(10:30AM - 3/15/21) A storm system will be moving through the region through Tuesday, bringing a snow/sleet/ice event to Northern and portions of Central Illinois and windy conditions to much of the state.
A storm system will move from the Plains today and into the Ohio Valley by Tuesday morning. This storm system will bring a period of precipitation to the state through tonight, and windy conditions to the state through later this afternoon. Model guidance and real time observations suggest the forecast is on track for the most part.
An area of precipitation has been spreading across Northern Illinois this morning. Precipitation has been a mix of snow/sleet/freezing rain, with generally all snow across far Northwest Illinois. This area of precipitation will continue to spread across Northern Illinois through this evening, continuing as a mix for many areas, with the exception being far Northwest and North-Central Illinois where all snow is expected. Periods of moderate to heavy snow will be possible at times across far Northwest and North-Central Illinois. Precipitation will fully come to an end across Northern Illinois tonight.
Further south across portions of Central and Eastern Illinois, enough evaporation cooling has been occurring to allow precipitation to fall as sleet/freezing rain for many areas East-Central Illinois. This precipitation will end by mid-afternoon.
In addition the the snow potential, windy conditions are expected through this evening. High winds aloft, characterized by a low level jet of 45-65KT, will be in place. The amount of mixing will be limited, thus preventing even higher winds. However, expected mixing depth will support easterly wind gusts of 25-45MPH across the state, through this evening.
An axis of snowfall totals of 1-3" is expected across Northern Illinois, with higher accumulation expected across Northwest Illinois where upwards of 2-5" or 4-7" is expected. Across other portions of Northern Illinois, generally from I-88 on south, minor sleet and ice accumulations are expected, in addition to tapering snowfall amounts.
Below is the snow/sleet, ice and wind forecasts for this event.