EXPLAINER: April 2009 Archives

Chicagoans haven't endured a cloudier April in 14 years. Just 43 percent of the city's
possible sunshine was observed---short of the 53 percent considered typical. Nearly
half a foot of rain fell during the month, a good deal more than the 3.68 inch average.
Final April city precipitation tallies included 5.80 inches at Midway and 5.19 at O'Hare.
Precipitation fell measurably (0.01-inch or more water equivalent) on 14 of the month’s
30 days---the most of any April in 7 years. As frequent as that may seem, the tally is
actually quite close to the 138 year average of 12 measurably rainy days.

Year to date rainfall values continue to outpace the normal value of 9.71 inches in the
city. Midway Airport's 17.37-inch total remains the wettest in 81 years of observations
there. Other 2009 area totals include 14.94 at O'Hare, 16.80 Oak Brook, 14.67
Arlington Heights and 13.88 at St. Charles.

With the April’s close, two thirds of the three-month March through May meteorological
spring period is now behind us, and the city’s third-fastest warming month is
underway. Over the next 31 days, the city picks up an additional 57 minutes of daylight
propelling normal daytime highs from 64-degrees on the first to 75-degrees May 31.

Weekend wildcard here: Potential for Saturday night/Sunday rain

Saturday looks dry---but whether downstate rains reach a portion of the Chicago area
Saturday night into Sunday, is being monitored. While most computer forecast models
keep rains south, the predicted jet stream configuration is one which makes the Navy
NOGAPS model’s rainy prediction here over at least southern sections of the Chicago
area plausible. Stay tuned!

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

Wednesday offers a second day free of the downpours that have pushed rain tallies for
the spring season and for 2009 to date to the highest levels in 80 years--11.97 inches
and 16.78 inches respectively--based on observations at Midway Airport. Each total is
nearly twice the long-term average.

But the break in the rains isn’t likely to last long. Long-range computer projections
suggest four precipitation-generating systems could visit the Chicago area during the
next two weeks. A suite of two-week computer models puts total rainfall for that period
at 2 to 4 inches--well above the 1.68 inches that typically falls over 14 days this time of year.

The first of the four systems involves the same powerful front that shifted Chicago
winds northeast and slashed temperatures by more than 30 degrees along Lake
Michigan and 20 degrees inland between Monday and Tuesday. The front is predicted to
head north Wednesday night as the same moisture-laden air mass that set off 1-2-inch
rains late Monday over much of the metro area ignites new thunderstorms.

The development of a wave along that front may enhance rainfall Thursday--an
unwelcome development with rivers high and standing water already in parts of the
area.

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

Chicago's first four-day string in 2009 with temperatures 70 degrees or higher arrived right on schedule--but came to an unceremonious end amid driving rains late Monday. Weather records show the average date of Chicago's first four consecutive days with readings of 70 or higher has come around April 29 in more than eight decades of weather records at Midway Airport. The warm-up has increased Lake Michigan surface water temperatures more 5 degrees in the past week.

By late Monday, downpours had pushed Midway's spring rain tally (since March 1) to 11.37 inches, making it the wettest meteorological spring on record to date in 81 years of weather observations at the South Side site. The total is nearly a half a foot (5.53 inches) higher than the long term average for the period (5.84 inches). With many rivers near bankful, Monday's cloudburst was the last thing the area needed. Preliminary Monday rainfall totals included 1.38 inches at Tinley Park and 1.29 at Frankfort—and the rain was still falling.

Temperatures have crashed overnight. Another pneumonia front has swept across the area and Chicagoans awaken to full fetch northeast winds in its wake.

Illinois, Indiana farmers rained out of their fields

It's planting season on Midwest farms. And while the process has proceeded expeditiously in Iowa, Nebraska and Minnesota, the U.S. Department of Agriculture says Illinois farmers have only been able to plant 4 percent of the state's corn. That compares to a five-year average of 43 percent. Only 2 percent of Indiana's corn is in the ground versus an average of 25 percent.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

