textproduct: La Crosse

KEY MESSAGES

- A stray shower or storm possible (10-20%) in central Wisconsin this afternoon.

- Large scale pattern shift brings periodic potential for showers and thunderstorms Thursday onward. Temperatures will also tend to shift to the 70s and perhaps 80s, above normal for mid-May.

- Monitoring Sunday and Monday for low severe storm potential.

DISCUSSION

Issued at 219 PM CDT Tue May 12 2026

Stray shower possible in central Wisconsin

18z satellite shows an area of cumulus developing over central/northern MN into northwest WI as a stout upper wave dives southeast over the Great Lakes. While cumulus field is flat at this time, cannot rule out a stray shower or thunderstorm developing as the field advances southeast over central WI given the strength of the upper wave and efficient mixing in the low levels. Aside from lightning, risk with any of this convection would be strong gusts at the surface given deep, well-mixed boundary layer.

Pattern shift ahead - periodic rain and warm weather

Persistent northwest flow aloft quits persisting past Thursday as quasi-zonal flow alot becomes predominant through the weekend before southwesterly flow takes over early next week. The end result will be warmer conditions and multiple chances for precip as some return flow does start to edge into the region, particularly into Sunday and Monday, as described below. While 12.13z NBM highs Friday/Saturday are in the lower 80s, inspection of components going into the NBM shows a disconnect between warmer bias corrected members and raw members, which are in the 70s. Therefore, while Friday and Saturday should be warmer than normal, do not be surprised if things remain below 80.

Aside from the severe storm potential discussed later, only period of potential intrigue looks to be Friday when a strong northern stream wave moves over southern Manitoba with a stacked 500/700/850mb jet on the equatorward side of this feature. This setup looks to bring relatively warm, dry, and windy conditions to portions of the upper midwest, leading to fire weather conditions. For our forecast area, operational guidance, probabilities within each of the 12.00z GEFS/ECENS/CMCE, and probabilities after cluster analysis of 12.00z LREF members suggest the overlap of strong winds and dry conditions should remain to our west.

Low potential for severe thunderstorms Sunday and Monday

Southerly flow in the low levels starting Saturday should bring enough moisture to the region for thunderstorms as a shortwave ejects northeast Sunday and the main body of an upper trough approaches Monday. Given increasing southwesterly flow aloft atop southerlies at the surface, this could lead to severe thunderstorms depending on the timing of the aforementioned upper trough and lead shortwave and, for Monday, if ongoing convection prevents destabilization from occurring. 5 to 6 days to go so cannot make any big pronouncements other than both 12.00z ML guidance and LREF probabilities suggest continued monitoring is prudent.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1223 PM CDT Tue May 12 2026

VFR conditions should prevail over the next 24 hours however there is potential for a few clouds around 3-4 kft to be present north/east of a RGK-OVS line between 06z and 18z Wednesday. Northwesterly gusts to 35 knots are expected this afternoon west of the Mississippi valley while areas to the east will see these gusts up to 25-30 knots as winds turn from southwesterly to northwesterly.

ARX WATCHES/WARNINGS/ADVISORIES

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