textproduct: La Crosse

KEY MESSAGES

- There are chances (20-50%) for light rain showers across the area today, with the highest chances across NE Iowa and SW Minnesota.

- Cooler than normal conditions are expected throughout much of the week with highs in the 60s.

DISCUSSION

Issued at 1223 AM CDT Mon Sep 21 2026

Today: Rain Shower Potential

As an upper level cutoff low churning over the High Plains slowly shifts eastward through the early morning hours, scattered showers are expected to develop across the Upper Mississippi River Valley. Forcing for these showers is weak at best, primarily driven by an area of 1000-500hPa Q-Vector convergence. However, some convective enhancement is possible this afternoon given 25-50 J/kg of 3CAPE associated with slightly steepened 900-800hPa lapse rates seen in RAP/RRFS soundings. Given the weak forcing over much of the area and the track of the upper low, thinking the greatest potential for scattered showers exists along and south of I-90 today (40-70%). 21.00z CAM solutions are beginning to suggest that those north of I- 90 could see some scattered shower development this afternoon as well (10-30%) given the steeper low level lapse rates, though shallower moisture with northward extent would likely keep any development fairly isolated.

As far as amounts are concerned, expectations remain on the lower end around 1/4 inch at most, although there is a low signal for localized amounts near 1/2 inch across northeast Iowa and southwest Wisconsin in the 21.00z HREF (10-20%) if any convective enhancement occurs.

Tuesday - Friday: Staying Cool and Drier

Beyond today, northeasterly surface flow and high pressure south of the Hudson Bay will allow for cooler and drier conditions to advect into our region. As a result, median high temperatures in the NBM throughout the week generally remain in the 60s for most of the local area. As we head into Wednesday morning, upper-level ridging will push into the local area which in turn should both allow for a gradual warming trend and clearing skies during this period. Consequently, not seeing much for precipitation chances till later into the week when maybe some shortwave perturbations try to sneak back into the region during the Thursday and Friday timeframe. However, predictability with these waves remains very low at this time. In any case, will have to watch Wednesday morning for some frost potential across north-central WI with median low temperatures in the middle to upper 30s.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 538 AM CDT Mon Sep 21 2026

MVFR conditions are being observed at the terminals. KRST has the higher potential to remain MVFR for much of the daytime hours, whereas KLSE should break out of the low clouds by mid to late morning. Scattered rain showers are expected today with minimal impacts expected at the terminals. KRST continues to have the best chances for rain showers, so have continued to maintain a PROB30 group for minor visibility reduction. VFR conditions are forecast beyond 00z through the remainder of this TAF issuance. The wind will remain out of the east at 10-15 kts or less.

HYDROLOGY

Issued at 538 AM CDT Mon Sep 21 2026

Minor flooding continues at a few sites along the Root and Turkey Rivers, but many sites along these rivers have crested or are close to cresting and are expected to fall below flood stage in the next 24 hours. Some additional rainfall is expected today, mainly along and south of I-90, but overall amounts are expected to be low, generally up to 1/4 inch at most although very localized areas along/south of Highway 18 may see amounts around 1/2 inch (10-20%). Regardless, these amounts are not expected to contribute to additional flooding impacts. Mostly dry conditions are then expected through the remainder of the week.

ARX WATCHES/WARNINGS/ADVISORIES

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