835
FXUS63 KARX 291822
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
122 PM CDT Tue Sep 29 2026

.KEY MESSAGES...

- Widespread rainfall potential increases this afternoon and
  lasts into Thursday. The heaviest rainfall is shifting
  further south but still could impact northeast Iowa into far
  southwest Wisconsin. The potential for 2+ inches of rain is
  still around 40-60% for these areas.

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

&&

.DISCUSSION...
Issued at 118 PM CDT Tue Sep 29 2026

This afternoon to Thursday: Widespread Rainfall

Light rain showers are moving east across Iowa and Minnesota at
this time. This activity will reach the western portions of the
forecast area here shortly and should continue to move east
over the region the rest of today. This activity is forming in
an axis of increased mid level moisture and it has synoptic
support with PVA associated with shortwave troughs. This first
initial round of rainfall likely will not be all that heavy,
since instability will be very low today and PWAT values are
still rising. Still, some areas may receive upwards of 0.50-0.75
inches of rain before sunrise tomorrow morning. As this first
round of rain ends from west to east tonight, fog may form in
its wake due to the increased surface moisture. The latest hi-
res ensemble output has the higher potential for fog across
central Minnesota, however there are members that bring the bank
of fog into western Wisconsin into southeastern Minnesota. Any
fog that does develop should dissipate a few hours after sunrise
on Wednesday morning.

A break in the rainfall is likely for most of the forecast area on
Wednesday before the second and heavier round of rainfall forms
during the afternoon into Thursday morning. PWAT values will
continue to climb into the 1.5-1.75 inch range with the potential
for the far southern counties to approach 2 inches based on mean
ensemble PWAT values. Model guidance is now finally starting to
agree with the location for the heaviest rainfall and it has been
trending further south compared to 24 hours ago. The EC/EC AIFS have
been indicating that this corridor of heavy rain would mainly set up
in Iowa into southern Wisconsin for multiple days whereas other
model guidance has had no consistency with the placement of the
heaviest rainfall. A majority of guidance is now leaning
towards the southern solution and the trend may even continue to
push the heaviest rain further south out of the CWA. If the
heaviest rain still reaches our area, only the far southern
counties are expected to get this rainfall and it should hold
off until Wednesday night into Thursday morning based on the
latest hi-res models. Rainfall amounts are still pretty
uncertain, but the latest 29/13z NBM still indicates a 40-60%
chance to reach or exceed 2 inches for Fayette county to Grant
county. High end amounts from this system continues to be
upwards of 3-4 inches so if those amounts are actually achieved,
some flooding or river flooding concerns may arise. Rain will
come to an end on Thursday from northwest to southeast as a cold
front ushers in a drier airmass.

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 /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1239 PM CDT Tue Sep 29 2026

Impending rain and associated MVFR visibilities and MVFR to IFR
ceilings will move in west to east this afternoon. While rain
will eventually focus south of RST/LSE, low ceilings will likely
(70%) remain. Am doubtful widespread VFR conditions will return
before the end of the period. The good news is that the
potential for TS is pretty low (20% or less) and winds should
remain consistently out of the southwest over the next 24 hours.

&&

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

&&

$$

DISCUSSION...Muscha
AVIATION...Ferguson