999
FXUS63 KARX 041058
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
458 AM CST Thu Dec 4 2025

.KEY MESSAGES...

- Persistent pattern expected over the next 7 days,
  bringing multiple shots for snow to the region, appearing to
  focus on four periods: Friday into Friday night, Saturday
  night, Monday night, and Tuesday night into Wednesday. The
  latter three have a chance for impactful (3"+) amounts to
  occur.

- Below normal temperatures continue over the next 7 days.
  Sunday night into Monday morning may feature widespread
  subzero lows.

&&

.DISCUSSION...
Issued at 311 AM CST Thu Dec 4 2025

Periodic snow chances ahead

Northwesterly flow aloft is expected to dominate proceedings over
the next week with broad agreement across GFS/EC/CMC and their
respective ensembles that this will continue. Given this pattern,
attention will be paid to any disturbances that eject downstream as
these would bring potential for snow. At this time, guidance is
focusing on 4 periods for snow - Friday into Friday night, Saturday
night, Monday night, and Tuesday night into Wednesday.

Friday into Friday night, wave currently over Alberta reaches the
Upper Midwest. Modest ascent ahead of this wave should saturate the
DGZ leading to at least a couple hours of light snow. Given lack of
mesoscale forcing mechanisms and the brief period of saturation,
looks like a high PoP, low amount scenario. Indeed, 04,00z HREF
suggests a 50-95% chance to receive at least measurable snow by
Friday evening and the 04.00z LREF has a 55-100% chance to get
something measurable with highest chances along and north of I-90.
Have therefore increased PoPs over NBM, which appears too low, as is
typical for high PoP, low QPF weather patterns. Amounts in guidance
are indeed low, with 04.00z LREF/HREF 99th percentile snow, and
04.01z NBM 95th percentile snow at 2 inches or less. Aside from
reduced visibility and patchy slick spots, expect little impact from
snow this period.

In contrast, potentially impactful snow is on tap for Saturday
night. GFS/EC/CMC remain in good agreement on timing with an upper
trough with the 04.00z cycle but placement difference between
operational GFS/EC continues with impactful snow occurring to our
south in the GFS and in NE IA in the EC due to differences in the
placement of an 850mb frontogenetic zone. That said, signs of model
convergence are seen as the past 3 runs of the GFS have brought the
snow closer to our CWA and, crucially, operational GFS now appears
to be on the southern side of 04.00z GEFS which has come largely
into line with EC solution. Therefore, confidence is increasing that
snow will affect NE IA and perhaps portions of SE MN and far SW WI.
Adjusting for a 15:1 snow ratio given likelihood of a saturated DGZ
with lift through this portion of the column, 04.00z LREF has a 30-
55% chance to reach 3 inches of accumulation along and southwest of
a Dodge City MN to Prairie du Chien WI line. Primary limiting
factor for snow amounts will be the quick motion of the upper
wave, keeping snow duration to around 6 hours or less.

Two additional clipper type systems look to dive southeastward
Monday night and Tuesday night into Wednesday. Each has a chance for
impactful snow (5-35% and 20-50% respectively) so will need to keep
a close eye on both periods over the coming days.

Cold temperatures continue

Persistent Hudson Bay upper troughing and reinforcing shots of cold
air associated with the upper waves discussed above will keep
temperatures below normal, likely below freezing over the next
week. At this time, Sunday night into Monday morning appears to
have the best chance for a repeat of this morning with light
winds, clear skies, and potentially subzero lows (45-65%
chance). Despite the cold, relatively light winds through much
of the period should keep highly dangerous wind chills from
occurring.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 458 AM CST Thu Dec 4 2025

VFR conditions are expected through much of the morning and
afternoon today with mostly clear skies expected. Sky cover will
begin to increase late this afternoon and into the evening as a
weather disturbance begins to approach the region with generally VFR
cigs expected. However, did include some MVFR mention at KRST after
09z as the 04.06z HREF has high probabilities (50-80% chance) for
ceilings below these heights. Otherwise, some LLWS is likely this
evening as low-level wind fields in the recent RAP increase to
around 40-50 kts at around 2kft, however surface wind gusts may
mitigate this some. Winds will begin the TAF period from the south
and will increase into the afternoon and evening to around 12-18
kts across the area with gusts to around 25 kts possible in
unsheltered areas of southeast MN and northeast IA. Light snow
will move into the local area after 12z Friday likely bringing
MVFR to IFR cig and vsby reductions, primarily near and north of
I-90.

&&

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

&&

$$

DISCUSSION...Ferguson
AVIATION...Naylor