textproduct: La Crosse

KEY MESSAGES

- Periodic showers and thunderstorms are possible (20-50%) through Monday. Low potential for a stronger storm exists (<10%) Monday afternoon/evening.

- Primarily dry conditions are expected Tuesday through the end of next week.

- A warming trend is very likely (80-90%) this weekend into next week with above normal temperatures favored Sunday onward, especially Tuesday into the end of next week.

DISCUSSION

Issued at 1241 AM CDT Sat May 23 2026

Today - Monday: Periodic Shower and Thunderstorm Chances

Periodic chances for showers and storms exist through Memorial Day as several shortwaves traverse the mean upper level flow.

Today, a cold front is expected to shift eastward across the Upper Mississippi River Valley. While moisture profiles are shallow, forcing along the boundary should prove enough to spark some isolated to scattered showers throughout the day as suggested by the various CAMs, which depict the greatest activity along and east of the Mississippi River late this morning into the afternoon. Probabilities for showers in the 22.18z REFS and 22.19z NBM sit around 40-60%, so there's medium confidence that some showers should be able to pop up. 22.18z RAP/HRRR soundings also suggest some weak instability developing along ahead of the front, around 150-300 J/kg of MUCAPE mainly over southwest Wisconsin, which would support some rumbles of thunder.

The next wave shifts eastward across the northern Great Plains and into the Upper Midwest on Sunday, with moisture pooling across central Iowa into central Minnesota during the afternoon and evening. With the increasing moisture, MUCAPE climbs into the 1500- 2000 J/kg range, mainly for those across southeast Minnesota, although instability profiles are quite skinny. The main point of uncertainty is if convection can develop given weak capping in the 800-700hPa layer. Given this uncertainty and variation between ensemble members, probabilities for rainfall sit around 20-40% and 10-30% in the 22.12z LREF and 22.19z NBM, respectively. If storms are able to develop in this environment, Inverted-V signatures in the soundings suggests that convective development could bring a stronger splat of wind.

Monday continues to look interesting from a convective weather perspective, especially if you're a fan of the GFS/NAM solutions. MUCAPE in the 22.18z deterministic GFS climbs into the 2500-3500 J/kg range Monday afternoon, 2000-3000 J/kg in the 22.18z NAM. The 22.18z GEFS is far closer to the NAM solution as the ensemble mean sits around 2000 J/kg of SBCAPE whereas the 22.18z EPS mean is far lower, topping out around 1250 J/kg. Regardless, this instability would certainly support storm development. However, the overall wind shear in this environment is lacking. Assuming surface based parcels, 0-6km bulk wind shear is a modest 20-30kts, but the greatest wind shear continues to look as though its confined to the 0-3km layer, limiting storm organization. There also continues to be the issue of rising heights as upper level ridging builds eastward and the subsidence associated with it suppressing upward vertical motions.

All of that said, probabilities for precipitation remain relatively low Monday afternoon and evening, generally only 20-40%, given plenty of variation amongst the various ensemble suites and their members. However, if the GFS/NAM solutions come to fruition, a strong to severe storm can't be ruled out with strong winds and hail the primary threats, but AI/ML guidance continues to suggest <10% probabilities for this potential.

Tuesday - Friday: Mostly Dry and Warmer

As mentioned previously, ridging will build into the Upper Midwest Tuesday and will remain the dominant feature through the end of the week. Under the rising heights, temperatures are expected to rise above normal with highs in the low to mid 80s. The 22.19z NBM continues to suggest highs in the upper 80s to low 90s Tuesday given its seasonal bias correction issues, values that exceed the 90th percentile of the other ensemble suites. Continue with the trend of lowering high temperatures from the NBM for next week.

Primarily dry conditions are expected through next week under the upper level ridge. There is still some potential for showers/storms Wednesday afternoon/evening as a shortwave attempts to lift northward from the Lower Mississippi River Valley, but current probabilities are broad and sit around 30%.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 552 AM CDT Sat May 23 2026

A band of light rain continues to make its way eastward across southeast Minnesota and northeast Iowa this morning. This line will weaken a little as it reaches the Mississippi River before reinvigorating a bit this afternoon along and east of the Mississippi River. Heading into the afternoon a 15 to 30% chance of a thunderstorm is possible for areas along and east of the Mississippi River. All precipitation chances diminish later this evening. Light southeast winds shift to the southwest this morning and afternoon before shifting again to the northwest for the evening. Mostly VFR CIGS through the TAF period with the exception of a 3 to 6 hour time frame behind this band of rain that will result in MVFR CIGS mostly between 1500 and 2500ft.

ARX WATCHES/WARNINGS/ADVISORIES

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