Sun-Thur, Aug 8-12th Severe T'Storm Event Update #7

(11:00PM - 8/10/21) Several disturbances will continue to move through the region through Thursday, bringing daily severe t'storm potential to portions of the state, through Thursday night.

Summary...
Several disturbances will continue to move across the Plains, Midwest and Great Lakes through Thursday. These disturbances will bring severe t'storm potential to portions of the state, through Thursday night. With this update we have updated tonight's forecast based on current trends, and no significant changes were needed for Wednesday's forecast

Forecast...
Tonight, Aug 10th...
In the wake of the large severe t'storm complex that affected Northern Illinois this evening and a few areas of scattered showers and t'storms in Central and Southern Illinois, additional areas of showers and t'storms may develop overnight tonight across portions of Northern and Central Illinois. As the low level jet continues to increase tonight and rides over an outflow boundary left over from the Northern Illinois severe t'storm complex, there may be enough forcing to allow for scattered showers and t'storms to develop. Should this occur, this activity would affect portions of Northern and Central Illinois overnight tonight and into Wednesday morning. However, the confidence in this overall scenario lower than average due to model guidance disagreement. Should activity occur, an isolated severe t'storm threat would exist, with damaging winds and hail being the main severe weather threats.

Wednesday Morning - Wednesday Night, Aug 11th...
Areas of rain and t'storms may be ongoing Wednesday morning across portions of Northern and Central Illinois. Should this activity be ongoing, it will gradually clear the state by midday, allowing for clearing and destabilization to occur across the state. With additional disturbances moving through and a frontal boundary in place, widespread development of showers and t'storms is expected Wednesday afternoon across Wisconsin, Iowa, Northwest Illinois and Missouri. This activity will likely congeal into multiple clusters, and will then spread southeastward across much of the state, Wednesday afternoon through Wednesday night. An environment will be in place supportive of a severe t'storm risk with this activity. This environment will feature high instability of 4,000-6,000J/KG, dew points in the low to upper 70's, good shear, good forcing, and high lapse rates of 7.0-8.5C. This environment will be supportive of upwards of an isolated to sporadic severe t'storm risk (levels 1-2) across a large portion of the state. Damaging winds, hail and an isolated tornado threat will be the severe weather threats.

Thursday Morning - Thursday Night, Aug 12th...
​Severe t'storm potential will once again exist across portions of the state for Thursday. More information regarding this potential will be provided in future updates.

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

​Recap...
Sunday Afternoon - Sunday Night, Aug 8th...
A large complex of t'storms that originated across Missouri spread northeastward across a large portion of the state, Sunday afternoon into Sunday night. Isolated to sporadic t'storms were severe with this complex, producing damaging winds. A few additional clusters of rain and t'storms moved across portions of the state Sunday night into early Monday morning, however none of this activity was severe.

Monday Morning - Monday Night, Aug 9th...
A large complex of t'storms that originated across Iowa on Sunday night, spread eastward across Northern Illinois Monday morning. No severe weather occurred with this activity. Additionally, a complex of rain and t'storms developed across Central and Southern Illinois Sunday night, which pushed across Central and Southern Illinois through Monday morning. No severe weather occurred with this activity. The main focus was Monday afternoon into early Monday night, as several supercell t'storms developed and moved southeastward across Northern Illinois. Scattered activity was severe, producing several tornadoes, and a few instances of damaging winds and hail.

JP