Wed-Thur, April 17-18th Severe Weather Threat Update #2

​(12:45PM - 4/17/19) Update on the severe weather threat across the state over the next two days...

Wednesday afternoon and night:
A disturbance moving across Iowa, Minnesota and Wisconsin this afternoon and evening will likely aide in the development of scattered showers and t'storms along and ahead of a cold front during the afternoon across Minnesota and Iowa. This activity will likely push across portions of Northwest and Western Illinois later this afternoon, evening and night. An environment in place featuring low instability, decent moisture and decent shear will help support a low end severe threat across the aforementioned area during this period. There is also a chance that a scattered shower and t'storm could develop in the vicinity of a triple point and warm front across Northwest Illinois, Northeast Iowa and Southern Wisconsin during the mid-late afternoon, pushing east into the evening. Should development occur and overcome capping in place, an increased severe risk would be likely and an upgrade to higher probabilities would be needed. However, this is highly conditional at this time as forcing appears weak and capping strong.

Further south, a complex of rain and t'storms will develop across portions of Oklahoma, Kansas and Missouri during the afternoon and evening. This activity will likely push into portions of Western and Southwest Illinois tonight, spreading across portions of Central and Southern Illinois into late night and early Thursday morning. A similar environment will be in place as is further north; low instability, decent moisture and decent shear...which will help support a low end severe threat. This activity will likely have the best severe potential during this two day period, though still lower end. 

Thursday morning and afternoon:
The complex of rain and t'storms mentioned above that will push across portions of Central and Southern Illinois Wednesday night will be ongoing Thursday morning across portions of Eastern and Southeast Illinois, and will likely exit the state by mid-late morning. A low end severe threat will likely still be possible with this activity. 

In the wake of morning activity, re-development of showers and t'storms is likely along the cold front across portions of Eastern and Southern Illinois Thursday afternoon. This activity will sweep across these areas, exiting the state by late Thursday afternoon or evening. One again, an environment featuring low instability, decent moisture and decent shear will be in place, supporting a very low end severe threat. It is looking more likely this threat will be very low end, with minimal destabilization and clearing following the morning round of activity.

Below is our updated TAM severe weather forecasts for each day. The main threats with any severe t'storms will be hail and wind, though an isolated tornado cannot be ruled out...especially if the conditional threat across portions of Northern Illinois is realized this afternoon and evening.

JP

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