textproduct: La Crosse

KEY MESSAGES

- The potential for rain later this afternoon and tonight has increased rapidly from previous forecasts--now up to a 40-70% chance--though rainfall amounts look to be light with only a 10-20% chance of >0.25" west of the Mississippi River.

- The potential for rain lingers into Friday and Saturday west of the Mississippi River (20-50% chance). Amounts look light as well and the showers more scattered in nature.

- The end of the weekend and start of next week is shaping up to be dry before another stretch of wetter weather pushes through Tuesday into midweek.

- Little change in temperatures into next week with readings running slightly below seasonal norms.

DISCUSSION

Issued at 1200 AM CDT Thu Sep 24 2026

This Afternoon - Tonight: Rapidly Increasing Rainfall Potential

The one big change to the near-term forecast has been a rapid increase in the probabilities for light to moderate rainfall spreading eastward from central MN after noon, reaching the Mississippi River towards sunset and lingering for many locales through the night into Friday.

A small eastward wobble of the lower tropospheric ridge axis is all it took for the eastward extent of the rain shield to shift from the I-35 corridor to now western and central WI. The signal in the short and medium range ensembles (LREF/EPS/GEFS/HREF) is nearly unanimous in there being rain west of the Mississippi River, with the number of dry members increasing as one heads further east. While the rainfall probabilities are quite high, the intrusion of dry air from 850-700-mb will limit rainfall amounts with the probabilities for >0.25" west of the Mississippi River only 10-20% and less than 10% elsewhere.

Friday - Saturday

Weak 290K isentropic ascent and broad lower tropospheric confluence look to keep the risk for showers going west of the Mississippi River through Friday--again with minimal rainfall amounts. How the rain on Saturday unfolds is of somewhat lesser confidence with there likely being a sharp cutoff in the eastward extent of the rain between I-35 and the Mississippi River--exactly where is to be determined. Once again, in the absence of deep moisture or lift, rainfall amounts should be minimal with a 20-50% chance of >0.25" and 10-20% chance of >0.50" west of the Mississippi River. Upper tropospheric ridging builds to the west for Sunday and Monday, bringing a reprieve from the light rain to start the new week.

Tuesday - Wednesday: Next Widespread Rain Risk

A longwave trough will move east through the Mid- and Upper Mississippi River Valley. This will bring rain into the region. There are some models that bring tropical moisture northward into the region. Meanwhile, other models show that this plume of tropical moisture will be southeast of the area.

High temperatures will be in the mid- to upper 60s. Low temperatures will range from the mid-40s to mid-50s.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 552 AM CDT Thu Sep 24 2026

A few locations east of the Mississippi River have seen mist/fog develop early this morning which should dissipate around 13z. Scattered showers move into the region this afternoon (50-70%), primarily impacting those west of the Mississippi River into the evening hours, but showers will be light so expecting conditions to primarily remain VFR through the afternoon and evening. Looking towards the end of the TAF period, ensemble guidance suggests that MVFR/IFR ceilings may develop south of I-90 given saturated low levels, around a 40-60% chance in the 24.00z HREF and 23.19z NBM. Otherwise, light east to southeast winds continue throughout the day.

ARX WATCHES/WARNINGS/ADVISORIES

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