037
FXUS63 KARX 210520
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1220 AM CDT Fri Aug 21 2026

.KEY MESSAGES...

- Scattered shower and storms move through the area through the
  morning and early afternoon with some potentially on the
  stronger side, especially for areas in southwest Wisconsin.

- Seasonal temperatures continue into next week with highs in
  the 70s to lower 80s.

- Dry weekend with the next potential round of storms coming
  Tuesday and Wednesday of next week.

&&

.DISCUSSION...
Issued at 1205 AM CDT Fri Aug 21 2026

Today: Storm Potential

Invigorating upper level northwest flow is driving storm development
upstream through central Minnesota overnight, focused along an
enhanced area of low level convergence on Central to Northern Plains
VWPs. A meager open perturbation well to the north over Lake
Superior on GOES derived upper level wind plots has prevented storms
spreading as far south as the local forecast area as subsequent
supplementary forcing from the low level frontal boundary trails
well behind, struggling to traverse the Missouri River Valley into
west-central Minnesota. Eventual synoptic assistance from an
additional perturbation crossing the International Border from
Saskatchewan into Northern Dakota will drive said frontal boundary
southeast through the Upper Mississippi River Valley.

Ahead of a cold front that will push through the region this morning
and afternoon, a few weak perturbations and a slight increase in the
nocturnal LLJ will help to initiate some storms, as recent CAMs have
supported, during the early morning hours. With limited instability
and minimal shear and mid-level subsidence, these showers and storms
should remain below severe limits, however small hail and gusty
winds will be possible. Heading into the mid morning to early
afternoon timeframe, the cold front will begin to enter our CWA.
Dependent on diurnal timing and southeastern extent of this low
level frontal boundary across the forecast area, these prefrontal
storms will likely continue for some of the local forecast area
primarily from northeast Iowa into southwest Wisconsin. While
instability is expected to be ample, around 2000 to 2500 J/kg of
MLCAPE, there will be minimal shear present. With the increase in
instability though and the fact that any storms that due form along
and just ahead of the cold front will be in their developing phase,
a storm or two could have severe hail up to 1". The better severe
ingredients remain in southeast Wisconsin and northern Illinois and
back west into Nebraska and southern Iowa. All precipitation chances
diminish by the early afternoon. Total rainfall from these storms
could be over 1" in some locations as the 00Z HREF LPMM has some
spots of over 1" along the I-94 corridor and in far southwest
Wisconsin.

Saturday - Midweek: Dry Early, Storms Return Tuesday

Northwest flow returns to the region as a trough amplifies to our
east and the ridge sets up to our west. This ridge decays as it
moves eastward into early next week. With our region in between
these two features, we look to be mostly dry and slightly cooler
through the weekend until the ridge breaks down on Tuesday. High
temperatures stay in the low 70s to low 80s from Saturday through
Monday. Storm chances return Tuesday as a trough moves down from
northern Minnesota. The latest GEFS and EPS have a widespread 60 to
90% chance for measurable storms. The exact timing and placement
details of this rain will be hammered out as we get closer to the
event.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1217 AM CDT Fri Aug 21 2026

Primary concern over the next 24 hours will be potential for TS
over the next 12 hours as a cold front pushes southeast. TS is
likely (60-80%) overnight northeast of a EAU-82C line but could
(30%) extend to near LSE. Have retained PROB30 mention and
adjusted timing compared to previous TAF cycle. Probability is
too low to keep a mention at RST (20%). Otherwise winds will
turn clockwise from out of the southwest to out of the northwest
over the next 12 hours as well and continue to be out of the
northwest at 10-15 knots Friday afternoon.

&&

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

&&

$$

DISCUSSION...Cecava/JAR
AVIATION...Ferguson