Wednesday afternoon’s 11-degree increase over Tuesday just the start—atmospheric pattern undergoing huge changes which are to continue boosting temps—warming to be muzzled by easterly winds off 46-degree lake waters—shifting pattern to bring spells of wetter weather into the area Sunday and next week
Each of the coming 15-days is to post a temp surplus as North America’s upper air pattern undergoes a MAJOR CHANGE. The atmospheric blocking aloft is breaking down. This is allowing the Chicago area freedom from the dominance of a mammoth spring storm which crept across the area at a snail’s pace since last Friday.
TO DATE, May has posted an 8-degree deficit and is running 2.7-degrees cooler than the opening 3 days of the month a year ago.
PATTERN SHIFT BRINGS CHICAGO UNDER THE CONTROL OF THE SOUTHERN JET STREAM
That plus the development of blocking pattern as a huge dome of warm air develops over Canada next week means access to chilly air to our north is over for the forseable future.
At the same time, a more westerly flow aloft, something which is to continue through next week and beyond, is to send milder air into Midwest.
CHECK OUT THIS GOES WEST ANIMATION showing the streams of moisture onshore: https://rammb-slider.cira.colostate.edu/?sat=goes-18…
What chill DOES OCCUR in and around Chicago will be the product of winds off Lake Michigan’s 46-deg water–and that’s to happen due to easterly winds blowing ashore into lakeside areas.
WEEKEND TO BE 15-DEGREES MILDER THAN LAST (THOUGH WITH COOL LAKE BREEZES IN SHORELINE AREAS)—AND NEXT WEEK IS TO COME IN 12-DEGREE WARMER THAN THIS WEEK
Slideshow of the Developing Pattern
The highlighted storm system is the spring system which lingered over the Midwest producing winds, clouds, sporadic showers and unseasonably cool temps in Chicago, heavy snows in the Upper Midwest, the deadly downstate I-55 dust storm Tuesday near Springfield and the first EF3 tornado to hit Virginia Beach, Virginia. The atmospheric blocking pattern which slowed the storm’s movement for days is breaking down. 
Here’s the retreating spring storm which has regenerated off the East Coast. 
This Wed afternoon satellite derived precip analysis comes from CIMSS (the Cooperative Institute for Meteorological Satellite Studies) at the University of Wisconsin-Madison. 
This 7am CDT Wednesday morning UPPER AIR ANALYSIS from Environment Canada shows bi-coastal storm systems—one moving off the Eastern Seaboard and a second closing in on California from the Pacific. 
Closer look at the 7am CDT 34,000 ft. upper air set-up Wednesday morning 
Wednesday afternoon temps across the U.S. 
An analysis of the 24 hour temp change over the Lower 48 and Canada through Wednesday afternoon 
Surface winds Wednesday afternoon 
TEMP DEPARTURES Wed afternoon showing how far temps at the time were from “normal”. 
FORECAST of TEMP DEPARTURES for Days 1-5 off the National Weather Service’s GFS ensemble model 
Day 11 to 15 FORECAST TEMP DEPARTURES 
Here are the predicted high temp departures over the 50day period from Friday through next Wednesday 
Predicted TEMP DEPARTURES over the 6 to 10 DAY period 
FORECAST HIGHS Friday 
HIGHS Sat 
Highs Sunday 
Highs Monday 
Highs Tuesday 
Highs Wednesday 
Highs Thursday 
A good look at the storm system coming onto the West Coast. 
