An unseasonably strong low pressure system will track across the upper midwest today, producing one or several squall lines. The primary threat will be damaging straight-line winds up to 75 mph. There is also a risk of hail up to the size of quarters and isolated tornadoes. The storms are expected to develop and intensify very rapidly in the late afternoon, and then quickly move east.
The rapid speed of development and movement is of particular concern in this situation. Storms of this nature increase the threat of widespread significant impact.
Clouds may play a role in limiting the extent of the severe weather threat. If the clouds are dense and widespread enough, they may limit instability enough to reduce the threat.
The Storm Prediction Center has placed much of the area along and north of Interstate 80 in a high risk... with the remainder of the area in a moderate risk. The convective outlook from SPC can be accessed here.
Please see the latest Hazardous Weather Outlook for the latest information.
Reference these links for some safety tips.