127
FXUS63 KARX 301107
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
607 AM CDT Wed Sep 30 2026

.KEY MESSAGES...

- Heaviest rainfall locally affecting southernmost counties from
  northeast Iowa into far southwest Wisconsin through Thursday
  with 1" to 2" expected, heaviest tonight into Thursday
  morning.

- Diminishing, low (<20%) flooding (river/areal) threat due to
  southern shift in forecasted heavy rainfall amounts.

&&

.DISCUSSION...
Issued at 111 AM CDT Wed Sep 30 2026

Through Thursday: Widespread Rainfall

Widespread light to moderate showers have overspread much of the
Upper and Mid Mississippi River Valleys overnight with QPE totals on
the low side generally at or below 0.25 inches. This activity is
forming within an axis of increased mid-level moisture with
synoptic support from strong southwest flow aloft ahead of an
upper low/trough across the Desert Southwest. Totals through
the overnight hours and into mid morning may reach 0.5-0.75,
mainly for areas south of the IA/MN border where some heavier
returns are showing up on radar. Heavier rainfall expected later
in the day with limited instability as pWats increase overnight
and through the day tomorrow from strong 850 mb moisture
transport into the region.

An break in rainfall is expected for much of the area before
subsequent, likely heavier, rainfall forms during the afternoon,
continuing into early Thursday morning. As mentioned earlier,
with strong 850 mb moisture transport into the region, pWats
will likely climb to 1.75+ inches, potentially approaching 2"
across our far southern counties (Grant/Clayton) (30.00Z HREF).
Similar to previous forecasts, the overall axis for heaviest
rainfall continues to shift south into Central Iowa, aligning
with the overall trend in the EC ensemble for many days now.
Therefore, current forecast confidence for locally heaviest
rainfall looks to be limited to far southern portions of
Southwest Wisconsin (Grant and potentially Crawford/Richland
Counties) and far southern portions of Northeast Iowa (Fayette
and Clayton Counties) with less than 1" likely elsewhere locally
by Friday morning.

NBM 30.01Z 1"+ rainfall probabilities from 60 to 80% in the
aforementioned counties appear slightly earlier with a sharp
gradient/cutoff to the north. LREF 29.12Z has a more broad area
across northeast Iowa and Southwest Wisconsin for its
probability of 1 inch of rainfall or greater (40-90%) with mean
totals generally in the 0.5-2 inch range across the region. With
the southern shift in heavy rainfall, the flooding threat is
starting to dwindle, especially for area rivers. 90-95th
percentile amounts from this system looked to be in the 2.5-4.5
inch range and this would likely create some areal and river
flooding concerns but this concern seems to be diminishing for
our local area. A cold front is expected to move in through the
day on Thursday which will start to usher in a drier airmass. It
will make slow progress through the region as high pressure
builds in behind it with rain slowly ending from northwest to
southeast late Thursday night.

Friday into Early Next Week: Mostly Dry and Trending Cooler

The H300 jet stream is forecast to sit across southern Canada and
may dig south at times into the Great Lakes region to northeastern
US this weekend into early next week. With a cold front south of the
local forecast area and some cooler air filtering in due to the
troughing, daily high temperatures will be a few degrees cooler into
early next week. The cooler air mass will be more noticeable at
night with lows dropping into the 40s to 30s. As of now, Monday
morning looks to be coolest morning over the next week with the
coldest temperatures potentially approaching freezing across
central Wisconsin. Mostly dry conditions are expected during
this time frame with the exception being on Saturday as there
are low chances for light rain showers over the northern half of
the CWA.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 604 AM CDT Wed Sep 30 2026

Impacts from low ceilings have abstained from both TAF sites
overnight as LIFR-IFR observations have mostly affected northwestern
peripheral smaller airports from southeast Minnesota into central
Wisconsin. Expect low ceilings to eventually reach both sites
through the morning hours, lasting until tonight.

&&

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

&&

$$

DISCUSSION...Barendse/Muscha
AVIATION...JAR