WGN Weather Center Blog

A slow-moving weather system moved into the Chicago area late Saturday afternoon, and its soggy effects won’t totally move out of the region until late tonight or early Tuesday.
Through Sunday evening, the city’s official weekend storm total at O’Hare Airport had reached 1.25”, while Midway Airport recorded an even 1.00”. Those totals helped bring April precipitation back to about normal, after a two-week dry spell that followed the wet and stormy Easter Sunday.
Mild conditions should continue into Thursday before a sharp cool-down takes aim at the city by the end of the week.
With chilly air from central Canada pouring into the region on gusty northwest winds, high temperatures should hold in the lower or middle 50s on both Friday and Saturday before milder air returns next Sunday.
--Steve Kahn, WGN Weather Center Meteorologist

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Basketball fans have become used to the Chicago Bulls last-minute comebacks, and for now it has carried over to weather as well. Heavy rainfall last night and today is expected to make up for an April deficit that as of Friday had grown to over an inch.
Occasional downpours may well push this storm’s metro area average rainfall totals well over an inch, and by midnight tonight boost the official O’Hare April total rainfall in excess of the normal 3.68". Unattached from the primary polar jet stream far to the north and steered by weak westerly winds aloft, a low pressure system will slowly drift through the western Great Lakes and Ohio Valley the next few days allowing May 2006 to start off on a cloudy cool and damp note.
The polar jet is expected to migrate south, absorb the weakening Great Lakes low pressure system, and reconnect with the upper air wind pattern over the U.S. by next weekend—leading to a touch of Canada cold Saturday.
-Paul Dailey WGNTV Meteorologist

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It’s the 9th weekend of meteorological spring, and it’s likely to become only the second of the season to log measurable rain on both Saturday and Sunday. The steady stream of eye-catching computer rainfall projections for Chicago continue, and suspicions that the area is on its way to 2006’s heaviest single rain tally still persist. Such forecasts have converged on weekend tallies near 2”, which would eclipse the 1.20” that fell here Feb. 15-16 and mark only the third official 1”-plus rain of 2006.
It won’t be difficult to dodge raindrops Saturday morning. Rainfall is likely to consist of scattered showers which look more impressive on radar than they really are. The first raindrops may evaporate in dry air near the ground as the day begins. But, the atmosphere is to moisten rapidly Saturday afternoon once a band of 80 m.p.h. winds organize less than a mile above the ground. Those winds, with Gulf origins, promise rapid delivery of moisture expected to fuel impressive downpours.
--Tom Skilling, WGN-TV Meteorologist

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The month’s 11th excursion above 70° Thursday—the most of any April since 1977—lasted just an hour before a back-door cold front swept the area. Such fronts derive the “back-door” label because their motion is opposite the norm—some would say “backwards.” Thursday’s front approached from the east rather than the west. By nightfall, the westbound front had cleared the Fox Valley and was continuing its westward trek.
The area’s precipitous return to chilly temperatures resulted from a vigorous post-frontal temperature plunge, which first commenced on Lake Michigan’s western shore around midday from Waukegan south to Chicago’s lakefront. By 2:05 p.m. Thursday, it had reached O’Hare. Readings there fell the remainder of the afternoon and evening, reaching 54° at 6 p.m. and 45° at 10 p.m. The 26-degree plunge over 10 hours rendered Thursday’s 71° high the city’s shortest spell of 70° warmth so far this month.
--Tom Skilling, WGN-TV Meteorologist

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Huge temperature swings are a part of any Chicago spring season. The warming strength of the sun was demonstrated Wednesday, only the fourth day since March 1 to produce 100% of the area’s possible sunshine. In just nine hours area thermometer observers watched one of the three latest occurring 27° morning lows on record in over 135 years of official weather records evaporate at the hands of a 37° temperature surge. Afternoon readings peaked 18° above Tuesday’s 46° high at a seasonable 64°. Even warmer readings are predicted Thursday. Converging winds ahead of a southbound Wisconsin cold front ought to induce a bit of compressional warming—a process which occurs as any gas is squeezed or compressed. Should Thursday’s 72° high verify, it would make the 11th reading at or above 70° this month—already the 7th warmest April since 1871.
-Tom Skilling

