See the bottom of the post for a summary.Discussion... Front lifting slowly northward will continue to slow down or come to a halt in the North IL/South WI area out west through Iowa. Storms will initiate tonight along that front. These storms will be heavy rain producers, and flash flood watches have been posted for South WI and portions of North IL. The same goes for a small portion of NE Iowa. As these thunderstorms initiate, the SPC believes these storms could have tornado potential. The storms could have a supercell twist, with energy so high. As a matter of fact, the latest SPC discussion laid out indicated that CAPE values are 1000-2000 j/kg HIGHER than expected. This means a larger threat for severe weather on a fairly larger scale. There are some issues, though. Warming is beginning to develop aloft, which would suppress storms. There is weak large scale forcing in the area, and heights are rising slowly. That said, there is certainly a threat for severe thunderstorms, but there are issues in the process of initiating them.
Timing of these storms is crucial. The Rapid Refresh Model is indicating the storms beginning at 7 PM CDT of earlier, with impact time at 7-8 PM CDT.
The RUC model projects the storms to fire around 6 PM CDT, and impact the region throughout at least 1 AM CDT.
-Storms will likely be severe in many aspects if they are to develop.
-It appears storms will begin to fire from 4-8 PM CDT, and impact the regions from 7 pm CDT onwards through the night.