(10:45PM - 3/14/21) A storm system will be moving through the region through Tuesday, bringing a snow event to Northern Illinois and windy conditions to the state.
A storm system will move from the Plains tonight and into the Ohio Valley by Tuesday morning. This storm system will bring a period of precipitation to the state tonight through Monday night, and windy conditions to the state through Monday afternoon. Model guidance continues to be in some disagreement regarding thermal profiles and snowfall amounts across Northern Illinois. However, all other aspects of the storm system have high agreement.
An area of precipitation will first enter Northwest Illinois late tonight/very early Monday morning. Precipitation will likely start as rain, before changing over to snow. This precipitation will then spread across the remainder of Northern Illinois Monday morning, also starting as rain or a mix, before changing over to snow. A period of snow is then expected across a good portion of Northern Illinois along/north of I-80, Monday morning through Monday afternoon. Snow will be of varying intensity during this time. This will be a heavier/wetter, with marginal temperatures expected, which will lead to some melting as the event is ongoing. Snow will then end Monday evening, potentially as a mix in some areas. Further south, along/south of I-80, after beginning as rain earlier Monday morning...Precipitation will likely be a mix of rain/freezing rain/sleet/snow for much of the event.
In addition the the snow potential, windy conditions are expected tonight through Monday afternoon. 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, tonight through Monday afternoon.
An axis of snowfall totals of 2-5" are expected norther of I-80 in Northwest and North-Central Illinois, with locally higher amounts possible. Snowfall amounts of 1-3" are expected in Northeast Illinois. Snowfall amounts will taper near and south of I-80. Near and south of I-80, there will also be minor sleet of a few tenths and freezing rain accumulation up to a glaze possible.
Below is the snow and wind forecasts for this event.