600
FXUS63 KARX 201045
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
545 AM CDT Wed Aug 20 2025

.KEY MESSAGES...

- River valley fog continues through the mid morning and may
  form again Thursday morning.

- Showers and storms may return Friday (20 to 35%) as a cold
  front moves through the region.

- Seasonable temperatures through the week with below normal
  temperatures beginning this weekend and lingering into early
  next week.

&&

.DISCUSSION...
Issued at 323 AM CDT Wed Aug 20 2025

Today-Friday: Seasonable and Mostly Dry Midweek, Showers and Storms
for Friday?

Latest satellite imagery continues to show fog expanding in many of
the river valleys. This is expected to continue through the mid
morning and may occur again Thursday morning as light surface winds,
saturated low levels from rain that occurred over the weekend, and
clearing skies are expected to linger. Surface high pressure
continues to build into the region as well as the northeast flow in
the low levels. Despite this normally meaning we are dry, there is a
slight uptick in the moisture transport this afternoon that could
result in a shower or two in central and southern Wisconsin. The
confidence on this occurring is low, so have opted not to bring in
higher PoPs for these areas. With the high pressure in place, high
temperatures remain near normal through the week with temperatures
in the upper 70s to low 80s.

Heading into Friday, a cold front ahead of a longwave trough sweeps
down from the northern Plains and impacts our CWA later Friday
afternoon and evening. PWATs rise again into the 1.2 to 1.5 inch
range ahead of the front with dewpoints returning to the upper 60s
to low 70s. Instability builds out ahead of the front as well with
MLCAPE values up to 1500 J/kg. Showers and thunderstorms are
expected fire out ahead of the front, however confidence in their
location and how widespread the development will be has kept PoPs
between 20 and 35%. This can also be seen in the moisture transport
as it is weaker than Thursdays moisture transport over the northern
Plains.

Saturday-Early Next Week: Cooler Temperatures

Drier conditions are expected behind the cold front, however with
cyclonic flow on Saturday, showers may form on the backside of the
surface low. After Saturday, PWATs dip below 1 inch as the drier air
lingers over the area. Cooler air comes down from Canada as the
longwave trough dips into the region with 850mb temperatures between
4 and 8C from Saturday through Tuesday, with the coolest
temperatures on Sunday and Monday. EFI values are also highlighting
early next week with values of -0.7 to -0.9 for the high and low
temperatures. With these values, the EFI is indicating that these
forecasted temperatures would be on the lower end of the
climatological normal. Current forecasted highs for this period are
in the mid 60s to low 70s with overnight lows in the upper 40s to
low 50s. There are even some low 40s forecasted for Tuesday morning.
With dewpoints decreasing for the weekend and these temperatures, it
is shaping up to be a pleasant weekend and beginning of next
week!

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 544 AM CDT Wed Aug 20 2025

Main taf concerns is fog/low level stratus deck early in the
taf period. Then possibly river valley fog after 06z Thursday.
Fog has developed mainly in low lying areas and river valleys
overnight. Latest nighttime satellite imagery shows fog mainly in
river valleys and stratus deck clouds over parts of
central/western Wisconsin. Question will be if the fog/stratus
deck will move over the LSE taf site. If it does...expect
IFR...possibly LIFR conditions. Localized fog has formed near
RST and conditions will bounce around MVFR to IFR early in the
taf period. Have introduced tempo groups for the in and out of
fog/stratus deck at both taf sites through mid morning. The
fog/stratus deck will eventually erode by mid morning and VFR
conditions are expected through late this evening. With light
winds and clear skies again tonight. Fog will redevelop in river
valleys and may impact the LSE taf site after 06z Thursday. At
this time introduced MVFR condition after 09z Thursday at the
LSE taf site. RST should remain in VFR condition through
tonight.

&&

.HYDROLOGY...
Issued at 323 AM CDT Wed Aug 20 2025

River flooding continues on parts of the Turkey, Trempealeau, and
Cedar Rivers as a result of the weekends rain. A few gauges remain
in minor flood stage as of this morning and are expected to
remain there through at least today. As a result, river flood
warnings remain in effect for portions of these rivers.

&&

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

&&

$$

DISCUSSION...Cecava
AVIATION...DTJ
HYDROLOGY...Cecava