textproduct: La Crosse

KEY MESSAGES

- A few rounds of showers and storms are possible tonight through Tuesday with a very low chance for damaging wind gusts.

- There are chances for periodic showers and storms from Thursday night through Saturday

- Near normal temperatures are forecast over the next week with afternoon highs in the 70s to low 80s.

DISCUSSION

Issued at 106 PM CDT Mon Aug 17 2026

Rest of Today into Tuesday: A Few Rounds of Showers and Storms

Mild conditions are forecast for the rest of the afternoon with partly cloudy skies and temperatures rising into the upper 70s to low 80s across the region. Shortwaves embedded in the westerly flow aloft will likely move over the Upper Midwest later this afternoon into tonight. Initial development of showers and thunderstorms is forecast to begin in the Dakotas to northern/western Minnesota this afternoon. This activity should move towards the east/southeast as the upper level wave moves towards the Great Lakes region. Just how far east/southeast the linear complex of showers and storms gets varies in the deterministic and ensemble guidance. Unfortunately, the potential is certainly there that most of the convection dissipates before reaching the Driftless Region, but current thinking is that the lift provided by the waves and the sufficient mid level moisture will be enough to bring convection to at least the northwestern half of the area tonight. Severe storms are not expected since the line of storms would be moving in well after sunset this evening and CAPE values are mostly below 1000 J/kg by the time any convection reaches this far east.

The showers and, more notably, the severe storm potential later in the day on Tuesday will be highly contingent on how the first round of potential showers/storms pans out. If a potential line of storms moves through tomorrow morning, rain-cooled air will likely remain in its wake leading to a lesser threat for severe storms with the secondary wave that should move over the area later in the morning through the afternoon. Even if everything were to align for severe storms during the day tomorrow, the main hazard would be damaging wind gusts as another linear system propels east over the Upper Mississippi River Valley. If any storms can remain discrete, a threat for large hail may arise, but confidence in very low in that potential. The more likely scenario is that showers and storms remain below severe levels during the day on Tuesday with the main hazard being lightning. Most of the convective activity should be off to the east of the area by mid afternoon, but there could be a few isolated showers or storms that move into the western zones once again during the afternoon.

Wednesday through Saturday: Periodic Rain Chances

The region should be underneath the base of an H500 trough on Wednesday which should keep the weather quiet as lift provided by the trough should stay just to the southwest of the CWA. Active weather may quickly return by Thursday afternoon however as ridging builds northward over the western CONUS into British Columbia and Alberta late this week into the weekend. Additional waves embedded in the northwest to north flow should lead to additional shower and storm chances through Saturday morning. With the forecast area in between these two systems, relatively mild conditions are likely with highs right around to a few degrees below average each day.

Saturday Night into Early Next Week: Dry and Mild Conditions

The upper level pattern in the forecast guidance diverges beginning Saturday through the remainder of this forecast period. Ensemble guidance is in fairly good agreement that Sunday will remain on the dry side but that may once again lead to an active pattern to begin the next work week. Even if the shower and storm potential increases once again next week, temperatures are still looking to be mild with a majority of guidance keeping highs in the lower 80s to upper 70s.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 643 PM CDT Mon Aug 17 2026

Main forecast concern for the 00Z TAF period revolves around potential shower/storm chances late tonight into Tuesday. Current upstream convection over Minnesota and the Dakotas lies within a more favorably unstable airmass. Expectation is for weak instability to spill eastward into the Upper Mississippi Valley overnight, supporting a chance (30-40%) of storms at the TAF sites from about 06Z through 13Z, with a lingering small chance (30%) of showers through mid-afternoon. Visibilities and/or ceilings may briefly drop to MVFR. However, given uncertainties in storm track and coverage, have continued with PROB30 mention in the TAFs and will monitor trends for later updates.

Winds will be light out of the SW to S overnight, swinging around to the W-NW during the day Tuesday.

ARX WATCHES/WARNINGS/ADVISORIES

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