textproduct: La Crosse

KEY MESSAGES

- Scattered storms possible in southwest Wisconsin early this afternoon, some of which may be on the stronger side.

- Seasonal temperatures continue into next week with highs in the 70s to lower 80s.

- Dry weekend with the next potential round of storms coming Tuesday and Wednesday of next week.

DISCUSSION

Issued at 1220 PM CDT Fri Aug 21 2026

Early this Afternoon: Storm Potential

As of midday, our weak cold front stretches along a line from near Oelwien, IA to east of Eau Claire, WI. Forecast profiles in the prefrontal airmass show ample instability on the order of 2000-2500 J/kg of MLCAPE, but the wind profiles--while linear to the southeast--will initially struggle to support organized convection given that the stronger mid to upper level flow looks to not arrive until 21-00Z. By the time the stronger flow arrives and the hodographs elongate, the front will have progressed out of the forecast area and taken the severe weather threat with it. Therefore, while one cannot rule out a pulse storm capable of producing lower end severe hail in southwestern Wisconsin between 18-21Z, the main severe weather threat window for the day continues to look to be just to the south and east of the forecast area.

It is also worth noting the 175-200 J/kg of 0-3-km CAPE available in southwestern Wisconsin ahead of the front. If a local surface vorticity max were to co-locate under an updraft for a prolonged period of time, we could see landspout processes in play.

Saturday - Midweek: Dry Early, Storms Return Tuesday

Northwest flow returns to the region for the weekend as a trough amplifies to our east and the ridge sets up to our west. This ridge decays as it moves eastward into early next week. With our region in between these two features and under the influence of surface high pressure, we look to be mostly dry and slightly cooler through the weekend until the ridge breaks down on Tuesday. High temperatures stay in the low 70s to low 80s from Saturday through Monday.

It will not be until Tuesday as a shortwave crests the flattening ridge that the next risk for storms arrives with the medium range ensembles in good agreement (60-80%) that there will be storms during this period. The exact timing and placement details of this rain will be hammered out as we get closer to the event. Beyond Tuesday, the forecast is looking relatively dry for the middle to latter part of next week as the upper level ridge rebuilds to our west.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1220 PM CDT Fri Aug 21 2026

Mainly VFR conditions are forecast for the TAF period with scattered thunderstorms over southwestern WI before 21Z this afternoon that could bring brief restrictions. Valley fog may develop over the Wisconsin River valley overnight and dissipate after sunrise Saturday. Winds veer to the northwest behind a passing cold front this afternoon at 10-15 kts, becoming 5-10 kts overnight and then increasing again to 10-15 kts for the day on Saturday. No additional rainfall is expected through the weekend, through overnight/morning valley fog may impact some sites into early next week.

ARX WATCHES/WARNINGS/ADVISORIES

WI...None. MN...None. IA...None.