(12:30AM - 12/15/19) The expected winter storm is set to move across the region Sunday through Tuesday, bringing several inches of accumulating snow to a large portion of the state during this time, as well as some ice.
With this update no significant changes were made...only small/fine-tuning to expected snowfall amounts. Model guidance is in fairly good agreement overall, with just some minor differences.
This winter storm will come in two distinct parts...
Part 1: As a lead disturbance ejects out into the region, an area of snow is expected to enter Western and Southwest Illinois by late morning to midday Sunday. This area of snow will then spread across Central Illinois during the early afternoon, continuing through Sunday night or early Monday morning. Periods of moderate to heavy snow, with snowfall rates of 1"/hour, will be possible during this time. Some light snow may also make it into portions of Northern Illinois for a time, Sunday evening and night. Across Southern Illinois, mixed precipitation is likely during this time-frame, in the form of rain/snow/freezing rain.
A lull in the snow and mixed precip will likely occur for much of the state, during a couple to several hour period of time Monday morning.
Part 2: As the main disturbance ejects out into the region, another area of snow will push into Central Illinois later Monday morning, then continuing through Monday evening, before ending later Monday night or early Tuesday morning. Once again, periods of moderate to heavy snow, with snowfall rates of 1"/hour, will be possible during this time. Across Southern Illinois, mixed precipitation is likely during this time-frame, in the form of rain/snow/freezing rain. Monday morning and evening rush hour travel will likely be significantly impacted across Central and possibly Southern Illinois.
A large swath of 3-6" snowfall totals will be likely across the heart of the state, with a corridor of higher snowfall amounts of 6-9” possible. On either side of the main axis, amounts will quickly taper. Additionally, some ice accumulation is likely across Southern Illinois, with the potential for in excess of 0.10" for some areas.
Below is the TAM snowfall and ice forecasts for this winter storm.