March 2009 Archives

Few Chicagoans are likely to shed any tears at March's passing. The 5.2
inches of precipitation at O'Hare made it the fifth-wettest March since
1871. There hasn't been a wetter March in 33 years. At Midway Airport,
the picture was even soggier. The month generated 6.76 inches of
rain-the most ever in a March since weather records began at the South
Side site in 1928. But for all its nastiness, March had some redeeming
qualities. Its average temperature finished more than 2 degrees above
normal, and the paltry 2.1 inches of snow that fell at O'Hare was only
one-third of the normal 6 inches.

A brief, scary funnel

Northwest suburban residents in sections of Boone and McHenry Counties
had a bit of a scare as weather sirens sounded just after 5:30 p.m.
Tuesday. A narrow line of a gusty downpour and small, hail-generating
showers produced several funnel clouds. A spotter in Belvidere reported
a funnel about 5:35 p.m. Despite the funnel's brief, scary appearance,
residents were never really at risk. Doppler radar wind scans showed a
very weak, shallow circulation that dissipated quickly. The showers
within which the short-lived circulation briefly appeared were only
17,000 feet tall.

Dear Tom,
Does Hawaii have a tsunami season?
Bill Jahn
Dear Bill,
Tsunamis are an ever-present danger on the ocean coasts of the Hawaiian Islands and
around the entire Pacific Basin, but there is no such thing as a "tsunami season" does
because tsunamis are not weather-related.

Tsunamis are sea waves caused generally by earthquakes, less commonly by submarine
landslides or massive landslides into the ocean, and infrequently by submarine volcanic
eruptions. Those phenomena are geologic in nature and occur randomly, not
seasonally.

On average, the Pacific Basin experiences a destructive tsunami about every seven
years, but none has occurred in 34 years. Oceanographer and tsunami expert Dr. Walter
Dudley has said, "We will soon have approached the longest period in recorded history
without a Pacific-wide tsunami, so one could say we're due now."

Rainbow in the wake of Tuesday evening's storm on Chicago's Northwest Side

Photo courtesy of Tom Nava, Chicago

Heres a picture sent to us by Tracey Surface of a double rainbow over Montrose Harbor in Chicago Tuesday evening.

Photo courtesy: Tracey Surface

The cold front associated with low pressure in southern Minnesota moved through
Chicago between 6:30 and 7PM this evening preceded by a line of showers and
thunderstorms. The line of storms and cold front extended from Milwaukee south just off
the Lake Michigan shoreline all the way south to Terre Haute, Indiana. Southeast winds
ahead of the front shifted abruptly southwest at 15 to 25 m.p.h.

-Paul Dailey WGN-TV Meteorologist

At approximately 5:35PM Tuesday evening, a weather observer near Belvidere High
School reported a rotating wall cloud extending about 35 percent of the way down to
the ground. Shortly thereafter, sirens went off and a brief tornado touchdown was
sighted near the intersection of Irene Road and Interstate 90. The sighting has not been
officially confirmed and no reports of damage or injuries have been received.

This storm was part of an eastward-moving broken line of showers and thunderstorms
that extended from near Rockford/Belvidere southward through Elgin to Yorkville.There
were scattered reports of reports of strong winds and small hail along this line.

Here are some pictures of the storm that rolled through Yorkville at about 5:50 p.m.
Tuesday

Photos courtesy of Walt Stagner, Yorkville, Ill

Photo courtesy of: Stephanie Beasley, Yorkville, Ill

Check out this link from the Alaska Volcano Observatory showing a video time lapse of the recent activity of Redoubt Volcano on March 27 2009

Photo courtesy of Alaska Volcano Observatory

Rain is on its way and is expected to reach Chicago toward lunchtime. A windy storm is
on a track well north of its weekend counterpart and is likely to introduce its warm
sector rather than the wind-driven snows on its north side. Snows halted travel within a
wide swath of the Plains from Wyoming to the Dakotas. Conditions there Monday
included gusts approaching 60 m.p.h, visibilities near zero and snow totals topping 2
feet. It marked the second time in only a week that the region has been assaulted by
wind-driven snows. In Lead, S.D., 26 inches of new snow had fallen by late Monday.

In Chicago, the latest system's howling southeast winds are to veer south later Tuesday,
a development likely to allow noticeably milder air into much of the metro area.
Southern suburbs could see low 60s, while 50s will visit much of the remainder of the
area away from the lake.

Active pattern shows no letup

Another storm lifts from the southern Plains to the southern Midwest on a track that
may produce a chilly rain over part of the area late Thursday. A more significant system
will have to monitored this weekend.

Dear Tom,
Could our nation's 200th birthday- July 4, 1976 been a day without precipitation
anywhere in the country? I seem to remember no adverse weather. Can you check it out?
Ge Breu

Dear Ge,
Though sprawling high pressure brought much of the nation beautiful weather on its
bicentennial, there was still plenty of rain. Showers and thunderstorms fell from eastern
New Mexico to the Carolinas, then north to New York. Rain was heavy in many areas,
with 1-inch plus totals in Alabama, Georgia and Tennessee.

Severe thunderstorms produced damaging winds in Georgia, and least five tornadoes
were reported, three in Texas and one in Wyoming and Colorado. Light showers also
dampened the Pacific Northwest. Rain-free periods across the entire lower 48 are
extremely rare and would last only for a few hours--not an entire day.

Sunday's spring snow photos
A cold, windy and rainy Saturday night transformed into a snowy Sunday across the Chicago metropolitan area. The heavy, wet snow was plastered across the area's greening spring landscape by strong north winds creating beautiful snow scenes. We thank all of our readers and viewers who took the time to send us their wonderful pictures documenting nature's handiwork.

Steve Kahn WGN Weather Center

Snow covered Easter eggs in Homewood

Photo by Amy and Phil Dillman

Crocuses in a snow-covered Darien garden

Photo by Anna Dolder

A robin in a plum tree in Lake in the Hills
Photo by Chellie McCarthy

Another snowy robin

Photo by Kevin McDevitt

A "weather-stick" in Geneva

Photo by Bob and Barb Powell

Springy the snowman in Wheeling

Photo by the Stanonis family

A snowy Lincoln Park

Photo by Jessica Zernhel

Pancake ice off Wilmette

Photo by Julia and Jim Baillet

The Chicago area was transformed into a wintry wonderland Sunday as heavy, wet
snow plastered itself across the greening spring landscape. However, the weight of
the snow, coupled with strong north winds, broke branches and downed power lines.
Northern and western suburbs caught the brunt of the snow, with Mundelein and
Cary logging more than 7 inches as Chicagoland received its first snow cover in
more than a month. Even Downstate could not escape the snow. Springfield
recorded a record 5.8 inches for March 29.
Milder temperatures will make quick work of the snow Monday, but an active
weather pattern will bring the city at least three shots of rain this week.
March’s precipitation tally is already the seventh-wettest, and Tuesday’s rain could
push it closer to the top.
Red River Valley bracing for snow
With rivers already at record levels, Fargo, N.D., residents are facing the prospect
of a major snowstorm that is expected to bring a foot of snow and high winds
Monday and Tuesday.
--By Steve Kahn, WGN Weather Center Meteorologist

Dear Tom,
The name "Alberta Clipper" denotes both origin and speed of the storm. Are
there any other names for northerly storm systems that affect Chicago? What
about systems that arrive courtesy of our southern neighbors?
Mark Welch, Tinley Park
Dear Mark,
In addition to "Alberta Clippers," fast-moving snowstorms that originate a
bit farther east in Canada have been dubbed "Saskatchewan Screamers." A
persistent cross-polar jet stream bringing a parade of frigid arctic high
pressure systems to the Midwest is often called the "Siberian Express." As
far as systems originating in warmer areas, a winter pattern that brings
mild but stormy weather from the Pacific to the West Coast and Alaska is
called the "Pineapple Express." Snowstorms that develop in the
Texas/Oklahoma region are referred to as "Panhandle Hooks," and those that
develop in the lower Mississippi Valley sometimes carry the name "Louisiana
or Mississippi Rebel."

A potent early spring storm will be exiting the Chicago area Sunday morning after lacing the region with cold rain and even some thunderstorms Saturday evening. Although most of Chicago and areas to the south received rain, areas to the north and west of the city from DeKalb to Waukegan, where the mercury hovered around the freezing mark, were glazed by a mixture of sleet, freezing rain and snow. The icy wetness coupled with north winds gusting to 40 m.p.h. made for a raw, damp evening.