It was a weekend of temperature chaos in the Chicago area. After Friday’s burst of
warmth sent readings well into the 80s across the region, the mercury plunged Saturday
afternoon as a “pneumonia front” dropped temperatures into the upper 30s and lower 40s across the city and north suburbs. This bizarre scenario resulted in wind chills along the North Shore and heat indexes in south suburban areas.
Cold front moving in
Warm weather returned to most of the region Sunday afternoon as gusty south winds
boosted readings back into the 70s and lower 80s, but it also set the stage for another round
of showers and thunderstorms expected to arrive Monday ahead of a cold front approaching
from the Plains. This front generated a rash of hail and high winds from the
southern Plains to the mid-Mississippi Valley Sunday afternoon, but at least 10 tornadoes
were reported, one as close as Dickeyville in southwest Wisconsin.
Several clusters of showers and thunderstorms are slated to move through the Chicago
area Monday. With the atmosphere brimming with moisture and frontal systems
enhancing the area’s sharp temperature differentials, heavy rainfall, hail and gusty winds will be possible.
--By Steve Kahn, WGN Weather Center Meteorologist

After reveling in the first truly warm days of the year Friday and Saturday, a strong cold
front sent temperatures crashing across the area Saturday afternoon. At Highland Park
the mercury plunged 28 degrees from 70 to 42 in just 14 minutes shortly after 1 p.m.
and by 5 p.m. the temperature there hovered at 37 degrees while the Kankakee area still
basked in the lower 80s. The large temperature disparity generated waves of showers
and thunderstorms across the region that produced heavy downpours and hail.

Sunday morning will open rainy, damp and chilly, with brisk southeast winds holding
temperatures in the lower and middle 40s. But the early season warmth is expected to
surge back into the area Sunday afternoon with the mercury rapidly rebounding to the
lower 80s, as gusty southerly winds initiate the temperature comeback. Scattered
showers and thunderstorms will develop in the increasingly humid air mass, but a more
general thunderstorm outbreak is slated for Monday as an approaching cold front
threatens to trigger thunderstorm clusters capable of producing repeat heavy rain
episodes.

THE WEEK AHEAD

Skies skies are expected to partially clear by Tuesday, and the remainder of the week
should feature seasonable temperatures and generally dry conditions except for some
rain late Thursday into Friday.

Temperatures surged to July levels Friday, topping out at 84 degrees at
O'Hare International Airport and 85 at Midway-but soaring as high as 88
degrees in northwest suburban Libertyville, 87 at Wheaton and 86 at
Gary.
More than six months has passed since an 80-degree temperature graced
the area. Only one year in five produces warmth at Friday's levels so
early in the season. Last year, it took another five weeks-June 2-for an
84-degree temperature reading here.
A dramatic but temporary break in Saturday's unseasonable warmth
threatens to ignite the Chicago area's first organized outbreak of
severe weather. The same powerful temperature-slashing cold front that
lopped more than 50 degrees off readings in Plains on Friday is to sweep
across Chicago with potentially thundery weather between 3 and 5 p.m.
Saturday. The windshift it produces is likely to send temperatures into
a dive off the day's low 80-degree highs-a decline which may reach 40
degrees by evening.
Thunderstorms bombard Midwest with ground-burying hail
A barrage of hail battered areas from southeast Nebraska to Upper Michigan
late Friday. Two-inch diameter hail fell in several communities near La Crosse, Wis.,
while hail two inches deep covered the ground near Rockland in western
Upper Michigan.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Temperatures on Friday jump to summer levels. It's a change guaranteed to capture Chicagoans' attention in a month that has averaged 2.5-degrees below normal to date. Wind trajectory forecasts, which allow the tracking of air movement, indicate Friday's warming originated 24 hours ago in Mississippi and Louisiana, where Thursday highs hit the mid-to-upper 80s. Powerful southwest winds--expected to reach 60 m.p.h. several thousand feet above the ground this afternoon--will transport that warmth into Chicago so swiftly that the usual level of cooling that occurs in northward moving air is likely to be overcome. This suggests Chicago’s official high Friday may well reach 85 degrees--a level 24 degrees above normal and more typical of July than April. It took another five weeks for similarly warm temperatures to occur a year ago.

Not only are temperatures to warm here, humidities surge in coming days as well contributing to a dramatically different, more spring-like feel to the air--but also possibly fueling thunderstorms as a cold front sags south toward the area late Saturday. That front could shift Saturday’s strong and unseasonably warm south/southwest winds to the east Saturday night into Sunday morning producing cooling before warm air resurges Sunday afternoon.

