WGN Weather Center Blog

Powerful thunderstorms erupted in downstate Indiana and Illinois Wednesday unleashing half a dozen twisters—five of which touched down in the area surrounding Monticello, Indiana. It's fortunate most of these touchdowns occurred in fields, reports WGN-TV weather observer Mary Anne Best of Remington, Indiana, because they did little damage. Our thanks to Mary Anne for forwarding these pictures to us of one twister—the photos provided to Mary Ann by Mike Prangley, Chief Meteorologist at WLVI in West Lafayette, IN. Mary Anne notes that Monticello was one of the communities severely damaged in the infamous "Super Outbreak" of 1974--the country's biggest single outbreak of tornadoes.
- Tom Skilling

Posted by wgnweather at 11:21 PM | Permalink

The same front responsible for Chicago’s temperature downturn Wednesday produced powerful thunderstorms downstate, including a half dozen tornadoes and thundery downpours which flooded fields. Initial reports indicate four twisters touched down around 2:40 p.m. Wednesday afternoon near Monticello, Indiana, 100 miles southeast of Chicago. Two other tornadoes occurred in central Illinois—one in Champaign County and the other south in Douglas County. Spotters monitoring the storms indicated no damage, saying the twisters’ paths remained away from most structures, traveling the area’s open fields.
Dust thrown into the air by the tornadic winds lent the storms a dramatic appearance. Torrential rainfall, including 5.50” in less than 2 hours near Pesotum, Illinois—15 miles south of Champaign—produced pools of standing water 2 feet deep.
-Tom Skilling

Posted by wgnweather at 11:12 PM | Permalink

Posted by wgnweather at 11:12 PM | Permalink

Posted by wgnweather at 11:11 PM | Permalink

Posted by wgnweather at 11:09 PM | Permalink

Powerful thunderstorms erupted in downstate Indiana and Illinois Wednesday unleashing half a dozen twisters—five of which touched down in the area surrounding Monticello, Indiana. It's fortunate most of the touchdowns occurred in fields, reports WGN-TV weather observer Mary Anne Best of Remington, Indiana who forwarded these pictures of one twister taken by a friend. Mary Anne notes that Monticello was one of the communities severely damaged in the infamous "Super Outbreak" of 1974—the country's biggest single outbreak of tornadoes.
-Tom Skilling

Posted by wgnweather at 7:40 PM | Permalink

The powerful thunderstorms which swept sections of the Chicago area
Tuesday are captured blowing into the heart of the city in these images
relayed to us by Nick Liveris.
-Tom Skilling

Posted by wgnweather at 4:35 PM | Permalink

A barrage of cloud-to-ground lightning strokes accompanied clusters of downpour-generating thunderstorms Tuesday. At the storms’ peak in the late afternoon and evening, AM radio broadcasts included a nearly continuous chorus of thunderstorm sferics—the unmistakeable crackling which pours from radio receivers as lightning occurs. The generation of lightning produces electromagnetic pulses responsible for the radio crackles. Cloud-to-ground lightning from all the thunderstorms within a 150 mile radius of Chicago was measured at a rate of more than 900 strokes every ten minutes late Tuesday afternoon and evening. The day’s heat and humidity produced t-storms—some 52,000 ft. high. Thundery downpours swamped localized areas with as much as 1-2” of rain, covering some roads in McHenry, Lake and Grundy counties—among others—with as much as 4-6” of water.
-Tom Skilling

Posted by wgnweather at 11:23 PM | Permalink

Posted by wgnweather at 11:21 PM | Permalink

Posted by wgnweather at 11:12 PM | Permalink

Posted by wgnweather at 9:47 PM | Permalink

Monday's powerful Memorial Day storms were captured as they bore down on the west suburban Naperville area in these shots from Scott Sanborn. The storms generated 1" diameter hail near Elgin and produced rainfalls approaching 0.80" in under an hour's time near St. Charles and Arlington Heights. Kankakee County was drenched by rains estimated by Doppler Radar at a few locations to have topped 4" Monday.

