546
FXUS63 KARX 141049
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
549 AM CDT Mon Sep 14 2026

.KEY MESSAGES...

- Showers and storms beginning later this morning and continuing
  through the overnight will lead to heavy rain and some
  localized flooding. Total rain amounts of 1 to 2" with some
  areas seeing up to 3".

- Seasonal temperatures for the week with additional storm
  chances for mid to late week.

&&

.DISCUSSION...
Issued at 240 AM CDT Mon Sep 14 2026

Today:

An upper level extratropical cyclone that made landfall along the
Pacific Northwest Saturday morning on satellite water vapor imagery
loops has slowly been shifting east over the last 24 hours driving a
large area of confluence from the Klamath Mountains in northern
California to the Coconino Plateau in Arizona. The resultant uptick
in mid and upper level winds on GOES derived motion winds is
initially advecting tropical moisture through gaps in the Desert
Southwest towards the Northern Plains with 400 kg m-1 s-1 IVT racing
north through Wyoming overnight. Supplementary, stronger low level
moisture advection, evident in 90th to daily record PWATs (SPC
Climatology) at GJT and RIW in 14.00Z RAOBs combines with a directly
Tropical sourced airmass through the early morning, resulting in a
1000+ km plume of 1000-1500 kg m-1 s-1 Integrated Vapor Transport
from northern Kansas to the Canadian border with Minnesota.

Ongoing confluence of the aforementioned airmasses eventually causes
PWATs near 2" (EPS/GEFS) near the main directionally convergent
boundary, near and southwest of the local forecast area tonight into
early Tuesday morning.

Rain Today:

Initial rainfall expected with warm/moist air advection through the
afternoon moving from southwest to northeast. Local rainfall rates
expected to remain mostly subdued as the nose of the low level jet
will be focused north towards the triple point of the deepening,
closing, and phasing low pressure. Supplementary cyclogenesis near
the forecast area will re-enhance local heavy rain potential in
spots late Tuesday evening before a northwest to southeast advecting
frontal boundary sags southeast overnight into Tuesday morning. Deep
warm cloud depths from the surface to 600mb raise heavy rain and
flooding concerns where strongest storms form and linger over the
forecast area. Current confidence for a widespread 1" of rainfall
with 2"+ possible in spots where heaviest rain sets up tonight into
early Tuesday morning. While highest confidence for 1"+/hr rainfall
rates remain southwest of the local forecast area in central Iowa,
multiple ingredients support nearing those values in northeast Iowa.

Rain Returns Wednesday:

The warm, moist airmass remains just south of the local forecast
area as passing anticyclonic low level flow mostly drying things out
for Tuesday before a similar trajectory ejecting upper level low
lifts northeast through the Northern Plains for Wednesday. While the
anomalous moisture will remain on the southern doorstep of the local
forecast area, meridional extent of the low`s path leaves
discrepancies and lower confidence for northern surge of moist air.
Therefore, have kept NBM precipitation probabilities Wednesday
through Saturday. The long duration of rainfall potential would
increase additional flooding concerns through the week.

Storm Chances Friday:

The warm, moist airmass will be lingering over the forecast area
through late week when a Rocky Mountain Low is expected to eject
north into the Northern Plains. Subsequent easterly advection along
the lingering low level boundary raises strong to severe storm
concerns across the Upper Midwest.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 549 AM CDT Mon Sep 14 2026

Showers and storms will move into the region later this morning
and continue through the overnight. At times there may be
lowered flight categories when there is heavier rain which could
lead to lowered visibilities. During the evening and overnight,
MVFR to IFR CIGS arrive for all locations. Southeast winds this
morning increase with sustained winds of 15 to 25 mph and gusts
of 25 to 35 mph. These winds gradually decrease this evening and
begin to turn more northwesterly as a front arrives during the
early morning. By mid Tuesday morning all locations should have
northwest winds.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Frost Advisory until 8 AM CDT this morning for WIZ034-042.
MN...None.
IA...None.

&&

$$

DISCUSSION...JAR
AVIATION...Cecava