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

Chilly air loosens its grip on the Chicago area Wednesday--the first stage of a dramatic multiday warm-up expected to carry area temperatures to the highest levels since early September. Tuesday's blustery 43 degree peak reading matches the normal high here on March 8. And while a chilly rain fell much of the day across Chicago, record snows walloped the upper Midwest--focusing on Michigan’s Upper Peninsula, where up to 21.2 inches of snow fell at Rockland near Houghton. Other Upper Peninsula totals included 19.1 inches at Sidnaw, 18 inches at Alberta and 10 inches at Twin Lakes.

By contrast, record-breaking heat headlined western and southern U.S. weather. The eastward expanding dome of unseasonably warm air, expected to bring Chicago the warmest weekend since early October, produced sizzling early-season highs of 107 degrees at Thermal, 101 at Riverside and 95 at Los Angeles--all in California--while Corpus Christi, Texas, topped out at 95.

Warm air holds more moisture than cool air and computer projections suggest the water content of the air over Chicago is to more than triple over the next five to six days. The atmosphere here is to hold an estimated 0.40 inches of evaporated water Wednesday--but by late Sunday, that amount is to surge to 1.40. Dew points, meteorologists’ preferred measure of atmospheric water content, are to surge to 60 degrees this weekend for the first time since Oct. 6. Increased dew points lend a warmer "feel" to the air.

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

The late-season snowflakes, which threaten to flutter earthward in
above-freezing ground-level temperatures Tuesday, aren't as unusual in
Chicago as many here may think. The final flurries of the season came on
April 28 last year, and a review of Chicago's official snow records
dating back to 1885 reveals 66 of the past 124 seasons-53 percent of
them-have produced at least a trace of snow beyond April 21. Lengthening
days and strengthening spring sunlight have all but eliminated prospects
for anything resembling a significant snowfall here (6 inches or more).
But, the pool of unseasonably chilly air has settled south into the area
overnight and computer models have dropped subfreezing temperatures to
within 1,000 to 1,200 feet of the ground Tuesday. Snowflakes have been
known to fall through as much as 1,000 feet of above-freezing air
without completely melting-reasoning which backstops Tuesday morning's
prediction of snowflakes. With the ground warm, the threat of
accumulation is nil.

A huge late-week temperature surge, predicted to ride powerful south
winds into the area by Friday and Saturday, is to propel Friday's high
to 86 degrees-just a degree away from the record.

Gusty south to southwest winds-at times up to 40+ m.p.h. Friday-are
predicted to push late-week warmth right up to the lake, completely
overpowering lake winds that would otherwise cool the area-and setting
the state stage for the year's warmest weather to date.

Midway having its 2nd wettest year in 81 years

Wet weather has kept farmers from their fields to date this spring.
The 9.81 inches of precipitation on the books at Midway Airport since
March 1 is the site's second heaviest in 81 years of weather records.

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

As low pressure makes its way northeast into lower Michigan on Monday,
clouds and rain stay over northeastern Illinois. The farther north the
low pressure area moves, the more cold Canadian air is drawn into the
system. Heavy snow is forecast for upper Michigan on Monday and Tuesday.
As the colder air is pulled south, there is an increased chance of rain
and wet snow in northeastern Illinois. Precipitation finally ends over
Chicago later Tuesday.

Heat west, severe storms south
Record or near-record heat occurred Sunday in California. The heat
should continue and even intensify Monday. Severe storm watches and
warnings were issued in Mississippi, Alabama, Georgia and Tennessee.

80s expected in Chicago
The midweek temperature turnaround peaks Friday as southerly flow and
sunny skies allow Chicagoland readings to climb into the 80s. The warmth
may continue through next weekend, but a cold front could sink south
through Chicago and create huge temperature disparities: Readings could
range from the 50s north of the front to the low 80s south of it.
--By Paul Dailey, WGN Weather Center Meteorologist

As a deep low pressure system moves out of the southern plains into the Ohio
Valley, a broad area of rain on the north side of the storm will spread into
the southern Great Lakes. Counter-clockwise flow around the low will steer
easterly winds off 40-degree Lake Michigan waters into northeastern Illinois
and southeastern Wisconsin. South of the storm center, and east of the
associated cold front, the area of severe storms will shift east, impacting
Tennessee, Mississippi, Alabama and Georgia today.

WEST COAST WARM-UP

As a high pressure ridge moves over the West Coast, an off-shore flow is
developing over southern California which will bring upper 90s and
100-degree readings to the valleys over the next few days. Los Angeles is
forecasting highs in the low to mid 90s through Tuesday.

