Sat-Sun, May 8-9th Mother's Day Spring Storm Update #1

(10:30AM - 5/8/21) A storm system will move through the region today and Sunday, bringing a low end/isolated severe t'storm risk, windy conditions, heavy rainfall and snow to portions of the state.

Summary...
A storm system will eject out across the Plains on today, then pushing through the Ohio Valley on Sunday. This storm system will bring a low end/isolated severe t'storm risk, windy conditions, heavy rainfall and snow to portions of the state. Model guidance continues to be in overall good agreement with all aspects of this storm system, with little to no change needed with this update.

​Forecast...
...Severe T'Storm Risk...

Saturday Night-Sunday Morning:
A complex of rain and t'storms that will be moving across portions of Nebraska, Kansas, Iowa and Missouri Saturday evening, is expected to southeastward across Central and Southern Illinois, overnight Saturday night and into Sunday morning. Ahead of this activity, elevated instability of 500-1,500J/KG and lapse rates of 7-9C will be advecting in. Combined with decent shear and decent forcing, this will allow for an isolated (level 1) severe t'storm risk to be possible across portion of far Western, far Southwest and far Southern Illinois...Overnight Saturday night and into Sunday morning. Damaging winds and hail will be the main threats.

Sunday Morning-Sunday Evening:
In the wake of early day activity, some clearing and destabilization may occurring ahead of the main storm system and trailing cold front. Additional scattered showers and t'storms are expected to develop along this cold front, across portions of Southern Illinois, Missouri and Arkansas. This activity will then push eastward, affecting Southern Illinois, Sunday afternoon and early evening. A marginal environment featuring instability of 250-1,000J/KG, dew points of 56-63, good forcing and good shear is expected to be in place. Given the aforementioned environment expected, this will set the stage for an isolated (level 1) severe t'storm risk across Southern Illinois, late Sunday morning through early Sunday evening. Hail, damaging winds and an isolated tornado will be possible.

...Windy Conditions...
High winds aloft, characterized by a low level jet of 45-70KT, will be in place. Mixing depths will support wind gusts of 30-45MPH across much of the state, Saturday night through Sunday afternoon. Winds will be northeasterly across Northern and Central Illinois, and southerly across Southern Illinois.

If that is not enough, a large portion of Northern and Central Illinois is expected to receive 1-2" of rainfall with this storm system. This is much needed rainfall, given a large portion of the state is seeing drought conditions. In addition to the rain, portions of Northern Illinois may see a rain/snow mix or a period of all snow, later tonight on into early Sunday morning. Some areas could see a dusting of snow.

​Below are the severe t'storm and wind forecasts for this event.

JP