WGN Weather Center Blog

Winds shift to the southwest and increase today as a warm front moves through northern Illinois into Wisconsin. Moisture from overnight showers and thunderstorms will evaporate back into the air as the sun breaks out, making it feel more humid almost from the start.
A weak cold front will pass through the area Sunday, but a stronger cold front is not expected to push through northeast Illinois until later Monday or early Tuesday. The National Weather Service Storm Prediction Center has northern Illinois outlooked for potential severe thunderstorms Saturday through Monday. A wide range in rainfall amounts may be recorded over the metro area as slow-moving storms could give well in excess of an inch in some areas.
After a midweek cool-down, another warm-up is in store next weekend. The Climate Prediction Center indicates warm high pressure will dominate the following week with little or no rainfall.
--By Paul Dailey, WGN-TV Weather Center Meteorologist

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Especially hot summer air continues to spread eastward into the Plains, with 100° readiings spilling into the Dakotas and Nebraska. This dome of hot air continues its relentless march eastward, reaching Chicago Saturday. Some moderation from the intense Plains’ heat is expected as it mixes with the current pleasant air mass retreating eastward from Chicago. Heat and humidity linger into Sunday and even Monday, but increasing clouds help restrain temps.
In this regime, the jet stream is close enough to our north to keep the upper atmosphere unstable, and southwest winds straight from the western Gulf bring in the humidity with enough moisture for a good chance of thunderstorms Saturday and an even better chance Sunday and Monday. From Tuesday on, heat and humidity retreat southward, replaced by a strengthening Canadian high pressure cell complete with pleasant temperatures and humidity.
-Dennis Haller, WGN-TV Meteorologist

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Wednesday’s thunderstorms in Chicago brought the monthly rainfall total to 3.79", some 0.40" above normal and over five times the 0.72" total by the same time last June during last summer’s drought. The upper level trough stalled over the Midwest for the past four days is finally drifting eastward, bringing along the recent soggy weather and cool temperatures. In its place, the rain ends and temperatures climb.
By the weekend, the heat in the West finally crosses the Mississippi, causing temperatures to climb past 90° across the region. Gulf moisture is injected into the mix, so humidity also climbs to uncomfortable levels while overnight temperatures linger above 70°.
The increased humidity provides fuel in the fairly unstable upper atmosphere—enough that thunderstorms with significant rainfall are possible from Saturday through Monday.
-Dennis Haller, WGN-TV Meteorologist

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Scalding summer heat continues to avoid the Chicago area, choosing instead to bake the West. From San Diego (96°) and Los Angeles (94°) north to Boise, Idaho (101°) at least a dozen new temperature records were set Tuesday, part of a hot air mass expected to send a tentacle of heat into Chicago by Saturday. To date, June 2006 has only two days of 90s—half the normal number. With no additional 90s likely before the month closes, this June is likely to join only 22 others since 1928 to produce so few 90s at Midway Airport. The summers which have followed similar Junes have trended modestly cooler than normal, with the final June-August average finishing about 0.5° below normal and the city’s annual 90° tally closer to 18 than the “normal” 21.
But July arrives Saturday and may do so with the first 90° air here in two weeks. The upcoming 2 weeks has produced at least one 90° high 91% of the time in the past 78 years at Midway Airport.
-Tom Skilling

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Early Monday’s thunder-peppered downpours produced the Chicago area’s heaviest 24 hour rain total in nearly 3 years. The 1.66” collected before sunrise in the official rain gauge at O’Hare hasn’t been equaled since the 2.26” which fell July 31 and August 1, 2003.
Midway Airport was drenched by 1.47”—1.15” of which fell in a blinding 15 minute cloudburst which started around 12:15 a.m. Even more impressive rain tallies originated from National Weather Service cooperative observers in western suburban Wheaton (3.14”), Glen Ellyn (2.75”), Elmhurst (2.05”) and McHenry (2.03)”.
Heavy as recent rains have been here, the totals pale in comparison to those observed recently out East. With new downpours looming, Boston reported a combined May/June rain tally of 22.39” Monday—the heaviest two month total in 135 years of official records dating back to 1872.
-Tom Skilling

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With a stubborn upper-level low pressure circulation parked above the Midwest, a persistent pattern of cloudy, cool and showery weather is in store for Chicago for the first part of this week. Daytime highs should remain in the 70s with a daily dose of showers and thunderstorms.
Sunday’s storms were innocuous for the most part, but a few strong cells brought heavy rainfall and hail to areas mainly west and south of the city. Far northwest suburban Marengo was pelted by nickel-size hail, and nearly 2 inches of rain flooded streets there.
Heavy rainfall drenched the East Sunday with nearly a foot swamping portions of Maryland’s eastern shore, while more than 2 inches fell in portions of Florida and Virginia.
In contrast to Chicago’s coolness, triple-digit heat is baking the Northwest. Portland, Ore., logged a 101º high Sunday—the hottest June temperature ever in the City of Roses. Record highs were also set at Reno (102º) and Seattle (88º).
--By Steve Kahn, WGN-TV Weather Center Meteorologist

