textproduct: La Crosse

KEY MESSAGES

- Showers and storms may continue (20 to 50%) for much of the early morning for areas east of the Mississippi River. There is a heavy rainfall threat with some areas potentially receiving up to 4 to 5 inches of rain, however the exact location of the heaviest rain is uncertain as it could be outside of our forecast area.

- Storm chances return this afternoon and early evening (15 to 30% mainly for areas along and south of I-90.

- Shower and storm chances persist through the holiday weekend and into early next week.

DISCUSSION

Issued at 1244 AM CDT Fri Sep 4 2026

Today: Heavy Rain Potential This Morning and Storm Potential for the Afternoon

Current IR satellite view shows an area of convergence from just south of the Twin Cities metro over to near the Green Bay metro. Storms have begun to fire north of I-94 along this boundary. This boundary should gradually shift south through the overnight hours. South of this boundary the low level jet continues to push 25 to 40kts of southwest flow into our CWA. PWATs remain quite high (1.8 to 2.1") with instability values around 1500- 2500 J/kg of MLCAPE. Limiting factor is 75-200 J/kg of MLCIN through the morning. With veering winds aloft through the morning, in addition to the above parameters, training storms are possible (20 to 40%) which could lead to localized flooding, particularly for areas east of the Mississippi River. Total rainfall amounts could be upwards of 1 to 3 inches with some locations potentially seeing 3 to 5 inches as the 12Z HREF LPMM has shown for areas along the I-90 corridor in Wisconsin. The location of the highest rainfall amounts will likely change as shown by the 00Z CAM suite where the location of heaviest rainfall may fall along the I-90 corridor in Wisconsin, or does it set up more in GRB or MKX's forecast area.

Conditions for the mid-morning to early afternoon should remain mostly dry as the boundary from the morning continues to shift south through the CWA. All CAMs have this boundary roughly through the middle of our forecast area during the early afternoon. Daytime recovery will be ongoing as instability builds back in, giving the area anywhere from 3000 to 4500 J/kg of MLCAPE to work with. Given that there is a boundary, however would like to see better surface convergence along it for more widespread development, storms may initiate along this boundary during the afternoon and early evening as it progresses southward. Compared to Thursday, there will be little to no shear (10 to 25 kts of effective shear) available so storms will struggle to get going. For the storms that can get going and stick around for a little while, gusty winds and hail up to 1" would be the main threats with any strong to severe storm that develops.

Saturday - Early Next Week: Continued Shower and Storm Chances with Slightly Above Normal Temperatures

By the weekend, ridging builds into the central US with the main ridge axis setting up to our west. Our region remains in northwest flow aloft with various waves moving along the northern part of the ridge giving us a continued chance (15 to 40%) of seeing showers and storms for Sunday and Monday. There is better agreement within the longer range models depicting a shortwave trough moving through the Upper Midwest Monday night into Tuesday. NBM PoPs for that timeframe are 40 to 75%. Temperatures cool down slightly from what we have seen this week, but remain slightly above normal with highs in the upper 70s to low 80s for Sunday and Monday with a brief warmup for midweek with highs back into mid 80s.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 620 AM CDT Fri Sep 4 2026

Convection and stratus/fog concerns will be present over the next 24 hours. At issuance time, belt of SHRA and TS is occurring around a CCY-LSE-Y50 arc with this axis expected to shift southeast over the next few hours. Have included a VCTS at LSE to cover this given the widely spaced nature of the TS. Stratus/fog to the north is advancing southward, currently located along a MVE-MDZ line. Expect that surface insolation should halt the advance of this soon. However, continued presence of a moist air mass should lead to this redeveloping tonight and guidance is in good agreement this will spread to LSE/RST sometime after 06z. Have therefore included IFR at both sites late in the period.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Heat Advisory from 1 PM this afternoon to 7 PM CDT this evening for WIZ061. MN...None. IA...Heat Advisory from 1 PM this afternoon to 7 PM CDT this evening for IAZ029-030.