204
FXUS63 KARX 172359
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
559 PM CST Wed Dec 17 2025

.KEY MESSAGES...

- Moderate confidence in snow squall potential through the day
  Thursday. While confidence is high for plummeting temperatures
  and flash freeze, wavering confidence in exact timing limits
  overall confidence.

- Increased south winds near 40 mph tonight further increase out
  of the west Thursday, from 40 to 50 mph west of the
  Mississippi River Valley where a Wind Advisory is in effect
  from 12PM to 6PM.

&&

.DISCUSSION...
Issued at 122 PM CST Wed Dec 17 2025

Precipitation Chances Increase Tonight:

An upper level trough progressing east over the Rocky Mountain
West advects through the Plains tonight, driving local weather
impacts tonight through Thursday. Amplified quasigeostrophic
forcing sustains the strong surface low (978mb), seen reforming
along the parent low`s triple point. HREF/LREF confidence for
<985mb MSLP traversing the Missouri River Valley from North
Dakota into Minnesota near 18.06Z. Above freezing temperatures
result in liquid precipitation type initially tonight through
Thursday morning with initial frontal passage.

After the initial low level front progresses across the
forecast area Thursday morning, subsequent deepening of the mid
level extratropical cyclone intensifies potential local impacts
through Thursday. Amplification in prefrontal low level return
flow tied to initial phasing of the trough tonight increases
low level moisture, providing additional wraparound moisture for
snowfall impacts through Thursday.

Thursday Snow Squall & Flash Freeze Impact Potential:

A break in precipitation Thursday morning from a slot of dry
air after the morning frontal passage and before subsequent
reorganization of the extratropical cyclone. Top-down cooling
brings surface temperatures near freezing from northwest to
southeast through the late morning into the early afternoon as
subsequent snowfall chances increase into the early afternoon
while also limiting freezing rain chances.

The polar cold front will be quite strong with a tight low
level theta e gradient and intense low level frontogenesis. A
stronger inter/intra ensemble solution to the surface low
increases accompanying isallobaric winds and accompanying snow
squall concerns. While current confidence for required
parameters such as instability, frontogenesis, flash freezing,
and a thick DGZ residence align, exact timing between high
resolution models leaves some uncertainty. Earliest solution in
the HRRR & RAP models quickly advect a line of snow east by the
early afternoon with the Fv3 initiating snowfall along our
western periphery during that time. This earlier solution would
reduce impacts due to the warmer temperatures limiting DGZ
growth.

Increased messaging for snow squall concerns given the signal
but will need to continue to monitor.

Increased Winds Tonight & Thursday:

Low level confluence tightens the pressure gradient and
increases south winds tonight with gusts near 40 mph at times
primarily west of the Mississippi River Valley with frontal
passage.

Subsequent increasing west winds accompany the strong low level
CAA and strong extratropical cyclone Thursday through Thursday
night with overall forecast confidence for 40-50 mph gusts west
of the Mississippi River Valley and 30-40 mph elsewhere.

Temperatures Through The Weekend:

The colder airmass through Thursday ushers another bout of
below zero apparent temperatures Thursday night into Friday
morning and single digit apparent daytime highs Friday.
Subsequent upstream cyclogenesis through the end of the week
tracks in the wake of midweek cyclogenesis, affecting confidence
in local temperatures through the weekend as the local forecast
area is placed between potential low level return flow and a
canadian polar airmass.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 551 PM CST Wed Dec 17 2025

Impending cold front bringing widespread precip, windy
conditions, and MVFR to IFR ceilings remains the main focus of
the aviation forecast. Confidence remains very high (90%) rain
will occur ahead of the front overnight into early Thursday with
accompanying reductions to IFR ceilings. Have therefore largely
retained previous forecast with a few adjustments to timing.
After a late morning lull in precip, after 18z, some -SN may
occur. Confidence in this remains low (20-40%) so have omitted
mentions in the TAFs with a view to add them in later cycles if
necessary.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Wind Advisory from noon to 6 PM CST Thursday for MNZ086-087-
     094-095.
IA...Wind Advisory from noon to 6 PM CST Thursday for IAZ008-009-
     018-019.

&&

$$

DISCUSSION...JAR
AVIATION...Ferguson