Colder air spreading across the metropolitan region Saturday night was expected to switch the precipitation to all snow before sunrise. Accumulations should total as much as 8 inches in areas north and west of the city, tapering to an inch or two of snow in southeast sections.

A ROUGH DAY TO RUN

Runners in Sunday morning's Shamrock Shuffle will be severely tested, facing freezing temperatures and gale-force north winds (gusting in excess of 40 m.p.h.). They will likely find it slushy underfoot after the overnight snowfall.
Temperatures will rebound to seasonable readings the rest of the week, but rain is expected Tuesday and Thursday.

Dear Tom,
Right after a March 22 high near 80 degrees at Rapid City, S.D., a blizzard brought up to
30 inches of snow. What is the warmest Chicago has been before a major snow?
Martin Shanahan Jr., Joliet

Dear Martin,

The Chicago area basked in record 65-degree warmth on Jan. 24, 1967; two days later
the city was shut down by its biggest snowstorm, the 23-inch Big Snow of Jan. 26-27.
To this day, many Chicagoans become apprehensive when unseasonable winter warmth
invades the city. Since 1885, the city has recorded half a dozen 6-inch-plus
snowstorms that have developed within three days of high temperatures of at least 60
degrees, and an additional 10 major snows that have closely followed days with highs
in the 50s. The large variations in temperature are indicative of a volatile atmosphere,
ripe for major storm development.

A storm responsible for a crippling Plains blizzard Friday while stoking
100-degree temperatures in south Texas, bears down on the Chicago area
Saturday afternoon. Air ascends so quickly in such a system, barometric
pressures plunge, encouraging winds to rush in from the periphery. The
process can lead to eye-catching wind velocities -- like the 45+ m.p.h. gusts
expected to sweep this area as cold rain moves in later Saturday. Lakeshore
flood warnings have been issued on the Indiana and Illinois shorelines,
likely to be lashed by 10-12 foot waves which may lead to minor flooding.

It’s what happens next which may define this system. Rising air in storms
moves to higher elevations where atmospheric pressures are lower. As this
happens, air expands and cools. The speed with which that process takes
place will dictate whether and how fast the cold rains of later today
transition to sleet then snow. Current indications suggest the switch is to
begin late Saturday in northwest suburbs then proceed southeastward into the
city during Sunday’s pre-dawn hours. Converging winds above the surface may
lead to embedded, precipitation-enhancing thunderstorms as well. With snow
and sleet expected to fall longest west of the city -- particularly from the
Fox Valley and McHenry County westward, snow accumulations may be heaviest
there. But the city isn’t likely to completely escape. The arrival of snow
and sleet -- and the real possibility of a period of fairly healthy snowfall
for a time Sunday morning -- could lay down 2-5” in the city, while 5 to 8”
can’t be ruled out in the far west and northwest suburbs. Chicago typically
sees a 6”+ snow later than March 28 approximately once every 10 years.

Up to 20” down in the Plains, drifts tower to 10 ft.
Powerful gusts to 50 m.p.h. in the western Plains piled up 10 ft. drifts
from western Kansas south to the Texas Panhandle with 19” accumulations
reported at Ulysses, Kan.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
My mother always told a story about our family moving during a blizzard on
my first birthday on March 26, 1944. How much snow actually fell that day?
George Pratl, Willowbrook
Dear George,
I'm sure the snow put a crimp into your family's move, but the snowfall that
day was hardly the "storm of the century." The record books show that just
2 inches of snow fell that day, and combined with the 1.7 inches from the
previous day's snowfall, the city received a two-day total of 3.7 inches.
Temperatures were in the middle 30s that day, and there was some rain mixed
with the snow, so the streets were probably a slushy mess. Just two days
earlier on March 24, spring was in the air and the mercury reached a balmy
65 degrees. However, in typical Chicago spring fashion, a cold front passed
and temperatures plunged, setting the stage for the ill-timed moving-day
snowfall.

Temperatures surged Thursday, making it feel like spring-yet snow may
fall this weekend in parts of the Chicago area. Most prone to get snow
appear to be areas away from Lake Michigan, which could see chilly,
wind-driven rain switch to snow or sleet late Saturday afternoon or
night.
So many factors are at work this late in the season to prevent snow
from occurring-longer days, more intense sunlight and warmer ground and
lake temperatures among them. But 65 percent of the past 124 years have
produced measurable snows (0.1 inch or more) beyond March 27. The
intensity of the most intense snows has been eye-catching, like the 12.6
inches that accumulated March 30-31, 1926; the 10.7 inches on April 1-2,
1970; and the 9.8 inches on April 2-3, 1975.
This weekend's snows aren't likely to be as intense. But sub-32-degree
dew-point air, which cools through evaporation once rain begins falling
into it, and the "dynamic cooling" brought on by the strong upward rush
of air as a strong batch of jet stream winds sweeps in, argue for a
shift to at least some wet snow and sleet later Saturday and Saturday
night-especially away from Lake Michigan. Rising air cools because the
surrounding air pressure drops, encouraging it to expand and cool. The
storm's backside north winds are also likely to latch on to chilly air
south from the Upper Midwest and Canada.
Colorado was declared a disaster area Thursday as blizzard
conditions-including 20 inches of snow and gusts that reached 100 m.p.h.
in some canyons-brought travel to a standstill.

Thursday's "warmth" to prove fleeting

It was like spring Thursday! Highs reached 61 degrees at Chicago's
lakefront as well as in Libertyville, Wheaton and New Lenox.

Dear Tom,
Has there ever been an April in Chicago that did not register an 80 degree
or higher day?
--James L. Stewart

Dear James,
April usually brings Chicago its first really warm spring weather, but only a
little more than half of the April's here since 1871 have registered an 80
degree or higher temperature. Climatologist Frank Wachowski checked the
record books and found that 77 of the 138 Aprils (56 percent) since 1871 have
recorded 80 degree or higher temperatures. April 1977 holds the record for the
most, with eight, followed by 1915, with seven, and 1896, with six.
The last April failing to reach 80 degrees was in 2000.

Chicago has also recorded some 80 degree temperatures in March. The city's earliest
was an 80 degree high logged on March 3, 1974, and Chicago's warmest March day was
March 29, 1986 when the mercury spiked to 88.

With March in its final week, North America's atmosphere has lurched
into an energetic state-a situation predicted to continue over the
coming two weeks. It's a setup that leads to a cooler and wetter than
normal overall weather pattern. Winds are significantly calmer here
Thursday than in recent days, but barometric pressures are in a dive
across the Plains-a wind-generating development. Winter weather
advisories posted late Wednesday in 15 states include blizzard watches
in sections of Texas, Oklahoma and Colorado. The terrain in those states
slopes upward from east to west, and that's why the howling 40+ m.p.h.
east winds predicted to develop there are to cool as they blow into
these states' higher elevations. This "upslope cooling" is likely to
ring much of the copious moisture flooding into the region from the Gulf
and may generate 12-inch-plus snow accumulations.

Windy storm is Chicago-bound

The windy storm is to sink from Colorado into Texas then take an
ominous turn to the northeast, tracking across central Illinois and
lower Michigan. Cold, wind-driven rain is due in Chicago for the start
of weekend, beginning as some spotty sprinkles late Friday and becoming
steadier overnight. There are early indications the temperatures within
this storm may support a mix of wet snow in far northwest sections of
the Chicago area and a swath of accumulating snow from western Missouri
into east Iowa, northwest Illinois and sections of Wisconsin later
Saturday and Saturday night. Chicago wind gusts may top 40 m.p.h. at the
height of the storm Saturday afternoon and evening.

Dear Tom,
What are the strongest winds we've ever had in the Chicago area?
Bob Klicpera Romeoville

Dear Bob,
Officially the windiest day in the Chicago area occurred more than a century ago on
February 12, 1894. On that day a raging blizzard not only brought more than 10 inches
of snow to the city, but the ferocious northeast winds that accompanied it piling the
snow into huge drifts, also produced the city's all-time official highest wind of 87
m.p.h. Of course the area has been frequently blasted by strong wind gusts during
severe thunderstorms. On August 26, 1965 Midway Airport measured a record wind
gust to 88 m.p.h. and at O'Hare a wind gust reached 84 m.p.h. during a severe
thunderstorm on March 27, 1991. Throughout the years thunderstorm wind gusts
approaching 100 m.p.h. have been reported throughout the metropolitan area but are
not considered to be official.

