Tuesday afternoon weather update

2pm Update: The severe thunderstorm watch has been canceled for Winnebago, Rock, and Walworth counties. 

 A Severe Thunderstorm Watch was issued for Rock and Walworth counties in southern Wisconsin as well as for Winnebago, Boone, and McHenry counties in northern Illinois until 4pm.

An outflow boundary that formed from storms in Wisconsin earlier in the morning continues to move across southeast Wisconsin and northeast Illinois, producing isolated storms as it does. Cumulus clouds have started to develop, and grow, in some locations allowing storms to slowly begin to develop. One such storm is just north of Poplar Grove in Boone County (Illinois).

The short duration of the watch means that the risk for widespread severe weather through the afternoon is low, but it's there. And as the outflow boundary moves into an extremely unstable environment - given temperatures in the 90s and dew points in the upper 70s and low 80s - quickly developing storms are possible. However, the warmer temperatures have also put a cap - or lid - on the atmosphere which has made it somewhat difficult for more widespread storm activity to form along the boundary.

So, for the remainder of the afternoon isolated storms will be possible with a low-end risk that a storm could become strong to severe. If we do see severe storms form, damaging winds and large hail would be the primary concerns, along with heavy rainfall. Additional thunderstorms remain possible later this evening ahead of a cold front, with the risk still in place for scattered severe storms through Midnight.