Wed-Thur, July 28-29th Severe T'Storm Episode Update #1

(10:30PM - 7/27/21) A storm system is expected to move through the region on Wednesday and Thursday, bringing severe t'storm potential to portions of the state Wednesday afternoon through Thursday night.

Summary...
A storm system will move across the Northern Plains tonight, and will push eastward across the Midwest and Great Lakes on Wednesday and Thursday. This storm system will bring severe t'storm potential to portions of the state, Wednesday afternoon through Thursday. Little to no change was needed to forecasts with this update.

​Forecast...
Wednesday Afternoon - Wednesday Night, July 28th...
While a few isolated showers or t'storms will be possible Wednesday morning into Wednesday afternoon, the main focus will be Wednesday evening through early Thursday morning. Development of scattered showers and t'storms is expected Wednesday afternoon across portions of Minnesota and Wisconsin, in the vicinity of a storm system advancing southeastward. This activity is likely to grow upscale into one or more clusters, which will then push southward across Wisconsin, Western Michigan, Northern Indiana and Northeast Illinois from Saturday evening through early Thursday morning. An environment will be in place supportive of a severe t'storm risk with this activity. This environment will feature high instability of 3,500-5,500J/KG, dew points in the low to upper 70's, high shear, ample forcing, and high lapse rates of 7.0-8.5C. This environment will be supportive of upwards of an isolated to widely scattered severe t'storm risk (levels 1-2) across portions of Northern Illinois. Damaging winds and hail will be the severe weather threats, though an isolated tornado can't be ruled out.
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Thursday Morning - Thursday Night, July 29th...
Clusters of rain and t'storms from Wednesday night may be ongoing Thursday morning across portions of Northern Illinois. In the wake of this early day activity, a new round of scattered showers and t'storms is expected to develop Thursday afternoon along a cold front moving southward across Central Illinois. After development, this activity will push southward across portions of Central and Southern Illinois, Thursday afternoon into Thursday night. An environment will be in place supportive of a severe t'storm risk with this activity. This environment will feature high instability of 3,500-5,500J/KG, dew points in the low to upper 70's, modest shear, modest forcing, and modest lapse rates of 5.5-6.5C. This environment will be supportive of upwards of an isolated severe t'storm risk (level 1) across portions of Northern Illinois. Damaging winds and hail will be the severe weather threats, though an isolated tornado can't be ruled out.

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

JP