Chicago-area weather was a study in contrast Tuesday. Welcome 70-degree
temperatures (the last likely to occur here for a while) surged north,
reaching the area from Aurora east across the southern half of Chicago.
Midway Airport's high was only the second time it reached 70 degrees
this year, and readings as warm as 73 occurred from Naperville to
Kankakee.
Powerhouse southerly winds, stacked vertically tens of thousands of
feet into the atmosphere, were enhanced as showers poked aloft into 70
m.p.h. winds just 3,000 feet above the surface. It's a development
responsible for directing the high winds down to the surface, downing
power lines and trees in scattered areas near Peoria, Springfield and
Macomb. Chicago-area winds gusts reached 52 m.p.h. at Midway just before 5 p.m.
and topped 50 m.p.h. at Lombard and DeKalb.

But as springlike warmth paid the south half of the Chicago area a visit, chilly air off the
lake continued to flood ashore in north lakeshore communities. The chill contributed to
waves of heavy rainfall, which exceeded 2 inches by 10 p.m. in Rockford (2.02 inches, a
record for the date). To the north in Wisconsin, Stoughton and Madison were swamped
by 2.81-inch and 2.50-inch totals.

Dakotas' snows stack up to nearly 3 feet!

Snow continues Wednesday in eastern North Dakota but diminishes to the west after
accumulating as much as 30 inches near South Dakota's Black
Hills.

Dear Tom,
Although it is said that in Chicago we cannot produce vitamin D from exposure to the
sun during October through April, I sometimes wonder. I have read conflicting reports.
Laurie Black

Dear Laurie,
Oak Park dermatologist Dr. Bryan Schultz tells us that exposure to 5 to 10 minutes of
sunlight (ultraviolet light) in the summer will produce adequate vitamin D in light-skin,
but up to five times as much exposure is required for dark skin.
However, Schultz explains that Chicago's sunlight "... is not usually adequate from late
fall to early spring, thus increasing one's risk for deficiency in the winter. Milk, fortified
juice and salmon are on the very short list of foods supplying vitamin D, so a
multivitamin with 400 I.U. (800-1000 I.U. for older adults) can help, in addition to
allowing one to reduce the aging and carcinogenic effects of UV by using sunscreen."

Temperatures surge toward 70 degrees Tuesday amid howling south/southeast winds likely
to top 40 m.p.h. frequently-and all this as Chicago forecasters keep an eye on the
potential for active thunderstorms capable of producing their own powerful gusts. A scattering
of fast-moving northbound showers is embedded in Tuesday's southerly winds. With the
southerly flow stacked vertically, the stage is set for a pattern likely to transport
noticeably milder, more humid air into the area. The fear is of more numerous thunderstorms
embedded within the same powerful winds and potentially damaging thunderstorm wind gusts
later Tuesday and/or Tuesday night.
Just how warm it gets Tuesday will be affected by the extent of rainfall and cloud cover
as well as the predicted wind shift from an easterly to more southerly direction. East winds
can transport chilly lake air ashore, while a more southeast to south flow, like the one
predicted to take hold Tuesday, should allow noticeable warming away from the lake.

Storm hammers the Plains
At one point Monday, a tornado touched down at Brownlee, Neb., while blizzard conditions
were occurring only 110 miles to the west at Pine Ridge, S.D.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
I recall an Easter, I think in March 1965, with at least 8 inches of snow.
Can you confirm and provide some details?
Maryellen Shute
Dear Maryellen,
The Easter that you remember did not occur in 1965, but one year earlier on
March 29, 1964. That Easter remains the city's snowiest on record with
officially 7.1 inches of snow on the books. The snow began falling shortly
before sunrise and continued through late afternoon. Strong winds gusting as
high as 37 m.p.h. reduced the visibility to near zero and piled the snow
into large drifts. Motorists were stranded in the near blizzard conditions
as traffic slowed to a crawl. It was a very cold day for late March with a
high of 29 degrees and a low of 18. The city's second snowiest Easter took
place back in 1920 when 6.4 inches of snow fell on April 4.

Chicagoans should experience a continuation of above-normal temperatures
with periods of showers and thunderstorms. Because of easterly winds off
Lake Michigan, a wide range of high temperatures occurred across the
area Sunday. Along the lakeshore, highs struggled to reach the 50s while
readings farther inland climbed to the 60s. It could be more of the same
Monday, with gusty southeast winds off the cold lake waters holding
readings to the upper 40s to low 50s near the lake and north, while
highs warm into at least the low 60s inland.
With strong southerly winds, readings should warm well into the 60s to
low 70s on Tuesday. But the approach of a major storm system should
trigger thunderstorms and downpours, especially at night as a cold front
pushes through. More than an inch of rain is possible.

Blizzard in the northern Plains
and severe storms south
Forecasts are for 1 to 2 feet of snow in eastern Wyoming and western
North and South Dakota on Monday and Tuesday, complicated by 50 m.p.h.
north winds. Severe storms could develop south, especially later Tuesday
in Arkansas, Missouri, Tennessee and Kentucky.
--By Paul Dailey, WGN Weather Center Meteorologist

Dear Tom,
When is the sun the closest to Illinois? I have a bet with my husband and he
believes everything you say!
Cheryl Hanson
Dear Cheryl,
The Earth completes an orbit of the sun in approximately 365.24 days, but
the path is not perfectly circular. Rather, it's an ellipse -- a slightly
flattened circle -- and the sun is not quite in the center of the elliptical
area. The Earth (and Illinois) is consequently closest to the sun when it
travels through the "end point" of its elliptical path that lies nearest the
sun; it is farthest from the sun at the opposite "end" of the ellipse.
Those points are known as perihelion (closest to the sun) and aphelion
(farthest). Perihelion and aphelion dates vary by a few days from year to
year, but in 2009 perihelion (91.7 million miles) occurred at 9 a.m. CST on
Jan. 4 and aphelion (94.8 million miles) will occur at 9 p.m. CDT on July 3.

As low pressure intensifies in the Plains, an extended period of
southerly flow from the Gulf of Mexico up the Mississippi Valley into
the Midwest should see temperatures rising well into the 60s, and
occasionally the low 70s over northeast Illinois early this week. Sunday
to Tuesday, high readings may average nearly 20 degrees above normal.
Highs will probably peak Tuesday. Vertically stacked strong southerly
winds from the surface up to the jet-stream level just ahead of an
approaching cold front are responsible for Chicago's warm-up Tuesday. On
the same day, severe storms are expected to develop across parts of
Arkansas, Louisiana, Tennessee and Mississippi as the cold front
combines with low-level southerly winds and diverging jet-stream winds
aloft.

More rain and cooler

Computer models indicate a complex low-pressure system will surge out of
the southern Plains into the Midwest on Friday preceded and accompanied
by another wave of showers and thunderstorms. Northerly winds behind the
low center could usher in a sharp shift to colder weather and maybe snow
showers next weekend.

Dear Tom,
I was curious: How many days in the 138 years of records have had the same high and
low for a given day.
Cole Turgeon, Brookfield

Dear Cole,
Such days are rare, but they do occur. A computer sweep of Chicago's official
temperature data base from Nov. 1, 1870, through Dec. 31, 2008--that’s 50,465
days--reveals only three days on which temperatures remained absolutely steady
through the entire 24-hour day: March 13, 1878, when the city's official thermometer
registered a constant 44 degrees; March 24, 1891, with 32; and Feb. 6, 1942, with 35.
The range between the city's maximum and minimum temperatures was only 1 degree
on an additional 24 days, most recently six years ago on April 8, 2003, when the high
and low temperatures were 32 and 31 degrees.

Warmer temperatures are on the way as the Chicago area moves into its
first full weekend of spring. Days have lengthened more than three hours
since December and the energy delivered by the sun's rays is nearly
three times as strong. Add to these factors the southerly winds
predicted to sever Chicago's link to the cold air over Canada's
snowpack, and the day's predicted 16-degree temperature increase appears
a good bet.
The meteorological wild card for lakeside areas revolves around the cool
lake breezes that threaten to temper warming there. Large-scale winds
must blow from the land out over the lake at velocities of at least 10
m.p.h. to keep the chilly layer of air hovering above the 38-degree lake
surface from moving inland.
Saturday's southerly winds appear just strong enough to keep the lake
air from penetrating inland as deeply as it has in recent days, but they
may not be strong enough to completely overcome cool air sweeping
shoreline areas. That suggests Saturday's peak temperatures are likely
to vary from 60 degrees at the mildest inland locations to the 40s with
the arrival of afternoon lake breezes on (and near) the shoreline.

