407
FXUS63 KARX 291110
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
610 AM CDT Fri Aug 29 2025

.KEY MESSAGES...

- Showers ongoing near the Twin Cities will move southeastward
  through portions of Wisconsin this morning. Additional showers
  and storms are possible this afternoon, primarily west of the
  Mississippi River (20-40%).

- Mostly dry conditions are expected for the holiday weekend,
  but scattered showers and storms may develop west of the
  Mississippi River (10-30%). Showers and storms become more
  probable mid-week (20-50%).

- Temperatures will be near normal through Tuesday with a
  cooldown by the end of the week.

&&

.DISCUSSION...
Issued at 310 AM CDT Fri Aug 29 2025

Today

Fog has developed this morning in the more fog prone valley
locations given the mostly clear skies and sufficiently light
winds overnight. Fog is expected to linger into the mid-morning
hours before dissipating.

Ongoing showers along an axis of 850hPa moisture transport over
the Twin Cities will continue southeastward through the morning
hours into the afternoon, bringing light rain to areas along
and east of the Mississippi River. Given a lack of instability,
lightning is not anticipated with these showers.

As we head into the afternoon, a 500hPa shortwave trough
propagates southward through the Upper Mississippi River valley
which will coincide with a convergent surface boundary across
the region. Along this boundary, instability builds across
southeast Minnesota into portions of northeast Iowa and western
Wisconsin, albeit weak, with 250-750 J/kg of MLCAPE depicted in
the 29.03z RAP/HRRR soundings. This instability combined with
the aforementioned forcing should be sufficient for isolated to
scattered shower and thunderstorm development (20-40%) primarily
along and west of the Mississippi River. Organized convection
is not anticipated given the weak instability and displacement
of stronger 0-6km wind shear to the northeast.

Additional Shower and Storm Probabilities

Cyclogenesis occurs over the Northern Great Plains today into
Saturday, under cutting 500hPa ridging that is supporting high
pressure over much of the Great Lakes region. How far east this
cyclogenesis occurs will ultimately determine to how likely
precipitation is this weekend over our area, although it appears
to largely remain over south-central South Dakota given the
influence of the aforementioned ridge and high. Currently, the
highest probabilities for showers/storms lie west of I-35 with
only a 10-30% probability of showers and storms for areas west
of the Mississippi River during the afternoons this weekend.

The 28.12z LREF cluster analysis suggests an anomalously deep
500hPa trough will move into the Great Lakes region by mid-week,
a solution favored by roughly 60% of the members. This trough
will shift the upper ridging and surface high pressure eastward
while ushering a cold front through the region. This cold front
will be the next focus for any appreciable precipitation across
the Upper Mississippi River Valley, although variations within
the cluster analysis exist regarding depth and location of the
trough. As such, current precipitation probabilities sit at
20-50%.

Near Normal Temperatures Then Cooler

As high pressure remains in place across the Great Lakes region
with little in the way of airmass change, temperatures are
expected to remain near normal through early next week. Highs
will generally be in the mid to upper 70s and lows in the mid
50s. Behind the aforementioned trough and cold front, a cooler
airmass will be ushered into the region. However, it`s
challenging to pinpoint exact temperatures behind this front as
quite a bit of spread exists within the interquartile range of
the ensemble guidance, upwards of 10 degrees by late next week
as indicated by the 29.01z NBM, largely owing to variations in
depth of the trough. However, there is a consistent trend
amongst the ensembles towards below normal temperatures by the
end of next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 612 AM CDT Fri Aug 29 2025

A shortwave will produce showers and maybe a storm as it moves
southeast through the area today. This rain threat will end at
the the TAF sites between 29.21z and 29.24z.

With light winds up to 800 mb, mostly clear skies, and southeast
winds, there will once again some valley fog. Due to
uncertainties whether it will impact KLSE, just went BCFG at
this time.

&&

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

&&

$$

DISCUSSION...Falkinham
AVIATION...Boyne