textproduct: La Crosse

KEY MESSAGES

- Slight chance (15-25%) for very light showers Sunday.

- Widespread rain is a near certainty (95%) Monday into Tuesday with the potential for localized flooding. If exact details come together (<5%), a severe storm could occur Monday.

- Periodic rain potential continues Wednesday through Friday. While this is favored to focus to the south of our area, some areas could see multiple rounds of rain with an attendant risk for flooding issues as the week goes on.

DISCUSSION

Issued at 124 PM CDT Sat Sep 12 2026

Spotty light showers Sunday

Upper wave currently over Saskatchewan looks to dive southeast over Lake Superior Sunday. In addition to helping advance the cold front moving through the forecast area today this may also kick off a few very light showers as the mid-levels will still have a decent amount of moisture remaining in them as the base of the upper wave moves through the forecast area. Have therefore added 15-25% mentions of light showers with very low QPF. Those outdoors shouldn't be surprised if rain occurs briefly but impacts are not expected.

Rain with localized flooding risk Monday into Tuesday

In the wake of Sunday's upper wave, surface high builds in the Great Lakes. First bona fide Fall-like temperatures look to occur Monday morning when some areas in our northeast could (20-50%, highest in Taylor County) see temperatures in the upper 30s.

As this upper wave continues to head east over the Atlantic Ocean, surface high shifts eastward accordingly. As this occurs, upper low churns eastward over MT toward southern SK/MB. Strong southwesterly jet aloft on the equatar-ward side of this feature will both lead to the low deepening and broad lee surface pressure falls across the central and northern High Plains. Consequently, robust southerly moist advection will occur between the eastern surface high and the lee trough across the Plains with 700/850mb moisture transport ramping up over our CWA Monday morning. Expect showers and perhaps a few thunderstorms to develop as a pair of disturbances eject downstream during the afternoon and evening hours and then again when the surface front arrives from the northwest early Tuesday. With high PWAT values expected (12.13z NBM values approach 2") and deep warm cloud layers, showers will produce rain efficiently with a good chance (50-70%) for rain totals to exceed 2". Given the setup with 1-2 round of moderate to heavy rain developing in the vicinity of a warm front before additional rain occurs with the crashing cold front, there exists potential for localized high end amounts with the small (5-15%) chance for 4"+ to occur focusing on portions of northeast Iowa. Thus, while the progressive nature of the overall system and probabilistic output suggest little risk for widespread flooding issues, the potential for localized problems looks to be present.

Very low severe storm potential Monday

With the aforementioned southwesterly jet sliding closer to the CWA by Monday afternoon/evening and southerly winds ramping up at the surface, oodles of wind shear look to be present, including at the near surface, where sfc-500m SRH could top 200 m2/s2 per 12.12z GFS. However, given the strong moist advection, destabilization will be an issue as increasing clouds limit insolation and profiles begin to trend moist adiabatic. Therefore, while we cannot let our guard down as even modest amounts of surface-based instability would be enough for a tornado risk, at this time it appears highly unlikely (95%) said instability will in fact develop.

Periodic rain Wednesday through Friday

With moist of the upper support for they Monday/Tuesday system remaining to our north, cold front looks to stall across NE/IA/IL with quasi-zonal flow aloft persisting over the northern CONUS. Thus, as shortwaves move across the Midwest, additional rounds of rain look to develop in the vicinity of the front. Some of this activity may (20-60%) sneak into our CWA, particularly in northeast Iowa and southwest Wisconsin. While no additional hazardous periods stick out at this time, would need to monitor any areas that receive heavy rain Monday/Tuesday for additional flooding concerns.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 124 PM CDT Sat Sep 12 2026

VFR conditions are expected over the next 24 hours. Clouds will generally decrease over the next 6 hours before increasing once again from 00z to 18z Sunday. Lowest cloud bases should remain at 5 kft or greater, however. A light shower or two may (15-25%) occur after 12z Sunday but visibility reductions are not expected.

ARX WATCHES/WARNINGS/ADVISORIES

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