Posted by wgnweather at 4:59 PM | Permalink

Monday’s muggy, moisture-saturated atmosphere destabilized explosively as temperatures surged. Destabilization is the term applied by meteorologists when temperatures decline more rapidly than usual with height. It encourages air to ascend vigorously, a process which on Monday converted the 1.5”-2” of water which permeated the lower 3.5 miles of the steamy Memorial Day atmosphere in vapor form into banks of towering thunderstorms—some up to altitudes of 55,000 feet. At that height (though it was hot at ground level) readings dropped below -80° F. Much of the day’s t-storm clouds were below freezing, fostering the growth of huge hailstones—some as large as 1”—which crashed to Earth in driving downpours and wind gusts to 75 m.p.h. like those in Crete, Ill., and Schererville, Ind.
Kankakee County was the epicenter of the area’s heaviest rain. Doppler radar estimates topped 4” in parts of the county. Water stood 2-3 feet deep in Bourbonnais.
--Tom Skilling, WGN-TV Meteorologist

Posted by wgnweather at 11:14 PM | Permalink

Posted by wgnweather at 11:13 PM | Permalink

Posted by wgnweather at 11:12 PM | Permalink

Posted by wgnweather at 11:10 PM | Permalink

Memorial Day for Chicago will start out sunny and mild, but humidity is expected to rise as clouds increase during the day. Temperatures should reach well into the 80s, perhaps reaching the 90° level—some 15 degrees above the normal (75°) for this date. Showers and thunderstorms in southern and central Illinois will be pushing north, possibly reaching the metro area later this afternoon. Yesterday was hot with the 94° at Midway Airport establishing a new record high for May 28 at that site, while the 92° at O’Hare just missed the old record by a single degree. Humidity remained just low enough to hold area heat index values in the middle 90s.
However, dermatologist Dr. Bryan Schultz, who provides sunburn times for the weather page, indicated Sunday’s almost unlimited sunshine resulted in the highest ultraviolet radiation readings to date in 2006.
Record highs were set Sunday in at least six states from the Plains to the western Great Lakes.
--By Paul Dailey, WGN-TV Weather Center Meteorologist

Posted by wgnweather at 8:44 PM | Permalink

Posted by wgnweather at 8:42 PM | Permalink

Posted by wgnweather at 8:41 PM | Permalink

Posted by wgnweather at 8:40 PM | Permalink

With the upper jet stream flow pattern favoring the advance of warm humid air from the south and west into northern Illinois, temperatures are expected to climb through the 80s into the 90s today. The air mass will carry dew points in the lower 70s which when combined with the season’s first official 90° high could result in a triple-digit heat index. A pocket of unstable air prompted a severe thunderstorm watch just to Chicago’s west and north yesterday and produced scattered t-storms a few of which brought damaging winds and 3/4-inch hail. Weakened storms passed through Chicago, and the weather system is moving east into Lower Michigan today.
An upper air pattern shift is forecast mid-week with a cold front expected to produce a period of potentially severe t-storms and heavy rains. Subsequent northerly flow out of Canada will usher in significantly cooler and less humid air to NE Illinois the latter half of this week.
-Paul Dailey, WGN-TV Meteorologist

Posted by wgnweather at 7:25 PM | Permalink

Posted by wgnweather at 6:55 PM | Permalink

Posted by wgnweather at 6:53 PM | Permalink

Posted by wgnweather at 6:52 PM | Permalink

Friday’s 83°, the warmest of 2006 and the highest temperature logged here since Oct. 5, is just the beginning if cloud cover and winds behave as predicted. The Chicago area and much of the Midwest is headed for the region’s first string of 90° highs Sunday through Tuesday. The heat is expected to arrive in the midst of the most humid weather in nine months. Dew points, the preferred measure of atmospheric moisture by meteorologists, are to hit the low 70s Sunday afternoon. That implies a level of mugginess not unlike that found regularly on this nation’s Gulf Coast and in the tropics.
The incoming round of summerlike weather, tempered in lakeshore areas Saturday by southeast winds off still-chilly lake waters, will put the Memorial Day holiday on track to become the warmest weekend of the past 37 weeks overall. Not since Sept. 10-11 has a weekend produced higher temperatures in Chicago.
—By Tom Skilling, WGN-TV Meteorologist

Posted by wgnweather at 12:00 AM | Permalink

Posted by wgnweather at 11:59 PM | Permalink

Posted by wgnweather at 11:57 PM | Permalink

Posted by wgnweather at 11:56 PM | Permalink

Posted by wgnweather at 10:56 PM | Permalink

It may feel more like the 4th of July instead of Memorial day in Chicago this weekend, as the city prepares for the arrival of the season’s first 90º days and muggy 70º dew points. Lingering clouds and light showers should depart later today setting the stage for weekend sunshine that will send the mercury soaring.
Chicago’s heat will arrive in force Sunday as winds lose their lake trajectory, blowing in from the southern Plains, where numerous record highs were established Thursday, including 92º at Joplin, Missouri and 96º at both Tulsa and Oklahoma City.
The severe thunderstorms that raked Chicago late Wednesday moved east to blast areas from Michigan to Kentucky on Thursday, with nearly 220 reports of severe weather. After reviewing damage from Wednesday evening’s storms, the National Weather Service determined that an F1 tornado struck southeast of Kankakee near Aroma Park.
-Steve Kahn, WGNTV Meteorologist

