Updated chase forecast... 7/22

Still like a southern Wisconsin target for this evening for a supercell or two. Current target is still in line with yesterday afternoon's thinking - Janesville, WI.

Currently, a large area of rain and embedded thunderstorms is moving across the target area from southern Wisconsin and far northern Illinois stretching westward into northern Iowa with the bulk of the rain shield across Wisconsin. An MCV is currently located just south of the Minneapolis area in SE Minnesota, very evident on radar imagery at the moment. An outflow boundary trails across SW Wisconsin into northern Iowa along and south of the current convection. Satellite imagery shows dense cloud cover associated with the convection over all of Wisconsin and far northern Illinois into northern Iowa. At the surface, temperatures have already reached the mid-80s in Iowa and north central Illinois south of the convection where at least partially clear skies are evident, with lower 70s td's over spreading the entire warm sector.

Current thinking is that over time the trailing convection should begin to erode first over northeast Iowa, and eventually into southern Wisconsin and northern Illinois. Any clearing over the warm sector along and south of the boundary should allow for rapid destabilization, and lead to a very moist and buoyant lower level. Given minimal capping, a potentially strongly unstable air mass and sufficient convergence along the trailing outflow boundary, scattered severe storms should begin to develop by mid-afternoon over northeast Iowa and southwest Wisconsin. The best chances for storm rotation will be near the warm front/ofb just ahead of the surface wave in southern Wisconsin where winds may remain southerly, or even back slightly to the SE, likely near Interstate 39 from Madison to Rockford, but more specifically I think near the Janesville, WI area.

It remains to be seen how much destabilization will occur, and to the extent that surface winds veer in the wake of early morning convection over the target area. While a best case scenario suggests a window for tornadic activity across the southern tier of counties in Wisconsin, and perhaps far northern Illinois... should sufficient destabilization not occur and/or surface winds do veer significantly in the wake of the lead wave an e-w oriented linear mode of convection with gusting outflow boundaries killing off tornado hopes is a very possible outcome.

For now, I will remain in DeKalb closely monitoring satellite and surface trends. The target is not all that far away, so I have the advantage of letting things play out. However, if today is going to produce, it may do so at short notice so close attention to boundaries and any clearing will be required.