textproduct: La Crosse

KEY MESSAGES

- A few showers and storms may affect the area overnight (20-30% risk for rain), but most locales should stay dry.

- Another period of showers and storms is possible Sunday afternoon (10-30%), mainly along and south of I-90.

- Warmer temperatures are expected for the beginning of the new week with periodic chances for showers and storms.

DISCUSSION

Issued at 640 PM CDT Sat Aug 29 2026

Tonight: A Few Showers and Storms Possible

We reside near the crest of a longwave ridge with multiple weak perturbations rippling over the ridge axis and across the region. These have been responsible for a few clusters of light rain showers for a few locales late this afternoon. A quasi- stationary surface baroclinic zone sharpens overnight with increasing low to mid tropospheric theta-e advection along this surface. While the explicit CAM reflectivity outputs are tame, a look at forecast soundings shows a nearly uncapped 1500-1700 J/kg of MUCAPE rooted at 800 mb should the aforementioned theta-e advection come to fruition. Therefore, have expanded low PoPs across much of the region--focused mainly east of the Mississippi River where this MUCAPE signal is more pronounced. The wind fields within the effective inflow layer are fairly weak and hodographs compact, therefore general thunderstorms would be the main threat. Given the warmer cloud depths in excess of 10 kft, these cells could be efficient rainfall producers and combined with the line parallel steering motion, there is a non- zero risk for training cells and rainfall amounts over 1" later tonight.

Sunday - Sunday Night: Shower and Storm Potential

The main story for Sunday is the potential for another round of showers and storms in the afternoon. 850hPa moisture transport and WAA noses into a warm front draped across the region, generally along I-90, which is expected to provide enough forcing for convective development along and south of this boundary. Instability looks to be on the lower side given the expected elevated nature of the showers/storms with MLCAPE sitting around 500-1000 J/kg across our region, higher to the northwest across central Minnesota. The more favorable kinematic environment for strong storms is also expected to exist north and west of the area, which is in line with where the SPC and AI/ML guidance highlights the greatest potential for a stronger storm.

Early Next Week: Warmer, Periodic Shower and Storm Chances Continue

Temperatures warm as we head into the beginning of the new week as persistent southerly low level winds continue to usher warmer air into the Upper Midwest and mid to upper level ridging remains across the central United States. An 850hPa thermal ridge axis sets-up across the region Monday with temperatures at this pressure level reaching 22-24C, translating to surface highs in the upper 80s with little spread in the 25th-75th percentiles of the GEFS/EPS/GEPS and their AI counterparts. The warmth will continue during the overnight hours when some near record warm low could be achieved, mainly across northeast Iowa.

Despite the upper ridge remaining in place, a shortwave trough will begin to flatten it on Monday, allowing additional shortwaves to traverse the mean flow through the middle of next week. Periods of showers and storms will develop in response to these upper level features with the potential for some stronger storms, particularly on Monday when AI/ML guidance has broad low end probabilities for strong storm potential, though details are murky as far as when/where storms occur.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 640 PM CDT Sat Aug 29 2026

Mainly VFR conditions are forecast for the period with the localized MVFR restrictions in isolated showers and storms throughout the period. Timing these low predictability storms out beyond 6-12 hours remains a challenge. Thus, while the TAFs are dry through the day on Sunday, there is a 10-20% chance of a storm at any given time during the day. Winds remain from the south to southeast at 5-15 kts, strongest at higher elevations and west of the Mississippi River.

ARX WATCHES/WARNINGS/ADVISORIES

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