348
FXUS63 KARX 120517
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1115 PM CST Thu Dec 11 2025

.KEY MESSAGES...

- Accumulating snowfall is expected this afternoon, primarily
  over northeast Iowa where 1-2 inches is expected. Additional
snowfall is possible (10-60%) Friday bringing a few tenths up to 1
inch of snow.

- Temperatures are on the decrease through the weekend, with
  highs on Saturday and Sunday in the single digits. Wind chills
  of -25F to -35F are expected Saturday and Sunday morning. A
  Cold Weather Advisory is in effect for portions of southeast
  Minnesota and west-central Wisconsin Saturday morning.

- Trending towards more seasonable temperatures and drier
  conditions for early next week with high temperatures
  rebounding into the 30s.

&&

.DISCUSSION...
Issued at 158 PM CST Thu Dec 11 2025

Accumulating Snowfall this Afternoon and Friday

A winter system driven by a 700-500hPa shortwave trough ongoing
across the central Great Plains will continue trudging
southeastward this afternoon into the evening hours. A band of
800-600hPa frontogenesis is expected to drive snowfall and
subsequent accumulations, but the southwest trend noted by the
global ensemble and deterministic guidance has now been
reflected within the high-resolution guidance, leading to high
confidence in the majority of snowfall accumulations remaining
southwest of our area. Accumulations around 1 inch are now
expected for portions of northeast Iowa with a few tenths
possible up to a line from Rochester, MN to Platteville, WI.
Despite the continued decrease in snow amounts, expect some
slippery travel during the evening commute where snow does
accumulate.

Another shortwave moves into the region Friday morning,
shifting eastward throughout the day. Positive vorticity
advection, influence from the left exit region of an approaching
jet streak, and weak 900-800hPa frontogenesis per the RAP
associated with this wave should provide enough upward vertical
motion to allow for snow development across the region. A
subtle moisture tongue also shifts through the area along the
wave, coinciding with a fairly deep DGZ depicted in RAP/HRRR
soundings. This combined with the adequate forcing should
provide some higher snow-liquid ratios, generally 15-20:1. On
the backside of the primary wave, cold air advection should
sufficiently steepen 0-1km lapse rates, generally 7-8C/km,
which combined with lingering moisture should lead to some snow
showers Friday afternoon into the evening, primarily along and
north of I-94. Overall, probabilities are highest along and
north of I-90 (30-60%) throughout the day, but some low
potential exists across the whole region (10-30%).

Amounts on Friday look to be fairly light given the general
lack of moisture and overall weak forcing, but with the
aforementioned deep DGZ and higher expected snow-liquid ratios,
accumulations should be on the order of a few tenths up to
around 1 inch per the 11.12z HREF LPMM.

Cold Temperatures This Weekend

Strong high pressure sinks southeastward out of Canada through
the weekend, ushering an Arctic airmass into the Upper Midwest.
The first bout of cold air comes Friday night into Saturday,
with wind chills falling into the double digits below zero, down
to -30F for locations towards north-central Wisconsin. Have
issued the season`s first Cold Weather Advisory for Saturday
morning for areas along and north of I-90 to highlight to
dangerous cold. This may need to be extended southward, but
given expected cloud cover, not as confident in the ultimate
wind chill values further south.

Higher confidence in dangerous cold comes Saturday night into
Sunday morning as the high pressure becomes more influential.
Clearing skies overnight should allow for efficient radiational
cooling, resulting in ambient temperatures falling into the
teens below zero. Wind chill values fall to -25F to -35F during
this period with the 11.00z LREF highlighting a 20-40%
probability to fall below -35F west of the Mississippi River.
These very cold temperatures will likely warrant additional cold
weather headlines in the coming days.

Before the coldest air arrives Sunday morning, a band of 700hPa
frontogenesis develops on the southern extent of the high
pressure, sparking another ribbon of snowfall across portions of
Minnesota and Iowa Saturday afternoon. This band of snow is
currently expected to follow a very similar trajectory to
today`s snowband with a 20-50% probability of precipitation
across northeast Iowa. With the similar trajectory, the
greatest snowfall amounts are expected southwest of our area.
Generally a few tenths of an inch of snow is expected as the
11.13z NBM highlights only a 10-20% probability for more than 1
inch.

Warmer and Drier Early Next Week

After the weekend, the upper level pattern finally begins to
shift as longwave ridging builds into the central United States.
This upper ridging is anticipated to bring a much needed
reprieve from the active northwest flow of the past week or two,
although there are a few shortwaves that traverse the mean flow
through the beginning of the new week. However, with the ridge
the dominant feature, these shortwaves tend to stay north of the
local area along with any precipitation potential associated
with them, so a few dry days are currently expected through at
least the middle of the new week. Temperatures also being to
warm with the rising heights and warm air advection under
southwesterly low level flow, with the 11.13z NBM mean
suggesting high temperatures will be far more seasonable, rising
into the mid 30s through the beginning of the new week. By mid-
week, ensemble guidance suggests the next winter system could
move through our area, but far too much variability exists to
glean much information apart from the possibility.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1115 PM CST Thu Dec 11 2025

CIGS: Mainly mvfr cigs return near/shortly after 12z Fri and will
hang around through the afternoon. Expect them to exit east and give
way to a bkn mid level vfr deck Fri evening.

WX/vsby: upper level trough/sfc cold front will produce areas of
-sn with the potential for a few shsn that could drop vsbys briefly
into the 1-2sm range. This activity will exit east by early
afternoon. Minimal if any accumulation expected.

WINDS: light winds become southwest then increase and go more
west/northwest with the passage of that cold front by late
morning/early afternoon. The winds look to stay "up" Friday night
through Sat as the pressure gradient doesn`t start to slacken until
later Sat night with the approach of high pressure.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Cold Weather Advisory from midnight Friday night to 10 AM CST
     Saturday for WIZ017-029-032>034.
MN...Cold Weather Advisory from midnight Friday night to 10 AM CST
     Saturday for MNZ079-086>088.
IA...None.

&&

$$

DISCUSSION...Falkinham
AVIATION.....Rieck