textproduct: La Crosse

KEY MESSAGES

- Widespread rainfall potential increases this afternoon and lasts into Thursday. The heaviest rainfall is shifting further south but still could impact northeast Iowa into far southwest Wisconsin. The potential for 2+ inches of rain is still around 40-60% for these areas.

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

DISCUSSION

Issued at 118 PM CDT Tue Sep 29 2026

This afternoon to Thursday: Widespread Rainfall

Light rain showers are moving east across Iowa and Minnesota at this time. This activity will reach the western portions of the forecast area here shortly and should continue to move east over the region the rest of today. This activity is forming in an axis of increased mid level moisture and it has synoptic support with PVA associated with shortwave troughs. This first initial round of rainfall likely will not be all that heavy, since instability will be very low today and PWAT values are still rising. Still, some areas may receive upwards of 0.50-0.75 inches of rain before sunrise tomorrow morning. As this first round of rain ends from west to east tonight, fog may form in its wake due to the increased surface moisture. The latest hi- res ensemble output has the higher potential for fog across central Minnesota, however there are members that bring the bank of fog into western Wisconsin into southeastern Minnesota. Any fog that does develop should dissipate a few hours after sunrise on Wednesday morning.

A break in the rainfall is likely for most of the forecast area on Wednesday before the second and heavier round of rainfall forms during the afternoon into Thursday morning. PWAT values will continue to climb into the 1.5-1.75 inch range with the potential for the far southern counties to approach 2 inches based on mean ensemble PWAT values. Model guidance is now finally starting to agree with the location for the heaviest rainfall and it has been trending further south compared to 24 hours ago. The EC/EC AIFS have been indicating that this corridor of heavy rain would mainly set up in Iowa into southern Wisconsin for multiple days whereas other model guidance has had no consistency with the placement of the heaviest rainfall. A majority of guidance is now leaning towards the southern solution and the trend may even continue to push the heaviest rain further south out of the CWA. If the heaviest rain still reaches our area, only the far southern counties are expected to get this rainfall and it should hold off until Wednesday night into Thursday morning based on the latest hi-res models. Rainfall amounts are still pretty uncertain, but the latest 29/13z NBM still indicates a 40-60% chance to reach or exceed 2 inches for Fayette county to Grant county. High end amounts from this system continues to be upwards of 3-4 inches so if those amounts are actually achieved, some flooding or river flooding concerns may arise. Rain will come to an end on Thursday from northwest to southeast as a cold front ushers in a drier airmass.

Friday into Early Next Week: Mostly Dry and Trending Cooler

The H300 jet stream is forecast to sit across southern Canada and may dig south at times into the Great Lakes region to northeastern US this weekend into early next week. With a cold front south of the local forecast area and some cooler air filtering in due to the troughing, daily high temperatures will be a few degrees cooler into early next week. The cooler air mass will be more noticeable at night with lows dropping into the 40s to 30s. As of now, Monday morning looks to be coolest morning over the next week with the coldest temperatures potentially approaching freezing across central Wisconsin. Mostly dry conditions are expected during this time frame with the exception being on Saturday as there are low chances for light rain showers over the northern half of the CWA.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1239 PM CDT Tue Sep 29 2026

Impending rain and associated MVFR visibilities and MVFR to IFR ceilings will move in west to east this afternoon. While rain will eventually focus south of RST/LSE, low ceilings will likely (70%) remain. Am doubtful widespread VFR conditions will return before the end of the period. The good news is that the potential for TS is pretty low (20% or less) and winds should remain consistently out of the southwest over the next 24 hours.

ARX WATCHES/WARNINGS/ADVISORIES

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