Thur-Sat, June 24-26th Severe T'Storm Event Update #3

(9:30PM - 6/24/21) 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. Tonight's forecast has been adjusted based on current real time data, but no real changes were needed for risk areas compared to previous outlook. Little change was needed for Friday/Friday night's forecast.

Forecast...
Tonight...
A large complex of rain and t'storms is ongoing from Central Illinois back west into Southern Iowa and Northern Missouri. This complex will spread across much of the state tonight. The best severe t'storm potential will reside across Western and Southwestern Illinois, as this area will be closer to a better environment supportive of severe t'storms. Elsewhere across the state, the environment for severe t'storms is on the low/marginal side. The environment across Western and Southwestern Illinois this afternoon through tonight will feature low instability of 500-2,500J/KG, dew points in the low 60's to low 70's, decent shear, decent forcing, and  good lapse rates of 6.0-7.5C. This environment will be supportive of upwards of a widely scattered severe t'storm risk (level 2) across portions of Western and Southwest Illinois, with a n isolated (level 1) severe t'storm risk across much of the rest of the state. 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 will 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 2,500-4,500J/KG, dew points in the upper 60's to upper 70's, decent shear, decent forcing, and  modest lapse rates of 5.5-6.5C. This environment will be supportive of upwards of a an isolated to widely scattered severe t'storm risk (level 1-2) across a large portion of the state. 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.

JP