236
FXUS63 KARX 141738
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1238 PM CDT Mon Sep 14 2026

.KEY MESSAGES...

- Several rounds of moderate to locally heavy rainfall from
  midday today through early Tuesday morning. Widespread total
  rainfall amounts around 1" with localized pockets of 2-3"
  could result in some river rises and flooding of poor drainage
  locations.

- Additional rounds of heavy rainfall are possible Thursday
  through the weekend. If these storms track over the same
  areas, the risk for flooding could increase.

- Seasonal temperatures for the upcoming work week with highs in
  the upper 60s to mid-70s.

&&

.DISCUSSION...
Issued at 1120 AM CDT Mon Sep 14 2026

This Afternoon - Tuesday Morning: Periods of Heavy Rain

Multiple waves of moderate to heavy rainfall affect the local
area over the next 24 hours. This first broad but not
necessarily intense wave of rain currently upstream over
southwestern MN and western Iowa lifts into the region through
the day as the associated zone of theta-e advection likewise
lifts northeast. While the mid-level tropical Pacific moisture
river will be in place by midday, the lower tropospheric Gulf
airmass lags behind by 4-6 hours, resulting in deep tropical
rainfall processes not being fully realized until late this
afternoon and tonight.

This late afternoon to overnight timeframe--with PWATs near 2"
and deep warm cloud depths of 10-12 kft (climatological highs
for this time of year)--is the period worth watching for higher
rainfall rates and potential flooding impacts. The good news is
that soils are dry heading into this event and the rainfall
looks to be on the progressive side with enough breaks between
each round to reduce the overall risk of any flooding. By
Tuesday morning, there is a solid signal in the CAMs that most
areas should see total rainfall amounts around 1" with localized
pockets of 2-3", with these corridors driven by the tracks of
the individual small convective cells containing the higher
rain rates (a 20-30% shot that a given location will fall under
one of these higher rainfall swaths). A cold front pushing
southeastward overnight will also aid in keeping the heavy rain
corridors fluid in space and gradually shifting off to the
southeast of the area by mid- morning Tuesday.


Later in the Week: The Rain Returns, Could be Heavy

Broad subtropical upper tropospheric ridging builds across the
southern and southeastern U.S. in the wake of our passing shortwave
tonight into Tuesday, lingering well into the weekend. This feature
and the attendant surface ridge act to keep the lower
tropospheric baroclinic zone from sliding too far south of the
forecast area for Tuesday into Wednesday, with the surface to
700-mb front likely pivoting over northern Missouri and southern
Iowa Tuesday night as a northern stream wave approaches along
the U.S./Canadian border and lee cyclogenesis takes place along
the Front Range. The mid-tropospheric front returns to the
region by Wednesday afternoon, which could serve to generate
elevated showers. Similar to this afternoon, the deeper moisture
lags to the south and doesn`t arrive until Wednesday night into
early Thursday. Therefore, any rain on Wednesday does not look
to be of much impact.

The zonal flow and subtleties of any upper level forcing make
the timing and amounts of any rainfall for Thursday difficult to
nail down. Nevertheless, the thermodynamic environment will be
primed and ready to produce efficient rainfall rates should the
forcing come to fruition. At this point, the threat for heavier
rainfall is progged to be south of I-90.

There is an increasing signal for Friday and the weekend that the
upstream pattern amplifies as a cutoff low begins to advance
eastward out of California. This facilitates a greater risk for
heavy rainfall, which will be dictated by the placement of near
surface baroclinic zone--lifting northward during this time
towards central Minnesota/Wisconsin. The recent EPS/GEFS runs
are honing in on this Friday into Saturday period for the next
widespread heavy rain potential with 40-50 percent of the EPS
members exceeding 2 inches for total rainfall amounts and upper
end ensemble members exceeding 3-4 inches. Given the strength of
this signal and the stronger synoptic forcing at play, it is
more of a question of where, rather than if, this heavy rain
occurs. Such details will be refined over the next few days
given that this event is still 5-6 days out. One cannot also
fully rule out the risk for stronger storms on Friday afternoon
and evening depending, again, on how far north the surface
front tracks.

What we can say with higher certainty is that temperatures should
remain solidly in the 60s and 70s for highs through the week, a
solid taste of late summer/early fall weather.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1238 PM CDT Mon Sep 14 2026

Widespread rain showers with scattered embedded thunderstorms
move into the region from west to east throughout the afternoon
and persist through the overnight with the heaviest storms
bringing MVFR to very localized IFR conditions. These showers
depart from northwest to southeast during the morning on
Tuesday. Winds this afternoon remain from the SSE at
10-20G20-30kts, with the strongest winds west of the Mississippi
River. LLWS develops after sunset and lasts until 06-09Z.
Surface winds lessen during the early morning hours as well and
then veer to the WNW during the morning on Tuesday.

&&

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

&&

$$

DISCUSSION...Skow
AVIATION...Skow