430
FXUS63 KARX 211044
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
544 AM CDT Mon Sep 21 2026

.KEY MESSAGES...

- There are chances (20-50%) for light rain showers across the
  area today, with the highest chances across NE Iowa and SW
  Minnesota.

- Cooler than normal conditions are expected throughout much of
  the week with highs in the 60s.

&&

.DISCUSSION...
Issued at 1223 AM CDT Mon Sep 21 2026

Today: Rain Shower Potential

As an upper level cutoff low churning over the High Plains slowly
shifts eastward through the early morning hours, scattered showers
are expected to develop across the Upper Mississippi River Valley.
Forcing for these showers is weak at best, primarily driven by an
area of 1000-500hPa Q-Vector convergence. However, some convective
enhancement is possible this afternoon given 25-50 J/kg of 3CAPE
associated with slightly steepened 900-800hPa lapse rates seen in
RAP/RRFS soundings. Given the weak forcing over much of the area and
the track of the upper low, thinking the greatest potential for
scattered showers exists along and south of I-90 today (40-70%).
21.00z CAM solutions are beginning to suggest that those north of I-
90 could see some scattered shower development this afternoon as
well (10-30%) given the steeper low level lapse rates, though
shallower moisture with northward extent would likely keep any
development fairly isolated.

As far as amounts are concerned, expectations remain on the lower
end around 1/4 inch at most, although there is a low signal for
localized amounts near 1/2 inch across northeast Iowa and southwest
Wisconsin in the 21.00z HREF (10-20%) if any convective enhancement
occurs.

Tuesday - Friday: Staying Cool and Drier

Beyond today, northeasterly surface flow and high pressure
south of the Hudson Bay will allow for cooler and drier
conditions to advect into our region. As a result, median high
temperatures in the NBM throughout the week generally remain in
the 60s for most of the local area. As we head into Wednesday
morning, upper-level ridging will push into the local area which
in turn should both allow for a gradual warming trend and
clearing skies during this period. Consequently, not seeing much
for precipitation chances till later into the week when maybe
some shortwave perturbations try to sneak back into the region
during the Thursday and Friday timeframe. However,
predictability with these waves remains very low at this time.
In any case, will have to watch Wednesday morning for some frost
potential across north-central WI with median low temperatures
in the middle to upper 30s.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 538 AM CDT Mon Sep 21 2026

MVFR conditions are being observed at the terminals. KRST has
the higher potential to remain MVFR for much of the daytime
hours, whereas KLSE should break out of the low clouds by mid to
late morning. Scattered rain showers are expected today with
minimal impacts expected at the terminals. KRST continues to
have the best chances for rain showers, so have continued to
maintain a PROB30 group for minor visibility reduction. VFR
conditions are forecast beyond 00z through the remainder of this
TAF issuance. The wind will remain out of the east at 10-15 kts
or less.

&&

.HYDROLOGY...
Issued at 538 AM CDT Mon Sep 21 2026

Minor flooding continues at a few sites along the Root and
Turkey Rivers, but many sites along these rivers have crested
or are close to cresting and are expected to fall below flood
stage in the next 24 hours. Some additional rainfall is expected
today, mainly along and south of I-90, but overall amounts are
expected to be low, generally up to 1/4 inch at most although
very localized areas along/south of Highway 18 may see amounts
around 1/2 inch (10-20%). Regardless, these amounts are not
expected to contribute to additional flooding impacts. Mostly
dry conditions are then expected through the remainder of the
week.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.

&&

$$

DISCUSSION...Falkinham/Naylor
AVIATION...Muscha
HYDROLOGY...Falkinham/Muscha