textproduct: La Crosse

KEY MESSAGES

- An MCS is expected to develop across North Dakota/Minnesota this afternoon before moving into northern Wisconsin tonight (40-70%). Strong wind gusts and heavy rainfall are possible, mainly along and north of I-90 and over Wisconsin.

- Additional, though lower, potential for storms exist across northeast Iowa into southwest Wisconsin Friday afternoon (10-20%).

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

DISCUSSION

Issued at 156 PM CDT Thu Sep 3 2026

This Afternoon - Friday Morning: Strong/Severe Storm and Heavy Rain Potential

A messy scenario continues across the region as ongoing showers and storms through much of the morning have been able to linger into this afternoon, and have really put a damper on the atmosphere's ability to recover and destabilize as we head into the evening and overnight hours. An area of storms has developed across eastern North Dakota this afternoon associated with a shortwave trough ejecting off the longwave trough across the Pacific Northwest. This area of storms is expected to grow upscale into an MCS through the afternoon before translating east-southeastward across Minnesota into northern Wisconsin this evening and overnight.

There are a couple different scenarios in the CAMs as far as how this potential propagates is concerned. Many model solutions suggest the MCS makes it into our northern tier of counties, mainly along and north of I-94 though possibly as far south as I-90 in Wisconsin. Other solutions suggest that it stays north of our area, closer to the Wisconsin/Upper Michigan border. What track it ultimately takes is a bit uncertain, but would tend towards more of a southern solution given the expected placement of a northward advancing warm front. However, because of the lingering showers and storms early this afternoon, the 03.15z RAP depicts a weakening MUCAPE gradient with southeastward extent from North Dakota into northern Wisconsin. This would suggest that if the MCS is able to maintain itself across Minnesota, it would tend to weaken as it approaches our area.

From a strong to severe standpoint, the greatest threat area would be along and north of I-90 and across Wisconsin where the MUCAPE gradient and effective shear is maximized. Would expect damaging wind gusts to be the main hazard given the linear mode and DCAPE values of 900-1000 J/kg though can't rule out an isolated tornado if the system becomes surface based (an unlikely scenario) given sufficient low level turning depicted in model hodographs and 0-3km shear values of 30-35kts. That said, it currently looks as though the bulk of any severe convection would occur to our northwest or southeast, especially if it tends to weaken as it moves into Wisconsin.

Even if stronger to severe convection is not able to sustain itself into our area, fairly efficient rain rates and heavy rainfall are a concern overnight given the west-east oriented boundary across the region with the aforementioned strengthening low level jet and moisture transport axis across the region. Conditions are ripe for heavy rainfall with PWATs over 1.5 inches and warm cloud depths of 10kft or greater. This heavy rainfall is most likely across western into central Wisconsin where storms are most favorable to frequent, though this potential is on the lower side (10-20%). Regardless, rainfall amounts in the 25th-75th percentiles of the 03.12z HREF are around 0.5-1.75 inches, respectively, although the potential for localized areas of 3 inches or more exists per the LPMM.

Friday Afternoon: Additional Storm Potential, Low Severe Chance

Mid to upper level ridging begins building across the central United States Friday but not before a shortwave trough is able to translate eastward into the Upper Midwest. Some model solutions suggest the quasi-stationary warm front shifts back southward Friday morning behind the MCS associated with its outflow boundary, stalling again somewhere around to just south of I-90. Forcing is expected to be weak while low level capping remains in place, so where or even if convection is able to initiate Friday afternoon will likely be dependent on how storms evolve tonight.

Assuming storms are able to develop, some stronger updrafts are possible given MLCAPE values of 2500-3500 J/kg which would support some hail development and some stronger wind gusts given DCAPE values exceeding 1000 J/kg. However effective shear will be meager, around 20kts, so updrafts that do develop will be unlikely to sustain themselves.

Outside of the storm potential, high temperatures reach around 90 degrees across northeast Iowa into southwest Wisconsin Friday afternoon. With the humid airmass remaining in place across the region, heat indices may approach 100 degrees during the afternoon hours, mainly for those along and south of Highway 18.

Holiday Weekend into Early Next Week: Persisting Shower/Storm Chances

Mid to upper level ridging continues to build across the central United States through the weekend with the main ridge axis located to our west while high pressure moves southward across the eastern Great Lakes region. As such, the Upper Mississippi River Valley remains in a state of northwest flow through the weekend and into early next week with various shortwave troughs traversing the mean flow. As such, expecting chances for showers and storms to persist through the holiday weekend with the 03.13z NBM suggesting 10-30% probabilities of precipitation. Some cooler temperatures are also expected Sunday into early next week with highs in the upper 70s to low 80s though a warming trend is depicted in the ensemble guidance by the middle of next week.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 627 PM CDT Thu Sep 3 2026

VFR conditions are forecast with this TAF cycle. The main area of concern and uncertainty is the potential for showers or storms near sunrise tomorrow morning. There remains high enough confidence in potential impacts to KLSE to keep a PROB30 mention for now. Outside of that potential, the wind should remain light around 10 kts or less and will switch from southeast/south to west to northwest towards the end of this 24 hour period.

ARX WATCHES/WARNINGS/ADVISORIES

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