Chicago area residents were treated to quite an open to the day as skies the first few hours of Thursday morning turned from day to night with the squall line which swept the area.  The fast moving t-storms accompanied a wind-shift cold front across the area.  It passed mid-morning as anticipated—then clearing ensued.

Wind gusts with the morning storms hit 47 mph at the Crib 3 miles off the city’s North Side  in Lake Michigan.  But other gusts hit 36 mph at Winthrop Harbor, Waukegan, in downtown Chicago and at O’Hare with 35 mph gusts at Kenosha and storm gusts to 32 mph at Grayslake.  Midway Airport was swept by 30 mph gusts.

Storm downpours deposited 0.96″ of rain at Sugar Grove, 0.86″ in Naperville, 0.78″ at Lisle and 0.70″ at Chesterton, IN.  Midway Airport received 0.50″ while only 0.20″ fell at O’Hare.

Comfortable—even some overnight temps which are a bit cool for the season—takes hold tonight and Friday,  Normal temps this time of year are 83/65—so to have nighttime lows down to 58 tonight at O’Hare is 7-deg below normal even though Friday’s high of 83 will be right on the money.

Wildfires continue to burn in the record breaking hot air mass which has seen triple digit daytime highs come in 20 to 30-deg above normal across the Pacific Northwest and Northern Rockies.  Upper winds are guiding smoke  off those fire eastward into the Midwest. Model forecasts suggest the smoke entering Chicago air space will become denser Friday then thin out a bit Saturday—so expect some colorful sunrises and sunsets in the next few days.

The atmosphere expands when heated—and our models measure that. For more than a week, model forecasts have indicated the development of a stunning dome of warm air—-the most expanded of the Summer 2023 season to date. Those forecasts continue. 

This is to lead to heat—and the hot airis to be joined by muggy Gulf Coast-level 70-deg dew point Sunday through Tuesday next week—with humid air likely to hang beyond that next week.  

Warming aloft shuts down t-storm development thus eliminating one of nature’s most effective way of cooling hot air masses.  So Chicago temps are likely to soar toward 90 Saturday and into the 90s Sunday through Wednesday. The weather looks beautiful for the weekend Chicago Air and Water show.

The one temperature wild card is the indication of a easterly wind at the surface Monday into Tuesday.  Those winds, coming as they will off Lake Michigan, are  likely to temper beach and lakeside heat a bit even as inland temps soar into the 90s.  But beyond that, it’s quite possible Tuesday and Wednesday will be the hottest days of the coming seven and likely to produce high temps which surpass the current summer high temp of 93-deg..

The jet stream sags a bit farther south around the periphery of the hot air dome later Wednesday through the end of next week. This plus the likelihood a surface front could follow suit then stall over or just south of Chicago could set the stage for RING OF FIRE-type t-storm clusters Wednesday into the following weekend. This is a development which will have to be monitored since storm cluster which erupt in that sort of atmospheric set up can be formidable at times.

ONE NOTE ON AUGUST TEMPS—They’re running pretty cloud to normal and 0.7-deg behind the opening 17 days of August a year ago.  Daylight continues to shrink slowly seasonally. Today see 2 minutes and 30 second less potential daylight than yesterday.

HERE’S MY LATEST THURSDAY CHICAGO METRO FORECAST (8/17/2023):

TONIGHT: Clouds scatter and diminish and gusty wind subside. Cooler and less humid overnight. Low 58—with some low and mid 50s cooler inland locations.

FRIDAY: Beautiful! Generous sunshine but with haze due to wildfire smoke aloft and just a scattering of puffy summertime fair weather cumulus clouds. Seasonably warm in the afternoon with low humidities. High 83—but mid to upper 70s beaches.

FRIDAY NIGHT: Partly cloudy. Low 62.

SATURDAY: Mostly sunny, turning breezy and warmer.  Gusty SW winds override any lake cooling. High 88.

SUNDAY and MONDAY: Mostly sunny, hot and noticeably more humid. Late morning and afternoon easterly lake breezes tempering the heat a bit along Lake Michigan and on area beaches. High Sunday 95.  Monday’s high 90—but low to mid 90s well inland.  Shoreline highs in the 80s.  Peak heat indices—especially Sunday and inland—in the low 100s.

TUESDAY: Mostly sunny, hot and humid. High 92—modestly cooler lake shore.

WEDNESDAY: Becoming partly sunny, breezy, hot and humid. High 94.

WEDNESDAY NIGHT AND THURSDAY: More clouds, continued humid. Growing prospects for some clusters of t-storms. Low Wed night 74.  High Thursday 88—but lower lakeshore.