textproduct: La Crosse

KEY MESSAGES

- An additional round of storms is possible this afternoon in southwestern Wisconsin. The overall severe threat is low, but a few could produce locally heavy rainfall.

- Severe weather threat for Monday evening hinges on *IF* storms can develop along and south of the warm front and the location of said warm front. At this time, storms look likely (70%) to develop along the warm front with this front likely (70%) being located north of the I-90 corridor. Large hail is the primary risk and there will be a window with a tornado risk as well before storms agglomerate. While this appears unlikely, if storms can develop farther away from the warm front, these would be more likely to remain isolated for longer and thus carry a longer-lasting tornado risk.

- Tuesday's severe weather threat, primarily a risk for hail, looks to be confined to far southwest Wisconsin and adjacent portions of northeast Iowa during the afternoon hours.

- Warm week ahead with high temperatures in the 70s to around 80. More storms dot the forecast later in the week.

DISCUSSION

Issued at 108 PM CDT Sun Apr 12 2026

Thunderstorm potential this afternoon

Period of modest descent in the wake of the morning shortwave and thunderstorms is occurring early this afternoon across the forecast area. Additionally, cloudy conditions are inhibiting insolation and thus limiting airmass recovery. That said, southerly winds through much of the area are still advecting warm, moist air into the region, so current thinking is that some conditionally unstable conditions will develop during the afternoon despite the suboptimal setup but will need some upper support to help cool the mid levels just enough for thunderstorms to blossom. This likely (60-80%) will come to southwest WI and parts of northeast IA in the form of the shortwave currently moving northeast of eastern KS while areas to the northwest remain capped. While some marginal shear will be present - around 35 knots of sfc-6km bulk shear - progged soundings indicate skinny CAPE profiles and only around 500 J/kg of MLCAPE and, with inhibited insolation due to cloudiness, a limited well- mixed boundary layer. Therefore, while a stray strong gust or hail report cannot be ruled out, severe thunderstorms appear quite unlikely.

Severe thunderstorms possible Monday late afternoon into evening

After a period of large scale descent tonight into Monday morning in the wake of Sunday afternoon's shortwave, moisture return to the low levels occurs as southerly advection resumes east of a lee cyclone developing in SD/NE. With southwesterly winds aloft increasing ahead of an upper wave over the Dakotas and southerly flow at the surface, deep shear will be on the increase, with 12.12z HREF having a 30-90% chance, highest north of I-94 and lowest in NE IA/SW WI, for at least 45 knots of sfc-6km bulk shear. A stout EML will also advect over the CWA with 12.12z HREF suggesting mid-level lapse rates will likely (50-75%) exceed 8.5 C/km. Given shear and the presence of this EML, large hail looks to be the primary threat with any storms that develop. However, the bottom of this EML may inhibit thunderstorm development and most guidance keeps things capped along and south of I-90. Indeed, convective allowing guidance shows convection initiating closer to the warm front, mainly affecting Clark/Taylor Counties. Have therefore endeavored to focus PoPs in our north while keeping low mentions in our south as some parameterized guidance, mainly the EC, do suggest the cap could be overcome farther south. In any case, if convection can get going south of the warm front, this would carry a tornado risk in addition to aforementioned hail concerns given the deep shear supporting supercells and sfc-500m SRH values approaching 100 m2/s2. At this time, this risk looks to focus north of I-90 and, overall, convection may struggle to develop except close to the warm front, where the along-boundary nature of deep shear vector and resultant storm motions would favor quick upscale growth and thus a time- limited tornado risk.

Severe thunderstorms possible Tuesday afternoon

Influence of the upper wave over the Dakotas moving east over Lake Superior and outflow from thunderstorms Monday evening looks to shunt appreciable moisture southeastward for Tuesday with the moist axis including generally areas in far SW WI and adjacent parts of northeast Iowa. However, for those areas, a risk for severe storms would be present given MLCAPE in the 1000-2000 J/kg range and deep shear still around 40 knots. The good news is that progged hodographs in our CWA show little turning in the low levels so thinking the tornado risk will be low. Should the moist sector remain in place farther northwest than currently favored, more areas would see a hail risk and a relatively higher tornado risk would creep into our south.

Warmth ahead with multiple chances for precip, storms

General trend with a western CONUS trough continues through Saturday with warm temperatures as a result. With multiple wave ejecting northeastward, will continue to have periodic chances for precipitation and, depending on moisture return, potential for strong to severe storms. At this time, potential for both rain and strong to severe storms looks to focus on Wednesday and Friday but, as timing of upper level features becomes uncertain, cannot rule out adjustments in timing over the coming days. Longwave upper trough finally arrives Saturday, bringing a cold front through the area, returning temperatures to around normal (50s) by the end of the week.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 653 PM CDT Sun Apr 12 2026

MVFR-VFR ceilings shifting slightly north across the forecast area affecting local airports expected to continue into early Monday morning. Storm chances increase through Monday morning and again Monday afternoon primarily across northeastern half of the forecast area.

HYDROLOGY

Issued at 114 PM CDT Sun Apr 12 2026

PWATs have been on the increase and now are nearing or exceeding values with respect to both NAEFS model climatology and observed climatology at MPX (1.22" observed at 12.12z) with DVN (1.03" observed at 12.00z) above the 90th percentile. With PWATs remaining at least around the 97.5th percentile over the next 3 days, concerns for localized heavy rain will continue. That said, threat for axis of heavy rain immediately repeating on a following day is low - for example, today favors SW WI and NE IA which may struggle to see precip Monday before being favored for thunderstorms again Tuesday. At this time, relatively higher concern for several hours of training storms focuses on the warm frontal convection discussed above. Should initiation focus along the warm front Monday, an east-west axis of west-central WI could easily see 2"+ of rain, an outcome reflected in 12.12z HREF PMM data. As discussed, this axis is favored (70%) to be somewhere north of the I-90 corridor which would tend to affect the Black and Wisconsin basins. Still a good amount of uncertainty in the frontal position but watching the position of the warm front closely tomorrow for both hydro and severe storm concerns.

CLIMATE

Issued at 114 PM CDT Sun Apr 12 2026

Potential Record Warmth Monday & Tuesday (Record/Forecast):

April 13th High Temp Warm Low ----------- -------- ------- Rochester, MN 83 (2023) / 75 59 (1941) / 54 La Crosse, WI 85 (2023) / 77 63 (1941) / 57

April 14th ---------- Rochester, MN 87 (2003) / 71 56 (1976) / 55 La Crosse, WI 90 (2003) / 76 60 (1883) / 58

ARX WATCHES/WARNINGS/ADVISORIES

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