WEATHER TRANSITIONS MIDWEEK IN CHICAGO

Later Wednesday, a southerly flow should return to Illinois. By Thursday,
the strengthening flow will pull significantly warmer air into
northeastern Illinois with readings reaching the lower to middle 70s.
Computer models indicate this flow will continue into next weekend with
Chicago in store for it's first 80s of 2009 on Friday and Saturday.

Chicago temperatures head back into the 70s Saturday afternoon for only
the third time this year -- and over a wider area than on Friday. The cool
easterly lake breezes predicted to develop in the afternoon are likely
to be the weakest in days, limiting the inland penetration of
lake-cooled air to within a mile or two of the shoreline. While readings
surge back to the mid-70s observed Friday at west suburban Oswego (76
degrees), Elgin (75), Geneva (75) and Darien (74), immediate lakeshore
area highs will hold to the low and mid-60s from Grant Park north to
Waukegan and Kenosha.

Highs on Friday reached 70 degrees at O'Hare and Midway Airports while
low 50s occurred from Hyde Park to the North Shore. The 74-degree high
predicted at O'Hare on Saturday would equal 2009's highest reading
recorded a month ago on St. Patrick's Day -- but changes loom. A cold
front passes Saturday night as an approaching storm draws cooler air
into its circulation. That storm is to lift from Texas into central
Illinois between midday Saturday and Sunday. Initially, light
post-frontal winds Sunday morning are to strengthen as air rushes into
the intensifying system. This should send Chicago-area temperatures
plummeting into the 40s as showers build into steadier rainfall by
Sunday afternoon.

Thundery, wind-driven Colorado snows reach 30-plus inches; Texas hit with
deluge!
Thunder-embedded snow whipped by 63 m.p.h. wind gusts at Denver
International Airport fell with such intensity across Colorado's
foothills and mountains Friday that 4.5 inches came down in a single
hour near Aspen -- as heavy as any ever observed here in Chicago. By late
evening, 34.5 inches had been measured at Pinecliffe, Colo., and to the
north, Cheyenne, Wyo., had 21 inches down.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

For those Chicagoans desperately in search of some meteorological
affirmation that spring would eventually produce a mild day, Thursday
was the gift that just kept on giving. Not only was it sunny (for the
first time in a month, there wasn't a single cloud in the sky) but
temperatures surged above 60 degrees at O'Hare and Midway Airports for
the first time in April. A number of western suburbs even recorded low
70s, among them Wheaton with 73 degrees, Oswego with 72 and Plainfield
with 71. So slow is the eastward progression of weather systems across
the U.S. that Friday and Saturday's predicted sunshine here-in marked
contrast to the late season snowstorm lambasting the Rockies, including
the Denver area-is to continue heating the air mass in place. That lays
the groundwork for the back-to-back 70-degree highs predicted both days
in all but lakeside areas. The light easterly lake breezes that
occur-weaker and less able to deliver their chill as far inland as in
recent days-should yield shoreline temperatures that lag those farther
inland. Not since St. Patrick's Day has the city been treated to a 70
degree or higher official temperature. That's unusual. Weather history
indicates 80 percent of years here since 1928 have seen more than the
single 70-degree high on the books so far this season.

The 74-degree high predicted Saturday would be the area's
first weekend 70-degree reading in six months.

A blustery temperature downturn hits with a cold frontal passage late
Saturday night, and rain follows Sunday and Monday. But signs of even
stronger warming grow and a suite of computer models suggest an
atmospheric setup capable of delivering 80-degree warmth late next week.

It's not easy this time of year keeping temperatures as chilly as Tuesday's March-level
44-degree high--a reading 14 degrees below normal. The factors critical to making that
happen were all in place--a solid overcast, sporadic light rain and a northeast wind off
Lake Michigan. The reading marked Chicago's chilliest April 14 high in nearly three
decades--since the 35-degree peak reading on the date in 1980. The appearance of
sunshine late Tuesday in Rockford and Janesville and Madison, Wis., warmed readings in
those cities to 54, 57 and 59 respectively--levels significantly higher than the stinging
37- and 38-degree highs at Wilmette and Glencoe. The increasing amount of energy
delivered by sunlight will in the months to come ultimately defeat any move on the area
by the reservoir of cold air over what's left of Canada's steadily melting snowpack.
Chicagoans have watched the hours of daylight here lengthen from 9.1 hours in December
to Wednesday's 13.4 hours--an increase of more than 4 hours. At the same time, the
sun's daily track across the sky places it more than 30 degrees higher at midday than four
months ago as winter was getting underway. This sends sunlight three times as energetic
as in December cascading down on Chicago--a development which boosts temperatures.