Storm threatening tough week in Plains -- from snow
to twisters -- and big warm-up here
Jet stream winds are buckling and expected to generate a huge,
storm-generating trough aloft. The southwest upper steering winds that
result are to pump temperatures to 70 degrees here Monday and Tuesday.
But the system could bury the western Plains under snow while unleashing
a tornado and a severe storm outbreak from Texas and Louisiana north to
Nebraska and Missouri.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
Is rainwater safe to drink? I've heard that it is pure, but I wonder about
it.
John Koldinger
Dear John,
We receive this question frequently, and your skepticism is warranted. Even
ignoring the effect of atmospheric pollution, meteorologist and former
Chicagoan Dr. Keith Heidorn tells us it is a misconception that raindrops
are pure.
Referring to condensation nuclei, Heidorn says, "The fact is, rain would not
fall without some degree of impurity in the air to act as a seed. This seed
may be a chemical salt, an acid droplet, a speck of dust or soil, or even a
bacterium."
Consider also that every cloud droplet begins as moisture condensing onto a
tiny airborne "nucleus." Because a raindrop might consist of a million or
more individual cloud droplets, it is likely that each raindrop contains the
material from a million or more condensation nuclei.

A wintry chill roared back into Chicago on icy north winds late
Thursday, offering dramatic evidence of March's perennially finicky
weather. In stark contrast to record warmth just two days ago,
homeward-bound commuters were confronted with 30-m.p.h. wind gusts which
delivered temperatures ranging the upper 20s to the mid-30s in lakeside
areas from northwest Indiana across Chicago and north into Wisconsin.
At many locations, the readings marked a 45-degree or greater 48-hour
temperature pullback. The frigid air had origins nearly 600 miles north
over the 12 to 18 inches of snowpack covering Ontario province north of
Lake Superior. Water temperatures on Lakes Superior and Michigan
preserved the chill as the air swept south.

Spring gets under way at 6:44 a.m. Friday, the moment the sun's
northward-shifting most direct rays fall on the equator. Weather records
indicate 91 percent of Chicago's snow has typically fallen by March 20.
Half of the years since weather records began here have produced at
least one additional day in which temperatures have failed to reach
freezing. Rains in 2009 are already 150 percent above normal and there
could more than 2 inches next week.

A spring storm is set to deliver gusty south winds and warmth next
week.

Dear Tom,
A recent column referred to a tornado that hit Chicago near O'Hare Airport. I was in
school then and remember a warning being issued. Can you provide some details?
Sam Schaumburg, Ill.

Dear Sam,
March 12, 1976, was an active severe weather day with four F2 or stronger twisters
touching down in northeast Illinois and northwest Indiana. The twister near O'Hare had
a 17 mile-long intermittent path that stretched from Northlake to Wilmette. The F2
storm killed two, injured 66 and inflicted heavy damage to an industrial park near the
airport. It also damaged buildings near Cumberland and Higgins Road.

This twister made national headlines when it passed within one-quarter mile of
President Gerald Ford's motorcade, who was in town campaigning for the upcoming
Presidential Election.

Tuesday's rare early season 70s are just a memory as the area enters a
second day of cooling. Wednesday's high temperatures, which were as much as
30-degrees lower than St. Patrick’s Day’s remarkable 74-degree high, are to shed
another 5 to 10-degrees Thursday, retreating to more seasonable levels--a situation
which repeats Friday. With clear skies, dry air and diminishing winds predicted
Thursday night, the stage is set for temperatures to dive after sunset, reaching the mid
to upper teens in the coldest locations away from the lake.

Despite the downturn, March 2009's average temperature to date is
37.6-degrees--a reading 5 degrees warmer than the same period a year ago and
3.4 degrees above the long-term average. It's a reading that places the
month among the warmest 25 percent of all Marches in the past 139
years. Only eight other years since 1871 have recorded readings as warm as
Tuesday so early in the season. Abnormally early 70s offer no guarantee that
temperatures that warm will return soon. In 1983, after a four-day spell of
70s March 3-6, it took until April 25 for the return of 70-degree
readings. This year looks different. An intense spring storm is to send strong south
winds and a possible new round of 70-degree warmth into the area next Monday and
Tuesday.

Dear Tom,
I recall the spring of 1977 being one of the warmest in memory. Was it?
John Zang Bolingbrook

Dear John,
Chicago's spring in 1977, with an average temperature of 56.2 degrees, was by far the
city's warmest, beating out runner-up, spring of 1921, by 2.3 degrees. Most
Chicagoans welcomed spring 1977 with open arms because it followed the very severe
winter that featured 54.1 inches of snow, 23 days of zero or below temperatures and a
record 43 consecutive days below freezing. Spring, 1977 brought some unbelievable
early-season warm spells. March logged 13 days in the 60s and 70s and April
registered eight days in the 80s. However, it was a May heat wave that really turned
heads. For nearly two weeks from May 13 to 25, daily high temperatures reached 86
degrees or higher, including nine straight days with highs in the 90s.

Jay Kleeman forwarded this beautiful shot of Tuesday’s sunrise in Chicago’s northern
suburbs! THANKS Jay—it’s spectacular!

Tom Skilling

Photo courtesy of Jay Kleeman

Chicagoans reveled in warm temperatures not seen here in five months
Tuesday, and many were unaware of just how unusual the record-tying
74-degree highs at O'Hare and Midway Airports were this early in the
season. The metro area enjoyed its warmest St. Patrick's Day in 115
years. Only 9 of the past 139 years have logged a temperature of 74
degrees or higher through March 17. The infrequency of
70-degree-or-warmer days this early is further evidenced by the fact
that only 40 of the 17,950 days credited with such warmth have occurred
by March 17 since official Chicago weather records dating back to the
closing months of 1870.

The area's warmest readings Tuesday included 76 degrees at Buffalo
Grove and New Lenox. Records were broken in Rockford (75 degrees) and
Milwaukee (74). Powerful southwest winds gusted to over 40 m.p.h.
Wednesday's promises much different weather. The passage of a cold
front overnight shifts winds northeast, forcing lake-chilled air into
the city. Predicted highs will be nearly 30-degrees colder than Tuesday.
Warming is slated to begin again this weekend and 70s could return by
Monday.

Tuesday's 70s marked warmest temperatures in 5 months

Not since Oct.ober 13 when the high hit 77 degrees has the city enjoyed
warmer weather.

Dear Tom,
Many Chicagoans firmly believe that a tornado cannot touch down in the city. That's
not true, is it?
Scott Robertson, Chicago

Dear Scott,

No it is not! Tornadoes do hit within the city. At least a dozen tornadoes have been
documented in Chicago, though many have been weak. Only one has been recorded
downtown--an F3 storm that swept from near 18th Street and the Chicago River to the
current site of Navy Pier on May 6, 1876.

On March 12, 1976, an F2 twister clipped the far northwest side near O'Hare and on
March 4, 1961 an F2 tornado killed one and injured 115 as it cut across the South Side.
The tail end of the F4 Oak Lawn tornado on April 21, 1967 traveled across the South
Side before dissipating over the lake near 79th Street. Chicago's earliest recorded
tornado struck the Norwood Park area on May 22, 1855.

Tuesday takes on the feel of May, with temperatures predicted to surge
to 73 degrees--a reading within striking distance of the date's
115-year-old record of 74 degrees set in 1894. Such a high reading would
make this the warmest St. Patrick's Day here in 6 years-and one of the
four warmest on record since 1871. Air sinking, compressing and warming
beneath the leading edge of a 160-m.p.h. jet stream sets the stage for
this remarkable spell of early season warmth. Surface winds are likely
to gust to near 40 m.p.h., particularly this afternoon and evening, as
warm air surges eastward out of the Plains, where it produced record
highs of almost 80 degrees in Nebraska.
The average date for Chicago's first 70-degree reading in the past 138
years has been March 29, which makes Tuesday's 70s two weeks early. The
first 70-degree high here didn't occur a year ago until April 16.

Lake Michigan water level more than a foot above a year ago

Lake Michigan's surface water temperature bottomed out two weeks ago at
33.6 degrees and has begun its seasonal rise. Lake levels, thanks to a
winter of heavy precipitation, are now 13 inches higher than a year ago.

