930
FXUS63 KARX 281816
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
116 PM CDT Mon Sep 28 2026

.KEY MESSAGES...

- Dry conditions continue through Tuesday morning.

- Widespread rainfall potential increases Tuesday afternoon
  through Thursday. There are medium chances (40-60%) for
  rainfall totals to reach or exceed 2.5 inches south of I-90.

- High temperatures will remain seasonal in the 60s to 70s.

&&

.DISCUSSION...
Issued at 112 PM CDT Mon Sep 28 2026

This afternoon into Tuesday Morning: Dry Conditions

Visible satellite early this afternoon shows low level clouds
remaining across much of the region. The low clouds should slowly
clear out today and temperatures should rise into the upper 60s to
mid 70s this afternoon. Some patchy fog may develop once again
tonight over portions of the Upper Midwest, but it is not expected
to be as widespread or as dense as it was this morning. Some
isolated locations could still see visibility drop down to a mile or
less though.

Tuesday Afternoon through Thursday: Widespread Rainfall

An upper level low pressure system will begin to become cutoff over
the Desert Southwest on Tuesday into Wednesday. Out ahead of the
low, moisture will surge northward towards the Southern Plains and
then eventually the Northern Plains to Great Lakes region. The
increased moisture will even be aided by Hurricane Polo after it
moves northeast out of Baja California into far northern Mexico. The
combination of synoptic scale forcing and a rich moisture
environment will lead to widespread heavy rain from the Desert
Southwest, to the Plains, and portions of the Upper Midwest.
Widespread totals of 2+ inches are possible throughout this entire
area given this set-up.

As for our area, rain is expected to begin across western portions
of the local forecast area on Tuesday afternoon. This initial round
of rain will occur at the same time as PWAT values begin to increase
upwards of 1.5-1.75 inches. MUCAPE values may only be as high as a
few hundred joules throughout the entire time period, so moderate to
heavy rain may occur at times aided by convective processes. It
still appears the best potential for heavy rainfall that may lead to
flooding concerns will be from Wednesday afternoon into the night.
This will coincide with the stronger push of moisture and it will
occur out ahead of a southeastward moving cold front. Model
guidance continues to vary on where the highest rain totals may
fall, ranging from just to the northwest of the FA or across the
southern half of the FA. Based on the synoptic set-up, we are
leaning towards the southern solutions panning out which would
bring in heavier rainfall totals to northeastern IA into far
southwestern WI. Most likely rainfall totals continue to be in
the 1-3 inch range, with the higher totals (2.5-3 inches) across
northeastern IA. For some isolated locations, higher totals of
3.5-4+ inches cannot be ruled out. These rainfall totals would
lead to flooding concerns, especially for rivers and locations
that had just received a lot of rainfall in the last few weeks.
The rain potential will end from northwest to southeast on
Thursday as the cold front moves through and the mid level
moisture becomes displaced to the east/southeast of the region.

Friday into the Weekend: Drier and Trending Cooler

In the wake of the cold frontal passage, temperatures should slowly
trend cooler this upcoming weekend as broad scale troughing attempts
to dig south over the Great Lakes region. Daytime highs are not
forecast to be all that much cooler, with temperatures remaining in
the mid 60s. Where the cooler air will be more noticeable will
be overnight, with overnight lows drop into the lower 40s to mid
30s. Dry conditions are currently expected but there may be a
low chance for light rain on Saturday if moisture moves in quick
enough out ahead of another southern surge in the upper level
trough.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1226 PM CDT Mon Sep 28 2026

MVFR stratus deck continues to erode this morning but, as the
boundary layer is becoming established following insolation,
cumulus is developing at the top of the mixed layer, with this
cumulus also at around 2500-3000 feet at issuance time. Have
therefore continued to carry MVFR for at least 1-3 hours at
RST/LSE. Tonight, some chance (20-60%) for fog to return,
primarily to the Wisconsin River valley. Have refrained from
inclusion in the TAFs with this cycle due to low confidence in
occurrence and expected increase in wind speeds in the boundary
layer overnight.

&&

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

&&

$$

DISCUSSION...Muscha
AVIATION...Ferguson