Posted by wgnweather at 10:56 PM | Permalink

Posted by wgnweather at 10:54 PM | Permalink

Posted by wgnweather at 10:08 PM | Permalink

Thunderstorms hit the area in a series of powerful waves Wednesday, prompting severe weather watches and warnings and targeting a multi-county east/west corridor to Chicago’s south for the meanest meteorological assault. The wild weather followed Chicago’s first official May 80°. By late evening, sections of Iroquois, Kankakee, and Livingston counties—east into Indiana’s Jasper and Newton counties had suffered storm damage ranging from downed trees to snapped utility poles. Thundery downpours swamped sections of Kankakee County stranding cars in high water. 2.60” fell at Bonfield while 2.80” was reported just northwest.
The strongest of Wednesday’s storms towered into the stratosphere—an atmospheric layer through which temperatures warm with height rather than cool—a situation which checks the vertical cloud development of all but the most powerful storms.
-Tom Skilling

Posted by wgnweather at 11:16 PM | Permalink

Posted by wgnweather at 11:15 PM | Permalink

Posted by wgnweather at 11:11 PM | Permalink

Posted by wgnweather at 10:30 PM | Permalink

Strong, potentially severe thunderstorms threaten to erupt in parts of the Chicago area later Wednesday. The storm threat is to follow only the third 80° high to date this year—the first daytime reading to surge above 80° in the nearly five weeks since April 14 when an 81° high occurred.
Humid air and the rich supply of stored energy it delivers in the form of latent heat, may interact with strong jet stream winds to produce clusters of rotating supercell thunderstorms capable of generating high winds, hail and even a few twisters in sections of the Midwest later today. Additional thunderstorms could fire Thursday as a pool of cold air positions itself above the warm, moderately humid air predicted here. A comparable set-up produced 10-mile high t-storms in the Plains late Tuesday, including one which blasted Hastings, Neb. with 81 m.p.h. gusts.
-Tom Skilling

Posted by wgnweather at 11:06 PM | Permalink

Posted by wgnweather at 11:05 PM | Permalink

Posted by wgnweather at 11:03 PM | Permalink

Posted by wgnweather at 10:25 PM | Permalink

Big weather changes, including the city’s first 80° high in 5 weeks are getting underway. Temperatures surge back into the 70s Tuesday afternoon with the first 80° of May due Wednesday. But, warming really gathers steam this weekend, offering Chicago its first shot at a 90° Memorial Day high for the first time in the 12 years since 1994.
Monday’s cloud-free skies produced only the second day this month with 100% of its possible sunshine, but the sun’s rays were unable to overcome lake cooling. Monday was the 12th straight day to produce a temperature deficit. The period’s average 61.1° daily high is the 2nd lowest May 11-22 on the books since the start of weather observations at O’Hare in 1959.
The story in the Plains couldn’t have been more different. Temperatures sizzled with new records at Chadron (93°), Alliance (92°) and Imperial (94°)—all in Nebraska.
-Tom Skilling

Posted by wgnweather at 11:11 PM | Permalink

Posted by wgnweather at 11:11 PM | Permalink

Posted by wgnweather at 11:10 PM | Permalink

Posted by wgnweather at 11:09 PM | Permalink

It turned chilly in Chicago Sunday as brisk northeast winds blowing down the entire length of Lake Michigan allowed highs to only reach the lower 50s near the lake and the lower 60s inland—a sharp decline from Saturday’s mild 70s. The chill was prevalent throughout the Great Lakes region with late-season snow falling at Marquette, Mich., Sunday and frost or freeze conditions expected Monday morning across a broad area from Minnesota to Ohio.
However, a change is under way as a northward shift in the jet stream will allow summer-strength heat that has been building for weeks over the South and West to shift north into Chicago later this week. The city should record this month’s first 80º day by Wednesday and possibly the season’s first 90º by the upcoming Memorial Day weekend.
Today marks the 151st anniversary of Chicago’s earliest recorded tornado that killed three and injured six in the Norwood Park area on May 22, 1855.
--By Steve Kahn, WGN-TV Weather Center Meteorologist