Dear Tom,
I want to put my snow blower away for the season. What are the chances of a heavy
snow in March or April?
Mike Hunnicutt Woodridge, Ill.

Dear Mike,

You can put your snow blower away, but don't be surprised if you have to do some
shoveling. In Chicago, late season snowfalls tend to be heavy and wet, "heart-attack"
snows. Even though the average date of the city's last 1-inch-plus snowfall is March
20, some of the city's biggest snows have occurred after that date, including 19.2
inches March 25-26, 1930 and 10-11 inches April 2-3, 1975. In 1970 Chicago was
rocked by two late-season snows--14.3 inches fell March 25-26 with an additional
10.7 inches falling April 1-2. Chicago's latest major snow was a 6.8 inches April 15-17,
1961; so it is a good idea not to put your snow blower away until you file your income
taxes on April 15.

Spring - "astronomical spring" - arrives March 20, the date (known in
astronomical circles as the vernal equinox) on which the sun's rays
shine directly down on the equator as the sun makes its annual trek into
the Northern Hemisphere. More figuratively, our seven-day forecasts
suggest that spring arrives in Chicago this week, though its arrival
will be in fits and starts. Afternoon temperatures in the low 60s Monday
will jump 10 degrees into the low 70s on Tuesday, but then the spring
feel will give way to a midweek reality check with Canadian air and rain
Wednesday. That's followed on Thursday by a genuine - albeit brief - cold
punch that delivers temperatures more typical of January than mid-March.
BIG STORM SYSTEM FOR WEEKEND
It's mainly a Northwest U.S. affair as it blasts from the Pacific Ocean,
then swings northeast into Canada. Computer models indicate its wind
field will be so expansive that it will generate strong southerly flow
across the Midwest, nearly 2,500 miles away. Chicago's temperatures will
surge toward the weekend, along with a heightened thunderstorm risk as
increasingly unstable air arrives from the south.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
It's not wise to take shelter under a tree or swim in open water during a
thunderstorm. Is it okay to take a shower in one's house under the same
circumstances, or is that also not advisable?
Joe Bednar, Downers Grove
Dear Joe,
In very rare cases, the electric charge from a lightning strike to or near a
house will transfer along a conducting path (such as copper plumbing pipes)
to the interior of a house. For that reason, showering or bathing is
discouraged while a thunderstorm is in progress and for a half hour
afterward.
That's the word from Richard Kithil, president and CEO of the National
Lightning Safety Institute (NLSI). Kithil comments that NLSI has uncovered
no reports of deaths or injuries in those situations, but he adds that "the
absence of evidence is not evidence of absence." Common sense, caution and
prudence is therefore advised.

In many respects March is a fascinating month because it's a month of
transition and there is an abundance of variety to its weather -- more
variety and more frequent changes, in fact, than in any other month.
We're currently in a warming regime in the short term, and it will
culminate with afternoon readings in the middle or upper 60s on Tuesday.
That's a far cry from the wintry chill of last week. Tuesday's expected
high of 67 degrees will be the mildest temperature here in 130 days --
since 71 degrees last November 5. Weather-seasoned Chicagoans understand
full well that a lengthy string of 60-degree days is an expectation
unlikely to be fulfilled in middle March. And as if on cue, the next
surge of much cooler air arrives Wednesday and daytime temperatures full
back into the upper 40s (which is the climatological normal high for
March 18).

Rain douses the South

Widespread steady rain that began in Texas on Thursday has spread across
a broad expanse of the South, and it's very welcome. Most of the region
from Oklahoma and Texas east to the Atlantic Coast is suffering through
moderate to severe drought conditions. A long-duration soaking rain is
exactly what
those areas want and need.

Dear Tom,
While lying in bed recently, I had a south-facing window open about an inch and could
feel cold air coming into the bedroom. I wondered if warm air from inside was leaving at
the same rate. There was no wind blowing the air in and the bedroom door was closed so
there really was no cross ventilation.
Dan Oshea, Oak Lawn

Dear Dan,
Air moves in response to differences in air pressure, always moving from higher to lower
pressure. The driving force is known as the pressure gradient force and it absolutely
controls air movement. Other things being equal, the internal pressure in cold air is
greater than in warm air, and so cold air will always try to undercut warm air. The
American Society of Heating, Refrigerating and Air-Conditioning Engineers assures us
that warm air exiting your bedroom balances the cold air entering it through the open
window.

The mercury reached the 40-degree mark Friday in Chicago, signaling the beginning
of the end of this week’s temperature set-back. Under abundant sunshine, tempera-
ture readings will surge to nearly 50 degrees Saturday, though areas near the lake
will still feel the chilling effects of a light onshore air flow. Warmth will return to the
area in earnest by Tuesday as southerly winds eliminate lake-shore cooling, boost-
ing temperatures throughout the area well into the 60s. The warmth will be fleeting,
however, as the passage of a cold front Wednesday signals a return of northerly
winds that will send temperatures crashing into the 30s for the rest of the week.

Ice and snow blast areas south of the Ohio River
Spring weather was definitely on the back-burner Friday in portions of the Mid-
South. The storm that brought copious rainfall to areas from Texas to Georgia
brought ice and snow to portions of Kentucky and Tennessee.
Lufkin, Texas, was soaked by 1.35 inches of rain while Jackson, Miss., received 1.63
inches. Further north, freezing rain brought widespread power outages to por-
tions of central Tennessee, and nearly 4 inches of snow fell near Jackson, Ky.
--By Steve Kahn, WGN Weather Center Meteorologist

Dear Tom,
When was Chicago's coldest winter and what has been its coldest month?
David J. Nennich
Dear David,
Chicago's coldest winter occurred more than a century ago during 1903-04
when the December-February period averaged just 18.3 degrees, fending off
the winter of 1978-79 by a scant 0.1 degrees. The winter of 1903-04 was not
only cold, but very snowy with 59.5 inches of snow falling. The ground was
continuously snow covered for 56 straight days, and the winter's deepest
snowpack reached 10 inches. During that winter the city logged 17 days with
temperatures of zero or below with the season's lowest reading falling to
minus 15. The city experienced its all-time coldest month in January 1977,
which averaged only 10.1 degrees. The mercury never broke freezing that
month (30 degrees was the month's highest) and fell to zero or below on 17
of the 31 days.

More frozen breakfast treats

These pictures of pancake ice taken Thursday from the north breakwater at Waukegan were sent to us by Tom Harris.

Photos by Tom Harris

Steve Kahn WGN Weather Center

The weather swings through cycles, and the Midwest has finally entered a
period of relatively tranquil atmospheric conditions. That's welcome
news to Chicagoans, who endured a cold, snowy winter then the tumultuous
meteorological events of the first 10 days of March. Two major storm
paths have emerged, both distant from Chicago. A northern track is
directing snow-bearing weather systems eastward across southern Canada,
and a southern track is carrying rain-producing systems across the Deep
South.

DROUGHT BUSTER IN THE SOUTH

Heavy rains sufficient to cause flooding began across Texas on Wednesday
and continued Thursday. Despite flood problems, Texans are welcoming the
water because it has put a big dent in the state's severe drought. Much
of the southern United States from Texas to the Carolinas has
experienced droughts of varying intensities for the better part of three
years, and three-year precipitation deficits are impressive. Locations
from Louisiana to South Carolina and Georgia have logged deficits of 25
inches since early 2006. Heavy rains are targeting those areas in
upcoming days.

Dear Tom,
Spring is almost here and that means Chicago's lake-breeze season is about to begin.
How far inland does the lake breeze typically reach?

William P., Lindenhurst, Ill.

Dear William,

In the "old days" -- that is, prior to the early 1990s when the National Weather Service's
Doppler radar became operational in Romeoville--28 miles southwest of the Loop --
area meteorologists could not locate the position of the lake-breeze front with
precision. Now, however, the powerful Doppler radar reveals the inland penetration of
the lake breeze quite clearly.

Meteorologist Mark Ratzer of the Chicago NWS tells us that it's a mixed and highly
variable bag. On some days the lake breeze front lies only a few hundred feet from the
lake shore, but on other days it surges 40 miles inland and can deliver lake-cooled air
to the entire metropolitan area. Its inland penetration is very difficult to anticipate.