Strong storms sweep drought-stricken Florida

Potent thunderstorms, at times more than 10 miles tall, brought much needed 1-inch+
rains to the Sunshine State on Tuesday, but the storms also generated a tornado
touchdown near Holiday, Fla. The twister—of EF1 intensity (95+ m.p.h.)— damaged at
least 50 homes.

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

Chicagoans brace for early March level temperatures Tuesday, with readings more than
15 degrees below normal, as the area moves into an 11th consecutive day of subnormal
temperatures. This month's 41.0-degree average temperature is 3.6-degrees below the
long-term 138-year average--cool enough to rank among the chilliest 20 percent of
April 1-14 periods on the books. It's the first April here in 25 years that has failed to
host a single 60-degree daytime high.

The Chicago area remains mired in the same damp, raw northeasterly flow responsible
Monday for the chilliest Cubs home opener since 2004. The storm system behind the
gray skies, expected to linger into Wednesday morning, has become ensnared in what
meteorologists refer to as an atmospheric blocking pattern. These patterns involve jet
stream configurations that impede the forward movement of weather systems under
their control. In this case, a pool of warm air aloft over southern Canada has
encouraged jet stream winds to split into two distinct channels. As these streams
re-converge over the Northeast U.S., the confluent winds produce a pressure build-up
aloft that forces air to sink to the surface on a massive scale. A high pressure system
results which slows weather system movement to the west.

City's wettest meteorological spring in 26 years

The 8.61 inches precipitation tally since March 1 at Midway Airport is not only twice
the long-term 81-year average, it makes this the wettest spring to date since 1983
and second wettest of the past eight+ decades at the South Side site.

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

Brisk east winds held spring warmth in Chicago at bay once again Sunday,
keeping most area temperatures in the 40s near the lake and 50s inland. It
has been nearly three weeks since the city's last 60-degree day on March 24
and almost a month since this spring's singleton 70 was recorded on St.
Patrick's Day when the mercury soared to a balmy 74 degrees.
Monday will be anything but springlike here with temperatures hovering in
the lower and mid 40s as the area is soaked by a wind-driven rain. Sunshine
should return my midweek, but the persistent lake winds will continue to
chill the area with the city continuing to struggle to reach the elusive
60-degree mark. More rain is expected by next weekend, but southerly winds
ahead of the approaching storm system could finally boost the mercury well
into the 60s Friday.

Easter sunshine fades in the afternoon
Despite Sunday's coolness, the area was bathed in total sunshine much of the
day. It was looking like the city would record its first Easter with 100
percent of possible sunshine since 1977, but advancing clouds ahead of
Monday's rainstorm arrived by mid-afternoon, capping the day's sunshine at
just 76 percent.
--By Steve Kahn, WGN Weather Center Meteorologist

Chicago's spring has been a cool one to date, but the upcoming week shows some signs of milder weather--especially for areas away from the lake. The city has not recorded a temperature of 60 degrees since it reached a balmy 69 degrees on March 24, and so far, this year has logged only one day in the 70s: a delightful 74-degree high on St. Patrick's Day. With plenty of sunshine expected on Easter, the city’s official thermometer at O’Hare International Airport could possibly reach the 60-degree mark, though areas near the lake will struggle to get out of the 40s as chilly east winds blow. Monday promises a different story as a storm system spins into the Midwest, dropping readings back into the 40s and setting up a steady rain that could delay or postpone the Cubs home opener. This could be the second year in a row that rain will impact Opening Day. The start of last year's Cubs home opener was delayed by a chilly rain, but once skies cleared, readings rose to around 60 degrees as a warm front passed. Milder conditions with more inland 60s are slated to return Wednesday and linger through Friday, but lake winds will continue to chill shore areas.

