457
FXUS63 KARX 052045
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
245 PM CST Fri Dec 5 2025

.KEY MESSAGES...

- Light snow rest of the afternoon, exiting east by mid evening. Generally
  minor amounts (1/5 to 1") and mostly confined from around
  I-90 northward.

- Saturday winter storm trending more northward, putting more of
  the local area under the threat for several inches of snow. A
  Winter Weather Advisory is in effect for much of southeast
  MN, northeast IA and parts of southwest WI for 3 to 6" of
  snow.

- Periodic snow chances continue for next week.

- Unseasonable cold also persists, but could creep above
  freezing for a few hours Tue.

&&

.DISCUSSION...
Issued at 244 PM CST Fri Dec 5 2025

> REST OF TODAY-THIS EVENING:

Ongoing snowfall this afternoon tied to a frontal boundary evident
in significant surface wind shift along western peripheral counties
in southeast Minnesota and northeast Iowa slowly sagging southeast
while tightening through morning hours from an accompanying upper
level trough on GOES water vapor imagery. A meager intensification
in synoptic and mesoscale forcing with the tightening of the
boundary increased radar reflectivity returns early this afternoon
as the snow traversed the Mississippi River Valley. Resultant
snowfall rates ushered in lower visibilities, closer to 1SM
climatology during -SN, across most of the forecast area. Expect
snowfall to continue southeast, providing up 1" in accumulation,
through the evening hours. While previous concerns regarding
freezing drizzle remain, off surface temperatures <-10C in the
saturated airmass would suggest ice introduction and flurries
instead of drizzle.

> SATURDAY: winter storm taking aim on the region with storm
track trending more northward, bringing more of an
impact/potential for higher snow amounts to the local area.

The northward shift of storm system for Saturday continued with some
of the latest short term guidance - namely the RAP and HRRR. This
resulted in approx 100 mile jump north in accumulating snows earlier
this morning. NAM did a similar shift. There is still some shifting
in the track as some of the later morning runs are not as aggressive
with the northward push - so track is not locked in, but trends do
back some of this northward shift.

Deep QG convergence, good isentropic upglide on the 280:295K
surfaces, sloping Fgen, along with upper level jet support and the
shortwave itself provide ample lift with plenty of moisture to
produce a swath of snow. It`s a fairly quick mover with CAMS pushing
snow across locations west of the Mississippi river by mid/late
afternoon Sat, spreading eastward through the evening and exiting
east by 12z Sun.

While storm track, and thus where the greater snow amounts are
realized, continues unclear, the trends for 5 to 7" in the "heart"
has remained for the past few days. With some shift north looking
reasonable, this brings a 3 to 6" area of snows from around I-90 in
southeast MN, east to the MIssissippi River, and then south of
there. Per coordination with surrounding offices, have elected to
issues a Winter Weather Adv for these locations. 12z HREF isn`t keen
on more than 6 with near 0% shot over northeast IA - albeit with a
10:1 ratio. With expectations more in the 15:1 arena, chances from 5
to 10% are probably closer to the mark. That said, the 09z run of
the REFS push 60+% threat for 6 or more inches across parts of SE
MN/NE IA. Big difference. Do believe that locally higher 6"+ are
possible, mostly for northeast IA. An upgrade to a winter storm
warning for a portion of the local area can`t be ruled out.

A shot of colder air follows in the the wake of the storm system.
Highs Sunday will top out in the teens with single digits
above/below zero Monday morning.


> NEXT WEEK: periodic precipitation chances with below normal temps
persisting.

Progressive, northwesterly upper level flow looks to hold through
next week with good agreement in all the WPC clusters. Some hints of
ridge building moving into the weekend, but not much clarity that
far out.

GEFS and EPS members continue to parade a myriad of shortwave
troughs across the region. Decent consensus in most of the ensemble
members for a couple ripples in the flow to push across the region
Mon/Mon night. Relatively weak with more focus across the north.
Chance for light snow with both with minimal accumulations.

Tue night looking more interesting with a stronger shortwave progged
to drop out of Canada and across the upper mississippi river valley.
GEFS and EPS paint an elongated swath of snow mostly across northern
MN/northern WI. A few/several inches of accumulation could result.

The busy pattern continues after that, but with more discrepancies
between the ensemble suites, thus less predictability.

Temperatures look to hold below the early December normals although
Tuesday shows some promise to reach/exceed freezing for a few
locations. The last above freezing day for the area was just before
Thanksgiving. Its been awhile.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1137 AM CST Fri Dec 5 2025

Ongoing light snowfall seen on radar reflectivity over south-
central Minnesota moving east over west-central Wisconsin at
05.18Z TAF issuance. Slightly later onset compared to previous
forecast has delayed onset of widespread IFR until 18Z TAF
issuance or shortly thereafter. Overall accumulations and
intensity will be limited, keeping lowest impacts in IFR
visibilities and ceilings.

While snowfall probabilities decrease from west to east this
evening, IFR ceilings expected to linger into the overnight
hours as low level cold air advection saturates low levels.
Confidence in continuing IFR impacts through Saturday morning is
low with potential for lifting ceilings.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 6 PM Saturday to 6 AM CST Sunday
     for WIZ061.
MN...Winter Weather Advisory from 3 PM Saturday to 6 AM CST Sunday
     for MNZ086-087-094-095.
     Winter Weather Advisory from 6 PM Saturday to 6 AM CST Sunday
     for MNZ096.
IA...Winter Weather Advisory from 3 PM Saturday to 6 AM CST Sunday
     for IAZ008>010-018-019-029.
     Winter Weather Advisory from 6 PM Saturday to 6 AM CST Sunday
     for IAZ011-030.

&&

$$

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