Posted by wgnweather at 8:39 PM | Permalink

Posted by wgnweather at 8:38 PM | Permalink

Posted by wgnweather at 8:37 PM | Permalink

Posted by wgnweather at 8:35 PM | Permalink

Chicago has been mired in a cool and showery funk this May, devoid of any hint of warmth from the fast approaching summer season. With two-thirds of the month already gone, the highest May temperature on the books here has been a paltry 74º, and the city has been peppered with measurable showers on 11 days. All that is about to change, as a dome of heat that has been setting records across the West and South appears ready to make a move toward the Midwest.
Saturday afternoon highs reached the 90s across the nation’s southern tier with triple digit heat common in the Desert Southwest and western Texas. Record highs were established at Lubbock (101°), San Angelo (102°) and Midland (103°), all in Texas.
The heat here will arrive in stages. After today’s brief cool down, highs should stair-step through the 70s and 80s, possibly reaching the 90º mark for the first time this year, just in time for the Memorial Day weekend.
-Steve Kahn WGN-TV Meteorologist

Posted by wgnweather at 8:24 PM | Permalink

Posted by wgnweather at 8:16 PM | Permalink

Posted by wgnweather at 8:14 PM | Permalink

Posted by wgnweather at 8:13 PM | Permalink

Temperatures surge back into the 70s Saturday afternoon and may become May 2006’s highest to date if a bit of compressional warming—the heating which results as air sinks and compresses—materializes as predicted. Low 70s are assured with or without any enhanced warming. But, with the Chicago area predicted to sit beneath a pocket of especially strong jet stream winds (the jet streak), a region where air sinks and warms on a large scale, a 75° high appears within reach later Saturday. It’s a reading one degree warmer than May’s previous warmest temperature of 74° back on the 10th.
The passage of a wind-shifting cold front, predicted to occur here between 8-10 p.m. Saturday, may generate several gusty thunderstorms and introduce cooler air for Sunday—especially near the lake with NNE winds locking in during the afternoon.
Heat to the west broke records Friday and produced 100° highs in parts of Kansas and Oklahoma.
--Tom Skilling, WGN-TV Meteorologist

Posted by wgnweather at 12:51 AM | Permalink

Posted by wgnweather at 12:51 AM | Permalink

Posted by wgnweather at 12:49 AM | Permalink

Posted by wgnweather at 12:48 AM | Permalink

This week certainly had its share of active weather moments—especially on Wednesday when storms raked the area. Here are a few pictures that highlight the events of the past few days:

Here's a close up of some hail stones—the dime shown gives you an idea of their size (photo courtesy of J. Crocker, Uptown-Chicago)

Here are a few snapshots of some heavy hail that fell in Norwood Park (photo courtesy of Thomas Nava)

Here's a look at the late-afternoon cumulus clouds near Algonquin on Wednesday (photo courtesy of Matt Hoelter of Cary, Ill.)

Posted by wgnweather at 3:13 PM | Permalink

It’s been nearly 5 weeks since Chicagoans have enjoyed 80°. Since 1928, only 13 Mays have failed to produce at least one 80° in the month’s opening 19 days. Even more remarkable, May 2006—averaging 1.2° below normal—hasn’t even managed a 75° high. That hasn’t happened since 1948.
Small hail within several scattered thunderstorms pelted parts of the Chicago area for a second day Thursday. With cloud tops Thursday morning at 29,000 ft. and freezing temperatures just 5,000 ft. above the ground, the majority of Thursday’s shower clouds were below freezing—a situation which fostered hailstone development and growth.
Thursday’s 0.03” of rain marked the 9th consecutive day this month with measurable precipitation. Only three other Mays—including 1949 (with 11 straight days of measurable rain), 1945 and 2001—have hosted as many consecutive days with measurable rain.
-Tom Skilling

Posted by wgnweather at 11:32 PM | Permalink

Posted by wgnweather at 11:30 PM | Permalink

Posted by wgnweather at 11:16 PM | Permalink

Posted by wgnweather at 11:12 PM | Permalink

What started out as a beautiful Wednesday with sunny skies and temperatures reaching the lower 70s, took an abrupt downward spiral in the afternoon as waves of showers and thunderstorms spread into the area from the northwest. The storms turned severe with hail peppering much of the area, some of it as large as golf balls. Winds shifted to the north reaching speeds as high as 40 m.p.h. as the mercury plunged 20º into the lower 50s erasing all memories of the delightful morning. The Chicago area was not alone in Wednesday’s storminess with hail and strong winds reported throughout the Great Lakes region.
The weather will continue on the cool side into this weekend, but longer-range computer forecasts hint at a substantial warm-up by the first of next week with readings headed for the 80s, uncharted territory for Chicago temperatures so far this May.
-Steve Kahn, WGN-TV Meteorologist

