Wed-Thur, April 17-18th Severe Weather Threat Update #1

(9:00PM - 4/16/19) Another storm system moving through the region is set to bring a severe weather threat to portions for the state Wednesday afternoon through Thursday afternoon. 

Model guidance from this afternoon and evening continues to be in fairly good agreement regarding the overall severe threat the next few days. We have upgraded the severe risk over portions of Central Illinois for Wed evening and night, as there is growing confidence in slightly higher severe potential there during that time. Outside of that, no changes are needed and will continue with the going forecast.

Wednesday afternoon and night:
A disturbance moving across Iowa, Minnesota and Wisconsin during the 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. This activity will likely push across portions of Northern and Western Illinois later Wednesday 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. Note: There is also a conditional chance an isolated shower and t'storm could develop in the vicinity of a warm front near the Illinois/Wisconsin border during the afternoon, however this is highly conditional at this time as forcing appears weak and capping strong. However, should any development occur, a low end severe threat would exist as well.

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 Wednesday night. 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. There is growing confidence that 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 Western and Southwest Illinois Wednesday night will be ongoing Thursday morning across portions of Central and Southern Illinois, and will likely exit the state by 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 Central 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 low end severe threat.

Below is our updated TAM severe weather forecasts for each day. Should any storms become severe, hail and wind will be the main threats, though an isolated tornado cannot be ruled out.

JP

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