textproduct: La Crosse

KEY MESSAGES

- Severe storms expected near the Interstate 90 corridor overnight. The main threat is damaging winds.

- Several mesoscale convective complexes will affect the area nightly through the upcoming weekend. The one on Thursday night might produce damaging winds.

DISCUSSION

Issued at 145 AM CDT Tue Sep 2 2026

Overnight: Strong to Severe Storms

As the 30 to 40 knot 850 mb nocturnal jet gradually veers from southwest to west overnight, the a severe thunderstorm complex will gradually turn and move along the Interstate 90 corridor. As the cold pool continues to coalesce, this complex will become a progressive linear mesoscale convective complex. The biggest question at this time will be when will this eastward turn occurs. If this occurs too late (between 2 and 4 am), this system will have less downdraft CAPE and more convective inhibition (CIN) to contend with as it moves further east. In this scenario, the winds would remain aloft and the system would rapidly weaken as it moves away from the better instability. If this system turns east by 2 am, the CIN would be less than 50 J/kg and the downdraft CAPE would be around 1000 J/kg. Under this scenario, there will be a possibility for narrow band of strong to severe winds (40-65 mph) on the southern edge of bowing complex. The wind threat would be 1 to 2 counties wide in southeast Minnesota and along and north of I-90 in western Wisconsin. There might also be a brief QLCS tornado threat near the Minnesota and Iowa corridor. At this time, scenario looks more likely.

Further east, there is a quasi-stationary boundary stationed along the I-90 corridor. Storm parameters of MLCAPE ahead of the trough are between 1500 and 2500 J/kg with sufficient deep layer shear (0-6km) of 45 to 55 knots. The expectation is that these storms will grow upscale and merge into the MCC. Soundings suggest that these elevated storms will occasionally split with the left movers being favored to produce large (hail up to golf ball) as they move northeast at 40 to 45 knots.

Today: Scattered storms continue

The quasi-stationary boundary will remain near and south of the I-90 corridor. With 0-1 km most-unstable CAPES of 2500 to 3500 J/kg and 30-40 knot 0-6 km shear, there will be the possibility of scattered strong to severe storms.

High temperatures will range from the upper 70s to mid-80s north of Interstate 94 and from the mid-80s to lower 90s elsewhere.

Tonight and Thursday morning: Another thunderstorm complex

Another mesoscale convective complex will develop across northwest Minnesota this evening on a nose of a 25-30 knot 850 mb jet. As this nocturnal jet gradually veers overnight, this complex is expected to shift east and then southeast. With weakening 0-6 km shear overnight, not expecting any severe organized severe weather.

Low temperatures will range from the upper 50s to mid-60s north of Interstate 94 and from the mid-60s to lower 70s.

Thursday night into Friday Morning: Another thunderstorm complex

Showers and storms will develop ahead of a shortwave trough late Thursday afternoon and evening over northeast South Dakota and central and northwest Minnesota. As these cold pools coalesce, a thunderstorm complex will gradually develop. Over time as the low level jet veers and the cold pool grows large, this will likely become a rather progressive linear mesoscale convective complex which will move southeast through the Upper Mississippi River Valley. The main severe weather threat will be damaging winds.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 548 AM CDT Wed Sep 2 2026

Scattered showers will continue through 02.15z for KLSE. Additional showers and sstorms will be possible this afternoon and tonight. Location and timing is rather uncertain so left them out of the TAFs at this time.

ARX WATCHES/WARNINGS/ADVISORIES

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