Frozen "breakfast treats" surround Navy Pier

Jeanne DeVore who works on Navy Pier sent us this interesting shot of ice circles which started to show up in the lake near Navy Pier last Monday. They appear to be broken bits of ice with snowy edges which prompted one of her co-worker to remark that they looked like frosted Cheerios. By Tuesday the entire area was filled with them and by Wednesday they were gone.

Photo by cmannlink

Area rivers and streams, most swollen to overflowing after the
relentless rains of recent days, now have the opportunity to drain. A
welcome pattern of dry weather has settled across Chicago and northern
Illinois, and computer models suggest the dry interlude will extend
through the weekend.

The trade-off, though, is very cold temperatures for this time of year.
On average, on only one day in 88 does the city's temperature fail to
rise to 30 degrees during the afternoon in the March 10-15 period, and
today's expected high is pegged in the upper 20s. That's about 17
degrees below the day's normal high of 44 degrees, But the March sun is
powerful and cold air covering the area will moderate steadily.

Deluge moves south

While the Midwest sits cold and dry in air of Canadian origin, the
southern periphery of the air mass has stalled along the Gulf Coast.
It's a turbulent transition zone between chilly air to the north and
tropical air to the south -- and the focus for at least a few days of welcome
rain throughout the drought-ravaged South.

Dear Tom,
What is the chance that we won't have any more troublesome snow storms this winter
-- say two inches or more?
Terry Vance

Dear Terry,

The portion of the year during which Chicago can experience snow extends well into
the spring, but history tells us the city's snow season winds down in March. The
likelihood of another significant snow storm is diminishing with every passing day --
but history also cautions that it would be premature to put away the snow shovel just
yet.

Late-season snowstorms occur at relatively high temperatures, tend to occur in a
moisture-laden environment and produce heavy, slushy snow that is colloquially
known as "heart-attack snow." The probability of a snow of 2.0 inches or more from
this date forward stands at 46 percent, and it does not diminish to 0 percent until May
2. Chicago logged. 3.7 inches of snow on May 1-2, 1940, its latest-ever 2-inch snow.

Weather reflections
Thanks to Florence Bayci for passing on this interesting shot of a placid reflection taken by her neice Michelle Knierim from Mokena.

Photo by Michelle Knierim

Another punch of arctic air settles across the city Wednesday and Thursday, and
afternoon temperatures in the middle and upper 20s are more representative of mid-January than
mid-March. Wednesday, however, will be by far the worst of the two days because northwest
winds gusting occasionally above 40 m.p.h. add an icy feel to the air. Vigorous winter
storms draw additional strength from sharp temperature contrasts, and startling disparities
prevailed across the Midwest on Tuesday afternoon. A blizzard was raging across
Minnesota and North Dakota and residents in St. Louis basked in warmth that is quite unusual for
early spring. At 5 p.m., Fargo, N.D., registered a wind-chill temperature of 23 below
zero and St. Louis reported a heat-index temperature of 80 -- a "feels-like" temperature
difference of 123 degrees across 658 miles.
ABRUPT PATTERN CHANGE
Following Wednesday's wind and cold, relatively placid conditions and temperatures
finally return. It will remain dry through Saturday.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
Why is the Lake Michigan water temperature reported this time of the year?
Doug Bober

Dear Doug,

While the lake water temperature is obviously an important consideration for
swimmers during the summer, it additionally provides valuable information
the rest of the year. A lake that is warmer than normal during late fall or
early winter may well spare the city from a major snowstorm by keeping the
precipitation as rain.

A knowledge of lake temperatures allows forecasters to determine if cold
outbreaks will produce lake-effect precipitation, and whether it will be
rain or snow. Marine interests can gauge when ice formation will begin as
water temperatures slide toward 32 degrees. Finally, lake temperatures
influence the degree of warming or cooling to be expected when onshore winds
prevail -- especially helpful when predicting fog or glazing for areas near
the lake.

Fog shrouds the lakefront
Our thanks go out to Mary Brophy for passing along these photos of her biking along Chicago's fog-shrouded lakefront on Tuesday. Fog was blowing onshore off the icy-cold lake.

Photos by Carol Garsee

Steve Kahn WGN Weather Center

Following quickly on the heels of the weekend deluge that put 2 to 4 inches of rain
across metropolitan Chicago and tossed in a few thunderstorms for good measure, a second and
considerably more vigorous weather system is roaring across the area today. It's bringing
a variety of weather conditions ranging from merely the inconvenient to the genuinely
dangerous. The day starts with chilly temperatures and plenty of rain. That's bad news
because area rivers and streams cannot handle much more water. Rain diminishes to scattered
afternoon showers, but moist and unstable Gulf air arrives in the afternoon, triggering a
round of active thunderstorms that will draw additional energy from 160-m.p.h. jet stream
winds. Temperatures jump into the 60s and severe storms are a possibility. Total
rainfall by evening: up to 2 inches.
ARCTIC BLAST ARRIVES LATE TUESDAY
And it won't be pleasant. Northwest winds gusting to 40 m.p.h. and temperatures plunging
40 degrees from evening readings near 60 degrees will drive wind-chill temperatures into
the single digits by dawn Wednesday.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
Glaciers move, but glacial ice starts as snow. How much snow has to fall before it
becomes moving ice?
Shawn Coren

Dear Shawn,

Meteorologist Anton Kapela of the Milwaukee Weather Forecast Office spent three
months in Antarctica in 1976 and he tells us, "Once snow reaches a depth of 60 feet, its
structure changes such that the crystals re-align themselves (due to internal pressure)
into layers, and that allows slippage. Once the snow depth reaches 90-100 feet, gravity
becomes a factor. The ice starts to move and a glacier has been born!"

How much snow does it take to make 100 feet of ice? Assume a glacier is composed of
snow that had a snow-to-meltwater ratio of 20:1 when it fell. It would therefore require
at least 1,847 feet of snow (because one foot of water produces 1.083 feet of ice) to
compress into the minimum necessary depth of ice to form a glacier.

Flooding from Sunday's storms

John Gardner passed along this picture of flooding near Ransom, Illinois in LaSalle County after Sunday's heavy rainfall.

Photo by John Gardner

Steve Kahn WGN Weather Center

More shots from Sunday's storms

Thanks to Michael Landelius (KC9TVS) a member of Skywarn and Kane/Du[Page County ARES for sending us these pictures taken Sunday afternoon near I-57 and Illinois Route 116 near Ashkum, Illinois. Michael passed on his report of a rotating wall cloud to the National Weather Service at Lockport and a tornado warning was issued. No tornado ever formed, but the storm did produce 60 m.p.h. winds and nickel-sized hail.

Photos by Michael Landelius

Steve Kahn WGN Weather Center

Personal rainbow in Crown Point, Indiana
Rachel Ritter of Crown Point , Indiana passed along this photo of what she calls her "personal rainbow". It appeared after a fierce storm that prompted a tornado warning for the area moved through on Sunday afternoon.

Photo by Rachel Ritter

Steve Kahn WGN Weather Center

Sunday's storm from the Joliet area
Thanks to Tim Tibbott for passing along these dramatic shots of Sunday afternoon's storm rolling through the Joliet area. These shot were taken near I-55 and Black Road.

Photos by Tim Tibbott

Steve Kahn WGN Weather Center

Someone once remarked that meteorologists have a technical term to describe a dry day
following two rainy days. It's called Monday -- and that describes the
Saturday-Sunday-Monday situation.
The weekend deluge put down 2 to 4 inches of rain (isolated locations recorded even
more) that sent rivers and streams out of their banks. It takes a few days for water levels
to recede because the terrain is so flat, and the larger rivers (such as the Fox and Des
Plaines) drain so slowly.
HERE WE GO AGAIN
Another powerful storm system is blasting toward the area. Energized by a jet stream
whose core winds will attain speeds of 160 m.p.h. at 30,000 feet in north and central
Illinois on Tuesday afternoon, the approaching rain producer is a system to be watched.
Rain and thunderstorms arrive by midnight Monday -- only 30 hours after the flooding
rains ended Sunday afternoon. In addition to flood-exacerbating rain, severe storms are
possible Tuesday. Then the bottom drops out: Arctic air sends temperatures tumbling 40
degrees by midweek.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
Snow is measured in tenths of an inch, but how can they measure rain, which is reported in hundredths of an inch, in such tiny increments?
Scott Burgess, Chicago
Dear Scott,
Measuring snow depth is straightforward: Use a ruler graduated in tenths (0.1) of an inch and find a representative snow depth. Rain is a different matter because, as you suggest, one hundredth (0.01) inch of water is too thin a depth to be measured directly.
A standard rain gauge utilizes the principle of multiplication. Rainwater drains via a funnel from a collection area (typically a circular area eight inches in diameter) into an accumulation tube whose area is only one-tenth as great. Every hundredth of an inch of rain from the collection area therefore stands 10 times as deep, or one-tenth inch deep, in the accumulation tube. A ruler graduated to tenths of an inch is then used to measure the depth of the water.

