(11:45AM - 3/16/21) A storm system will move through the region Wednesday into Thursday, bringing a low end severe t'storm threat to the southern half of the state and windy conditions to Northern and Central Illinois.
A storm system will move from the Plains on Wednesday, into the Ohio Valley on Thursday. The northern side of a larger and more significant severe t'storm risk to the south will reach into the southern half of the state, with a low end severe t'storm threat being possible Wednesday afternoon through Thursday morning. Additionally, a period of windy conditions are expected across Northern and Central Illinois, Wednesday evening through Thursday evening.
Scattered showers and t'storms will spread across Southern Illinois Wednesday morning into Wednesday afternoon, as a warm front lifts towards and into Southern Illinois. In the wake of this early activity and with the warm front in the vicinity, a marginal environment will develop. This marginal environment will feature low instability, modest moisture and great shear. Scattered showers and t'storms that develop along a cold front across Missouri and Arkansas during the afternoon, will spread across the southern half of the state Wednesday evening through early Thursday morning. Given the aforementioned marginal environment in place, a low end severe t'storm threat will exist with this activity, with a few severe t'storms being possible. Hail, damaging winds and an isolated tornado will be possible with any severe t'storm.
In addition the the severe t'storm potential, windy conditions are expected Wednesday evening through Thursday evening across Northern and Central Illinois. High winds aloft, characterized by a low level jet of 40-60KT, will be in place. The amount of mixing will be limited, thus preventing even higher winds. However, expected mixing depth will support northeasterly wind gusts of 25-45MPH across Northern and Central Illinois, Wednesday evening through Thursday evening.
Below is the severe t'storm and wind forecasts for this event.