Thursday, March 3, 2011

Marginal storm threat along I-55

I wouldn't be surprised to see a few marginally severe thunderstorms along Interstate 55 in western and central Illinois tomorrow (Friday the 4th) afternoon or evening. Weak lapse rates will likely limit the overall severe threat, but given substantial clearing and insolation sufficient low level buoyancy in the warm sector ahead of a deepening surface low could be enough to ignite a broken line of thunderstorms along the cold front and perhaps near the warm front as far north as Interstate 80 in north central Illinois. Widespread thunderstorms will develop in central Missouri by mid-afternoon, and more isolated development will then likely expand northeast along I-55 in central Illinois around sunset. The threat for any severe storms will likely be short-lived and limited to an hour or two around sunset as convection becomes more widespread after dark and a flooding threat becomes the main story. The area most under the gun for heavy rains and thunderstorm activity should be along a Springfield to Pontiac line.

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