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Chicagoans shivered through one of the city’s most potent late April daytime temperature pullbacks in nearly 20 years Tuesday. The 46° high was 27° colder than Monday’s 73° peak reading and the coldest April 25 afternoon temperature here in 30 years (since the 45° high in 1976). Only twice since city weather observations moved to Midway Airport in 1942 then to O’Hare in 1980 has April 25 been any colder. The temperature plunge between Monday and Tuesday was the equivalent of the change in “normal” highs which would occur if the clock could be turned from mid or late May back to the middle of March.
Readings Tuesday were so chilly, rare late season ice pellets and flurries were observed. A trace or more of snow has been observed in the city a total of 7,560 days since 1885. Yet snow or ice pellets have fallen only 74 times in that 121 year period beyond April 25.
-Tom Skilling

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Chicago’s delightfully mild April, which currently ranks fourth warmest in 135 years of records dating back to 1871 is facing a brief but potent setback. A slug of cold air barreling down icy Lake Michigan will drop Tuesday’s temperatures more than 25º from Monday’s balmy 73º high and even bring a threat of frost to inland areas early Wednesday. The chill will be brief, departing as quickly as it came with the mercury rebounding nearly 20º back to the middle 60s Wednesday.
Chicago’s change won’t be quite as dramatic as the one that hit Valentine in central Nebraska where Sunday’s high topped out at 73º followed by an unseasonably chilly 40º high and 4” of snow Monday.
Severe weather broke out across the southern Plains Monday with more than 125 reports of severe weather, including a twister at El Reno, Oklahoma about 30 miles west of Oklahoma City.
-Steve Kahn WGNTV Meteorologist

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The week ahead will be very springlike, starting out with perhaps the warmest day of the week followed by what may turn out to be the coldest day tomorrow. If clouds from an approaching low pressure system hold off, highs today may warm well into the 70s. Then as low pressure passes to the south Tuesday, chilling north winds will make 50° temperatures “feel” like the 40s. Midweek weather should be very seasonable, but on Friday a low pressure center will “cut off” or become detached from the main jet stream flow in Canada, centering over the western Great Lakes where it will drift slowly east over the weekend, giving Chicago another “cool down” along with extensive cloudiness and frequent showers.
The Atlantic hurricane season approaches, but it’s now for Australia as the country’s north coast braces for monster Category 5 Tropical Cyclone Monica, carrying wind gusts well over 200 m.p.h. and 30-foot waves as it approaches the mainland today.
--Paul Dailey, WGN Weather Center Meteorologist

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Earlier in the month it was up,up up as the city experienced 38° of warming over a six day period from a chilly 43º high on April 8 to a summer-like 81º reading on April 14. But for now, it’s all downhill as Chicago temperatures have begun an extended slide from last Thursday’s high of 75º to an expected 54º maximum by Tuesday. In fact, some frost may occur in inland areas early Wednesday as early morning temperatures there are expected to drop into the lower and middle 30s.
The early season warmth that has engulfed not only Chicago this month but also the entire Midwest has been depressed south as a pool of cold air sinks into the region from Canada. Record warmth was widespread across Texas on Saturday as Beaumont, Galveston and Houston topped all previous April 22 readings with highs in the middle and upper 80s.
Warmth returns to the Chicago area by the end of the week.
-Steve Kahn WGNTV Meteorologist

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The opening three weeks of April 2005 and 2006 have been delightfully mild. Last year, the city racked up nine days of 70º or higher including three days in the 80s, similar to our current eight days with two in the 80s. However, the warmth ended abruptly in 2005 with highs for the rest of that month mainly limited to the 40s and 50s.
Cooler weather is headed for the area again this year with weekend readings in the 60s heading down to the 50s by the middle of next week as winds turn northwesterly. The chilly weather may even bring a threat of frost to outlying areas by Wednesday morning. Such a cool-down is not unexpected this time of year: The city’s average date of the last sub-50º high is May 1.
Precipitation has been a different story: In April 2005, scant rainfall contributed to the start of last year’s drought, while frequent rains and even some flooding this year have significantly improved the area’s moisture deficit.
--Steve Kahn, WGN Weather Center Meteorologist

