another winter storm which could result in significant snow and/or ice accumulation late Thursday into Friday.
To hear more about this wintry weather, Tom Skilling has all the details on Tonight's Before the Forecast. Thanks to our weather interns Andrei Evbuoma and Eric Szos, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

After the snow let up around 9:30 p.m. Tuesday evening, Nick Liveris took these
beautiful shots near Dearborn and Maple in Chicago. Thanks Nick!
--By Paul Dailey, WGN Weather Center Meteorologist

Photos courtesy of Nick Liveris

Snow fell steadily for nearly 10 hours Tuesday, producing the season's heaviest official
snowfall tally to date. By late evening, totals were approaching 5 inches at O'Hare,
solidifying the 2008-09 season as one of the 13 snowiest at this early point in 124 years of
weather records. The ill-timed snow crippled Tuesday evening's rush hour, producing
inflated travel times reminiscent of the infamous 1990 Valentine's Day rush-hour storm. Its
9.7-inch tally was nearly twice Tuesday's snowfall, yet each induced gridlock on area
thoroughfares, hampering snow removal.
The cold temperatures Tuesday turned the 0.30 of an inch of precipitation (water
equivalent) into a volume of snow nearly twice that which might have been expected in a warmer
environment. Snow formation is especially efficient at low temperatures which leads to
bigger flakes.
CONCERN GROWS OVER NEXT SYSTEM
An even more potent storm appears to be taking aim at the Midwest Thursday night into
Friday. The Chicago area is to be positioned precariously close to the boundary between ice
and snow in a storm predicted to produce as much four times the precipitation of
Tuesday's disturbance.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
Recently, it was snowing at my place but the radar showed only green
(indicating all rain) over my area. Why would the radar become confused like
that?
Randy Walker, Portage, Ind.
Dear Randy,
Displays of precipitation "echoes" from National Weather Service Doppler
radars are artificially colorized images of the strength of the radar energy
that is reflected from precipitation particles back to the radar. Echo
strength is closely related to precipitation intensity.
The radars cannot determine precipitation type (such as rain or snow), but
certain kinds of precipitation (like hail) produce characteristic radar
images from which its type can sometimes be deduced.
Artificially colorized displays of precipitation type (green for rain, pink
for "ice" and white or blue for snow) are computer-generated, taking into
consideration weather observations and other non-radar data.

Tonight's snow to wind down in a few hours...another storm to follow Thursday night-Friday

The snow will be gradually winding down across the Chicago area as the evening wears on with only flurries expected in the area by about 10 p.m. Through 6 p.m. storm snow totals were approaching 4 inches at O'hare and 3 inches at Midway. By the time the snow ends area most area totals should be in the 4-6 inch range.

Before this storm's snow is even cleared, forecasters are already taking note of another storm that threatens the Chicago area during the late-Thursday-Friday period. This storm will have considerably more moisture to work with than tonight's storm and temperatures will be warmer so the area could be facing a messy mixture of heavy snow, ice and even rain before it is over. Winter storm watches are already posted across southern portions of Wisconsin and Lower Michigan and may be issued for northern Illinois and the Chicago area by Wednesday morning.

Beyond that another snow threat looms late Saturday and Sunday followed by an arctic blast that could bring the season's first widespread subzero temperatures.

Stay tuned!!

Steve Kahn WGN-TV/Chicago Tribune Meteorologist

Hoffman Estates snow scene
Thanks to Frank Bavaro for this great picture taken during Tuesday evening's snow showing two bucks enjoying the snowfall in his Hoffman Estates backyard.

Photo by Frank Bavaro

Thanks to Midway observer Frank Wachowski for providing us with the actual thermograph temperature trace of the precipitous temperature fall that sent readings crashing 45 degrees in just 12 hours from a balmy 51 degrees at 8 p.m. to a frigid 6 degrees above zero at 8 a.m. Monday morning.


Chart provided by Frank Wachowski

Lake effect snow has developed Tuesday morning ahead of the main "system snow" due to overspread the area this afternoon and continue Tuesday night

Lake effect snow has developed in areas along Lake Michigan Tuesday morning in advance of the main snow expected to be generated by the latest wintry weather system to affect the area this afternoon and tonight. Light easterly winds and the intense cold situated over and adjacent to Lake Michgian are to blame for the early onset of lake-effect snow in areas closest to Lake Michgian including the city of Chicago.

The amount of snow weather systems produce is linked in part to the temperature of the atmosphere through which their snowflakes fall. While most weather systems produce snow in a ratio of about 10 inches for every inch of moisture available to them, temperatures with the Tuesday/Tuesday night system are at levels which will approximately double the volume of snow which falls from the roughly 0.30" water equivalent moisture the current disturbance is to generate. It's likely this system will produce 15 or 20-to-1 ratio snow. In other words, snowflakes will be fluffier and have one and a half to two times the volume of most systems' snow here. It if for that reason, our accumulation predictions have been set at 3 to 6"--where in a warmer environment, a system with the same level of moisture available to it might be expected to produce only 3" of snow. Since the city and southern suburbs have yet to receive a 3" or greater snow to date this season (our northern and northwest suburbs already HAVE seen 3"+ snows)---the current system is to produce the city and southern suburb's heaviest snow to date this season. Weather updates will be issued as necessary.

Tom Skilling
Chief Meteorologist-WGN-TV/Chicago Tribune

UPDATED FORECAST FOR THE FIRST DAY OF THE 7DAY FORECAST ONLINE

...WINTER WEATHER ADVISORY THROUGH TONIGHT....

