textproduct: La Crosse

KEY MESSAGES

- Severe weather possible between 7 PM and 1 AM tonight. All hazards are possible mainly west of the Mississippi River.

- Another round of severe weather possible on Monday night between 9 PM and 4 AM. The main threat will be damaging winds. With isolated threats of hail and maybe a few QLCS tornadoes.

DISCUSSION

Issued at 1257 PM CDT Sun May 17 2026

This Afternoon

The remnant MCV which brought rain mainly south of Interstate 94 will continue to move northeast away from the area this afternoon. As it does, the showers and isolated storms currently along Interstates 90 and 94 will move east northeast away from the area. Additional rainfall amounts will be up to a half inch. As a warm front gradually lifts northward, temperatures along and south of Interstate 94 will warm into the 60s and lower 70s, and into 60s north of this Interstate. This will result in surface-based CAPES climbing into the 1000 to 2500 J/kg along and south of Interstate 90 by 7 pm.

Tonight

Late this afternoon and evening, 2-3K J/kg CAPES will develop ahead of a squall line moving east across eastern South Dakota, eastern Nebraska, northern Iowa, and southern Minnesota. with 0-6 km shear approaching 40 knots, there could potentially be some supercells located along the line (these would likely stay west of the Upper Mississippi River Vally) and along the warm front near the Minnesota and Iowa boarder. In addition to the deep shear, there is 200-300 EHI along the Minnesota and Iowa boarder and downdraft CAPEs up to 1K J/kg. The discrete supercells ahead of the squall line would be capable of producing wet microbursts, large hail, and isolated tornadoes between 7 PM and 10 PM in southeast Minnesota and northeast Iowa. The threat will then shift to more damaging winds and maybe a few QLCS tornadoes as the squall line moves into southeast Minnesota and northeast Iowa between 10 PM and 11 PM. This line will then gradually weaken as the instability wanes. The severe weather threat will likely wane by 1 AM Monday.

Monday night

A cold front will move east through the area. There will be 1-2K J/kg CAPES ahead of this front. With much of the deep (0-6 km) shear located post frontal, not anticipating any supercells. As a result, if there is severe weather, it would be located along the cold front as a squall line. The primary threat would be damaging winds with secondary threats as hail and QLCS tornadoes. Timing looks to be rather similar tonight with the squall line moving into northeast Iowa and southeast Minnesota between 9 PM and 10 PM. It will exit the area between 2 AM and 4 AM. By this time, the winds will likely be sub-severe.

Friday into Saturday

A shortwave trough will move east through the area. This will result in another round of showers and isolated storms. With CAPES less than 250 J/kg and 0-3 km and 0-6 km shear less than 25 knots, not anticipating any organized severe weather at this time.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1235 PM CDT Sun May 17 2026

MVFR to IFR conditions currently present across the region with some isolated instances of LIFR along the I-90 corridor. While the main axis of rain moves into Central/North Central Wisconsin into this afternoon, low clouds are expected to linger for most areas through later tonight with some low precip chances. The main chance for storms looks to push east into the region late this evening - likely around 04-07Z for the terminals. The main threat with this line of storms will be strong winds and heavy rainfall so have continued with the TEMPO groups that bring stronger winds in for a short time period. This will likely need to be further refined this evening as the storms start to get closer and a more accurate timeframe can be deduced. Rain chances will continue into tomorrow morning behind the line of storms with most locations lifting back to VFR CIGs through the morning. Some lower MVFR/IFR CIGs may linger across portions of SE Minnesota and WC Wisconsin but confidence in this being BKN and not SCT is too low to include this for the RST terminal tomorrow morning.

HYDROLOGY

Issued at 106 AM CDT Sun May 17 2026

One to two inch totals are still forecast across the area, with areas further west more favored for the 2 inch totals. This will likely not cause river flooding, only within bank rises.

ARX WATCHES/WARNINGS/ADVISORIES

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