Tue, April 20th Late Season Snow Event update #4

(9:45PM - 4/19/21) A storm system moving through the region on Tuesday will bring a minor late season snowfall to a large portion of the state, early Tuesday morning through early Tuesday night.

Summary...
A storm system will eject out from the Plains tonight, then moving eastward through the Mid-Mississippi Valley and Ohio Valley on Tuesday, and then into the Eastern Great Lakes by Wednesday morning. Model guidance continues to be in generally good agreement regarding the location of the snowfall axis and snowfall amounts. The main change this update was to re-introduce the possibility for a dusting of snow to Northeast Illinois, where model guidance is now honing in on the potential for convective and trough enhanced snows.

Forecast...
An area of precipitation will spread across a large portion of the state, early Tuesday morning through early Tuesday night. While much of this precipitation will fall as snow across the state, the very front end of the precipitation early Tuesday morning and the very back-edge of precipitation Tuesday evening, could be rain or a rain/snow mix. Snow will be of varying intensity during the event, though generally being light to moderate, possibly even mixing with rain at times, given the marginal thermal environment. Given it is mid-late April (Mild ground temps and sun angle of issue) and air temperatures will be marginal, greatest snowfall impacts and accumulations will be on colder surfaces, such as grass.

Additionally, across Northeast Illinois, there is the potential for scattered convective rain/snow showers in the vicinity of a trough axis expected to develop on Tuesday.

​What's expected...
A main axis with snowfall totals of 1-3" are expected across Central Illinois, with amounts tapering north and south of this main axis.

​Below is the snow forecast for this event.

JP