Some lake-effect snow has begun in areas along Lake Michigan. More general snow develops across the remainder of Chicago area this aternoon and falls steadily through much of Tuesday night accumulating 3 to 6" before tapering to flurries in Wednesday's pre-dawn hours. East to northeast winds 5 to 14 m.p.h. lead to less severe wind chills than on Monday.

The snow accumulation with this system is to be the biggest to date this season in the city and across soithern suburbs.

Caution advised for slippery travel. Tuesday's daytime high around 22-degrees with steady or slowly rising temps Tuesday night. Readings reach the mid 20s by Wednesday morning.

The brutally cold January-level arctic blast that roared into the area on 40 m.p.h. gusts,
accompanying a 12-hour 45-degree temperature plunge Sunday night, loosens its grip on
the area Tuesday -- but snow is the trade-off. Snow, likely to fall steadily over 10-12
hours and begin between 2 and 5 p.m. Tuesday, is to produce the first 3-inch-plus
accumulations of the season in Chicago and across the southern suburbs. Totals of 3 to 6
inches are expected over most of the area by the time precipitation winds down in
Wednesday's predawn hours.
It's the latest wintry assault on an area experiencing its fourth-coldest December open in
the past quarter century (since 1983).
The wintry weather isn't limited to Chicago. Thirty-six of the lower 48 states were under
winter weather advisories late Monday. Significant snows were falling in mountainous
areas outside Los Angeles, Las Vegas and Phoenix.
Temperatures remained below zero Monday over Montana, all of the Dakotas and most of
the upper Midwest. Monday afternoon's high at Dickinson, N.D., reached only 13 degrees
below zero, setting a new record low maximum for the date.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
Growing up in Chicago in the 1980s, I remember some brutally cold mornings
with the temperature lower than minus 20. When was the last time the city
was that cold?
Greg Patterson
Dear Greg,
The city's last encounter with truly cold weather was nearly 15 years ago
back on Jan. 18, 1994, when the mercury dipped to 21 below zero and the high
for the day was only minus 11. Your frigid memories cover some of Chicago's
historically coldest days. Who can ever forget the "frozen" Christmas of
1983 when temperatures plunged to minus 25 on Christmas Eve and 17 below on
Christmas Day? It was even colder in January 1985 when Chicago recorded its
all-time low of 27 degrees below zero on Jan. 20. In recent years, the
city's arctic blasts have been more modest. Since 2000 the lowest official
recorded temperature here has been 10 below zero on Feb. 5, 2007.

Thanks for joining us for this Monday edition of Before the Forecast! After bitter cold temperatures throughout the day today, we can now expect to see pretty good snows tomorrow afternoon/evening. Chicago could see anywhere from 3-6 inches. To hear more about this wintry weather, Tom Skilling has all the details on Tonight's Before the Forecast. Thanks to our weather intern Eric Szos, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Tom Caulfield e-mails to say he built these snowmen in his backyard in Elgin last week!
Great shot! Nice job Tom! Many thanks!
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Photo courtesy of Tom Caulfield, Elgin, Illinois

What a beautiful shot! The tranquility of winter is so evident in this
beautiful shot from Patrick Baron who snapped this near the Kankakee
State Park during a recent snow. THANKS Patrick!
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Photo courtesy of Patrick Baron

Even though temperatures peaked in the lower 50s across much of the Chicago area
Sunday, clouds and dampness coupled with strong south winds made it feel a lot
colder. The thaw removed much of the area's lingering ice and snow, but that was
quickly replaced by a burst of freezing rain and snow that swept northern Illinois on
Sunday night as a powerful arctic blast sent temperatures crashing more than 35
degrees in just a few hours.
Burlington, Iowa, reached a balmy 62 degrees at 3 p.m. Sunday, but by evening was
glazed by freezing rain with temperatures in the upper 20s.
Monday's daytime readings here should get no higher than the teens. Windchills will be
below zero as west-northwest winds gust in excess of 30 m.p.h.

MORE SNOW AND COLD ON THE WAY
With cold air firmly in place across the area, Chicago is facing at least three episodes of
wintry precipitation this week.
Several inches of snow are expected to fall here Tuesday night, followed by a wintry
mix by late Thursday and another round of snow late Saturday. By Sunday, a strong
arctic surge threatens the city's first subzero weather of the season.
--By Steve Kahn, WGN Weather Center Meteorologist

Dear Tom,
Would you please explain what constitutes a blizzard versus a snowstorm?
Robin Rembelski, Des Plaines
Dear Robin,
Despite the fact that the National Weather Service has strict guidelines for
qualifying a storm as a blizzard, the term is often erroneously applied to
snowstorms that don't fit the bill. The two key factors in categorizing a
storm as a blizzard are wind and visibility. Winds need to reach sustained
speeds or frequent gusts of 35 m.p.h. or greater, and visibilities have to
be repeatedly reduced to 1/4 mile or less by falling and/or blowing snow for
a period of at least three hours. A blizzard can actually occur with clear
skies if the visibility reduction is caused by blowing snow. While there are
no temperature requirements for a blizzard, the combination of strong winds
and below-freezing temperatures will drop windchills at least into the
single digits.