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As the first month of meteorological summer enters its final week, hot weather is on hiatus from Chicago. So far this June has produced only two 90º+ days here—a total not expected to change by month’s end. The heat remains entrenched in the western states with 100s expected Sunday from the southwestern deserts to the Pacific Northwest.
On Saturday, Death Valley, California set a record high with a scorching 125º, besting the old record by one degree.
In contrast, with an upper-level low pressure system settling over the Midwest, Chicago is in for a week of temperatures fluctuating between the 70s and lower 80s, along with an almost daily threat of showers and thunderstorms.
Despite recent rains here and the promise of more to come, the hit-and-miss nature of summer precipitation has left much of this region teetering on the verge of dryness, as the area tries to recuperate from last year’s severe drought.
-Steve Kahn, WGN-TV Meteorologist

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Blazing heat, which has staged a full but stormy retreat from the nation’s midsection the past two days, now grips the West and threatens new temperature records as far north as Portland, Ore. There, 90s predicted Saturday and triple-digit readings forecast Sunday afternoon are levels more than 25 degrees above normal.
Temperatures within the same air mass in California Friday hit 111° at Redding, 112° at Red Bluff and 105° at Sacramento—each a new record for June 23. Weekend highs are predicted to hit 112° both Saturday and Sunday at Las Vegas.
Chicago’s weather couldn’t be more different. Atmospheric moisture has dropped to 29 percent of the level observed only two days ago, as evidenced by the eminently comfortable humidities to which Chicagoans rise Saturday. But, the heat’s retreat set off waves of t-storms across 42 states late this past week, including nearly 4 dozen twisters and 1,600-plus reports of severe weather.
--By Tom Skilling, WGN-TV Meteorologist

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Nick Liveris shares these beautiful urban sunset shots taken just before 8:30 p.m. Thursday evening, June 22, from Dearborn and Maple Streets in Chicago's Gold Coast.

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Last summer’s most enduring hot spell began one year ago and included eight consecutive days with temperatures 90° or higher. The coming week will be very different, with little prospect of another 90° reading. It’s likely only four 90s will be on Chicago’s 2006 books as June closes. Past years with similar 90° counts heading into July have often gone on to produce cooler than average meteorological summers—below the long term average by 0.9°. Such years have also tended to finish with fewer 90s—19 versus the long term average of 24. There is no guarantee this season’s weather will respond in precisely the same way, but past trends can offer insights into what’s ahead.
T-storms Thursday produced some wild weather, including morning hail and downpours —ultimately slashing dewpoints (which reflect atmospheric moisture) from Wednesday’s four year high of 77° to 57° by nightfall Thursday.
-Tom Skilling

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The wind-tossed, wavy cloud pattern ahead of Thursday morning's (June 22, 2006) showers and thunderstorms proves a real eyecatcher. Based on some in-house research employing the World Meteorological Organization's "International Cloud Atlas-Volume II", the clouds which most closely resemble those which appear in these shots, are referred to as: Altostratus opacus and Altocumulus stratiform opacus mamma

These images were photographed and provided to us by Thursday by former Air Force weather observer Barry Stark. Turbulent winds surrounding approaching showers and embedded thunderstorms appears to be contributing to the wind-tossed, "angry" appearance of these clouds.
-Tom Skilling, WGN-TV Chief Meteorologist
Photo courtesy of Barry Stark

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Midwestern Video Productions provides us another perspective on the eycatching cloud formation observed with Thursday morning's storms in the Chicago area. What's so fascinating and unusual in these shots is the fact this isn't the typical "shelf" or "roll" cloud ahead of an incoming thunderstorm. Such clouds, like the darkest clouds pictured here, are low based clouds which often blend into a non-descript backround low-altitude cloud mass or wall of rain. By contract, these formations Thursday morning occurred beneath "mid-level" formations provide the backdrop for the Wednesday morning's approaching showers and thunderstorms, which turned severe to Chicago's south. Hail up to 0.88" in diameter in Chicago's southern suburbs and wind gusts approaching 60 m.p.h. whipped downstate in the Bloomington area of central Illinois, accopanied the fast moving storms.