After the storm

Ed Clapp sent usa this picture of a double rainblow taken in Valparaiso, Indiana this afternoon after the strong thunderstorms passed through the area.

Photo by Ed Clapp

Storm clouds over Highland, Indiana
Thanks to James Hartman of Highland, Indiana for passing along these photos taken as his area was placed under a tornado warning this afternoon. James reported a large wall cloud rapidly moving to the east-northeast with small vortices moving in a counter-clockwise direction

Photos by James Hartman

Steve Kahn WGN Weather Center

As has happened several times since last summer, metropolitan Chicago finds itself yet
again in a heavy rain situation. Following excessively wet weather during the latter half of
last year and far above-normal precipitation during the winter, the moisture content of
area soils is close to saturation.

Now, we must contend with another powerful storm system dripping with moisture
supplied by humid air from the Gulf of Mexico.

Widespread rain and a few thunderstorms threaten Saturday-Sunday rain totals of 2
inches, more than enough to send area rivers and streams out of their banks. Flood and
flash flood watches issued on Friday for northern Illinois and Indiana remain in effect
through Sunday evening.

Dear Tom,
Considering Chicago's daily record high and record low temperatures, what day has had
the greatest spread? For example, on Jan. 1 the record high was 65 degrees and the
record low was 10 below zero for a spread of 75 degrees.
--John Foley, Evanston

Dear John,
We took a look at Chicago's daily temperature records for each of the 365 days in the year
and found that Jan. 20 logged the greatest spread between the highest and lowest
temperatures ever observed on any given day: a range of 90 degrees from the day's record
high of 63 degrees (in 1906) to 27 degrees below zero (in 1985). Incidentally, that subzero
temperature stands as the lowest reading ever officially recorded in Chicago since the
inception of temperature records 138 years ago. Many area residents have vivid memories
of that day in which the windchill touched 77 degrees below zero.

A flash-flood watch is in effect for northeast Illinois this weekend. One to two inches
or more of rainfall on top of saturated soils could cause already swollen rivers and
streams to overflow.
Travelers should be alert for water across roads in flood-prone areas, especially later
Saturday, tonight and Sunday.
RARE CONSECUTIVE 65-DEGREE DAYS
Chicago's official high temperatures hit 65 degrees both Thursday and Friday. The last
time this happened so early in the season was nine years ago, on March 5-6, 2000, when
highs hit 69 and 70 respectively. The year's earliest back-to-back 65 degree or greater
temperatures in Chicago occurred March 2-3 in 1974 and 1983.
The warmest unofficial area high Friday was the year's first 70-degree-plus reading (72
degrees) at south suburban Lansing.
MORE RAIN TUESDAY, THEN COLDER
Another weather system hits Tuesday with highs again possibly warming into the 60s and
more showers and thunderstorms expected. However, much colder air is expected to follow
with highs some 10 degrees below normal Wednesday and Thursday.
--By Paul Dailey, WGN Weather Center Meteorologist

Dear Tom,
What is the origin of the expression, "I'm feeling under the weather"?
Paul Sarewich, Chicago
Dear Paul,
Like many phrases, a precise and undisputed origin of "I'm feeling under the
weather" may be lost in the mists of the past, but we were able to uncover
two compelling answers to your question. The "Facts on File Encyclopedia of
Word and Phrase Origins" by Robert Hendrickson credits the first use of
"under the weather" to American author Donald Grant Mitchell (1822-1908)
(a.k.a. Ik Marvel) in the book, "Reveries of a Bachelor."
"Salty Dog Talk: The Nautical Origins of Everyday Expressions" by Bill
Beavis and Richard G. McCloskey offers another explanation. The phrase,
"under the weather bow" originally meant, in mariners' jargon, to feel
seasick. Those so afflicted were sent below deck, and the "weather bow" was
that part of the ship that took the brunt of waves during a storm.

Chicago's daily normal high temperatures do not reach the lower 60s for another six
weeks (until April 21), but area residents will enjoy a second day of late-April-like
readings Friday as temperatures push above 60 degrees. Enjoy it while it lasts, because today
is likely to be the best day in the next two weeks. Cloudiness gradually increases today;
rain and possible thunderstorms arrive at night, then continue through Saturday and
Sunday. Rain totals, possibly in excess of 2 inches, are anticipated before the system
finally departs the area late Sunday. High water in flood-prone areas of metropolitan Chicago
cannot be ruled out. Chicago's weather takes a wintry turn by Wednesday. Upper winds turn
northwest and arctic air arrives mid-week, then settles in for a multi-day stay.

THURSDAY -- WARMEST IN 120 DAYS
Chicagoans basked in relatively warm temperatures Thursday, and vigorous southerly winds
that gusted at times to 40 m.p.h. carried the mild air right to the lake shore. The city
logged an official high of 65 degrees Thursday, the mildest reading here in four months
(since 71 degrees on Nov. 5), and 29 degrees above the year-earlier temperature of 36
degrees.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
We just experienced three straight below freezing days on March 1-3. What is the latest
in the spring that this has happened here?
Steve Billings, Chicago

Dear Steve,
We checked the record book with the help of climatologist Frank Wachowski and found
that the city's latest 3-day subfreezing snap was more than a century ago: April 1-3,
1899. During that period highs were just 27, 30 and 31 degrees. Strong high pressure
over the Plains and Rockies in conjunction with low pressure over New England kept a
brisk northerly flow of arctic air streaming across Chicago and the Midwest. That
early-spring cold snap came after the city shivered through an extended period of
record cold in February during which Chicago's temperature dropped as low as minus
21 degrees. Spring weather did return to the city after the early April freeze-out, with
readings climbing to a warm 80 degrees on April 13.

Stormy weather has brought copious precipitation to the drought-plagued western U.S.
while it's been tranquil here. That's changing. Western storminess is shifting into the
Midwest, accompanied initially by surging temperatures and showers and, by the weekend, heavy rain.
SNOWFALL BURIES SIERRA NEVADA IN CALIFORNIA
A trough of low pressure off the U.S. Pacific Coast sent a series of storm systems across north and central California beginning Saturday night and continuing into Wednesday.
As colder air moved in, snow levels in the Sierras lowered from 7,000 feet Saturday to
2,500 feet Wednesday. The highest elevations, generally above 7,000 feet, have been
measuring snow in yards. Kingvale, Calif., reported a four-day snow accumulation of 96 inches
(8 feet).
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
Who invented the word, "blizzard"?
Allan Standusky

Dear Allen,
The origin of the word "blizzard" is obscure. It first appeared in the United States 139
years ago and its first use was possibly on March 14, 1870, to describe a storm that
produced heavy snow and high winds in Minnesota.

Technically, a blizzard is an intense winter storm with sustained winds 35 m.p.h. or
higher and sufficient falling and/or blowing snow to reduce visibility below
one-quarter mile for at least three hours. Colloquially, the term is loosely applied to
any heavy snowstorm.

Blizzard conditions figured prominently in one of the worst-ever U.S. winter storms, the
"Storm of the Century" that raked the eastern quarter of the nation on March 13-14,
1993. It impacted 100 million people in 26 states from Florida to Maine, produced a
12-foot storm surge on Florida's west coast and 20-40 inches of snow and whiteouts
from Atlanta to Maine.