Readings are expected to surge into the lower 50s by late Sunday, the warmest readings
here since a 52-degree high on Nov. 14. The long-absent warmth will be propelled into
the area on southerly gales that will gust as high as 45 m.p.h.
Some light showers or drizzle will dampen the scene through the day Sunday, followed
by a period of steadier rain at night as a potent cold front approaches.
As temperatures plunge below freezing after the cold front passes late Sunday night,
the rain is expected to quickly change to snow that could accumulate up to an inch by
early Monday, a day that will feature strong west-northwest winds and falling
temperatures. The rapid freeze-up could create icy conditions for the Monday morning
commute.

SERIES OF IMPULSES TO BRING SEVERAL BOUTS OF SNOW TO THE CHICAGO AREA
With cold air back in place, the city faces several more chances for snow. Rapidly
moving impulses threaten repeat bouts of snow late Tuesday into Wednesday, Thursday
night and late Saturday. Several inches are possible with the Tuesday night-Wednesday
system with the threat of more sticking snow later in the week.
--By Steve Kahn, WGN Weather Center Meteorologist

Dear Tom,
When was Chicago's warmest Christmas?
Adam Bednarek, Dyer, Ind.
Dear Adam,
It was nearly 26 years ago in 1982 when Chicago experienced a Christmas that
was warmer than most Easters. The afternoon temperature peaked at a balmy 64
degrees, twice the day's normal 32-degree high. While most Chicagoans
celebrated a traditional holiday, some people were washing their cars,
barbequing and even playing golf. Excited children got an unexpected chance
to ride their new bikes and scooters outdoors. The very next year was
payback time as the city shivered through its coldest Christmas. After a
frigid Christmas Eve when the mercury dipped to minus 25, Christmas Day 1983
dawned with a low of 17 below and could only muster a high of minus 5. The
back-to-back Christmases had an incredible temperature spread of 81 degrees,
a true testament to Chicago's vigorous and volatile climate.

The surging temperatures predicted to sweep into Chicago on powerhouse southerly
winds this weekend are the product of a mammoth winter storm churning across the
Rockies. The system has prompted warnings for snow and blizzard conditions across
sections of 21 states on its cold side. However, its howling frontside winds -- likely to
blow at more than 70 m.p.h. not more than 3,000 feet above the ground later Saturday
into Sunday while gusting above 40 m.p.h. at the surface here -- are to boost
temperatures by Sunday afternoon more than 40 degrees above Friday's single-digit
lows. Sunday highs are to surge into the low 50s.
Fifty-degree temperatures are not unusual here in December. All but 24 of the past 138
years have produced a 50-degree high, and there have been 439 such readings in
December over the term of Chicago weather records since 1871.

NORTHEAST REELING AFTER
DEVASTATING ICE STORM
More than 1 million households across six states from New Jersey to Maine were
without electricity Friday in the wake of a huge ice storm. Officials fear restoration of
power may not come until late next week.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
I remember a frigid period in the 1980s when temperatures were below zero
for nearly two weeks. Can you confirm my recollections?
Todd Theurer
Dear Todd,
Chicago winters in the late 1970s and early 1980s were infamous for severe
cold, but we believe you are referring to the benchmark 1982 cold spell that
besieged Chicago Jan. 7-17. This 11-day period was marked by unprecedented
cold, ground blizzards and whiteouts, and dangerous windchills (based on the
old windchill formula) to minus 80 degrees. Temperatures fell below zero on
10 of the 11 days with the lowest reading crashing to minus 26 degrees on
Jan. 10. It was the coldest 11-day period in Chicago's history, averaging
0.6 degrees below zero. During this brutal cold wave, the city established
five new record minimums and logged four days of minus 19 or lower.

Tracey Surface was kind enough to share these beautiful photos of Friday night's full moon. Thanks Tracey!
--WGN-TV Weather Center

Photos courtesy of Tracey Surface

Thanks for joining us for this Friday edition of Before the Forecast! 23 states are under some form of winter weather advisories. While North Dakota and Minnesota are expecting blizzard like conditions, here in Chicago we could see 52 degrees here on Sunday. Tom Skilling has all the details on Tonight's Before the Forecast. Thanks to our weather intern Eric Szos, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in on Monday for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

The Midwest is in for a wild weather ride over the next three days. The weather of two seasons is to visit the region before the weekend closes. Friday's descent back into frigid arctic air is to be a brief one. The arrival of south winds Friday night initiates a period of rising temperatures. Saturday's strengthening south winds are to propel high temperatures nearly 20 degrees higher than Friday -- levels well above freezing. But the most eye-catching weather changes arrive Sunday. That's when a powerhouse winter storm takes control of the area's weather, promising a real meteorological roller-coaster ride between Sunday and Monday. Chicago, which is to find itself on the the "warm" side of the system at the start, will see 40+ m.p.h. south winds that push temperatures into the low 50s Sunday -- the highest levels in a month! Thunderstorms can't be ruled out Sunday night ahead of a precipitous temperatures crash Monday.

BLIZZARD, WINTER STORM WATCHES HOISTED FROM ROCKIES TO PLAINS AS WINTRY BLAST CRASHES OUT OF CANADA
Nine states are under winter-storm watch conditions through Saturday. Blizzard conditions are expected in Montana.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
People are talking about how cold it was at last Sunday's Bears game with temperatures
in the high teens. I remember a much colder game against Green Bay in December 1982.
As I right?
Vince Kerner
Dear Vince,

Not quite. The Bears and Packers did play in frigid conditions in Chicago in the early
1980s. But it was on Dec. 18, 1983 with the Bears winning 23-21. That game
goes down as the second coldest Bears home game on record with the game-time
temperature near 5 degrees. The Bears coldest home game was played at Wrigley Field
on Dec. 16, 1951 against the Chicago Cardinals with the mercury peaking at just 2
degrees. Cold weather does seem to give the Bears a decided advantage. We conducted
an in-house study focusing on home games played with temperatures in the 20s or
lower that showed the Bears winning more than 60 percent of them, giving credence to
the term "Bear weather."

