textproduct: La Crosse

KEY MESSAGES

- Periodic showers and storms will be seen this week. The highest rain chances will be tonight (mainly along and north of Interstate 90) and on Wednesday night and Thursday morning along and north of Interstate 94.

- Above-normal temperatures will persist through the remainder of the work week.

DISCUSSION

Issued at 1255 AM CDT Tue Sep 1 2026

This Afternoon

A shortwave trough will move out of Nebraska this morning and through northern Iowa, southern Wisconsin, and northern Illinois this afternoon. Ahead of this wave, the 0-1 km mixed- layer CAPES will climb into the 1500-2500 J/kg. This will result in isolated to scattered elevated showers and storms in northeast Iowa and southwest Wisconsin. With weak 3-6 km shear (10-20 knots) and the storms being mainly elevated, not expecting any severe weather.

High temperatures will range from the mid-80s to lower 90s.

Tonight

A shortwave trough will move out of South Dakota this evening and through the Upper Mississippi River Valley overnight tonight. As this wave moves into southwest Minnesota and northwest Iowa, a 30-knot 850 mb jet will intersect a frontal boundary in the region. This will result in the development of a mesoscale convective complex. As the nocturnal jet gradually veers, the complex will become linear and accelerate with time. While the 0-3 km is anywhere from 40 to 50 knots, soundings suggest that this system will likely remain elevated. We will have to watch the DCAPE through the night to make sure that remains the case. If the system happens to become surface-based, there would be the potential for damaging winds. The CAPE aloft looks rather skinny, so not anticipating any large hail.

The HREF has the highest rainfall amounts along and north of Interstate 90. Rainfall totals will likely range from a quarter to three quarters of an inch. The highest totals will be likely west of the Mississippi River. This is due to the eastward progression being just a bit slower. The ensemble localized probability-matched mean suggests that there could be some localized totals in the 1 to 2 inch range.

Low temperatures will be in the lower and mid-60s north of Interstate 90 and in the mid- and upper 60s across the remainder of the area.

Wednesday Night into Thursday

Another mesoscale convective complex will develop across northwest Minnesota during the evening on the nose of a 25-30 knot 850 mb nocturnal jet. As this jet gradually veers overnight, this complex will gradually shift east and then southeast. This should result in the heaviest rain (1-2 inches) falling along and north of Interstate 94. With weak 0-3 km and 0-6 km shear and this system likely remaining elevated, the threat for damaging winds look to be on the low side. In addition, skinny CAPEs in the sounding profile does not favor large hail.

Low temperatures will range from the mid-50s to mid-60s. High temperatures will range from mid-60s to lower 70s.

Labor Day Weekend

There remain plenty of uncertainty on what the upper air pattern will look like for the upcoming holiday weekend. This uncertainty comes from how the models deal with a retrograding ridge. Some models keep our area underneath the strong and very warm ridge. Others suggest that this ridge will retrograde much further west and this will in turn result in more northwest flow aloft. In this scenario, we would see near to below temperatures.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1255 AM CDT Tue Sep 1 2026

Light winds will be seen across the Upper Mississippi River Valley overnight. In addition, low-level moisture will pool along a weak frontal boundary. This will result some IFR/MVFR fog early this morning. This fog should dissipate by 01.15z.

There will be isolated to scattered showers and storms across northeast Iowa and southwest Wisconsin this afternoon. This may result in some gusty winds.

ARX WATCHES/WARNINGS/ADVISORIES

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