5/13/09 Forecast

Tomorrow is shaping up to be a decent severe weather day. If the morning convection can clear early enough for afternoon heating, and rapid destabilization takes place, we could be in for a few tornadoes in Central IL. CAPE values into the 2000+ J/kg at 0Z, LI's around -7 and excellent LCL's around Central IL make it prime territory. Excellent shear will be in place, with SFC to H5 crossovers at almost 90 degrees.

Hodographs also look excellent, with big curvature, representing excellent shear throughout all the levels of the atmosphere. The key thing we will need to watch, is how quickly the morning convection clears out, and also get on the first cells that initiate, as it's also a question as to how fast these cells will group together and become a linear mess as the NAM and GFS models are predicting. A MCS will develop, possibly a derecho, with very strong winds, hail, and embedded meso-vortices, with possible tornadoes, associated with excellent shear in the environment. The NAM Significant Tornado Parameter also paints a nice bullseye over North Central IL, with a tornado index of 7 to 8.


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