The 2009 U.S. tornado season -- noteworthy, until recent days, for a
twister count nearly 40 percent lower than a year ago -- erupted with
deadly consequences Friday. Powerful thunderstorms, which first exploded
late Thursday in the Plains, churned east Friday, spawning dozens of
tornadoes across six states from Tennessee and Alabama into the
Carolinas. One twister killed a woman and her 9-week-old infant in
central Tennessee while violent thunderstorms ripped roofs off buildings
and destroyed dozens of homes in Murfreesboro, 30 miles southeast of
Nashville. The 35 reports of twisters late Friday made it the most
active day of the 2009 severe weather season. It marked the sixth time
this year that 20 or more tornadoes dipped from U.S. skies in a single
calendar day. Ten such days had occurred by this time last year,
including three days with more than 50 touchdowns. Most active among
them was Feb. 5 when 131 twisters swept the U.S. The outbreak was
especially ill-timed because it coincided with Super Tuesday primaries
in 24 states.
Chill confirms 'lake wind' season
Chicago is in the midst of its "lake breeze season," widely recognized
to run from March into the first weeks of June. An easterly wind blows
of Lake Michigan's chilly waters 42 percent of the time in April --
second only to May, which sees an east wind 45 percent of the time.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Strong northeast winds rushing into the latest spring storm to churn across southern
Midwest will take a big bite out of the mild 50 and low 60-degree temperatures
observed across the Chicago area Thursday. The 58-degree high at O'Hare International
Airport was April, 2009's warmest yet-but areas spared a cooling easterly afternoon
lake breeze posted even warmer readings. Highs included 64 degrees at Libertyville, 63
at Oswego and 62 at Buffalo Grove, Itasca and Geneva.

Downstate Illinois and Indiana are in for a soaking Friday. Rainfalls exceeding 1 inch
are predicted from St. Louis east to Bloomington, Ind., and Louisville, and severe
thunderstorms could erupt north to the Ohio River. Monster thunderstorms exploded to
life Thursday afternoon, towering 46,000 feet into the atmosphere.

La Nina fading, but summer impact here is not clear

The chilly La Nina which may well have played a role in winter's active Midwest weather
pattern is fading. Climate forecasters suggest the coming summer (June through
August) is to be one of 32 since 1950 between a La Nina and El Nino in the equatorial
Pacific. It's a development offers few clues on summer temperatures.

Temperatures on Wednesday, benefiting from an abundance of sun and a
gusty west wind, made a run at 60 degrees at Libertyville, the Chicago
area's "warm-spot," where the high reached 58 degrees. But at the city's
official observation site, O'Hare International Airport, the 55-degree
high, though the mildest to date this month, was 5 degrees short. Nine
60-degree days are on the books in Chicago in 2009, yet not one has
occurred this month-and that's unusual. Since observations began in 1928
at Midway Airport, 67 of the past 81 years-83 percent of them-have
produced at least one 60-degree or higher April temperature by now.
It's not out of the realm of possibility that an easterly lake breeze,
expected to develop Thursday afternoon, might converge with the lighter
winds expected to dominate inland areas a good part of the day.
Converging winds, even with the comparatively low velocities predicted
Thursday, may be just enough to boost temperatures a few degrees through
"compressional warming" and send a few sections of the Chicago area into
the low 60s.
But jackets and sweaters are the order for the day along Lake Michigan
where an initial temperature romp into the 50s could be followed by a
pullback to the 40s as lake breezes get going.

It isn't easy keeping daytime temperatures as cool as they have been in
recent days. Monday's 40-degree peak reading was a whopping 24 degrees
colder than the 64-degree high on the same date a year ago and 14
degrees below the April 6 norm. It's just the latest afternoon
temperature this month to underwhelm area residents. The warmest
temperature that the opening week of April has managed has been 53
degrees. Only eight April 1-7 periods since 1928 at Midway Airport have
produced such limited daytime warmth. The chill is especially impressive
because the sunshine that bathes Chicago this time of year is three
times stronger than the sunlight of December.
Snow that fell heaviest across Chicago's west and south suburbs melted
quickly Monday as sunshine emerged from behind the clouds. But
lake-effect clouds were reassembling late Monday and were expected to
produce snow showers predicted to swipe Illinois' Lake Michigan
shoreline but directly hit sections of the Indiana and Michigan
snowbelt. A slow eastward shift of these clouds is predicted to take
the snow out of northwest Indiana as Tuesday proceeds.

