Earlier post: Chicago under Winter Weather Advisory; Southern sections including NW Indiana under Winter Storm Warning
The National Weather Service has upgraded the winter storm watch to a Winter Storm Warning for Chicago's southern suburbs and northwest Indiana that includes the counties of Ford, Iroquois, and Kankakee counties in Illinois and Benton, Jasper, Lake, Newton, and Porter counties in Indiana.
A clipper system from the north will merge with a developing low pressure system to the south to produce a winter storm across the Great Lakes and Ohio Valley regions today through Sunday. Light snow from the clipper system will overspread the region from west to east early this afternoon and will continue through this evening. A low pressure system will develop across southern Missouri/northern Arkansas late tonight. This low will track northeastward into southern Indiana and through Ohio on Sunday. With an already cold airmass in place and moisture being drawn into the system, an area of moderate to at times heavy snow will develop across the mid-Mississippi and Ohio Valley on late tonight through Sunday.
The track of this storm system favors the southern sections of the Chicago area to see the heaviest snow amounts. Locations along and south of Interstate 80 could see 5-10 inches of snow while areas north of Interstate 80 will see anywhere from 2-5 inches of snow. Areas to the north including the counties of Cook, DuPage, Will, Grundy, Kendall, and La Salle have been placed under a Winter Weather Advisory through Sunday night.
Potentially Historic Cold Sunday night through Tuesday night
A dangerously cold, possibly record breaking cold airmass will move into the region Sunday night and will lock into the region through Tuesday night. It's an airmass that will result in both high and low temperatures Sunday night through Tuesday night well below zero with wind chill readings 30 to 40 below zero.
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