textproduct: La Crosse

KEY MESSAGES

- Dry conditions continue through Tuesday morning.

- Widespread rainfall potential increases Tuesday afternoon through Thursday. There are medium chances (40-60%) for rainfall totals to reach or exceed 2.5 inches south of I-90.

- High temperatures will remain seasonal in the 60s to 70s.

DISCUSSION

Issued at 112 PM CDT Mon Sep 28 2026

This afternoon into Tuesday Morning: Dry Conditions

Visible satellite early this afternoon shows low level clouds remaining across much of the region. The low clouds should slowly clear out today and temperatures should rise into the upper 60s to mid 70s this afternoon. Some patchy fog may develop once again tonight over portions of the Upper Midwest, but it is not expected to be as widespread or as dense as it was this morning. Some isolated locations could still see visibility drop down to a mile or less though.

Tuesday Afternoon through Thursday: Widespread Rainfall

An upper level low pressure system will begin to become cutoff over the Desert Southwest on Tuesday into Wednesday. Out ahead of the low, moisture will surge northward towards the Southern Plains and then eventually the Northern Plains to Great Lakes region. The increased moisture will even be aided by Hurricane Polo after it moves northeast out of Baja California into far northern Mexico. The combination of synoptic scale forcing and a rich moisture environment will lead to widespread heavy rain from the Desert Southwest, to the Plains, and portions of the Upper Midwest. Widespread totals of 2+ inches are possible throughout this entire area given this set-up.

As for our area, rain is expected to begin across western portions of the local forecast area on Tuesday afternoon. This initial round of rain will occur at the same time as PWAT values begin to increase upwards of 1.5-1.75 inches. MUCAPE values may only be as high as a few hundred joules throughout the entire time period, so moderate to heavy rain may occur at times aided by convective processes. It still appears the best potential for heavy rainfall that may lead to flooding concerns will be from Wednesday afternoon into the night. This will coincide with the stronger push of moisture and it will occur out ahead of a southeastward moving cold front. Model guidance continues to vary on where the highest rain totals may fall, ranging from just to the northwest of the FA or across the southern half of the FA. Based on the synoptic set-up, we are leaning towards the southern solutions panning out which would bring in heavier rainfall totals to northeastern IA into far southwestern WI. Most likely rainfall totals continue to be in the 1-3 inch range, with the higher totals (2.5-3 inches) across northeastern IA. For some isolated locations, higher totals of 3.5-4+ inches cannot be ruled out. These rainfall totals would lead to flooding concerns, especially for rivers and locations that had just received a lot of rainfall in the last few weeks. The rain potential will end from northwest to southeast on Thursday as the cold front moves through and the mid level moisture becomes displaced to the east/southeast of the region.

Friday into the Weekend: Drier and Trending Cooler

In the wake of the cold frontal passage, temperatures should slowly trend cooler this upcoming weekend as broad scale troughing attempts to dig south over the Great Lakes region. Daytime highs are not forecast to be all that much cooler, with temperatures remaining in the mid 60s. Where the cooler air will be more noticeable will be overnight, with overnight lows drop into the lower 40s to mid 30s. Dry conditions are currently expected but there may be a low chance for light rain on Saturday if moisture moves in quick enough out ahead of another southern surge in the upper level trough.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1226 PM CDT Mon Sep 28 2026

MVFR stratus deck continues to erode this morning but, as the boundary layer is becoming established following insolation, cumulus is developing at the top of the mixed layer, with this cumulus also at around 2500-3000 feet at issuance time. Have therefore continued to carry MVFR for at least 1-3 hours at RST/LSE. Tonight, some chance (20-60%) for fog to return, primarily to the Wisconsin River valley. Have refrained from inclusion in the TAFs with this cycle due to low confidence in occurrence and expected increase in wind speeds in the boundary layer overnight.

ARX WATCHES/WARNINGS/ADVISORIES

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