textproduct: La Crosse

KEY MESSAGES

- Initial round of storms progressing southeast through Minnesota on RADAR imagery mainly a wind/hail threat should their strength persist. Overall risk of this being severe is low (<10%).

- Subsequent round of storms this afternoon and evening continues to have signficiant uncertainty due to dependency on departure of ongoing morning storms. If and where storms do form, they will have a higher potential of being severe (30-40%). All hazards will be possible including damaging winds, large hail, a few tornadoes, and heavy rain.

- Cooler temperatures are on the horizon with dry conditions expected starting Tuesday.

DISCUSSION

Issued at 408 AM CDT Mon Jul 20 2026

This Morning: Round 1 of Storms

A cluster of storms, currently ongoing across south-central Minnesota this morning, will move southeast through the Coulee Region as we approach daybreak. Members of the 00Z HREF have come into much better agreement as to the track of this MCS compared to earlier 12/18Z runs with it tracking into southeast Minnesota and generally along the Mississippi River. There is still some uncertainty as to the strength of this activity by the time it gets to our neck of the woods. While storm strength has persisted on RADAR, entirely elevated instability may continue to limit surface impacts as seen in recent observations.

Additionally, the nocturnal jet is expected to be on a downward trend as it is moving into our area. There will be some hail risk with these morning storms given the abundance of elevated instability (1000-2000 MUCAPE and 50 kts of effective shear). The main question will be how long these storms linger with some guidance pushing these storms out quickly and others building activity in the immediate vicinity behind it. How quickly these storms vacate the area will play a significant role subsequent storm development detailed below.

This Afternoon - Tonight: Round 2 of Storms - Strong to Severe Likely

An upper level shortwave trough over the Canadian Plains is expected to continue east southeast through the overnight hours, dropping into the Upper Midwest and Great Lakes Region by late morning/early afternoon. This will send a belt of strong mid and upper level winds through through region with 50-70 kts at 500 mb and 100+ kts at 300 mb. At the surface, a cold front is expected to push into SE Minnesota and Western Wisconsin, likely by mid-afternoon; with a warm front potentially in the vicinity of the Mississippi River.

Significant questions remain as to how the morning storms will impact the airmass for the afternoon storms. The potential parameter space is severe-supportive with 50-60 kts of shear and 3000-4000+ J/kg SBCAPE; should morning storms clear out fairly quickly, giving the airmass time to recover. It's possible that the southwesterly winds that are expected to materialize by late morning could help destabilize us regardless of lingering morning convection. Overall, the longer the convection lingers into the morning hours, the more complicated the forecast gets for the afternoon, regarding both timing and location.

Where storms can and do develop, an all hazards severe threat looks likely. As mentioned before, shear will be plentiful upwards of 60 (maybe even 70) kts with fairly significant veering in the lower levels and effective SRH values around 300 m2/s2 along and ahead of the front. Any storm development will have the potential to produce strong downburst winds with DCAPE values projected to be well over 1000 J/kg per 19.00 HRRR soundings. Cooling aloft will allow for lapse rates to exceed 7 deg C/km, increasing the significant hail threat. Dew points in the 70s and deep moisture through the profile will allow for pWats to climb into the 1.75-2+ inch range tomorrow, creating a brief heavy rain threat. Flooding does not look to be of concern as storms should be progressive enough to limit flooding problems but these will be efficient rain producers so quick bouts of heavy rain will certainly be possible. Initial storms along the front are expected to be supercells with the threat transitioning more to wind/hail as storms grow upscale into more bowing structures as they move to the east/southeast.

Tuesday - Beyond: Cooler Temperatures and Generally Dry

Once the cold front passes and the storms clear out late Monday night, there should be a noticeable difference across the area with an overall much cooler airmass expected for mid week. Temperatures Tuesday and Wednesday will finally drop below average into the upper 70s to low 80s with dry conditions expected as a weak surface high pressure moves in behind the front. While a quick moving disturbance may bring some low rain chances to the area by late week, expect generally dry conditions and near normal temperatures to round out the next work week.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1241 AM CDT Mon Jul 20 2026

Ongoing smoke impacts expected to lift east through the early morning hours as TSRA chances increase from northwest to southeast through the morning hours. Radar imagery at 06Z TAF issuance exhibits local morning storms crossing the South Dakota border into Minnesota. Strong to severe storms are possible depending on exact timing of storms.

Eastern extent of morning storms will determine subsequent storm chances at local TAF sites (KLSE/KRST). Higher threat and confidence in local storms at KLSE (over KRST) given the more eastern longitude and potential daytime recovery of low level instability.

ARX WATCHES/WARNINGS/ADVISORIES

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