Thur-Fri, June 24-25th Severe T'Storm Risk Update #1

(10:00PM - 6/23/21) Multiple disturbances will move through the region Thursday through Friday, bringing periods of severe t'storm potential to portions of the state Thursday morning through Friday night.

Summary...
Multiple disturbances will eject out of the Plains, and push eastward across the Midwest and Great Lakes Thursday through Friday. These disturbances will bring periods of severe t'storm potential to portions of the state, Thursday morning through Friday night. Model guidance has been showing this potential for several days.

Forecast...
This Afternoon-Tonight...
A very chaotic scenario is expected to unfold across the state for Thursday, with several clusters of showers and t'storms likely to spread across the state, from Thursday morning through Thursday night. The best severe t'storm potential will reside across Western and Southwestern Illinois, where a better severe t'storm environment will exist. Elsewhere across the state, continued the aforementioned several clusters of showers and t'storms moving through will tend to keep the environment for severe t'storms on the low/marginal side. The overall environment supportive of a severe t'storm threat will be in place across much of the state though. This environment will feature low instability of 500-2,500J/KG, dew points in the mid 60's to low 70's, decent shear, decent forcing, and  lapse rates of 6.0-8.0C. This environment will be supportive of upwards of a an isolated severe t'storm risk (level 1) across a large portion of the state, and a widely scattered severe t'storm risk (level 2) across portions of Western and Southwest Illinois. Damaging winds and hail will be the main severe weather threats, though an isolated tornado cannot be ruled out.

Friday Morning-Friday Night...
Once again, another very chaotic scenario is expected to unfold across the state for Friday, with several clusters of showers and t'storms likely to spread across the state, from Friday morning through Friday night. At this point, the current favored scenario is that a large complex of rain and t'storms that moves across the state Thursday night through Friday morning will dissipate and clear much of the state, allowing for clearing and destabilization to occur. This would allow for a new round of showers and t'storms to develop Friday afternoon across Northern and Central Illinois, as another disturbance moves through the area. The overall environment supportive of a severe t'storm threat will be in place across much of the state. This environment will feature moderate instability of 1,500-3,500J/KG, dew points in the mid 60's to mid 70's, decent shear, decent forcing, and  lapse rates of 6.0-7.5C. This environment will be supportive of upwards of a an isolated severe t'storm risk (level 1) across a large portion of the state. Damaging winds and hail will be the main severe weather threats, though an isolated tornado cannot be ruled out.

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

JP