EXPLAINER: 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.

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.

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

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.

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

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.

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.

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.

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

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

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.

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

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.

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.

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.

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.

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

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.

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

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.

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.

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

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

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

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.

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

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

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

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

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

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