textproduct: La Crosse

KEY MESSAGES

- Overall dry conditions and near normal temperatures expected through Tuesday although low potential exists (10-20%) for afternoon/evening showers and storms.

- Showers and storms are likely (60-80%) Wednesday afternoon and evening. Heavy rainfall is expected with these storms, with the highest amounts expected along and north of I-90 where 1 inch or more is possible (20-30%).

- Near normal temperatures look to take hold for the end of the week.

DISCUSSION

Issued at 134 PM CDT Mon Jul 6 2026

This Afternoon - Tuesday: Overall Dry, Low Precipitation Potential

Primarily quiet and dry conditions are expected through the remainder of the afternoon and into the overnight hours as high pressure continues to shift east. CAM guidance continues to suggest low probabilities for some precipitation tonight (10-20%) over portions of southeast Minnesota as a convective system across western/central Minnesota decays with southeastward extent associated with diminishing instability. Outside of this low potential though, a much needed reprieve from last week's rainfall looks to be in store.

Tuesday is expected to be another benign day as 700-500hPa ridging builds into the region from the west although a shortwave trough is depicted to move eastward atop this ridge late Tuesday afternoon/evening. RAP/HRRR soundings suggest some instability will be present over portions of the Upper Mississippi River Valley, mainly along/north of I-90 which would support shower/storm development as the upper wave moves through. Probabilities are fairly low at this point with the 06.06z REFS suggesting only 10-20% probabilities for measurable precipitation.

Tuesday Night - Wednesday: Showers and Storms, Heavy Rainfall Potential

A stronger wave moves along the northern extent of the aforementioned ridge Tuesday night while a surface boundary lays out west-east across the region. These features are expected to be the focus of shower/storm development overnight Tuesday into Wednesday as an 850hPa low-level jet and moisture transport are advected into the boundary. PWATs of 1.5-1.6 inches and warm cloud depths of around 12kft would be supportive of heavy rainfall along the boundary given the favorable orientation of the forcing mechanisms. Combine these factors with boundary parallel cloud layer/corfidi vector flow, conditions will be favorable for training storms as well.

The biggest uncertainty regarding the heavy rainfall Tuesday night is the placement of the boundary and thus the axis of heaviest rainfall. A bit of a bimodal situation exists amongst the various ensemble suites because of this: A more northward solution depicted in the EPS/GEPS/AIFS and a more southern solution in the GEFS/AIGEFS.

Currently, the greatest signal for the primary precipitation axis is north of our area, more in line with the EPS/GEPS/AIFS solutions. However, the instability axis within the ensemble suites sits further south, more in line with the GEFS/AIGEFS solution which would suggest that the strongest storms and heaviest rainfall would be favored further south. Of note as well is that the AIFS is displaced slightly south of its numerically derived counterpart which may suggest an eventual southward trend.

Depending on which solution becomes favored in the coming days will determine the impacts across our area. If the boundary remains to the north, the heavy rain and flooding risk across our area would remain to the north whereas a southern solution would result in a heavy rain/flooding risk for areas generally along and north of I-94.

Another shortwave moves through the region during the day Wednesday, forcing the boundary southeastward. Heavy rainfall is expected to continue as it moves through given the juiced up atmosphere, but the more progressive nature should reduce how much rainfall a single location receives. Those along and north of I-90 currently have the highest potential for 1 inch or greater, sitting at 20-30% in the 06.13z NBM. On top of the heavy rainfall potential, there is also some severe weather threat primarily in the form of damaging winds given MUCAPE of 1000-2000 J/kg, the high PWATs, and DCAPE on the order of 800-1000 J/kg.

Thursday - Friday: Near Normal Temperatures

Behind the frontal boundary that moves through the region Wednesday, slightly cooler temperatures look to be advected into the region, generally in the low to mid 80s for highs and low to mid 60s for lows, right around normal for this time of year. 25th-75th percentile spread in the 06.13z NBM is fairly low, generally 3-5 degrees, in agreement with other ensemble suites. Uncertainty in temperatures increases into the weekend as interquartile spreads increase to 6-10 degrees with even greater variation between the outlier members.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 622 PM CDT Mon Jul 6 2026

With light winds and clear skies tonight across the area. Patchy fog will form mainly in river valleys after 06z Tuesday. However...not expecting widespread fog in the Mississippi River valley at this time and will leave out mention of fog/reduced visibility in LSE taf. Otherwise VFR conditions will mainly prevail at both RST/LSE taf sites through the taf period.

ARX WATCHES/WARNINGS/ADVISORIES

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