(11:45AM - 12/30/20) A storm system will move through the region on Friday, bringing the chance for accumulating snow 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 on Thursday night, 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 Thursday night/early Friday morning through late Friday night. Precipitation will range from snow and ice across Northern Illinois, to ice and rain across Central Illinois, to rain across Southern Illinois. Model guidance has been generally split in two camps regarding this event, with a consistent more southerly group and a northern group, which has been trending south. Given observations, trends and the consistency of the southern group of model guidance, have opted to generally base our forecast on a more southerly solution. This more southerly solution will lead to a more widespread wintry threat across the state.
Freezing rain will spread into Northern Illinois, late Friday morning/early Friday afternoon. Freezing rain is expected across Northern Illinois from late Friday morning/early Friday afternoon through Friday evening. As colder air filters in, freezing rain will transition to snow across much of Northern Illinois. Snow will then continue into Friday night, before ending.
Late Thursday night/early Friday morning 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 late Thursday night/early Friday morning through late Friday morning/early Friday afternoon. By late Friday morning/early Friday afternoon temperatures will warm enough to change the freezing rain over to rain. Periods of rain will then continue into early Friday night, potentially ending as mixed wintry precipitation.
Rain will first push into Southern Illinois early Thursday night. 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 snowfall totals upwards of 1-3" are expected in an arc across Western and Northern Illinois. Widespread ice accumulation of 0.10-0.25"+ is expected across a large portion of Northern and Central Illinois. Wind gusts of 20-35MPH, combined with the expected ice accumulations, may lead to some tree damage and power outages for some areas.
Below is the snowfall and ice forecasts for this event.