textproduct: La Crosse

KEY MESSAGES

- Periods of showers and storms likely (40-80%) Tuesday and Wednesday. Highest rainfall amounts will likely be across northeast IA and southwest WI where there are increasing probabilities (10- 50%) for rainfall amounts over 1".

- Seasonable temperatures are expected throughout the week with high temperatures ranging from the 70s to middle 80s. Temperatures trend warmer this weekend with highs in the 80s to near 90.

- Additional shower and storms chances (20-40%) this weekend.

DISCUSSION

Issued at 121 PM CDT Mon Aug 3 2026

Tuesday - Wednesday: Showers and Storms Likely

A notable shift in the synoptic pattern occurs as we head into Tuesday with the upper-level ridging providing our clear skies for Monday pushes east and is replaced by a broader troughing regime. As this occurs, a surface boundary will push through the local area, with the recent REFS having very high probabilities (50-100%) for much of the local area to see measurable rainfall. Currently, the atmosphere is not overly favorable for severe weather across portions of northeast IA and southwest WI where more robust convective development seems more unlikely with very skinny instability profiles and not overly impressive hodographs. Consequently, thinking any organized severe convection appears unlikely during this timeframe.

However, the environment where precipitation forms Tuesday and into Wednesday appears relatively favorable for efficient rainfall producers across portions of northeast IA and southwest WI where precipitable waters are progged to reach 1.75-2" and warm cloud depths approach 4km. Consequently, the 03.12z REFS has fairly respectable probabilities (10-50%) for an inch or greater of rainfall across portions of northeast IA and southwest WI. In any case, with the frontal passage and precipitation/cloud cover lingering around for Wednesday, high temperatures will likely trend cooler than normal with highs struggling to reach 80 for most locations.

Thursday - Friday: Seasonable, Small Shower and Storm Chances

Thursday will likely feature a break in any precipitation chances as surface high pressure builds into the region in the wake of the aforementioned frontal passage. Additionally, with surface southwesterly flow pushing into the area, expecting temperatures to rebound slightly from Wednesday with highs in the middle 70s to lower 80s. As we head into Friday, a troughing regime pushes east into the region, with northwesterly flow bringing some small precipitation chances (10-30%) with the grand ensemble (GEFS/EC/Canadian ensemble) for Friday. However, with questions on where any surface forcing would be, confidence is low in any convective development at this point.

This Weekend: Increasing Warmth with Additional Storm Chances

By the time the weekend rolls around, zonal to northwesterly flow establishes itself into the region with continued southwesterly surface flow. Consequently, temperatures are expected to steadily warm through the weekend with the grand ensemble (GEFS/EC/Canadian ensemble) inter-quartile spread ranging from the middle 80s to middle 90s by Sunday for high temperatures across the region. With the zonal to northwesterly flow in place, the key question that will need to be monitored for over the weekend is how far northeast does the ridge situated west of the local area build. Currently, there are some respectable probabilities (20-40%) for 1000 J/kg of SBCAPE and 30 kts of shear, so there is certainly some potential for severe weather when also considering AI guidance (CSU/Pangu/FengWu) does paint some probabilities (5-15%) as well. That being said, it will be highly contingent on how quickly the ridge builds in, should it progress into the region faster, this would decrease any convective potential. Regardless, thinking the low-end precipitation probabilities (15-40%) in the NBM for this weekend seem appropriate given the uncertainty of how this weekend may evolve.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1252 AM CDT Tue Aug 4 2026

Main TAF impact will be MVFR-IFR ceilings accompanying weakening shower/storm chances through Tuesday morning. Have accounted for current timing from west to east and higher probabilities for more impacts (i.e., lower ceilings) at KRST compared to KLSE. Should the accompanying frontal boundary sustain strength farther east overnight, visibility impacts and RA/TS mention will require additional inclusion.

ARX WATCHES/WARNINGS/ADVISORIES

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