textproduct: La Crosse

KEY MESSAGES

- Showers and storms likely beginning tonight and continuing through early Wednesday. Rainfall amounts of around 1/2" to 1" are expected with locally higher amounts possible. Some storms may be strong with gusty winds and small hail possible.

- Additional precipitation potential (30-60%) for late Friday and into Saturday.

- Near normal temperatures are expected throughout the week with a possible cool down by late in the weekend.

DISCUSSION

Issued at 1258 PM CDT Mon Sep 7 2026

Tonight - Tuesday: Showers and Storms Likely

Precipitation chances will be on the rise overnight and into Tuesday as a pronounced 500mb trough pushes through south-central Canada tonight and into Tuesday. As this occurs, a surface low pressure center with a trailing front will move through the local area and increase precipitation chances. In addition, a fairly profound axis of 850mb moisture transport pushes through the region advecting precipitable waters up to around 2 inches into the region as shown across deterministic guidance. As a result, the recent HREF has fairly high probabilities (50-70%) for rainfall amounts over 0.5" across portions of north-central WI and northeast IA. This is due to the fact that the initial round of precipitation is favored generally north of I-94 with the initial front and a second potentially further where the front remains slower. As far as severe weather potential is concerned, confidence is fairly low in the potential as the better instability axis is generally collocated with the 850mb moisture transport axis which remains largely west of the local area. In addition, the speed max with the with the upper-level jet streak remains well to the west of the local area. Consequently, much of the deep-layer shear is absent with bulk shear values generally remaining under 30 kts based on RAP soundings. However, given the marginal DCAPE up to 900 J/kg along the front coupled with weak instability, cannot rule out some strong to marginally severe storms capable of producing strong wind gusts. Generally the aforementioned front exits the region by Wednesday morning and into the afternoon.

Wednesday - Thursday: Drier, Near-Normal Temperatures

As we head into Wednesday and Thursday, northwesterly flow builds into the region aloft with surface high pressure moving into the region in the wake of the aforementioned front. Consequently, expecting relatively precipitation free conditions during this period of the forecast. However, in spite of the frontal passage, not expecting temperatures to budge much with zonal flow and upper- level ridging attempting to build into the region. As a result, NBM generally keeps highs in the upper 70s to lower 80s through the end of the work week.

Friday - This Weekend: Rain Chances, Potentially Cooling Down

By the time late Friday and the weekend rolls around, a pronounced upper-level trough will move through the Upper-Midwest bringing additional potential for precipitation Friday night and into Saturday. Ensemble guidance is fairly enthusiastic about some precipitation during this time frame as the grand ensemble (GEFS/EC/Canadian ensemble) has fairly high probabilities (50-80%) for measurable precipitation during this timeframe. Overall not impressed with the severe potential with this round of precipitation as the timing is not overly favorable with the precipitation moving in overnight and instability being relatively lackluster. However, given some AI/ML guidance shows some small probabilities (~5% chance) Friday night and into Saturday for severe weather, cannot rule it out if the timing of this system ends up being slightly faster. Otherwise, in the wake of this trough passing through the region, the potential exists for northwesterly flow to entrench itself over the region resulting in some cooler temperatures late into the weekend. However, given the wide range in high temperatures by Sunday in the NBM with the 10-90th percentile ranging from the middle 60s to lower 80s, confidence remains fairly low in exactly how much modification to our summertime airmass this troughing regime will do.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1154 AM CDT Mon Sep 7 2026

A cold front will move slowly southeast toward the region late tonight and Tuesday. Scattered showers and storms will be located along and ahead of this front. These will move into KRST around 08.10z and KLSE around 08.14z. Visibilities may be reduced into the IFR/MVFR range in these showers and storms. Otherwise, ceilings and visibilities will be VFR.

ARX WATCHES/WARNINGS/ADVISORIES

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