March's open, as if taking a cue from a winter season that just doesn't seem to want to
let go, has made some news of its own. The month's first three days have failed to
produce a single 32-degree high. No March 1-3 period has done that for 31 years. But
Chicagoans face vastly improved temperatures in coming days. Wednesday's 44-degree high appears to
be just the opening act for surging readings expected to include a pair of 60-degree
highs -- or readings awfully close -- Thursday and Friday. A 63-degree high Thursday would
make the mild spell this area's warmest since last November. Though a second 60-degree
high seems a good bet Friday, easterly lake breezes threaten to deliver chilly shoreline fog
in the afternoon.
Early season warmth is always vulnerable to a number of meteorological factors. Clouds
can block sunlight and limit warming or winds can shift off Lake Michigan's icy waters.
But strong south winds, plus broad subsidence of air beneath the nose of powerhouse jet
stream winds, support predictions of strong warming Thursday. And with atmospheric moisture
expected to surge during the day, the air mass is likely to take on the feel -- even the
smell -- of those first warm surges of spring.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
My boyfriend and I are having a disagreement on whether or not it is warmer near Lake
Michigan in Chicago. It seems that the temperature is typically higher toward the lake
than the outlying areas. Is this true, and if so, why?
Monica Johnson, Plainfield

Dear Monica,
It's usually true, but the explanation is complex because conflicting factors are
sometimes at work.

Cities, and especially large urban areas like metropolitan Chicago, are heat islands. The
central portion of a large urban area experiences higher temperatures--winter and
summer--than surrounding rural areas. That argues for a warmer city and cooler
suburbs, and that is the case most of the time.

But Chicagoland sprawls adjacent to Lake Michigan whose relatively mild waters warm
areas near the lake in the winter and whose relatively chilly waters cool areas near the
lake in the spring and summer.

Paul Hadfield, whose photos always delight, sends us this amazing set of hoar frost
photos taken this morning: In his accompanying e-mail, Paul explains these shots:

With an air temp of around 11 this morning, I spotted something unusual and that was
the formation of patchy hoarfrost along the cracks and crevices of a wooden retaining
wall. The frost that formed on every other exposed surface was your typical fractal
variety. My guess is that as the temperature fell, warmer moist air from within the soil
behind the wall rose to escape and upon making contact with the cold outer edges,
generated the elongated hoarfrost crystals. It definitely made for an interesting effect
although i'm ready to say goodbye to the frost season as i'm sure all you snowy
northerners are too!

THANKS, as always, for sharing these with us Paul! They’re amazing!

Tom Skilling

Photos courtesy of Paul Hadfield, Central Illinois

The biggest calendar day snowstorm to hit Milwaukee in half a century buried Wisconsin's
largest city and a number of its southern suburbs under as much 14.4 inches of snow
Sunday night and Monday. A calendar day snow of that intensity hasn't occurred there since
16.7 inches on Feb. 10, 1960. The potent lake-effect snow setup that hit Sunday and Monday
left as much as 2.5 inches across sections of northeast Illinois from Orland Hills and
Palos Park north to Midway Airport and Gurnee. For 15 hours, a concentrated north/south
band of snow stalled over eastern Milwaukee and Racine Counties, producing waves of intense
snowfall that slashed visibilities to as little as a quarter of a mile. Visibilities
reflect snow intensity and those observed in Milwaukee occur only in the heaviest snow
systems.
East Coast residents were hit by the season's biggest snow -- a system that produced as
much as 14.5 inches in a corridor from Missouri and Tennnessee up the East Coast.

COLDEST MARCH OPEN HERE IN 12 YEARS
The opening two days of March included back-to-back 22-degree highs Sunday and Monday.
The two day average of 18 degrees made it the coldest March open since 1997.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
Are weather forecasts becoming more accurate? Many years ago, forecasts only went
out two days.
Brenda Matsco

Dear Brenda,

Tremendous advances in computer technology (such as faster calculation speed and
more computer "memory") have led to a steady (and ongoing) improvement in the
reliability of weather forecasts.

Today's sophisticated mathematical simulations of the atmosphere -- the so-called
"computer models" -- are more accurate than ever. Armed with this guidance, weather
forecasters are producing better and better forecasts. The National Weather Service has
been verifying forecast accuracy since the 1960s and reports that the five-day forecast
of today is as reliable as the three-day forecast of the 1980s. Short-range forecasts
have improved by a day. That is, the Day 2 forecast of today is as accurate as the Day 1
forecast of yesteryear.

Chris Lucarz says there's plenty of snow in Michigan's U.P. Check out this shot from Chris taken in the Keweenaw Peninsula.

Photo courtesy of Chris Lucarz

Anson Mount has sent us this picture of a snow cell, observed Monday.
Thanks for the photo Anson!

Photo courtesy of Anson Mount

Tribune photographer extraordinaire John Smierciak shares this beautiful
shot at sunset taken not long ago at a wind turbine farm here in
Illinois. In his e-mail to us, John gives us some backround about a
concern about this wind farm:

Wind turbines turn slowly in a cold winter sunset. As wind farms
expand nationwide, wildlife biologists are concerned that bats - far
more than birds - are vulnerable to the spinning blades of wind turbines
like these near Ransom, Il. IDNR officials are worried about the Grand
Ridge wind farm at Ransom because of its proximity - about 20 miles - to
the Blackball Mine, a protected habitat of the endangered Indiana bat.

(John Smierciak/Chicago Tribune)

Thanks John!

Tom Skilling

Photo courtesy of John Smierciak, Chicago Tribune

Carolyn Szepanski shares this snowstorm photo with us taken by her friend Donna George
in Hueytown, Alabama. Alabama was among the states hit hard by the late season
snowstorm which roared up the East Coast over the weekend. Thanks to Carolyn and
Donna for the great shot!

Tom Skilling

Photo courtesy of Carolyn Szepanski and Donna George

Our friend Anson Mount shares this shot of the lake-effect snow clouds as viewed from
Waukegan Airport looking toward Lake Michigan this morning. Anson reports
experiencing stretches of vigorous snowfall interspersed with sunny spells on his drive
from Algonquin to Waukegon. THANKS Anson!

Tom Skilling

Photo courtesy of Anson Mount, Algonquin

My Tribune colleague and 40+ year National Weather Service veteran Richard Koeneman,
who lives in the mountains of western North Carolina outside Asheville, sends us these
beautiful shots of the Eastern U.S. weekend snowstorm's aftermath in his area. Richard
tells us: "It was quite a snowstorm. 12.4 inches came down from noon to 11 p.m.
Sunday, then another 0.7 inches in mountain snow showers into early Monday afternoon
for a storm total of 13.1 inches. It was the heaviest snow here since 18 inches in mid
January, 1998. "

THANKS for these beautiful photos, Richard—and for the update!!

Tom Skilling

Photos courtesy of Richard Koeneman, Western North Carolina mountains outside Asheville

Thanks to our WGN Weather Center colleauge Richard Koeneman who forwarded these pictures from his home just outside of Asheville, North Carolina (elevation of 3,650 feet). Richard tells us that this 12 inch plus snowfall is most likely the biggest snow there in a decade since the area was hit by an 18 inch snowfall in January, 1999.

Photos by Gary Melton

Steve Kahn WGN Weather Center

After experiencing highs averaging 18 degrees below normal the first two days of the
week, Chicagoans are in for springlike readings 15 degrees above normal Wednesday to
Saturday. A strong northwesterly jet stream will hold cold Canadian-source high pressure over
the Midwest one more day. Then the winds will shift, becoming more west to southwesterly,
allowing a warming southerly flow to return to the Mississippi Valley and the Midwest by
midweek. Showers and thunderstorms will be in the forecast from Thursday into next
weekend.
MAJOR EAST COAST WINTER STORM
Low pressure moving up the Eastern seaboard late Sunday and Monday will dump over a foot
of snow from the southern Appalachians through Washington, D.C., to north of Boston.
--By Paul Dailey, WGN Weather Center Meteorologist

Dear Tom,
I have friends in the Los Angeles area and they are always complaining about
water shortages out there. Are they exaggerating?
Lewis Stinson
Dear Lewis,
Believe them. California is suffering through a long-standing drought (now
in its third consecutive year) and water shortages there are approaching
crisis levels. Gov. Arnold Schwarzenegger declared a state of emergency on
Feb. 27, an action that urges cities, towns and water agencies to reduce
water usage by 20 percent. Mandatory water rationing is an option if
conservation measures are insufficient.
The damage in California is staggering: Agricultural losses could reach $2.8
billion this year and 95,000 jobs are in jeopardy.
California derives much of its water from snow in the Sierra Nevada
Mountains, but the snowpack is presently at only 78 percent of normal.

Atlanta snowstorm

Thanks to former Chicagoan Richard Finn now living in Atlanta for sending us this picture of Sunday's snowstorm there. It was thundering in Atlanta this morning when Richard awoke but instead of rain it was snowing.

Photo by Richard Finn