(10:00PM - 1/13/21) A storm system will move through the region Thursday through Saturday, bringing a minor/nuisance accumulating snowfall to a large portion of the state.
A storm system is expected to develop in the Midwest on Thursday, quickly becoming occluded and vertically stacked as it meanders around the Midwest Thursday through Friday, eventually sliding through the Great Lakes on Saturday. A shield of precipitation that develops out west will spread across the state on Thursday, as the storm system initially moves into the region. As the storm system occludes and becomes vertically stacked, precipitation will continue to wrap around the storm system and across a large portion of the state, Thursday into Saturday. A period of rain is expected along the front portion of the precipitation shield on Thursday, before changing to snow for the rest of the event for affected areas. Model guidance has been all over the board with this storm system the past several days, but guidance has finally started to converge on a general outcome. With our initial forecast this morning we hedged towards what was a small consensus for a minor/nuisance accumulating snowfall for portions of the state, and given model trends through the day, it appears that was a good call...As model guidance is converging on a scenario which keeps the storm system tracking and meandering to our north/west, which would keep any snowfall on the minor side.
A shield of precipitation that develops out west will first spread across the state, from Thursday morning into Thursday night. It is likely that precipitation will initially start as period of rain for Northern and Central Illinois Thursday morning through Thursday afternoon/evening, before steadily changing over to snow Thursday evening/night. Behind the aforementioned initial shield of precipitation, periods of snow and snow showers are then expected across Northern and Central Illinois from Thursday night into Saturday afternoon, as the storm system becomes occluded and vertically stacked. Snow showers will possibly even make it into Southern Illinois, Friday morning into Saturday afternoon. Periods of snow and snow showers across the state will come to and end by Saturday evening.
Final snowfall totals upwards of 1-3" are expected across portions of far Northern Illinois, tapering to a dusting to 1.5" or so across the rest of the state.
Below is the snowfall forecast for this event.