textproduct: La Crosse

KEY MESSAGES

- Heavy rain possible across southwest Wisconsin and northeast Iowa from Tuesday afternoon into Wednesday.

- Excessive heat potential returns this weekend into early next week.

DISCUSSION

Issued at 307 AM CDT Mon Aug 3 2026

Today:

An upper level ridge will provide dry weather across the Upper Mississippi River Valley with high temperatures ranging from the upper 70s to the mid-80s.

Tonight through Tuesday Night:

The 03.00z models continue to show a shortwave trough moving along the US/Canadian border tonight through Tuesday night, flattening the upper level ridge over the Upper Mississippi River Valley in the process. This will allow a Canadian cold front to move slowly southeast through the Upper Mississippi River Valley on Tuesday. For areas along and north of the Interstate 90 corridor, this front will move into the area late tonight and Tuesday morning. This timing is not that favorable for widespread showers and storms. As a result, rainfall amounts will likely be less than a tenth of an inch north of Interstate 90.

On Tuesday afternoon and night, low level CAPE (0-1 km) up to 1500 J/kg will lie along and ahead of the cold front in northeast Iowa and southwest into central Wisconsin. With the better 0-3 km and 0-6 km shear trailing the front, organized severe weather appears unlikely at this time.

While the severe weather threat looks low, there is some concern for heavy rain with mean winds parallel to the frontal boundary and precipitable water values around 2 inches. Resultant training thunderstorms are therefore possible in the vicinity of the frontal boundary. Rainfall rates in excess of 1 inch per hour are possible at times with highest overall amounts likely ranging from 1 to 3 inches locally in in northeast Iowa and southwest Wisconsin.

Low temperatures will range from the lower 50s to mid-60s on Monday and Tuesday nights. High temperatures will range from the mid-70s to lower 80s on Tuesday.

Wednesday into Thursday:

Another shortwave trough shifts east through the Dakotas and the Upper Mississippi River Valley Wednesday into Thursday. An initially quasi-stationary front draped across northeast Iowa and southwest Wisconsin on Wednesday will gradually move southeast of the area on Wednesday night and Thursday. With little collocated shear, organized convection appears unlikely at this time.

The vertical lift across across northeast Iowa and southwest Wisconsin will be enhanced by the right entrance region of a 110- knot 250 jet on Wednesday afternoon. Precipitable water values nearing 2 inches may again result in rainfall rates of 1"+ per hour and potential for localized flooding in urban areas.

High temperatures will be in the 70s and lower 80s on Wednesday. Low temperatures will be in the 50s on Wednesday night. High temperatures will range from the mid-70s to mid-80s on Thursday.

This Weekend into Early Next Week

The northern extent of the upper level ridge is highly uncertain. The GEFS suggests high temperatures will be in the 70s and 80s. Meanwhile, the ECMWF suggests that there will be the potential for high temperatures to potentially range from the mid-80s to mid-90s with heat indices ranging from the lower 90s to around 100.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 556 AM CDT Mon Aug 3 2026

Main forecast concern will be ongoing LIFR ceilings/visibilities affecting River Valleys and MVFR visibilities elsewhere. Expect both to lift with daytime heating. Removed LIFR visibility restriction at KLSE based on airport webcam imagery showing impacts limited to low (003) ceilings.

South winds increase through the late morning hours ahead of subsequent precipitation and storm impacts through Tuesday morning, near the end of the 03.12Z TAF period terminus.

ARX WATCHES/WARNINGS/ADVISORIES

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