Photo courtesy of Midwestern Video Productions

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Despite harrowing moments as wind-driven downpours, cloud-to-ground lightning and powerful thunderstorm gusts fueled by the muggiest atmosphere here since August 1, 2002, rainfall tallies were disappointing. Three waves of thunderstorms swept northern Illinois and southern Wisconsin Wednesday. Morning storms only flirted with the city, but delayed air traffic at the city’s airports. Gusts to 67 m.p.h. snapped trees and downed power lines as close as the Beloit, Wisconsin area. But it was a cluster of afternoon t-storms which exploded to life in under 15 minutes across Kendall, Grundy, DuPage and Will counties, which produced cloud tops radar-scanned above 60,000 ft. The powerful 48 m.p.h. gusts which swept Midway Airport flipped one small aircraft and moved three others. The storms proceeded to Michigan City 59 minutes later, producing 78 m.p.h. gusts.
-Tom Skilling

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Chicago’s back in hot, humid tropical air Wednesday and on the precipice of the area’s fifth 90° high of 2006. But, areas downstate will really broil with mid to upper 90° highs combining with Gulf Coast-level humidities to produce a second day of triple-digit heat indexes.
St. Louis is headed for 98° Wednesday afternoon. Low 90s aren’t out of the question in sections of the Chicago area, where rain-cooled thunderstorm “outflows” are likely to produce impressive temperature gyrations as the storms swing across the region. Hot air is exceptionally buoyant—i.e. inclined to ascend through the atmosphere, cooling and condensing as it does—and is therefore an important ingredient in generating the mammoth clouds which parent thunderstorms.
Tuesday heat indexes in southern Illinois peaked at 104° at Fairfield and 102° at Mt. Vernon, Centralia and Carbondale.
-Tom Skilling

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Temperatures surge back to 90° briefly Wednesday afternoon. But, there are few signs Chicago is in for extended heat in the foreseeable future—the kind that takes up residence for days at a time. That’s no guarantee hot weather will continue a no-show here as Summer 2006 matures. Chicagoans who like their weather truly hot and laced with humidity may be comforted to learn that in 20 years with a 90° count by June 20 comparable to this year’s four at Midway Airport, an average of 26 readings in the 90s ended up occurring in 13 (or 65%) of those years. It’s a number which exceeds the 30-year average of 21.
Delightful weather dominates Tuesday. A “bubble” of high pressure is in control prompting east winds off the lake. June’s average temperature to date has been 68.0°—3.4° cooler than a a year ago. In 135 years of official weather records dating back to 1871, 50 June 1-20 periods have been warmer and 85 cooler.

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Sunday saw tornadoes touch down in Wisconsin, local flood-producing rainfall and wind damage in Lincoln, Ill., and scattered showers across northeast Illinois. In south-central and eastern Wisconsin, there were several funnel cloud and at least four tornado reports. Hardest hit was Hartford, Wis., just northwest of Milwaukee, where just before 3 p.m. multiple trees and power lines were downed, and a motel was destroyed along with damage to an elementary school. No serious injuries were reported.
This band of weather moved well to the east overnight, but more stormy weather is in store for Illinois and Wisconsin in the days ahead. Showers or thunderstorms are in the forecast each of the next four days. Just prior to a cold front, southwest winds could pull a brief surge of hot, humid air into northeast Illinois Wednesday. Indications are that a stalled weather system Thursday will result in the most widespread and heaviest rains this week.
--By Paul Dailey, WGN-TV Weather Center Meteorologist

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With periodic triggering impulses in the upper air pattern, intervals without showers or thunderstorms will be short-lived for Chicagoans during the coming week.
Yesterday severe thunderstorms concentrated in the Texas-Oklahoma area with widely scattered reports over the length of the Mississippi valley. Even some high winds occurred with storms in the Chicago area, but damages were negligible.
Father’s Day may see more clouds and thunderstorms across NE Illinois with peaks of sun this afternoon. A few showers are possible tomorrow and again overnight Tuesday into Wednesday. A brief intrusion of hot SW flow on Wednesday could send readings back into the 90s, but a 3 to 4-day cool-down may start next weekend.
The National Weather Service reminds the public of the dangers of lightning by declaring this June 18-24 Lightning Safety Awareness Week.
-Paul Dailey, WGN-TV Meteorologist

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Powerful thunderstorms unleashed nearly half a dozen small twisters and punishing barrages of damaging hail, ranging from dime to golf-ball size, for a second day Friday across the Plains. The storms acted to moderate blistering triple-digit heat so prevalent in that region earlier this week. Hail fell with such intensity in eastern Colorado, it stripped leaves off trees 14 miles north of Arapahoe, while drifts of hail accumulated to a depth of 5” nearby. Storms elsewhere in the state shattered car and home windows. To the east in Kansas, a semi-trailer truck was blown off the road by a twister-like circulation spawned at the leading edge of an approaching squall. This phenomenon, less intense and well-developed than a tornado, but damaging nonetheless, has been dubbed a gustnado by many of this country’s storm chasers.
Thundery downpours in Minnesota late Friday, part of the same storm complex, sent 3-6” of water across roads.
--By Tom Skilling, WGN-TV Meteorologist