Thanks for joining us for this Thursday edition of Before the Forecast! Tomorrow Chicago will struggle to reach 20 degrees, but we can expect quite a warm-up with near 50 degree temperatures on Sunday. Tom Skilling has all the details on Tonight's Before the Forecast. Thanks to our weather intern Eric Szos, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Gene Fitzwater forwards us this incredible lenticular cloud photograph taken by his
cousin Nicky Bartruff of Puyallup, Washington last Friday. “Standing waves”, which are
fixed currents of air most often created by air movement over mountains and other
terrain features which survive for an extended period of time in one locations---are
behind the formation of lenticular clouds. They most often form on the downwind side
of mountains and have been mistaken by some observers for UFO’s. This is certainly a
spectacular shot of several lenticular clouds which formed downwind of Mt. Rainier in
the Pacific Northwest’s Washington state.

Thanks Gene--and please than Nicky for us! This is a spectacular shot!

-Tom Skilling

Photo courtesy of Nicky Bartruff, Puyallup, Washington

Cold air has thoroughly dominated the past month with 23 of the past 26 days posting below normal temperatures. It's little wonder more snow has fallen in December's opening 11 days than normally falls the entire month at O'Hare International Airport. South suburban areas have been spared a good deal of the heaviest snowfall. But from Chicago to the north and west, snowfall this season is running at nearly twice the normal pace: 9 inches to date at O'Hare versus 5.2 inches. Just 7 inches had fallen at the site by the same time last season. A review of the 19 snow seasons with comparably heavy seasonal snow tallies by now indicates full season snow tallies finished an average of 34 percent heavier than the long-term average -- 48.9 inches versus the 36.6 inches.

HOUSTON RESIDENTS MARVEL AT A RARE SNOW -- THE FIRST IN 4 YEARS
On Wednesday afternoon and evening, Houston was seeing snow -- an infrequent visitor even in winter. It's the first time snow has fallen there in 4 years. Residents had to be surprised at the issuance of a winter weather advisory as temperatures dropped to freezing, causing icy patches on area bridges and overpasses.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
As a second grader in 1965 I vividly remember going to bed on Christmas Eve with the
ground bare and waking to a white Christmas. Can you check this out for me?
-Eric Field

Dear Eric,
Your recall is perfect. Christmas Eve, 1965, was mild and rainy with a high of 51
degrees. In fact it was Chicago's wettest Christmas Eve, with precipitation totaling 2.61
inches, accompanied by thunder and flooding. However, colder air moved in during the
evening as a cold front passed through the area and temperatures plunged into the 30s.
Rain turned to sleet and then snow with half an inch falling before midnight. At 6 a.m.
on Christmas, 2 inches of snow covered the ground at the then official site at Midway
Airport, and 1965 was officially declared a white Christmas. The snow cover remained
through Dec. 29 then vanished as the mercury climbed to 56 degrees on Dec. 30 and to
60 degrees on New Year's Eve.

Thanks for joining us for this Wednesday edition of Before the Forecast! After 1-4 inches of snow fell across the Chicagoland area last night, we can now expect to see some much colder temperatures the next couple of days. There is, however, a warm-up instore for us later this weekend. Tom Skilling has all the details on Tonight's BTF. Thanks to our weather intern Eric Szos, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

A month of cold weather finally eases---but only temporarily---this weekend. But, as
Brent Krauth demonstrates through this photograph, the chill is quite capable of
producing icicles.

Thanks for a terrific shot, Brent!

Tom Skilling

Photo courtesy of Brent Krauth

This photo comes to us from Thomas Nava on Chicago's northwest side. The shot was
taken this morning and followed a night with some blowing of the 2.3 inches of snow which fell there. THANKS Thomas!

Tom Skilling

Photo courtesy of Thomas Nova, Chicago's northwest side

Brandi Wall, who does such a great job of capturing Chicago scenes through her
photography, shares these shots taken Wednesday morning in the city's Edgewater
neighborhood. Edgewater sits astride Lake Michigan on Chicago's far North Side.
1-2 inches—locally as much as 2.6 inches---fell there late Tuesday and Tuesday night
with the latest snow system. Great shots, Brandi! MANY THANKS for sharing them with
us!

Tom Skilling

Photos courtesy of Brandi Wall, Chicago

Chicago recorded its third 2-inch-plus December snowfall Tuesday propelling the city's seasonal snow tally to 8.5 inches -- the third heaviest early season total here since 1980. Rain preceeded the snow -- lots of it. The day's 1.45-inch water equivalent precipitation tally set a new record for the day becoming the heaviest ever on Dec. 9. Had cold arrived earlier, snows that moisture could have generated -- 10 to 15 inches of it -- would have parallelled those recorded in a corridor of Wisconsin and Lower Michigan from north of Madison to Lake Huron. Snow falls there exceeded 12 to 16 inches.
Plummetting temps and 30+ m.p.h.gusts turned untreated roads into skating rinks late Tuesday. Snowfalls ranged from 2 to 4 inches north and west of the city and less than one inch in the south suburbs where rain persisted into the evening.

