textproduct: La Crosse

KEY MESSAGES

- Periods of light rain today southwest of I-94, focused mainly south of I-90. Overall impacts should be limited with rainfall amounts generally of 1/2" or less.

- Cool and dry for much of the upcoming week with near to slightly below normal temperatures.

- Next chance of widespread rain arrives over the weekend, but details of rainfall amounts and placement remain sparse.

DISCUSSION

Issued at 1200 PM CDT Mon Sep 21 2026

Today - Tonight: Periods of Light Rain

A stacked mid to upper tropospheric closed low meanders ESE across northern Iowa this afternoon and tonight, bringing with it periods of light to moderate showers. With the showers driven mainly by DCVA ahead of the low and little in the way of deeper moisture and mesoscale ascent, rainfall rates will be on the lighter side. As of 11 am, rainfall amounts around the I-35 corridor had topped out around 1/2 of an inch, but this band was starting to thin and weaken. While total rainfall amounts south of I-90 could approach similar values (20-30% chance), this rain will fall over the course of several hours and have little impact and any elevated river levels. The rainfall axis gradually spreads ESE ahead of the low centroid, persisting through the evening hours before departing to the southeast by sunrise on Tuesday. With the widespread clouds and rain today, highs will only top out in the low to mid 60s, a full ten degreed below average.

Rest of the Work Week: Cool and Mostly Dry

The region resides along the western periphery of a large southern Ontario/Quebec high pressure cell throughout the balance of the work week, keeping a cool and dry east/southeast fetch in place that will limit the intrusion of any rain into the region. A subtle shortwave grazes the Dakotas on Wednesday, with convection likely to move at least into central Minnesota by Thursday morning. However, how this rain shield evolves afterwards is a source of forecast uncertainty. Most solutions decay this system relatively quickly before reaching the Mississippi River, but there are a few outlier solutions (10%) that advect the rain farther east. However, odds are favoring more of a dry forecast during this period.

Upcoming Weekend: Next Chance of Rain

A deeper longwave trough approaches the region for the weekend, shunting the ridge to the east and opening the door for the return of rainfall. While the bulk of the medium to longer range guidance have this wave resolved, timing and placement of this trough make it difficult to ascertain any details about this rainfall. What is more certain is that given the lack of deeper moisture and progressive nature of the surface front, rainfall amounts do not look to be overly high with LREF rainfall probabilities of >1/2" being around 10-20%.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 649 PM CDT Mon Sep 21 2026

Low pressure center upstream of the forecast area causing widespread light rain across the forecast area. Higher impact MVFR-IFR cigs progressing into the western half of the forecast area expected to affect KRST TAF site shortly after TAF issuance. IFR visibilities expected to remain upstream of KRST although low confidence and may need further update before 06Z TAF issuance.

ARX WATCHES/WARNINGS/ADVISORIES

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