textproduct: La Crosse

KEY MESSAGES

- Showers and storms are very likely (75-95%) Thursday evening into the overnight hours. A few strong to severe storms can't be ruled out.

- Temperatures cool to near normal Friday through early next week. Highs in the 60s and lows in the 40s are expected.

- Another round of precipitation is likely (60-80%) Sunday night into Monday.

DISCUSSION

Issued at 101 PM CDT Wed Apr 22 2026

Thursday Evening - Friday: Showers and Storms

A 500hPa longwave trough currently situated over the intermountain west will eject eastward into the northern Great Plains late tonight, deepening a surface low over the Dakotas. The low and associated fronts shift eastward during the day Thursday with the cold front expected to move through our area late Thursday into the overnight hours.

Ahead of the main front, CAMs depict a period of showers/storms developing as moisture transport and warm advection increase, coinciding with MUCAPE upwards of 1500-1750 J/kg. While 0-6km shear is practically nil in this environment, 700-500hPa lapse rates of 7-8 C/km are depicted in 22.09z RAP soundings owing to the presence of an EML over the Upper Mississippi River Valley. If storms are able to develop during this period, some small hail development can't be ruled out given ample instability and favorable lapse rates. There is some uncertainty whether convective initiation can occur during this period though, especially south of I-90, owing to the presence of a warm nose in RAP/HRRR/RRFS soundings. It will largely come down to if the 850hPa moisture transport/warm air advection will be enough to overcome any capping present.

As we head into the evening hours Thursday, confidence is high that showers and storms along the cold front will move eastward into our area (75-95%). A fairly messy storm mode is expected as wind shear is generally confined to the lowest 3km. 0-3km shear sits around 25-35kts with little to no increase in the 3-6km layer. Instability on the order of 1000-1500 J/kg will support thunderstorms as they move through the region and possibly some stronger updrafts, although these will likely not be able to sustain themselves for long given the lack of deep layer shear. This leads to more of a linear storm mode through the overnight with strong to severe wind gusts being the primary threat with any storms. However, given there is a component of the 0-3km shear vector that is perpendicular to the surface front as well as curvature in the 0-1km layer per model hodographs, any bowing segments that are able to orient further perpendicular to this shear vector could see a weak tornado develop.

Rainfall should be pretty efficient during this period as well given skinny CAPE profiles and PWATs of 1.2-1.3 inches, above the 90th percentile of SPC sounding climatology. The main hindrance is warm cloud depths are generally 8-9kft, under the ideal values for heavy rainfall. That said, the interquartile range of the 22.13z NBM shows amounts between 0.5 and 1.0 inches, an increase since this time yesterday. Some isolated pockets upwards of 1.5-2 inches are also possible where thunderstorms frequent (30-50% per the 22.12z HREF). As such, low lying areas may see some ponding of water. Fortunately, while some area rivers may see rises with this rainfall, these amounts remain below those needed to run the risk of flooding.

Friday - Sunday: Cooler Temperatures and Dry

Cold air advection in the wake of the cold front Friday morning brings temperatures down closer to normal for this time of year, generally in the upper 50s to low 60s. This cooler air lingers through the weekend as the surface low churns across southern Saskatchewan and Manitoba. Apart from the temperatures, dry conditions are expected through much of the weekend given weak 925- 850hPa ridging shifting eastward through the region.

Sunday Night - Monday: Additional Showers and Storms

Deterministic and ensemble guidance depict a rather quickly moving shortwave trough and associated jet streak moving through the central United States Sunday. These features are progged to invigorate surface cyclogenesis across the central Great Plains before lifting northward into the Upper Midwest. Some variability exists amongst the ensemble suite regarding placement/track of the low, although there is considerably more agreement as compared to 24 hours ago. As such, probabilities for measurable precipitation during this period is 70-90% in the 22.00z LREF, 60-80% in the 22.13z NBM. Instability isn't overly impressive at this point, but the presence of 500-1000 J/kg of MUCAPE in the 22.00z EPS ensemble would support some storm development.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1230 PM CDT Wed Apr 22 2026

MVFR ceilings will move into the area late tonight and then continue through much of Thursday morning. Otherwise, VFR conditions are expected.

ARX WATCHES/WARNINGS/ADVISORIES

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