PATTERN CHANGE TO DELIVER MILDEST WEATHER IN TWO WEEKS THIS WEEKEND
Temperatures may be rising as early as Friday night as part of a new pattern which will see bitterly cold arctic air masses entering the country by way of the Rockies and Plains-much farther west than over the past month. Chicago highs are headed for the 40s this weekend.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Mr. Skilling,
Your recent graph of Chicago's winter temperatures reminded me of the harsh winters
that Chicago had in my childhood years from 1975 to 1985. Because of my name, I took
a lot of ribbing. How cold were those winters?
Jeff Winters, Chicago
Dear Jeff,

The answer will surprise you. We averaged Chicago's winter temperatures (December
through February) for each of the 11 years in the period that you mentioned,
1975-1985, and arrived at 23.0 degrees.

A similar averaging calculation for every set of 11 consecutive winters from 1870 to the
present yielded this startling fact: The 11 winters from 1975-76 through 1985-86 --
the period that constituted your childhood years -- were the absolute coldest in
Chicago weather history. No other period of 11 consecutive Chicago winters was
colder. The second coldest: 1976-77 through 1986-87 with 23.1 degrees.

Snowing hard in Antioch
Thanks to Carl Frystak for sharing this picture taken on a snowy Tuesday night in Anticoch.
Snowfall across the Chicago area so far tonight has ranged from 2 to 4 inches north and west of the city to the Wisconsin border to less than one inch in the south suburbs.

Photo by Carl Frystak

Thanks for joining us for this Tuesday’s edition of Before the Forecast! Rain has shifted over to snow and left stunning snow totals in its wake! Tom Skilling has all the details on Tonight's BTF. A big thank you goes out to our weather intern Ellen Lytle, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

It's rain -- not snow -- that greets Tuesday morning commuters as the latest winter storm sweeps the area. Despite the fact the metro area's been mired in uninterrupted cold air for a month -- responsible for the 9th coldest December opening in 139 years -- south winds have tapped mild air and temperatures have been rising during the night. The current "warmth" won't last. Cold air returns as winds shift north/northeast Tuesday afternoon changing rain to sleet and snow for several hours late Tuesday and Tuesday evening before ending. Only an inch or two of snow is to accumulate in the immediate Chicago area -- less south -- but as much as 3 inches near the Illinois-Wisconsin line. These totals pale in comparison to the 8 to 13 inches predicted through central Wisconsin and Lower Michigan.

This December's opening week average of 21.8 degrees -- more than 10 degrees below normal -- joins two others since 2005 in being unusually cold -- 2005 (16.5 degrees) and 2006 (18.3 degrees).
The collapse of a ridge aloft over the Atlantic has set the stage for a westward shift in the coldest air in the U.S. It's a pattern expected to bring 40s here Sunday while introducing much larger temps swings in coming weeks.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
Why doesn't the shortest day of the year have the earliest sunset?
James Stahr Sr. Wheaton

Dear James,
This year, Chicago's earliest sunset occurred on Dec. 8 at 4:19:46 p.m. Monday.

By the winter solstice Dec. 21, sunset will occur several minutes later, with the sun
dipping below the horizon at 4:23 p.m.

Despite this apparent inconsistency, the shortest amount of daylight does occur on the
winter solstice because of a later sunrise. Astronomer Dan Joyce from Triton College's
Cernan Space Center explains these discrepancies are related to the eccentricity of the
Earth's orbit around the sun. Joyce also points out that if we define afternoon to be the
time from solar noon, the moment of the sun's highest ascent each day (11:43 a.m. on
Dec. 21) to sunset, then the year's shortest afternoon does occur on Dec. 21.

Thanks for joining us for this Monday’s edition of Before the Forecast! Temperature "mood swings" are about to dominate our region over the next few weeks, which will lead to big changes. Tom Skilling has all the details on Tonight's BTF! A big thank you goes out to our weather intern Ellen Lytle, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

The astronomical community has been abuzz for some time regarding the remarkably low level of solar activity (sunspots) in recent months. Our astronomer Dan Joyce says the situation is truly abnormal--especially in a period in which the sun should be cycling into a more active phase as a new 11 year solar maximum approaches. This geomagnetic plot back to 2000 underscores just how anomalous the low level of solar activity has been. The sun is in a less energetic state when sunspots are so limited and there are some in meteorology and astronomy who believe this can have an effect on earth's weather. It's a situation which is going to be interesting to follow. Our thanks, as always, to Dan Joyce for his insight and expertise on this subject and for sending us this geomagnetic activity plot.

Tom Skilling

Graph courtesy of astronomer Dan Joyce, Cernan Earth and Space Center, Triton College

David Lastrucci shares these photos of Chicago’s wintry Monday skies as viewed from
the lakeshore. Thanks David!

Tom Skilling

Photos courtesy of David Lastrucci, Mount Prospect

A winter storm watch is in effect for much of Iowa and Wisconsin and areas just to the
north and northwest of Chicago. The first effects of low pressure developing in the
Texas Panhandle will be felt Monday morning over much of the Midwest.
A thin layer of ice may form on sidewalks and roads. As strong southerly winds aloft
pull warm, moist air over the top of subfreezing air close to the ground, light rain or
drizzle forming in the warmer air is expected to fall into the colder air below and freeze
on contact. Scattered sleet showers are also possible. Temperatures rising into the
lower 30s should minimize the ice threat Monday afternoon in most areas.

