(11:50PM - 12/13/19) A winter storm is set to move across the region Sunday and Monday, bringing accumulating snow to a good portion of the state during this time.
As seems to be the norm these days, model guidance has been significantly struggling with this expected storm system over past several days. More recently, a majority of guidance has honed in on a general overall idea regarding how this winter storm will evolve. Even with that, it should be noted there is some guidance that is not in agreement, and instead shows either weaker/south or amped/northern solution. At this time those solutions are limited and have been ruled outliers...but it goes to show that there is some disagreement still even at this stage, less that 48 hours away from the first flakes falling in the state.
A large area of snow is expected to begin to enter Western and Southwest Illinois by early Sunday afternoon. This area of snow will overspread much of Northern and Central Illinois Sunday afternoon, continuing through evening. There is the potential for a lull in the snow Sunday night, but this is not a certainty. If a lull does occur, snow would then re-develop and spread across Northern and Central Illinois Monday morning, continuing into the afternoon, before coming to an end. Further south, a mix of precipitation will be likely across Southern Illinois; including snow, ice and rain.
At this time is appears likely that a swath of 3-6" of snow will be likely across the heart of the state, with totals tapering to the north and south of this axis. Additionally, minor ice accumulation will be possible across Southern Illinois.
Below is the TAM snowfall forecast for this event.