Tue-Wed, Dec 29-30th Winter Storm Recap

(4:30PM - 1/5/21) A brief recap regarding the Tue-Wed, December 29-30th winter storm that affected portions of the state with significant snowfall and ice accumulation.

Overview...
A weak and loosely organized storm system ejected out from the Plains on Tuesday (Dec. 29th), and tracked northeastward into the Great Lakes by Wednesday (Dec. 30th). With cold air initially in place, snow was favored for a several hour period of time across Northern Illinois, before transitioning to mostly sleet and freezing rain. Across Central Illinois a period of snow/sleet/freezing rain occurred for a short time, before changing to rain.

Summary...
A large area of precipitation spread across the state, Tuesday afternoon through Wednesday afternoon. Precipitation, in the form of snow, first spread into Northwest and Western Illinois early Tuesday afternoon. Precipitation then quickly spread further across the remainder of Northern and Central Illinois the remainder of Tuesday afternoon, with much of it falling as snow across Northern Illinois and a wintry mix across Central Illinois. As warm air advection increased Tuesday evening, snow turned to a wintry mix (snow/sleet/freezing rain) across Northern Illinois, with the wintry mix having turned to all rain across Central Illinois. By Wednesday morning as warm air advection continued, a wintry mix (snow/sleet/freezing rain/rain) continued across Northern Illinois, with precipitation having ended by Wednesday afternoon.

An axis of snowfall totals of 6-12" occurred across the region, including across Northwest Illinois...With amounts gradually tapering with southward extent across Northern Illinois. An axis of ice accumulation of 0.10-0.25"+ occurred across a large portion of Western and Northern Illinois. This ice accumulation lead to some tree damage and power outages for some areas.

Below are map representations of final forecasts an observed snowfall and ice totals across the state and adjacent areas. 

JP