834
FXUS63 KARX 071049
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
549 AM CDT Mon Sep 7 2026

.KEY MESSAGES...

- Increasing rain chances overnight into Tuesday morning,
  increasing in probabilities and coverage Tuesday evening and
  night.

- Heavy rain main concern through Tuesday evening and night with
  strongest storms capable of hail and damaging winds.

- Near normal temperatures and mostly dry rest of the week into
  the weekend.

&&

.DISCUSSION...
Issued at 254 AM CDT Mon Sep 7 2026

Increasing Rain Chances Tonight:

An upper wave currently over the Pacific Northwest is expected
to eject into the Canadian High Plains through the day today. A
surface low pressure center is expected to deepen as is follows
a similar trajectory out of the Northern High Plains. This will
tighten the pressure gradient across the Upper Midwest,
increasing southeasterly winds across the region through the
day. This will serve to pool moisture across the warm sector,
initiating increasing pWats to over 1.5 inches. Showers and
storms are expected to start developing along and ahead of the
cold front late this evening and into the overnight hours as
lift from both a low level jet and shortwave jet max coincide.
These storms could pose a marginal risk for hail and wind into
the early morning hours, mainly across Southeast Minnesota and
West Central Wisconsin but they should tend to fizzle out with
time in the morning as the low level jet weakens.

Highest, Widespread Rain Chances Tuesday:

A short reprieve in shower and storm activity is expected into
Tuesday afternoon as forcing becomes more nebulous and focused
on the mesoscale. Development looks to increase again later
into the evening and overnight hours across the southeastern
half of the local area given reinvigoration of the low level
jet the short wave trough axis moving through. There will again
be a marginal threat for hail and wind with these storms. Given
the elevated instability these storms should be able to tap
into modest cloud layer shear. Another concern will be the
threat for heavy rainfall later during the day on Tuesday, with
continued southeast winds ahead of the frontal boundary, pWats
will continue to climb into the 1.75-2+ inch range. NBM 06.19
probabilities for 1 inch of rain in a 48 hour period ending at 7
PM Wednesday were between 30-50% across the region, 5-20% for 2
inches. Overall storm motions seem to be progressive enough to
keep flash flooding concerns at bay even though pWats and warm
cloud depths would suggest potential for highly efficient
rainfall producers. Rain will gradually push off to the south
and east through the overnight hours with most places looking to
be dry by 12Z Wednesday.

Drying Out, Near Normal Temperatures Into Weekend:

As the upper wave/trough axis move east, the trailing frontal
boundary from the occluding surface low well to our north in Canada
will sweep through the region early Wednesday. This will finally
usher in a drier airmass to the region as a whole with dew points
falling back into the upper 50s. A weak surface high is expected to
build into the Midwest by Thursday. This, in combination with zonal
flow to weak ridging aloft, will keep conditions dry for the late
week period. Temperatures behind the front won`t be much "cooler"
but they will be a bit closer to normal in the 70s to lower 80s
Thursday and Friday. The next chances for rain look to come by the
weekend as another upper wave looks to potentially swing through the
upper Midwest.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 534 AM CDT Mon Sep 7 2026

Increasing south-southeast winds through the daytime hours will
remain highest west of the Mississippi River Valley primarily
locally in southeast Minnesota affecting KRST TAF site.
Increasing precipitation chances near the end of the 07.12Z TAF
terminus, moving from west to east, will initially locally reach
KRST TAF site followed by KLSE shortly thereafter. Given the
longer forecast hour affecting confidence in exact timing of
onset, have included PROB30 at KRST for potential impacts as
further adjustment will be needed in coming forecasts.

Storm, precipitation, and impacts likely linger through Tuesday
night outside of a potential temporary reprieve Tuesday late
morning into the early afternoon.

&&

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

&&

$$

DISCUSSION...Barendse
AVIATION...JAR