748
FXUS63 KARX 071940
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
140 PM CST Sun Dec 7 2025

.KEY MESSAGES...

- Snow likely north of I-94 (60-80%) Monday night with up to 1"
possible.

- Winter storm impacts parts of northern MN/northern WI Tue night.
Current track favors keeping bulk of local snow accums along/north
of I-94. Severe inches possible. Considerable warming with 50-90%
chance to climb above freezing south of I-94...with rain, rain-snow
mix entering the picture. Keep a close eye on this period and expect
adjustments to the forecast.

- Much colder for 2nd half of new week. Sat trending as the coldest
day with single digit highs. Periodic light snow chances.

&&

.DISCUSSION...
Issued at 140 PM CST Sun Dec 7 2025

> MONDAY/MONDAY NIGHT: light snow chances. Minor accums possible
north of I-94

A couple ripples in the upper level flow look to spin across the
region. First one in the morning and more weakly forced of the two.
Also, time/height x-sections and forecast soundings depict mostly
low level saturation to work with. Temps should be cold enough for
ice in the cloud, and even some suggestion for a somewhat deep DGZ
in parts. Models aren`t enthused with a weakening trend as the
shortwave nears the local area - less areal outlay and less qpf with
the pcpn. Could just be some flurries. Will hold with low end (20%)
snow chances for western locations for now - but may need to move
toward scattered/widespread flurry wording eventually. Minimal/if
any impacts anticipated.

The second shortwave shifts west to east across northern portions of
the region Monday night and models show a bit more lift and deeper
saturation to work with. Greater threat for minor/light
accumulations. Current track holds most of any accums north of I-94
for the local area with the NBM and HREF showing a 20-50% shot for
1". Looks reasonable.


> TUESDAY: relatively mild - above freezing for most! Swath of snow
across the north (a few inches of accum) while temps suggest a
rain/snow mix in the south. I-94 approx delineator at this time.

GEFS and EPS remain in very good agreement with driving an upper
level shortwave trough from western Canada Monday night, to across
the northern plains and then the upper mississippi river valley Tue
night. Some small variances in timing/track/strength of the system`s
sfc low...but the preponderance of the models` members take the low
center from northcentral MN to across central WI. Latest runs of
both models also have more than 50% of their members in a slower,
bit stronger solution compared to the mean - indications of the
potential for a stronger system then currently depicted.

Favorable isentropic upglide leads the system in with deep QG
convergence as it moves through. Fgen is kind of disjointed at this
time, and mostly in the lower levels. Not a great signal for
enhanced banding, but still a few days out. Perhaps some upper level
jet support too. Ample saturation per forecast soundings and
time/height x-sections to work with.

Appreciable warming on the south side of the system bring pcpn types
into question. Vertical temp profiles lean into rain or snow for now
- with little suggestion for "icy" to enter the mix. Will hold with
snow/rain as the ptypes for now.

How much? QPF NAEFS and EPS are around +1 while EFIs for snow
(within the snow band) top out at 0.7 with a non 0 SoT. This is an
increase in the EFIs over its past few runs. LREF near 50% for 4+
inches of snow at 10:1 ratios in the heart of the snow band. Ratios
could very well be near that at the start of the event, but likely
kick up into the low-mid teens overnight. NBM leans into more snow
with 30-50% chances for 6+". Considering the models are showing some
signs of strengthening with this system, think 6+" could be reached
in heart of the deformation region, which current track keeps across
northeast MN/northern WI. Still, close enough that a Winter Storm
Watch might be needed for locations north of I-94 - namely Taylor
and Clark counties in WI.

Meanwhile, southward temp profiles suggest a mix of rain, rain-snow
or snow. Much less for possible snow amounts as a result. Again,
icing threat looks low at this time - but will have to keep an eye
on it.

Northwest flow post the system Wed, along with favorable low level
lapses rates-cold air advection, are likely to kick up snow showers
and/or flurries.

As for how warm? 25% of the latest EPS members push 40+ degrees on
the southerly flank of the winter storm. The GEFS isn`t quite as
warm, although a few high end outliers also like getting to 40. Both
model suites have warmed a degree or two each day - so definitely a
trend that bears watching. Obviously, temps will be reliant on how
the system tracks - if it moves more south, so will the milder air.



> REST OF THE WEEK: periodic snow chances, back into the cold.

The "busy", progressive northwesterly upper level flow persists for
the second half of the new week. Colder air on tap to return with
Fri-Sun looking rather chilly. 75% of the GEFS and EPS members hold
high temps in the single digits for Saturday - the coldest day of
the bunch. Winds aren`t looking particularity strong but apparent
temps for Sat morning in the low to mid 20s below zero are trending.

Bits of shortwave energy push near/across the upper mississippi
river valley over this period, but with the expected disagreements
in placement/timing/strength between the ensemble suites at this
time frame. That said, no suggestion of a stronger/higher impact
system. WIll hold with the model blend for pcpn chances.

The following week could hold some hope for warming as a west coast
ridge that the long range guidance has been tantalizing the region
with might (might) finally work east and across the area. A return
to normal, perhaps a bit above, temps would occur. A big IF though.
Mark and place in the "wait and see" file.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1144 AM CST Sun Dec 7 2025

Clear skies this afternoon fill in through this evening as north
winds become light and variable ahead of low chances for snow
tonight into early Monday morning. The responsible wave is driving
radar returns through the Northern Plains will be on a weakening
trend as it approaches the Upper Mississippi River Valley.
Therefore, have not added any mention of snow with <30% confidence
at either TAF site. Higher, albeit minimal, chances lie west of the
Mississippi River Valley at smaller airports and KRST TAF site from
6-12Z. Will require further amendment depending on how the wave and
observations continue through Minnesota this evening. Regardless of
snowfall, low level moisture and warm air advection expected through
Monday morning, strongest west of the Mississippi River Valley, will
cause MVFR-IFR ceilings.

Snowfall chances frequent the forecast area after the 07.18Z TAF
period. Initially Monday night primarily north of Interstate 94
locally affecting smaller airports in central Wisconsin.
Subsequent mixed precipitation chances Tuesday afternoon through
Wednesday morning will affect airports area wide with rain likely in
northeast Iowa to snow in central Wisconsin. Determining exact
location of precipitation type and accompanying impacts will be
forecast detail to monitor in coming TAFs.

&&

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

&&

$$

DISCUSSION...Rieck
AVIATION.....JAR