The main severe weather threat today exists across the parts of the central and eastern Corn Belt region and into the southern Great Lakes as a shortwave continues to move eastward with an ancillary cold front progressing southeastward across the risk area.  Convergence along the front as it progresses southward, combined with ample instability AOA 2000 J/KG across the region (spasmodic values > 3,000 J/KG are possible), should provide the synergist for convective development this afternoon.  Weaker forcing and rather mediocre 0-3km shear profiles of 20-30 kts should assuage a widerspead severe weather outbreak of any substantial, high impact over a broad area.

Latest 12z radiosonde data indicates largely unidirectional shear profiles exist across the region, with marginal mid and low level lapse rates <6 C/km and SFC-6 km shear profiles at 25-40 kts.  However, PW values at numerous sites currently sit at 1.5-2.0 .in, adumbrating a threat for heavy rainfall with some of these storms, though damaging winds remain the primary threat, with downdraft CAPE values progged (per SREF) to be AOA 500-1000 J/KG across much of the region.  Current thinking is that convection will initiate early this afternoon as the frontal boundary progresses southeastward and interacts with the unstable airmass ahead of the front.  While damaging winds will remain the primary hazard, a brief tornado or two is also possible.

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JLR