BRUNT OF STORM FELT TUESDAY
The low is projected to track northeast through southern Illinois and central Indiana
into northwestern Ohio. As the low approaches in the morning, rain should spread
north into Chicago. As the system moves away, rain will change to snow as winds shift
northeast, pulling colder air into northern Illinois while entraining moisture off of Lake
Michigan. A heavy, wet snow could accumulate to several inches over the Chicago area
Tuesday night and early Wednesday.
--By Paul Dailey, WGN Weather Center Meteorologist

Dear Tom,
I am a big fan of winter temperature records. When did Chicago have its
highest and lowest December temperatures?
Maximino Garza, Jr., Chicago
Dear Maximino,
By any standard, December is a genuinely wintry month in Chicago. It's the
city's third-coldest month (behind January and February), but it also has
surprisingly mild moments.
In 138 years of records dating from 1870, December temperature extremes here
have ranged 96 degrees from an all-time high of 71 degrees (Dec. 3, 1970,
and Dec. 2, 1982) to 25 below zero (Dec. 24, 1983 -- Christmas Eve).
Averaging 43.4 degrees, December 1877, was the city's mildest, and many
Chicagoans will remember the bitter December of 1983, the coldest, with an
average of 14.3 degrees. Incredibly, each day in December 1983, when
averaged through the month, was 29.1 degrees colder than each day in
December 1877.

Any warming Sunday will be limited by increasing and thickening clouds ahead of an
approaching low pressure system. Snow should spread over northeast Illinois from the
west later in the afternoon and continue overnight. Another inch or so accumulation is
expected on top of Chicago’s snow cover .

SIGNIFICANT SNOW POSSIBLE

Wet accumulating snow could begin later in the day Tuesday afternoon and continue
overnight. Over the Texas Panhandle Monday night, an intensifying jet stream flowing
from the Pacific Northwest is expected to merge with a strong Southern Pacific-origin,
upper-level, low pressure disturbance moving inland off the southern California coast.
A resulting strong storm is forecast to spread rain into the Ohio Valley and a mix of
rain and snow farther north that could change to all snow over Chicago later Tuesday.

Dear Tom,
You recently said the world’s wettest spot is in South America.
Where was that, and what about the driest spot?
Jim Lottman

Dear Jim,
South America is host to the world’s wettest and driest places: Lloro, Colombia, and
Arica, Chile. Located 440 miles north of the Equator, Llororeceives an annual deluge of
523.60 inches of rain (14.4 times Chicago’s average of 36.27 inches), and that makes it
the world’s wettest spot. Prevailing west winds bathe Lloro in moist tropical air from the
Pacific Ocean. The world’s driest location, the Atacama Desert extending 975 miles
along Chile’s Pacific Coast. Some locations have never recorded rain, though fog is
common. Arica, 1,500 miles south of the Equator, lies in the northern part of the desert
and registers annual rainfall of 0.02 inches, though some years arerainless.

Fresh snow and modestly milder temperatures greet residents as Saturday gets under
way. Gusty winds generate windchills cold enough to cancel out a good part of that
temperature increase. Wind- driven overnight snows, the latest meteorological assault
on area residents, are predicted to produce 1- to 3-inch accumulations before tapering
to flurries several hours into Saturday morning. Sporadic flurries follow, though better
organized snow showers may return ahead of a fresh surge of arctic air and powerful
jet-stream winds later Saturday. Arctic air sends readings into single digits over much
of the area before the sun rises Sunday.
Friday's daytime thermometer readings peaked at 18 degrees -- a level more typical of
January than early December. Though cold air is no stranger here this time of year, only
25 years of the past 139 have seen readings as cold as in recent days so early in the
season.

STICKING SNOW SUNDAY NIGHT AND MONDAY; TUESDAY STORM POTENTIAL
More accumulating snow hits Sunday night into Monday morning, and a complex storm
with snow or a mix of precipitation will have to be monitored for Tuesday.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
I remember as a child my dad telling me that it had to be above freezing in
order for it to snow. I'd like to trust his wisdom, but this seems wrong.
Was he right?
Alycia Pirc
Dear Alycia,
Snow can occur at temperatures above and below freezing (32 degrees), but it
forms in the clouds only in a below-freezing temperature environment.
Clouds develop when airborne water vapor condenses into visible particles --
water droplets when condensation occurs at or above 32 degrees and ice
crystals below 32 degrees. When cloud particles grow too large and heavy to
be supported by currents of rising air in the clouds, they fall to the
ground as precipitation (rain or snow).
If air at ground level is above freezing (but generally not warmer than
about 40 degrees) and the warm layer is not too deep, snowflakes falling out
of sub-32 degree air above can make it to the ground without melting.

Thanks for joining us for this Friday's edition of Before the Forecast! Friday marks the coldest day in Chicago in over nine months! The chill moderates briefly Saturday but with that comes more snow. What follows afterward? Tom Skilling has all the details on Tonight's BTF. A big thank you goes out to Eric Szos from Northern Illinois University for helping out with tonight's Before the Forecast?

