Warmth to continue through Saturday then a windy temp drop Sunday & Monday
WHAT A WEDNESDAY—FIRST 80-DEGREE HIGH OF 2023; WARMEST CHICAGO HIGH SINCE LAST SEPT 21st (NEARLY 7 MONTHS) AND THE WARMEST APRIL 12th in 46 YEARS!
Wednesday’s Temperatures: How much above normal?
Another gloriously sunny day with July level warmth is predicted Thursday–then more clouds mix with the sun Friday and Saturday as Gulf moisture flows into the area. But it’s Saturday which sees our first rain prospects–and there are signs the near 60-deg dew point–a measure of atmospheric moisture which suggest a far more “humid” feel to the atmosphere is likely later Saturday. That’s also when an approaching cold front may put together the ingredients for some t-storms in the Chicago area.
We have a REX BLOCK in place aloft
That’s a blocking pattern with a big dome of warm air over Lower 48 deflecting the storm-carrying jet stream to the north and a wet low pressure system on the Gulf Coast to the south. Blocking patterns in the atmosphere slow the progression of air masses, In this base, a BLOCKING PATTERN is GOOD NEWS because it locks the warm air in over Chicago through Saturday,
–In time, the air mass is to humidify—with Gulf moisture gradually moistening the air mass. Dew points, which have been limited to the 40s—indicating DRY AIR in place—-will continue in that range Thursday, which should be another glorious day with limited cloud cover and bountiful sun—but then creep higher, reaching the low to mid 50s Friday and to near 60 later Saturday. A 60-deg dew point indicates enough moisture has moved in to make the air FEEL more humid.
—That too should fuel shower development Saturday and the rains could grow thundery as a cold front approaches Saturday night and jet stream winds shift into the Midwest airspace Saturday afternoon and evening with cooling temps aloft further destabilizing the atmosphere. If some strong t-storms are going to develop, this will be the period to watch.
Cooler Air Arrives Sunday-Monday
VERY WINDY, MUCH COOLER AIR SWEEPS IN SUNDAY INTO MONDAY with gusts approaching or topping 40 mph each day a real possibility. And spotty instability showers Sunday afternoon or evening could even mix with a few snowflakes later Sunday night into Monday morning.
VIEW SLIDESHOW OF WARMTH AND UPCOMING COOL-DOWN WITH SHOWERS AND POSSIBLE SNOWFLAKES AHEAD:
PREDICTED THURSDAY TEMP DEPARTURES showing another day of 20+-deg ABOVE NORMAL TEMPS in Chicago 
FORECAST HIGHS THURSDAY 
HERE’S HOW MUCH WEDNESDAY TEMPS WERE FROM NORMAL—More than 20-deg ABOVE NORMAL in Chicago 
HIGHS WEDNESDAY 
DOME OF WARM, DRY AIR BETWEEN A GULF COAST SYSTEM AND A NORTHERN ROCKIES STORM–Each lift air which vents out the top of their precip-bearing clouds, migrates away from those systems then sink, warms and dries over the Plains and Midwest producing our unseasonably warm air! 
24 HOUR T-STORM CHANCES SAT & SAT NIGHT–with the highest concentration of rains Sat afternoon into Sat night. 
FORECAST FRIDAY HIGHS 
WATCH AS MOISTURE SWEEPS INTO THE CENTRAL U.S. IN COMING DAYS–This panel is the forecast of precipitable water (i.e. moisture in the lowest 30,000 ft. of the atmosphere) at 7am CDT Thu 
7am CDT Friday 
7pm CDT Fri 
7pm CDT Saturday 
7am CDT Sunday 
HERE ARE DAY TO DAY FORECASTS showing the shower and t-storms which will have moved across the Chicago area ahead of a pre-dawn Sunday temp drop. This panel is the forecast for 7am CDT Sunday 
1pm CDT Sunday 
Forecast map 7pm CDT Sunday 
1am CDT Monday morning 
7am CDT Monday morning–Note the potential for some mixed snowflakes 
