Spells of rainfall in Chicago over coming days are to accompany the arrival of Gulf moisture. But rainfall coverage and intensity is to vary in the Chicago area from day to day—maximizing Friday, dropping off as NE winds off still chilly Lake Michigan stabilize the air mass a bit Saturday. Rains will diminish to sporadic drizzle or sprinkles—and even stop at times Saturday. Then a surge of moist air up and over AN UNSEASONABLY COOL, FULL FETCH (that means “full length of Lake Michigan” flow into Chicago Sunday is likely to see rain coverage increase again Saturday night into Sunday.
FOLLOW THE LATEST SPRING STORM AND ITS PRECIP’S MOVEMENT in the series of FORECAST MAPS below (produced by the National Weather Service’s GFS ensemble model.) as it progresses from 7am CDT Friday to 7am CDT Monday, when precipitation has moved out, sunshine’s back and east winds off Lake Michigan will ease to allow temporary warming
HEAVIEST RAINS TO FALL IN THE PLAINS
Flood watches are out in those areas as you can see in the accompany watch/warning map:
CHICAGO: Looking Into Next Week
Rain scatters and ends later Sunday and Sunday night and we enter a dramatically different upper air steering pattern next week being driven by the build-up of a huge dome of unseasonably warm air over western Canada next week.
Such warm air domes produce northward buckles in the jet stream around the warm air’s periphery. The steering winds which sweep southward on the east side of such a warm dome latch on to cooler air which is then forced southward into the Midwest.
This sets up a situation where summer like warmth breaks high temp records over western Canada while unseasonable chilly air takes control in Chicago.
WARMING INDICATED IN THE WEEK WHICH FOLLOWS
Not to worry warm weather fans. The wavy jet stream pattern around the west Canadian warm air dome flattens in the week which follows and this is likely to produce significant warming here the week after next with temps likely to surge to 80 degrees—perhaps warmer.
So buckle up. We in for a some varying temps in the coming two weeks!
VIEW SLIDESHOW OF THE COMING WEATHER DEVELOPMENTS:
FOLLOW THE LATEST SPRING STORM AND ITS PRECIP’S MOVEMENT in the series of FORECAST MAPS which follow (produced by the National Weather Service’s GFS ensemble model. THIS PANEL verifies at 7am CDT Friday 
7pm CDT Friday evening 
7am CDT Saturday morning 
7pm CDT Saturday evening 
7am CDT Sunday morning 
7pm CDT Sunday evening 
7am CDT Monday–Precip has moved out, sunshine’s back and east winds off Lake Michigan have eased allow temporary warming 
ESTIMATED TOTAL PRECIP based on a National Weather Service model blend. These are anticipated precip totals through Monday 
National estimated precip from a computer model blend showing the heaviest rain totals likely to occur in the Plains–a number of those areas involved in drought. 
NOTE THE FLOOD AND TORNADO WATCHES (shaded green and yellow respectively) in effect late Thursday. 
Note the drought area over the Plains where, interestingly, rains and t-storms are being predicted in coming days. 
DAY 1 (Thu through Thu night) SEVERE WEATHER RISK forecast 
DAY #2 (Fri through Fri night) SEVERE WEATHER RISK FORECAST 
A HUGE DOME OF WARM/HOT AIR is to take shape over western Canada in the coming week which ‘BUCKLES” the jet stream–producing a sharp ridge over western North America. With the jet buckling north into the arctic then plunging southward into the Midwest, this sets the stage for a BELOW NORMAL OVERALL TEMP REGIME next week (even though 60s and 70s are to occur the opening 2 days of next week before the cooler air sweeps in. The coming weekend will see temps drop because of clo… See more 
FORECAST UPPER AIR Sunday night 
UPPER AIR FORECAST next Thursday morning 
UPPER AIR FORECAST Saturday evening forecast 
Here’s why we expect WARMING the week following next week. The “wavy” jet stream flattens out–turning westerly and sending warmer air across the country 
CHECK OUT HOW MUCH ABOVE NORMAL ground level temps are to be under the developing warm air dome in western and central Canada Tuesday next week 
FORECAST GROUND LEVEL TEMP DEPARTURES a week from Sunday over western Canada–showing temps there WELL ABOVE NORMAL 
24 t-storm probabilities for the period ending 7am CDT Saturday 
Day 1 to 5 FORECAST TEMP DEPARTURES per the NWS GFS ensemble model 
Day 6 to 10 FORECAST TEMP DEPARTURES 
DAY 11 to 15 FORECAST TEMP DEPARTURES
Abnormally Dry in Parts of the Chicago Area
Lack of widespread rainfall has parts of the Chicago area labeled “abnormally dry” by the latest weekly drought monitor:
Extreme, to locally exceptional drought conditions persist across sections of the Plains states:
Chicago rainfall tally April 1-May 11: 2.31″ vs NORMAL of 5.37″—–only 43% of normal
Chicago rainfall May 1-11: 0.29″ vs NORMAL of 1.62″—–18% of normal
Source: National Drought Mitigation Center (NDMC) at the University of Nebraska-Lincoln, the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Department of Agriculture (USDA).