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Chicago’s mild April, the fifth warmest to date, will continue in that vein through the weekend with daytime highs continuing to average 5 to 10° above normal. However, by early next week a cold upper low over central Canada will sink south into the Great Lakes region putting at least a temporary hold on the balmy weather. By Tuesday and Wednesday afternoon readings should hover in the lower and middle 50s as brisk northwest winds and sun-blotting clouds make the temperature downturn even more noticeable.
Cooler weather has already arrived in Texas. The Dallas-Fort Worth area which recorded its highest April temperature on record a few days ago with a torrid 101º, could only muster a cool 72º high Thursday.
Late snowfall reports from this week’s South Dakota Black Hills’ blizzard are amazing. Final snowfall totals topped 6 ft. (74") at Lead while Deadwood recorded more than 4 ft. (52").
-Steve Kahn WGNTV Meteorologist

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A raging late season blizzard dropped nearly four feet of snow on the Black Hills area of South Dakota Wednesday bringing traffic to a standstill as winds gusting to more than 70 m.p.h. piled the snow into huge drifts.
By late Wednesday, Deadwood, north of Rapid City had measured 46" of snow.
In contrast, mild, tranquil weather prevailed in the Chicago area Wednesday with temperatures in the 70s and more of the same is on tap for today. The quiet pattern is providing a welcome change from an active severe weather season in Illinois. So far this year 44 twisters have struck in central Illinois, many in the Springfield area, compared to only 2 at this time in 2005. Two years ago on this date the weather was anything but quiet, as more than a dozen twisters swept areas from LaSalle County to Chicago’s southern suburbs, including the F3 Utica tornado that tragically took eight lives.
-Steve Kahn WGNTV Meteorologist

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A sunny spring day prevailed across northeast Illinois yesterday while 60 mile per hour winds and heavy snow closed Interstate 94 in eastern Montana. At the same time several inches of heavy wet snow fell over western portions of the Dakotas as a strengthening low pressure system slowly drifted east. East winds traversed only a third the distance over the still cold (temperatures mostly in the 40s) Lake Michigan Tuesday than northeast winds did Monday (60 miles vs. 150 miles). Both days were sunny, but the shorter trek over the cold lake translated into significantly warmer temperatures across the metro area, especially inland. O’Hare for example recorded a 56° high Monday, then came in with a 10° warmer 66° high yesterday. Heat resulted in another day of record-breaking highs, but also contributed to another round of violent large hail-producing thunderstorms from Texas to Missouri and downstate Illinois.
-Paul Dailey WGNTV Meteorologist

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Sunday’s storm totals in excess of 4" in southern Cook County and extreme NW Lake County Indiana resulted in flooding in the Little Calumet River basin at Thornton, Munster, and South Holland. The river is expected to drop below flood level at those points today. The 5.13" rainfall measured at Lansing was the highest official report.
High pressure brought clearing skies and east winds here with most readings failing to warm out of the 50s Monday. However in Texas, Oklahoma, Louisiana and Arkansas it was an entirely different story with numerous record highs observed, perhaps the most noteworthy the 101° at Dallas which was the warmest April temperature ever officially recorded at that city. A slowly approaching low pressure system will move into the western Great Lakes and influence Chicago weather by midweek giving cloudiness and periodic showers into the coming weekend.
-Paul Dailey WGNTV Meteorologist

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Temperatures across Illinois ranged from the damp and chilly upper 40s near Waukegan to the very warm and sultry upper 80s around St. Louis Sunday afternoon, setting the stage for violent thunderstorms and heavy rainfall. The sharp temperature contrast, mixed by a strong low pressure system working east across the state, developed wave after wave of thunderstorms—many of them severe. At least 17 twisters were reported in Illinois along with numerous reports of hail and strong winds. Golf-ball hail pelted the Aurora area, while stones larger than baseballs slammed downstate Normal. Torrential downpours brought nearly 3 inches of rain in about an hour, flooding roads east of Joliet near Beecher and south of Kankakee near Chatsworth.
Substantial rainfall soaked the Chicago area with totals through late evening approaching 1.5 inches in southern sections, while northern areas lagged—but the rain was still coming down.
--Steve Kahn, WGN Weather Center Meteorologist

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A storm system moving east from the Plains threatens to make Easter Sunday here pretty much of a washout.
Showers and thunderstorms should occur intermittently today before tapering off tonight. A brisk east wind off of chilly Lake Michigan will restrict temperatures to the 50s from the city north, but southern sections should see readings rise into the 60s. With moist air feeding into storm, precipitation totals in the city are expected to top the one inch mark and if this occurs Easter 2006 will be Chicago’s wettest since 1.43” of rain fell on April 22, 1984.
Hot air surged north ahead of the storm system Saturday afternoon setting record high temperatures through the southern Plains and Southeast. Wichita Falls, Texas took the heat honors with a sizzling record high of 102º. The storm also spawned numerous twisters in Kansas and Nebraska adding to this season’s growing totals.

