666
FXUS63 KARX 131045
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
545 AM CDT Sun Sep 13 2026

.KEY MESSAGES...

- Shower chances move west to east this morning into the
  afternoon, minimal overall accumulations expected.

- Heavy rain likely Monday through Monday night with flooding
  concerns where heavy rain bands set up.

- Rain chances return Wednesday, potentially lasting into the
  weekend.

&&

.DISCUSSION...
Issued at 1245 AM CDT Sun Sep 13 2026

Today:

Shower chances through today will be tied to a mid level trough
passage and positive mid level vorticity advection through the
Upper Midwest. Overall limiting factor for coverage and amounts
will be available moisture.


Rainfall Chances Monday Night:

Heavy rainfall spreads northeast through Monday morning, becoming
widespread through of the rest of Monday and Monday night. The
responsible closed upper level anticyclone on upper level water
vapor imagery loops over the Pacific Northwest will rapidly advect
east into southern Canada, drawing 90th percentile (TOP 13.00Z RAOB -
 Climatology) north through the Central to Northern Plains.
Resultant local PWATs expected to near 2" by Monday Night (GEFS
12.18Z 30-60% ; EPS 12.18Z 50-90%). Initial, more widespread
rainfall expected to progress east within the closing warm, moist
sector advecting east across the Upper Midwest through Monday.
Solidification of the low level frontal boundary and intensification
of the low level jet with anomalous level moisture increases
flooding concern primarily across the southern half of the forecast
area Monday night. Exact location of the frontal boundary focusing
the heavier rainfall rates as the parent low exits east will
determine location of highest concern, varying from west-central
Wisconsin, east-central Minnesota, and northeast Iowa in the
available LREF (12.12Z). LREF (12.12Z) member mean precipitation
spreads from 0.6" (GEFS) to 1.4" (EPS) with intermember
interquartile spread from 0.25" (GEFS) to 1.2" (EPS), outlining the
current forecast challenge in fine tuning location of highest
impacts.

Rainfall Returns Wednesday:

Monday`s frontal boundary expected to remain just south of the
locale 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.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 545 AM CDT Sun Sep 13 2026

Light rain is possible this morning for areas south of I-90.
Rain chances subside by early this afternoon. Despite this light
rain, VFR conditions expected for the TAF period. CIGS during
the light rain will hang between 7kft to 10kft, then expect
skies to clear out for the afternoon. Light northwest winds at 5
to 10 mph for today switch to light and variable winds for this
evening.

&&

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

&&

$$

DISCUSSION...JAR
AVIATION...Cecava