(11:45AM - 12/31/20) A storm system will move through the region on Friday, bringing accumulating snow/sleet to Northern and Western Illinois, and accumulating ice to Northern and Central Illinois.
A storm system is expected to eject out from the Southern Plains/Gulf Coast tonight, tracking northeastward through the Ohio Valley on Friday, and into the Eastern Great Lakes by Saturday. A large shield of precipitation will spread across the state, late tonight/early Friday morning through late Friday night. Precipitation will range from snow/sleet and ice across Northern Illinois, to ice and rain across Central Illinois, to rain across Southern Illinois. Model guidance is in overall decent agreement regarding this event. With this update we have increased both snow/sleet and ice amounts within each swath cutting across the state, as confidence in the given outcomes increases.
A mix of freezing rain, sleet and snow will spread into Northern Illinois, mid to late Friday morning. A freezing rain, sleet and snow mix is then expected across Northern Illinois from late Friday morning through late Friday afternoon. As colder air filters in, the mix will transition to snow across much of Northern Illinois. Snow will then continue into Friday night, before ending.
Tonight precipitation in Southern Illinois will spread northward into Central Illinois. With colder air in place, precipitation will be in the form on freezing rain. Freezing rain is expected across Central Illinois from tonight through late Friday morning. By late Friday morning temperatures will warm enough to change the freezing rain over to rain. Periods of rain will then continue into Friday evening, likely ending as mixed wintry precipitation Friday evening/early Friday night.
A mix of rain and freezing rain will first push into Southern Illinois early tonight, before transitioning to all rain overnight. Periods of rain will then continue through Friday evening, with an isolated t'storm being possible. Rain will then come to an end early Friday night.
Final snow/sleet totals upwards of 1-3" are expected in an arc across Western and Northern Illinois, with a higher corridor of 2-5" totals nosing into the Quad Cities area. Widespread ice accumulation of 0.10-0.25"+ are expected across a large portion of Northern and Central Illinois, with higher totals of 0.50"+ possible into Western Illinois.
Wind gusts of 20-35MPH are expected on Friday. These winds, combined with the expected ice accumulations, will likely lead to widespread tree damage and power outages for some areas across Northern and Central Illinois. Additionally, across portions of rural Northern Illinois a large amount of ice still remains on trees from the recent winter storm on Dec 29-30th...Which may exacerbate the potential for tree damage and power outages.
Below is the snow/sleet and ice forecasts for this event.