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After breaking the 80° barrier for the second consecutive day, and with dew points rising into the 60s, the passage of a weak cold front Friday triggered late-afternoon and evening severe storms south of Interstate 80 and east into Indiana. There were numerous large hail reports, including tennis ball size at Milford in Iroquois County, golf ball size at Otterbein in Benton County, Ind., and monster grapefruit-size (4-1/4 inch) hail at Rochester in Fulton County, Ind. A possible tornado was reported in Ambia in Benton County, Ind.
Highs the past five days averaged more than 20 degrees above average. For the sixth consecutive day, highs were warmer than the previous day; that’s something that hasn’t happened here in nearly three years (June 2-8, 2003).
Friday’s warmth wasn’t limited to Illinois; including the 88° record high at Springfield, cities in 12 other states as far away as Texas, New York and the Carolinas also posted record highs for April 14.
--Paul Dailey, WGN Weather Center Meteorologist

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Chicago officially recorded its first 80º reading of the year Thursday, 11 days ahead of the typical April 24 first occurrence. It was the city’s fourth consecutive day where a new high temperature benchmark for the year was established, steadily upping the ante from Monday’s 71º.
In Chicago and near the lake afternoon warmth was fleeting as a windshift off of the chilly lake waters sent early evening temps crashing into the 60s.
Just to our west readings surged even higher Thursday as new records for the day were set at Rockford 83º, Moline 86º along with Cedar Rapids 86º and Burlington 87º both in Iowa.
The unseasonable warmth helped fuel violent thunderstorms that produced at least 15 tornado reports along with hail as large as grapefruit in eastern Iowa and northwest Illinois through late evening. Heavy damage was reported in Iowa City including some on the University of Iowa campus. -Steve Kahn WGNTV Meteorologist

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With a strong southwest wind and abundant morning sunshine, northeast Illinois is poised for a quick warm-up into the 70s today. Depending upon how fast clouds develop and move over the area this afternoon, high temperatures in the lower 80s are a distinct possibility, especially in southern locations. Chicago’s long-standing 82° record high for this date (set 65 years ago) could be in jeopardy. This will be the 4th straight day with a high in the 70s which has occurred only nine other times so early in the season, and if forecasts prove correct this string could extend to 6 days by Saturday. Six consecutive 70° days this early in the year has occurred only once previously in 1921. Winds shift east Friday and temperatures will drop off, most noticeably in areas close to the lake. Meanwhile low pressure off the west coast will continue to pound northern and central California with downpours and heavy snow at higher elevations.
-Paul Dailey WGN Meteorologist

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Water levels on Lake Michigan have fallen 5” from April a year ago. Although seasonal warming cuts into evaporation from the lake and causes its water to expand, producing a temporary seasonal increase in lake levels, the U. S. Army Corps of Engineers cautions mariners that lake levels are likely to wind up below last year’s during the upcoming boating season. Levels have fallen on the other Great Lakes as well, down 4 to 9” since last April. Waves of downpour-generating thunderstorms have largely bypassed the Great Lakes Basin from which precipitation drains into the Great Lakes.
Daytime 70s may dominate the rest of the week. Several computer model forecasts produce easterly winds off the lake Friday, a development which could impair warming if true. But, the forecast trend is indicated by only a handful of models at this time. It’s a period which will have to monitored.
-Tom Skilling

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For only the second time this year Chicago’s high temperature surged above 70°. Monday’s official 71° peak afternoon reading was 2006’s highest here, enough to beat the 69° highs in usually warmer Atlanta and Las Vegas. Not since Oct. 18 last fall have Chicagoans been treated to a temperature as warm. But, it’s a thermal benchmark likely to have a very short shelf life. Tuesday’s 74° predicted high is to top Monday’s high. An influx of high cloudiness filters the day’s sun and will determine the extent of warming. It would take only a slight reduction in the extent of this high cloudiness to allow the city’s official high to creep to 77°.
Longer days drive seasonal warming. Days have lengthened 4 hours in Chicago since winter’s op