RECORD BREAKING WARMTH in CHICAGO! FLOOD WATCH in effect!
Thundery downpours threaten up to 1.50" of additional rainfall Wednesday night
Temperatures have soared into the 60s across the southern half of the metro area---from Chicago south. Chicago's record high temp for the date (January 12) is 62-degrees set back in 1890--a reading within striking distance this afternoon. At the Midway Airport National Weather Service observation site, official observer Frank Wachowski reports the 2:20 pm Wednesday temp of 61-degrees has easily eclipsed the old record high there of 58-degrees in 1960.
A cluster of t-storms, which erupted in northern Kendall County around 7:30 am this morning raced northeastward into Cook County by 8:50 a.m. The storms, which towered to as much as 43,000 ft. according to Doppler radar scans here earlier today, produced more than 120 cloud to ground lightning strokes strokes in the city alone according to the area's lightning detection system, each accompanied by sharp crashes of thunder. Oakbrook saw 0.61" of rain and pea sized hail in the storm-generated downpours.
The warmth has eliminated much of the snow cover over the southern half of the metropolitan area while snow continues on the ground to the north--though substantial melting is underway and the run-off coupled with up to 1.50" of additional rainfall due to begin later today and tonight. These photos of this morning "advection fog" from weather observer Mary Anne in Remington, Indiana illustrates the interaction between lingering patches of snow on the ground and the incoming unseasonably warm, moist air. Fog cut visibilities at Remington to 100 ft. for a time this morning and visibilities of less than a tenth of a mile were widely reported over the metro area, especially the most heavily snow covered north and west suburban locations. Advection fog forms when warm air streams up and over the cold snow covered surface and undergoes cooling. This lowers temps to the dewpoint, which is the temperature at which the air holds all the moisture it can.
Eastbound hail and downpour generating t-storms to Chicago's west as of mid-afternoon, and which are also producing prolific lightning discharges, are an indication of the weather headed this way later Wednesday and Wednesday night. Heavy rainfall and the runoff from melting snow threaten to produce extensive flooding on area rivers. Standing water may also accumulate on roadways, particularly those with sewers clogged by ice.
Tom Skilling, WGN-TV/Chicago Tribune meteorologist
