FXUS63 KARX 240548
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1248 AM CDT Mon Aug 24 2026

.KEY MESSAGES...

- Temperatures and humidity gradually increasing through
  midweek with highs in the mid 70s to mid 80s.

- Thunderstorm chances return Tuesday afternoon and evening.
  Some could be strong, mainly across the northwest half of our
  forecast area.

- Lingering showers possible on Wednesday, with next chance of 
  rain over the weekend.

&&

.DISCUSSION...
Issued at 1239 AM CDT Mon Aug 24 2026

Fog potential this morning, gradual increase in warmth/moisture

Cirrus from convection over North Dakota will continue to spill
into the area early this morning. This complicates the forecast
for potential fog development in valleys and low-lying areas, 
in what would otherwise be a decent synoptic setup with high 
pressure overhead. But evening HRRR runs trended toward some 
breezier winds of 10-15 knots in the 500-1500 ft layer. All this
suggesting that fog may be more patchy this morning. 

There is an outside chance some decaying convective showers 
from the Northern Plains would be steered southeastward in the 
upper flow to clip areas west of the Mississippi River with some
showers this afternoon. Several 24.00Z CAMs are showing this, 
but the HRRR is mainly dry.

Daytime highs will be warming a bit today into midweek as 
southerly return flow develops. Moisture will also gradually be 
on the increase ahead of a pronounced upper shortwave trough 
progged to cut across northern Minnesota/Wisconsin toward 
Wednesday. Dewpoints will rise back into the 60s, and with a 
feed of Gulf moisture there is a >70% likelihood for 
precipitable water to climb above 1.25 inches by Tuesday 
afternoon. 

Storm chances on Tuesday, some could be strong

Strong storm chances on Tuesday will hinge on magnitude of 
instability and its ramifications on how robust updrafts can 
become. GEFS 23.18Z probabilities for CAPE >1000 J/kg range from
about 60-80% west of the Mississippi River to 50% or less in 
western Wisconsin. This was a slight decrease from the 12Z run 
as models are grappling with a potential EML and less favorable 
mid-level lapse rates. Capping and instability profiles will be 
most favorable for convection over our northwestern counties. 
That's also where favorable deep layer shear is most likely, 
with elongated hodographs perpendicular to an approaching cold 
front. Thus, it bears watching how all these elements will 
ultimately come together Tuesday afternoon-evening, with some 
strong to possibly severe storms looking to be a possibility. 

Rest of the week

Cyclonic flow aloft persists into Wednesday which could foster 
some diurnal shower activity. The upper shortwave departs by 
Thursday with 850mb temps decreasing slightly overhead through 
Friday. The overall pattern shifts heading into next weekend as 
warm air advection ramps up. This will support a return of 
rain/storm chances but details are pretty murky that far out.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1239 AM CDT Mon Aug 24 2026

Fog formation over the next 6 hours is the most uncertain part
of the forecast. While conditions seem favorable for fog at
issuance with light winds and mostly clear skies, surface
moisture has reduced over the past 2 days, some 15 knot winds
look to be present just off the surface tonight, and cirrus is
about to filter in from the north. Have therefore continued to
keep reductions out of LSE with a BCFG group as a heads up.
Otherwise, VFR conditions are expected over the next 24 hours.

&&

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

&&

$$

DISCUSSION...Kurz
AVIATION...Ferguson