A look at the latest WGN in-house RPM model shows the rain changing to snow in the next few hours changing to heavy snow in the post midnight hours The heavy wet snow is expected to accumulate rapidly overnight with total accumulation ranging from 1 to 4 inches north and west to the city to 4 to 8 inches in areas from the city and south. Some of the snow will be accompanied by thunder and will fall intensely with accumulation of 1 to 2 inch an hour possible.
Travel conditions will quickly deteriorate after the snow begins and strong gusty northeast winds will cause some blowing and drifting of the snow. The snow is expected to taper to flurries by early Wednesday morning but cause problems for the morning commute.
Winter storm warninga are posted for much of the Chicago Metro area with the exception of areas well north and northwest of the city.
Lemont- Pea size hail at 127th and Archer at 9:13pm
The opening round of tonight winter storm is spreading into the Chicago area this evening in liquid form as a band of showers and thunderstorms, some with small hail, arrive. However, to the north across far southern Wisconsin the precipitation is changing over to snow.
At 9pm snow or sleet was being reported at Racine, Milwaukee, Burlington and Waukesha. As colder air filters into the area, coupled with cooling from evaporation and cooling from increasing vertical motion, the precipitation in the Chicago area should change over to snow later this evening north of the city and in the post midnight hours from the city and areas south.
At 8:30PM CDT numerous showers and a few thunderstorms have developed in the past hour back to the west and southwest of Chicago (see current weather radar above). The showers are moving east-northeast, and should reach the Chicago area within the next hour or so. Some will produce pea-size hail. So far this evening pea to marble-size hail has been reported at Morris, Mendota and Princeton and Galva.
At the same time temperatures have fallen into the mid to upper 30s area-wide as strong northeast winds continue to pull cold air off the icy cold Lake Michigan. Chicago-area dew-points have settled into the upper 20s to lower 30s for the most part.
So the stage is set for a cold rain to settle into our area with a changeover to sleet and then a wet snow still looking viable later this evening.
8:15PM CDT temperatures
Update 7:25PM CDT..
As of 7PM CDT temperatures at O’Hare and Midway had fallen 11-degrees from their afternoon highs – to 38 and 39-degrees respectively. Northerly Island and Waukegan had dropped to 35-degrees. Most of the area temperatures were in the mid to upper 30s.
Note on the weather radar picture above a narrow band of showers was approaching the Ottawa area moving east-northeast and widely scattered areas of light rain were moving out of Wisconsin into northern Illinois.
Note 7:15PM CDT temperatures..
At 6PM CDT northeast winds off the cold waters and ice on lake Michigan were gusting to 3ern illinois.0 miles an hour at O’Hare and 28 miles an hour at Midway Airports where temperatures had dropped to 41 and 40-degrees respectively.
The Chicago area temperatures at 6:15PM CDT displayed below indicate Chicago-area readings have dropped into the upper 30s at several locations. Temperatures will continue to fall into the middle and lower 30s as the evening goes on – and the window of rain changing over to snow will be shortened considerably as the cool-down occurs this evening.
The latest heavy snow probability chart issued by the National Weather Service Weather Prediction Center Has Chicago and areas south and east included in the area of highest chance of 4-inches or more snowfall during the next 24 hours. Chicago is included within the 70-percent or greater probability (area encircled in red) that extends east through the lower Great Lakes up the St. Lawrence Seaway. The 40 to 70-percent chance of 4-inches or more is outlined in green and includes most of the Chicago area and much of northern Illinois east through a good portion of Indiana and Ohio into Pennsylvania.
The second chart shows the potential areas of 8-inches or more snow in the next 24 hours – and a good portion of the Chicago area is included in the 10 to 30 percent probability area (inside the blue outlined area).
Update 4PM CDT…
The Winter Storm Warning for 4 to 8-inches of snow or even more in a few locations associated with thunder-snow has been extended south and east into central Illinois and across the northern half of Indiana – valid from 10PM CDT this evening until 1PM CDT Wednesday. Northeast winds gusting to 40 miles per hour will cause considerable blowing and drifting and cut visibility to near zero at times. Below is the latest Chicago-area Winter Storm Warning (pink-shaded area) and Winter Weather Advisory 3 to 6-inches of snow in purple-shaded counties.
The center of lowest pressure is “winding up” in southeastern Kansas – set to move east through central Missouri this evening. A warm front extends east out of the low center through central Missouri and Illinois into Indiana and northwest Ohio.
A huge temperature differential exists across the warm front with readings in the 70s along and to the south of the front (Springfield and Decatur were around 70-degree at 4PM), while to the north temperatures drop off quickly into the 50s – resting in the 40s across the Chicago area. Strengthening northeast winds (already gusting over 25 miles per hour) pulling cold air off the ice-covered, 30-degree waters of Lake Michigan – will eventually force our temperatures into the 30s.
Rain is still forecast to spread across the Chicago area this evening – quickly turning over to sleet and then accumulating snow. Travel will quickly become hazardous later this evening as the snow builds up, roads become slush-covered and icy and strong winds cause blowing and drifting as well as cutting visibility.
Heavy wet 6 to 8-inch snowfall is forecast to hit the Chicago area tonight and Wednesday forenoon. A combination of a Winter Storm Warning and a Winter Storm Advisory valid from 10PM CDT this evening until 1PM CDT Wednesday has been issued by the Chicago National Weather Service Forecast Office.
The Winter Storm Warning for 6 to 8 inches (locally up to 10-inches possible in thunder-snow) covers much of the Chicago area, while the Advisory covers areas to the north, with lightest amounts in the 1 to 3-inch range anticipated to the far northwest at the Illinois-Wisconsin border along the northern fringe of the snow system. Embedded thunderstorms, especially in southern areas will cause temporary locally heavy, white-out conditions.
A low pressure system is forecast to track out of the central plains up the Ohio River Valley tonight and Wednesday, spreading first rain across the area and then as colder air feeds into the system on the wings of the strengthening northeast flow, the rain will change to sleet and then heavy wet snow later this evening and overnight. Blowing and drifting caused by 25 to 40 mile-per-hour northeast winds will cause near-zero visibility at times and create treacherous travel/driving conditions. The snow will be ending from west to east across the area Wednesday forenoon, but the morning commute will most likely be severely impacted, especially closer in to the city and south.
The map below shows the Chicago area with the Winter Storm Warning in pink, the Winter Weather Advisory in purple, and a Winter Storm Watch (that will probably soon be updated to a Warning or Advisory) in dark green. Winter Storm Warnings/Advisories/Watches have been or will be issued farther east through Ohio and Pennsylvania.
Larger picture of Winter Warnings/Advisories/Watches