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Thursday’s 86° at O’Hare and 85° at Midway ended six consecutive days of below-normal temperatures and qualified as June 2006’s warmest yet. It’s relatively rare for temperatures at those levels to rank as this month’s warmest two weeks into June. Nearly 90% of Junes—69 of the past 78 since records started in 1928 at Midway Airport—have hosted hotter temperatures by this point in June. The comparatively cool weather—8.2° below the June 1-15 period a year ago—has been a boon to home and business owners in terms of air conditioning. Based on temperatures to date, it’s estimated only 58% of the typical level of air condiitoning has been required this month—73% less than the same period a year ago.
That all changes Friday with the heat’s arrival. Temps soar to the year’s highest levels yet.
The heat produced more t-storms in the Plains Thursday. Tennis ball hail fell for 20 minutes SW of Mullen, Neb.
-Tom Skilling

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The eastbound dome of hot air, expected to bake Chicago at over 90° as early as Friday afternoon, scorched the western Plains with record-breaking triple-digit heat Wednesday. Denver, Colorado’s 102° high became the Mile High City’s earliest 100° ever—obliterating the previous record of June 24, 1954, by nearly 10 days. The line-up of blistering temperatures across the region was impressive. In Nebraska, readings of 108° at Imperial, 105° at Sidney, 104° at Alliance and 102° at Chadron were all record breakers, eclipsing the previous June 14 records by as much as 10 degrees. Rapid City, South Dakota topped out at 102°, 25 degrees above normal.
The heat provoked powerhouse 57,000 ft. tall late day thunderstorms across the northern Plains. Storm gusts reached 98 m.p.h. at Bloomfield, Montana while tennis ball size hail shattered car windows in the Miles City area.
-Tom Skilling

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The eastbound dome of hot air, expected to bake Chicago at over 90° as early as Friday afternoon, scorched the western Plains with record-breaking triple-digit heat Wednesday. Denver, Colorado’s 102° high became the Mile High City’s earliest 100° ever—obliterating the previous record of June 24, 1954, by nearly 10 days. The line-up of blistering temperatures across the region was impressive. In Nebraska, readings of 108° at Imperial, 105° at Sidney, 104° at Alliance and 102° at Chadron were all record breakers, eclipsing the previous June 14 records by as much as 10 degrees. Rapid City, South Dakota topped out at 102°, 25 degrees above normal.
The heat provoked powerhouse 57,000 ft. tall late day thunderstorms across the northern Plains. Storm gusts reached 98 m.p.h. at Bloomfield, Montana while tennis ball size hail shattered car windows in the Miles City area.

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Sizzling weather, absent here in the more than two weeks since the Memorial Day weekend, is on the way. Chicago’s first 90° high since May 29 seems a good bet as early as Friday afternoon. Until then, area residents can continue to monitor the impending heat in comfort. Humidities are still low—though a few t-storms may flare along a band of converging winds Wednesday afternoon—primarily west of the city.
With the coolest set of June 9-12 daytime readings at Midway Airport since 1928 now on the books, the impending shift to hot weather should be very noticeable. Higher humidities in combination with 90° highs, threaten to push afternoon heat indexes to within striking distance of 100° this weekend.
Record heat south of Chicago Tuesday offers a preview of what’s on the way. The 100° high at Houston, Texas’ Intercontinental Airport marked the earliest appearance of a triple digit reading there since 1900.
-Tom Skilling

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For a fourth consecutive day, Chicago’s high temperature failed to reach 70° Monday. The official high of 69° at both O’Hare and Midway fell far short of the 80° afternoon readings considered typical. In only three other years have four consecutive sub-70° highs occurred in mid-June since 1928. In terms of daytime temperatures, the 65.7° average reading since Friday is the coolest June 9-12 period here in the past 78 years.
Tropical Storm Alberto’s encounter with the loop current, an exceptionally warm body of water which flows out of the warm, comparatively shallow Caribbean into the central Gulf of Mexico, produced a surge in intensity Monday—as happened last season when Hurricanes Katrina and Rita surged to top-intensity “Category 5’s” as they passed over the energy-infusing warm water. Thunderstorms blossomed within the poorly organized system and winds increased to 70 m.p.h.
-Tom Skilling

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