Posted by wgnweather at 10:50 PM | Permalink

Posted by wgnweather at 10:35 PM | Permalink

Posted by wgnweather at 10:33 PM | Permalink

Posted by wgnweather at 10:32 PM | Permalink

Chicago’s temperatures pop into the lower 70s today, the first time that has happened since the city logged a 74° reading one week ago.
Normally, we would expect four 70° days in that period. And should measurable rain (that is, at least 0.01”) fall today, it will be the eighth consecutive day of rainfall. Total rain in those days has been 1.30”.
Let’s put that into perspective: 10.45” has drenched Boston in a comparable period—eight times as much water as has fallen on Chicago.
After today’s 73° reading (only slightly above the day’s normal high of 70º), cooler air locks in yet again and temperatures are forecast to run below normal through the weekend.
By next Monday, however, computer models indicate a major weather pattern change that suggests readings well into the 80s.
-Richard Koeneman, WGN-TV Meteorologist

Posted by wgnweather at 10:36 PM | Permalink

Posted by wgnweather at 10:32 PM | Permalink

Posted by wgnweather at 10:21 PM | Permalink

Posted by wgnweather at 10:18 PM | Permalink

Chicago’s string of sub-normal days extends to six with today’s reading in the lower 60s, but cool air will briefly relax its grip on the city Wednesday with temperatures expected to top 70º.
Elsewhere, national weather has taken some harsh turns. The same storm system responsible for Chicago’s cool temperatures has simultaneously delivered a multi-day deluge of rain to New England. Rainfall records have toppled in Massachusetts, hardest hit of that region’s states.
At only 15 days into the month, Salisbury, Mass., has logged 18.82 inches of rain, blowing away the state’s previous full-month May record of 15.60”.
The opposite end of the nation, meanwhile, is simmering in unprecedented early-season heat. Some Oregon records established on Monday: Portland, 95º (old record 81º); Astoria, 90º (76º); Medford, 96º (92º). Stockton, Calif., 97º (89º).

Posted by wgnweather at 10:50 PM | Permalink

Posted by wgnweather at 10:49 PM | Permalink

Posted by wgnweather at 10:49 PM | Permalink

Posted by wgnweather at 10:47 PM | Permalink

Sometimes the atmosphere settles into a rut, and this is one of those times. In terms of the weather, it’s as if the U.S. is two completely different countries. Chilly temperatures, widespread cloudiness and rain prevail from the Midwest to New England, whereas it’s hot and dry across the West.
The big story is serious flooding in the Northeast. Record rainfall and resultant river flooding have swamped portions of New England. Boston established two consecutive rainfall records with 3.84” on Saturday and 3.36” through 7 p.m. Sunday, with rain continuing.
Chicago’s scattered showers and sub-normal temperatures through Tuesday are inconsequential by comparison.
It’s all due to a large and stubbornly slow-moving storm system—meteorologists call it a “closed upper low”—that will not relax its influence on Midwestern and Eastern weather until Thursday.
-Richard Koeneman-WGN-TV Meteorologist

Posted by wgnweather at 11:07 PM | Permalink

Posted by wgnweather at 11:06 PM | Permalink

Posted by wgnweather at 11:04 PM | Permalink

Posted by wgnweather at 11:03 PM | Permalink

The last Mother’s Day with a high temperature in the 50s was just four years ago, and that fits Chicago’s climatology, which says in one out of every four years the second Sunday in May will have a high temperature in the 50s. Records also show that just as often on the second Sunday in May, highs warm into the 70s. The “average” high for Mother’s day is 66°, but there is a tremendous 50° range from a high of 39° observed in 1981 to an 89° recorded in 1986 and again in 1956. With a low pressure system stymied over the western Great Lakes the last four days forecast to continue to slowly drift east, Chicago’s string of days with high temperatures below 60° may well reach five before readings hit the mid 60s Tuesday. 70° is possible Wednesday before a change back to cooler conditions the remainder of this week. Latest computer models hint at development of a band of heavy rain early the following week, centering on NE Illinois May 23.

Posted by wgnweather at 9:00 PM | Permalink