569
FXUS63 KARX 011853
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
153 PM CDT Sat Nov 1 2025

.KEY MESSAGES...

- Isolated light showers may develop this afternoon (0-20%).
  Impacts from any showers will be minimal.

- Patchy fog is possible tonight into Sunday morning, primarily
  in river valleys and south of I-90.

- Potential for showers returns Sunday night into Monday
  morning, primarily for areas north of I-90 (20-40%).

&&

.DISCUSSION...
Issued at 151 PM CDT Sat Nov 1 2025

Isolated Light Showers This Afternoon

Isolated light showers may develop during the afternoon hours
today (0-20%) associated with steepened 850-700hPa lapse rates
of 6-7 C/km in the wake of a 500hPa vorticity lobe continuing
to shift southeastward. Some uncertainty as to how steep lapse
rates will be able to get under the cloud cover, but could prove
to be enough to promote at least some shower development given
saturation in the lowest 2km of the atmosphere. Low level
saturation begins to wane by the evening and better lapse rates
move southeast with the upper level pattern, bringing an end to
shower potential.

Patchy Fog Possible Tonight into Sunday Morning

With the brief upper ridging building into the region, some
patchy fog may be able to develop tonight given light winds and
moisture from the recent light rain. However, fog development
largely hinges on if skies are able to clear sufficiently
overnight. If skies are able to clear, fog will be favored
within river valleys and south of I-90 as the 01.12z HREF
highlights a 30-50% probability of visibility less than 1 mile
across these areas. However, there is lower confidence in fog
development for areas west of the Mississippi River as clearer
skies are favored further east.

Shower Potential Sunday Night into Monday Morning

A 500hPa shortwave and associated surface cyclogenesis shifts
eastward over southern Canada Sunday into Monday. As these
features track east, a tightening pressure gradient is expected
to increase 925-850hPa winds with the potential for some of this
momentum to translate to the surface based on 01.15z RAP/HRRR
soundings, leading to some breezy conditions in the afternoon.
Gusts of 25-35 mph are possible, primarily west of the
Mississippi River into north-central Wisconsin.

By Sunday night, a ribbon of positive vorticity and a surface
frontal boundary will be dragged through the region. Southerly
flow ahead of these features will promote warm air advection
along with an axis of increased theta-e nudging into the
Midwest, which could promote some shower development along the
surface front for areas primarily north of I-90. The 01.00z LREF
mean highlights 50-70% probabilities for measurable
precipitation through Monday morning, although this is largely
inflated by the EPS, as the GEFS has a much drier solution,
likely owing to discrepancies in the low level thermal profile
and southern extent of stronger forcing. The GEFS nudges the
850hPa thermal ridge slightly further northeast, resulting in
drier low levels as compared to the EPS and keeps the stronger
positive vorticity advection further north and east. Looking at
the 01.12z HREF, it depicts a solution similar to GEFS,
highlighting lower probabilities for showers. Given the
uncertainty between the ensembles, have gone with the NBM PoPs
of 20-40%, with the greatest potential over northern and central
Wisconsin.


&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1233 PM CDT Sat Nov 1 2025

Main taf concern through the taf period is potential for fog
formation after 06z Sunday...mainly in low lying areas and river
valleys. With daytime heating today ...ceilings this afternoon
should slowly improve from IFR/MVFR to VFR conditions at both
RST/LSE taf sites. Then...weak high pressure builds into the Upper
Mississippi River Valley this evening/tonight. With abundant low
level moisture near surface and light winds. Fog could form in low
lying areas and river valleys after 06z Sunday. The question will be
how much clearing skies will be...as mid to high clouds drift over
the region tonight. At this time...have patchy fog at both RST/LSE
taf sites with scattered deck of clouds around or just below 500
feet. Southwesterly winds increase to 10 to 15 knots after 14z
Sunday...this should erode any fog around the area.

&&

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

&&

$$

DISCUSSION...Falkinham
AVIATION...DTJ