A Winter Storm Warning is in effect beginning at 9 p.m. Sunday for an intense and dangerous lake-effect snowstorm that is vastly out-of-the-ordinary for this time of year in Chicago.
The Winter Storm Warning will be in effect through noon Monday for the entirety of Cook County, as well as eastern Will County, Kankakee County, and through 6 p.m. Monday for Lake and Porter counties in Indiana.
Intense lake-effect snow bands will move onshore and intensify after 9 p.m. Sunday. Near whiteout conditions will be seen at times through the night and into Monday morning.
Snowfall rates of 3 inches per hour are possible. Snow totals of 8 to 12 inches are expected in areas where lake effect snow plumes form. In areas where they linger, localized totals could be much higher, topping out at 12 to 18 inches — or 1 to 1.5 feet — at the edge of Lake Michigan.
Northwest winds of 35 mph could bring whiteout conditions and hazardous travel, and even thundersnow getting into Sunday night.
Travel conditions near the lake will be next to impossible where the intense bands form into the Monday morning rush.