UPDATED 4:00PM - A line of early spring thunderstorms will pass through Wisconsin tonight between 7:00 PM and 3:00 AM CST. Strong or severe thunderstorms with damaging winds and hail up to 1" will be possible; best chances west and southwest. A brief tornado is not out out of the question near the Mississippi River from I-90 south.
- HRRR model simulation for 8PM tonight showing line of storms moving in.
Tornado Watches have been issued just to the west across Iowa and Minnesota. For the majority of Wisconsin I expect the damaging wind to be the greatest concern. Thunderstorms should weaken gradually as they move east but may still be strong across the east. Given time of year (it hails a lot in March), low freezing level, and elevated character of t-storm updrafts I believe hail (up to 1" diameter) will occur.
In addition to thunderstorm activity, non-tstorm wind gusts near 40 MPH are possible south this afternoon ahead of the rain and cold front passage. Cooler weather moves in for Tuesday.
- Wind Advisories have been issued for much of Wisconsin tonight. Gusts up to 45MPH (NWS)
It probably doesn't feel like severe weather would be possible with air temperatures in the 60F's. Cold air aloft and low level warming will allow for weak but brief surface destabilization across western/southwestern Wisconsin. Tonight I don't expect that to last long; storms should become elevated with time. An elevated thunderstorm draws energy from a warm/moist layer only thousands of feed above the earth surface. This is enough to eliminate the tornado risk and weaken the storm in most situations, but will not erase the hail or damaging wind threat. Instability is a key ingredient to thunderstorms, but instability is really only a matter of temperature imbalance. This is how way severe weather can happen at 50F or less!