180
FXUS63 KARX 011041
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
541 AM CDT Tue Sep 1 2026

.KEY MESSAGES...

- Periodic showers and storms will be seen this week. The
  highest rain chances will be tonight (mainly along and north
  of Interstate 90) and on Wednesday night and Thursday morning
  along and north of Interstate 94.

- Above-normal temperatures will persist through the remainder
  of the work week.

&&

.DISCUSSION...
Issued at 1255 AM CDT Tue Sep 1 2026

This Afternoon

A shortwave trough will move out of Nebraska this morning and
through northern Iowa, southern Wisconsin, and northern Illinois
this afternoon. Ahead of this wave, the 0-1 km mixed- layer
CAPES will climb into the 1500-2500 J/kg. This will result in
isolated to scattered elevated showers and storms in northeast
Iowa and southwest Wisconsin. With weak 3-6 km shear (10-20
knots) and the storms being mainly elevated, not expecting any
severe weather.

High temperatures will range from the mid-80s to lower 90s.

Tonight

A shortwave trough will move out of South Dakota this evening
and through the Upper Mississippi River Valley overnight
tonight. As this wave moves into southwest Minnesota and
northwest Iowa, a 30-knot 850 mb jet will intersect a frontal
boundary in the region. This will result in the development of a
mesoscale convective complex. As the nocturnal jet gradually
veers, the complex will become linear and accelerate with time.
While the 0-3 km is anywhere from 40 to 50 knots, soundings
suggest that this system will likely remain elevated. We will
have to watch the DCAPE through the night to make sure that
remains the case. If the system happens to become surface-based,
there would be the potential for damaging winds. The CAPE aloft
looks rather skinny, so not anticipating any large hail.

The HREF has the highest rainfall amounts along and north of
Interstate 90. Rainfall totals will likely range from a quarter
to three quarters of an inch. The highest totals will be likely
west of the Mississippi River. This is due to the eastward
progression being just a bit slower. The ensemble localized
probability-matched mean suggests that there could be some
localized totals in the 1 to 2 inch range.

Low temperatures will be in the lower and mid-60s north of
Interstate 90 and in the mid- and upper 60s across the remainder
of the area.

Wednesday Night into Thursday

Another mesoscale convective complex will develop across
northwest Minnesota during the evening on the nose of a 25-30
knot 850 mb nocturnal jet. As this jet gradually veers
overnight, this complex will gradually shift east and then
southeast. This should result in the heaviest rain (1-2 inches)
falling along and north of Interstate 94. With weak 0-3 km and
0-6 km shear and this system likely remaining elevated, the
threat for damaging winds look to be on the low side. In
addition, skinny CAPEs in the sounding profile does not favor
large hail.

Low temperatures will range from the mid-50s to mid-60s. High
temperatures will range from mid-60s to lower 70s.

Labor Day Weekend

There remain plenty of uncertainty on what the upper air pattern
will look like for the upcoming holiday weekend. This
uncertainty comes from how the models deal with a retrograding
ridge. Some models keep our area underneath the strong and very
warm ridge. Others suggest that this ridge will retrograde much
further west and this will in turn result in more northwest flow
aloft. In this scenario, we would see near to below
temperatures.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 542 AM CDT Tue Sep 1 2026

Light winds will be seen across the Upper Mississippi River
Valley through mid-morning. In addition, low-level moisture
will pool along a weak frontal boundary. This will result some
IFR/MVFR fog early this morning. This fog should dissipate by
01.15z.

There will be isolated to scattered showers and storms across
northeast Iowa and southwest Wisconsin this afternoon. This may
result in some gusty winds.

A thunderstorm complex will move through northeast Iowa and
southeast Minnesota between 02.05z and 02.08z, and through
western Wisconsin between 02.08z and 02.11z.

&&

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

&&

$$

DISCUSSION...Boyne
AVIATION...Boyne