Persistent chill could break -- at least temporarily -- next week
Three wet-weather systems may impact Chicago into early next week, with
the next one due to arrive with gusty winds Friday. But a number of cold
weather indexes may be the first signs of warmer temperatures in the
longer range.

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

After a day that brought a variety of weather across the Chicago area,
including hail-producing thunderstorms and rain and sleet, the
precipitation potpourri shifted to a heavy, wet snow across the region
by Sunday evening. With temperatures hovering in the low 30s, colder
west and north suburban areas quickly acquired a snow cover, though some
melting was still occurring in the city and south suburban areas, where
temperatures were a bit higher.
With the snow expected to persist much of Sunday night, several inches
of accumulation were expected. However, totals could vary dramatically
because of melting and the potential for heavier bursts of thundersnow,
which appeared to be targeting the south suburbs and northwest Indiana.
This system brought heavy snow to portions of Iowa, where the town of
Conrad, southwest of Waterloo, received 10 inches of snow after
thunderstorms swept the area.
The snow should diminish to flurries Monday except for some heavier
lake-effect snow that is expected to gradually shift east into northern
Indiana. February-level highs in the middle and upper 30s will be the
rule, and strong, gusty winds will keep windchills in the low 20s much
of the day.
--By Steve Kahn, WGN Weather Center Meteorologist

A major early April storm gathers strength Saturday as it moves out of
Colorado into Kansas and heads for northern Missouri. Blizzard
conditions are forecast to develop over northeast Colorado and Nebraska
on Saturday and move into southeastern South Dakota, northwest Iowa and
southern Minnesota, with a foot or more of snow expected in those areas
Sunday. A winter storm watch is in effect for southwestern Wisconsin
Saturday night and Sunday. An extensive band of rain will spread east
and north of the low's center.

Chicago in for rain, then snow
The eastern edge of the rain shield should reach Chicago late Saturday
with rain continuing Sunday as the low moves through Illinois. An inch
or more of rain is possible, which could force swollen Illinois Rivers
out of their banks. Once the storm center reaches eastern Indiana,
strong northerly winds will pull colder air into northeast Illinois, and
rain will change to heavy wet snow Sunday night. The Chicago area could
experience significant accumulations as the snow is expected to continue
through Monday. Heavier lake-enhanced snow could move from the city's
West Side to the south as winds shift from the northeast to the north
and northwest.
--By Paul Dailey, WGN Weather Center Meteorologist

The year is off to quite a start. Even before the overnight rains, Chicago's precipitation
tally was closing in on 9.75 inches--an amount well ahead of the most recent 30-year
average of 6.25 inches. It is the sixth-wettest open tot a year in 138 years. It's little
wonder Lake Michigan's water level is running 13 inches ahead of the same time a year
ago.

With the growing season fast approaching, farmers will be closely monitoring
precipitation trends. Since March 1, Chicago's precipitation has fallen at nearly twice the
typical rate, totaling 5.2 inches. The period averages 2.87 inches.
South suburban areas basked in mild spring weather Thursday before winds shifted
northerly and a chill that gripped much of the area sent temperatures crashing.
By comparison, northeast winds limited readings up and down the Illinois and
Wisconsin shorelines to the 30s and 40s.

Severe weather breaks out as another storm looms

Thunderstorms towering more than 40,000 feet unleashed golf-ball-size hailstones
Downstate. At least 10 twisters dipped skies across Mississippi, Alabama, Louisiana
and Tennessee.

Warm spring weather continues to be a no-show as April's opening week
promises to bring a continuation of the cold and wet conditions that
dominated March's final days. Chicago has not recorded a 60-degree high
since March 24, when the mercury peaked at 69, and prospects of another
60 remain dim for the foreseeable future.

Rain is expected to return by late Thursday as another storm system
approaches from the Plains.

More than an inch of rain could fall here by Friday morning, and wet
snow could mix in-especially west and north of the city-as strong north
winds gusting to more than 40 m.p.h. send temperatures crashing.

Sunday night storm a wintry threat

A second storm scheduled to hit late Sunday has a reservoir of cold air
on its northern flank and places Chicago perilously close to the
rain-snow line. Forecast trends have precipitation beginning as rain but
changing to wet snow by Sunday night as colder air enters into the
storm. Monday's Sox home opener should be a frigid affair, with snow
showers possible.

--By Steve Kahn, WGN Weather Center Meteorologist