Thur-Sat, June 24-26th Severe T'Storm Event Update #4

(11:30AM - 6/25/21) Multiple disturbances will move through the region through Saturday, bringing periods of severe t'storm potential to portions of the state through Saturday night.

Summary...
Multiple disturbances will eject out of the Plains, and push eastward across the Midwest and Great Lakes through Saturday. These disturbances will bring periods of severe t'storm potential to portions of the state, this through Saturday night. Model guidance continues to show this potential, which a very chaotic evolution expected during this period,, with numerous rounds of t'storms likely across the state. With this update, little to no change was needed for today/tonight's and Saturday/Saturday night's forecasts, as previous forecasts are on track.

Forecast...
This Afternoon - Tonight...
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, through tonight. An initial large complex of rain and t'storms has been spreading across the state this morning. This activity will generally clear much of the state by early afternoon, allowing for some clearing and destabilization. With lingering outflow boundaries and disturbances moving through the region, areas of new scattered showers and t'storms will develop across the state this afternoon. This activity will spread across much of the state, this afternoon through tonight. Of focus will be activity that develops across Eastern Kansas, Missouri and Central Illinois, which will spread across Central and Southern Illinois this afternoon through tonight. Across this corridor an environment supportive of a severe t'storm threat will be in place. This environment will feature moderate instability of 1,000-3,500J/KG, dew points in the upper 60's to upper 70's, decent shear, decent forcing, and  modest lapse rates of 5.5-7.0C. This environment will be supportive of upwards of a an isolated to widely scattered severe t'storm risk (level 1-2) across Central and Southern Illinois. Further north, a more marginal environment is expected across Northern Illinois, which will be supportive of an isolated (level 1) severe t'storm risk across Northern Illinois. Damaging winds, hail and an isolated tornado will all be severe weather risks.

Saturday Morning - Saturday Night...
Areas of isolated to scattered showers and t'storms may be ongoing across portions of Northern and Central Illinois Saturday morning. In the wake of this activity there will be clearing and destabilization. A new round of scattered showers and t'storms will develop Saturday afternoon, spreading across a large portion of the state through Saturday night. 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 upper 60's to upper 70's, decent shear, decent forcing, and  modest lapse rates of 5.0-6.5C. 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, hail and an isolated tornado will all be severe weather risks.

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

Recap...
Thursday Morning - Thursday Night...
An initial complex of showers and t'storms spread across a large portion of the state Thursday morning into Thursday afternoon. Another large complex of showers and t'storms developed later Thursday afternoon and evening across Northeast Kansas, Southeast Nebraska, Southern Iowa, Northern Missouri and Central Illinois. This alrge complex then spread across much of the state, Thursday evening through Friday morning. Along the way, some severe t'storms occurred across portions of Western and Southwestern Illinois. Damaging winds, small hail and isolated tornadoes occurred with this activity.

JP