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

The coldest air to grip the Chicago area in more 9 months moves into a second day Friday. The average date on which Chicago's first official single-digit temperature has occurred over the past 138 years has been Dec. 14. Yet many suburban residents will step out into single-digit temps a second consecutive morning Friday, having experienced lows of 4 degrees in De Kalb, 5 degrees in Aurora and 6 degrees in South Elgin on Thursday. Despite sunshine, snow cover -- heaviest to the west -- will restrict warming Friday. Highs will be close to Thursday's peak reading of 22 degrees -- a January-level temperature which was 16 degrees below normal and the coldest daytime reading here since Feb. 20.
The chill comes at the end of a Nov. 8 through Dec. 4 period which has averaged 33.0 degrees -- this area's coldest in 12 years and a reading 4.8 degrees below the 138-year average.

ONLY FIVE SNOWIER STARTS IN PAST 25 YEARS IN CHICAGO

The 4.3 inches of snow on the books as Chicago's official seasonal tally has been topped only five times in the past 25 years. Weather history tells us 90 percent of the city's seasonal snow has yet to fall.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
We're having a discussion here at work regarding winter humidity versus summer
humidity. Tom (at work) insists there is more humidity in the winter than in the
summer. The rest of us question this. Help!
Sharon Plucinski

Dear Sharon,
Relative humidity (RH) is the percent saturation of air. In Chicago's low winter
temperatures, the RH is generally quite high, averaging 72 percent in January, because
as the temperature drops, so does the amount of moisture the air can hold. A very
small amount of water at low temperatures may come close to saturating the air and
yield a high RH.

The RH is usually lower in Chicago's warm summer temperatures, averaging 68 percent
in July, because much more water is necessary to give high RH values. However, the
average amount of water in Chicago's July air is seven times greater than in its January
air.

Thanks for joining us for this Tuesday’s edition of Before the Forecast! If you have been outside recently, you have undoubtedly noticed the cold air that has settled in the Chicago region. How long are we going to shiver and is snow in the cards for this weekend? Tom Skilling has all the details on Tonight's BTF. A big thank you goes out to Valparaiso University's very own Aaron Brackett, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

The arctic spigot is wide open Thursday. Chicago-area residents are in for a rendezvous with the area's coldest air since a 19-degree high Feb. 20 -- more than nine months ago. Thermometer readings Thursday are likely to rise no higher than the low 20s which, in combination with an 8 to 18 m.p.h. west/northwest wind, threatens to keep wind chills in single digits much of the day.
Near 40-degree temperatures were in place as the precipitation began Wednesday, bringing rain then sleet. That moisture has frozen overnight and area residents will have to be careful on untreated roads and sidewalks Thursday.
The chilly weather extends the colder-than-normal pattern which has dominated for nearly a month. Temperatures since Nov. 8 have averaged 4.5-degrees below the long-term average -- the chilliest such period in eight years (since 2000). It ranks 21st coldest of the past 139 years placing it among the chilliest 15 percent on record.

HEFTIER SNOW WEST AND NORTH INTO WISCONSIN

Snowfall decreased as it moved into Chicago on Thursday producing 1- to 2-inch tallies. Totals in the 3- to 4-inch range were common across northwest Illinois.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
I love sunshine and Chicago's never-ending cloudy days of winter depress me. Where is
the best place to get my "sunshine-fix"?
Barbara Allen

Dear Barbara,
Millions of Americans suffer to some extent from seasonal affective disorder (SAD), a
form of depression associated with the reduction of daylight that occurs during the
winter months. Often called the "winter blues", this type of depression is much more
common at higher latitudes where long dark nights and prolonged strings of cloudy
days are most prevalent. December is Chicago's cloudiest month, typically logging only
39 percent of the possible sunshine in a month where daylight is limited to a little more
than 9 hours each day. Areas receiving a great deal of winter sunshine include Arizona,
Nevada, Florida, Mexico and the Caribbean which makes them popular winter vacation
destinations.

Thanks for joining us for this Wednesday edition of Before the Forecast! Another round of snow took place over Chicagoland this afternoon. The heaviest recorded snowfalls were out to our northwest toward Rockford where they saw about 3". Here in Chicago we had anywhere from a half and inch to about one inch accumulation. For all the details and snowfall amounts across the area, Tom Skilling will fill you in on Tonight's BTF. Thanks to our weather intern Eric Szos, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Winter is off and running! The pattern of regular cold surges -- punctuated by brief temperature rebounds such as the one in progress as Wednesday dawns -- is to continue beyond mid-month. As if on cue, December's arrival initiated a parade of wintry weather systems across the Chicago area. The second such weather system -- armed with 6 to 8 hours of mixed precipitation and likely to reach the city shortly after midday -- threatens to have some impact on the afternoon and evening rush hour. This is not the huge, moisture-endowed system that hammered the area Sunday and Monday. Computer models late Tuesday were even beginning to suggest its heaviest precipitation is to target Wisconsin more directly than the Chicago area. But the disturbance buried Glacier County, Montana, with up to 9.3 inches of snow Tuesday. Precipitation totals are to be far less dramatic here. In fact, precipitation is likely to begin in an above-freezing environment and is to start as rain or a rain/sleet mix. The air should cool expeditiously with the onset of precipitation, switching to sleet and snow. A final period of snow is to occur as the disturbance exits the area early Wednesday. The best estimate is that 1 to 2 inches of snow may accumulate.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
What is the smallest range of temperatures in a single day in Chicago?
Frank Fleming, Chicago

Dear Frank,
Chicago's weather is always in a state of flux and rarely do temperatures hover at
exactly the same value for more than two or three hours. That's the reality we live with.

On very rare occasions, though, when the progression of weather systems across the
Midwest has greatly slowed and Chicago finds itself with high humidity, a foggy and
densely overcast sky and practically no wind, the temperature can remain stationary.

The answer to your question is, surprisingly, zero degrees of temperature change.
Chicago's temperature sat at 35 degrees for a record 30 hours from 9 p.m., Feb. 5,
1942, through Feb. 6, to 3 a.m. on the 7th. It happened on two other days as well,
though not for 30 hours: March 24, 1891 (32 degrees) and March 13, 1878 (44 degrees).

Nick Liveris shares this photo of the snowy world to which north suburban Deerfield
residents rose Tuesday morning. Great shots, Nick! Many thanks!

Tom Skilling

Photos courtesy of Nick Liveris, Chicago, Illinois

Thanks for joining us for this Tuesday's edition of Before the Forecast! Unfortunately we are experiencing some technical difficulties. Tonight's video should be up shortly, so keep checking in. As always, tune in tonight at 9 to see the most pressing weather news with Tom Skilling.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

An accumulation of snow has come to Scotland! These shots from the UK come to us from
Mark Vogan. Thanks Mark!!

Tom Skilling

Photos courtesy of Mark Vogan, Glasgow, Scotland

Thanks to Carolyn Szepanski for sharing these shots of Monday’s snow accumulation in
Whiting, Indiana. Great job, Carolyn!

Tom Skilling

Photos courtesy of Carolyn Szepanski, Whiting, Indiana

Southwest winds that take hold this afternoon are to boost thermometer readings. The problem is winds effectively cancel temperature increases by lowering wind chills. The breezes -- 30 m.p.h. at times by late Tuesday -- are likely to all but eliminate the normal overnight decline of temperatures. But, the cold air these winds attempt to displace is denser than the mild air they carry. This forces much of the warmer air up and over the cool air mass. Initially only mid- and high-level clouds are to result from this process. But as Gulf and Pacific moisture reaches the area Wednesday, clouds thicken and ice pellets (sleet) or a sleet-rain mixture will develop, possibly transitioning to snow late Wednesday. There's enough moisture to suggest slippery travel conditions may develop.
A succession of precipitation-producing systems the next 2 weeks, each followed by cold air, is producing generous computer snowfall estimates ranging from 9 inches to as much as 21 inches over the period.

STORM COULD HAVE BEEN WORSE HERE
Had more of Sunday's copious liquid precipitation fallen as snow, Chicago could have been buried by 7 to 11 inches of snow.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
As I look out at [Sunday's] snowfall, I noted that most of it melted as soon as it hit the
ground. How does weather observer Frank Wachowski measure the snowfall with any
accuracy?

William J Hopkinson, Maywood

Dear William,

Snow depth measurements are based strictly on accumulated snowfall. When falling
snow melts upon contact with the ground, snow depth is reported as "Trace -- melted
as it fell" and, if no measurable snow (0.1 inch or more) occurs during the calendar day,
a trace of snow enters the record books for that day.

Snow accumulation is measured on a designated surface, usually a snow board -- a
slab of wood, painted white, and placed where snow accumulation is representative of
the area. The water content of the snow (and all frozen precipitation such as sleet and
hail) is also measured and recorded.

Thanks for joining us for this Monday edition of Before the Forecast! After Chicago saw its first snowstorm of the season, there were some respectful totals across the area. Downers Grove saw the most snow with 5.7 inches, while O'Hare Airport had 3 inches. As this same weather pattern continues, we could be in store for some more snow over the week. Tom Skilling has all the details on Tonight's BTF. Thanks to our weather intern Eric Szos, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

More pictures from Brandi Wall taken around lunchtime Monday at Wacker and Randolph.

THANKS Brandi!!

Tom Skilling

Photo courtesy: Brandi Wall

Kris Bochenek captured this sunrise this past Thursday 11/27/2008) from the Evanston
lakeshore near Dempster and Sheridan. It’s Kris’ favorite location for sunrise
photography—and we can see why! This is a beautiful shot! Thanks Kris!!

Tom Skilling

Photo courtesy of Kris Bochenek, Evanston, Illinois

Arlington Heights is among the areas which takes on the appearance of a winter
wonderland in the Sunday/Monday snow

Our friend Curt Renz forwards us this beautiful photo taken around 2:50 p.m. of
Monday's (12/1) snow at North School Park in Arlington Heights. THANKS Curt! Your
photos are always great!

Tom Skilling

Photo courtesy of Curt Renz, Arlington Heights, Illinois

Check out these beautiful photos taken in the city in the midst of our first significant
snow of the season and submitted to us by Brandi Wall. Wonderful shots, Brandi—THANK
YOU for sharing them with us!

Tom Skilling

Photos courtesy of Brandi Wall, Chicago, Illinois

Friend of this blog and all around good guy Mark Vogan, who is so good about updating
us on the vagaries of UK weather, sends us these beautiful shots from Scotland and
reports the weather there and across the UK has been chilly. Mark tells us:

"We had a low yesterday morning of -12C / 9F up north in Braemar in the Highlands and with all of Scotland and much of UK shivering, this is easily the coldest period for late-Nov/early Dec since 2000. It's expected that we will remain below normal throughout much of December. VERY INTERESTING."

Great report as beautiful pictures as always, Mark! MANY THANKS!

Tom Skilling

Photos courtesy of Mark Vogan, Glasgow, Scotland