972
FXUS63 KARX 262308
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
505 PM CST Wed Nov 26 2025

.KEY MESSAGES...

- Chilly Thanksgiving with isolated snow showers near and east
  of the Mississippi River during the afternoon.

- Confidence is increasing for a prolonged and significant
  winter system to affect the region beginning Friday night and
  continuing through Saturday night. Probabilities for 6 inches
  of snow accumulation or greater are already high (70-90%) near
  and south of I-90. If you have post-Thanksgiving travel plans
  this weekend be watching the forecast closely!

- Staying cold into next week with highs in the teens and 20s. Overnight
  lows early next week will likely fall into the single digits
  above and below zero.

&&

.DISCUSSION...
Issued at 105 PM CST Wed Nov 26 2025

Rest of Today & Thanksgiving: Winds Diminish This Evening, Snow
Showers For Thanksgiving

Winter has arrived as northwesterly flow in the wake of the upper-
level low shown vividly on GOES-19 water vapor imagery passes to our
east. As this upper-low moves east of the local area and into the
Great Lakes region, winds will gradually diminish as the more
favorable synoptic wind field and stronger surface pressure gradient
push eastward. Otherwise, northwesterly flow will dominate the
synoptic flow regime throughout the remainder of the week which will
usher is continued cooler than normal air for the foreseeable
future.

Thanksgiving day will feature some isolated to scattered snow
showers that work through during the afternoon as steeper low-level
lapse rates to around 7-8 C/km and around 40 J/kg of 0-3km CAPE will
allow for showers to develop within the cyclonic flow regime.
Overall, would not expect much for accumulations but could see a
quick coating on most surfaces in any more intense snow showers.
Otherwise, as instability wanes, snow shower coverage and intensity
will after sunset. With northwesterly flow in place, highs will
remain cooler with much of the area not getting above freezing.

Friday - Sunday: Confidence Increasing for Significant Winter System

The main talking point for Friday and into the weekend will be a
fairly prolonged and complex winter system that will move through
the area beginning Friday night and continuing through Saturday. The
overall conceptual model for this event first features a warm
advective wing that pushes across the northern plains with some
decent 600-800mb frontogenesis along with it. As this works its way
into the region late Friday evening, snow will overspread the area
from the west to east. As this is occurring, a secondary
shortwave trough will eject from the Central Rockies and into
the Mid-Mississippi Valley. Accompanying this shortwave will be
a deepening surface low with an enhancing deformation zone that
will "catch up" to this frontogenetic region during the day on
Saturday and maintain the precipitation shield well into the
evening and overnight on Saturday as the low passes to our east
and eventually northeast Saturday night. Really the main point
of uncertainty with the synoptics at this point appears to be
the exact track of the shortwave and accompanying low pressure
center which will dictate exactly where the heaviest snow will
be.

Precipitation type with this event will likely be all snow as
soundings in the recent GFS show both saturation in the dendritic
growth zone throughout the event with no warm layer present anywhere
in the lower-troposphere. However, there is varying degrees of depth
in the saturation in the dendritic growth zone over the course of
the weekend, which will likely cause some variation in snow.
However, mean snow to liquid ratios in the NBM generally range
between 14-17:1 over the course of the event, suggesting a near to
slightly drier than climatology snowfall.

As far as snowfall amounts, ensemble guidance in the NBM is the most
aggressive but is quite eye catching with snowfall totals even
in the 5th percentile of the 26.13z NBM having a large swath of
6 inches south of I-94 over the course of this weekend.
Additionally, the 25th to 75th spread across the area in the
26.13z NBM is impressive with a general spread of 12-18" and
localized amounts nearing 20" along and south of I-94. Other
ensemble groups are slightly less impressive and keep the south
totals further south, such as in the 26.12z GEFS/EC which while
these ensemble groups assume a 10:1 snow to liquid ratio,
features very high probabilities (70-90% chance) for amounts
over 6 inches near and south of I-90. But again this is more
likely representative of the probability for 7-10" as snow
ratios will likely exceed 10:1. So overall looks like a very
high confidence forecast that a very impactful event will affect
the Upper Midwest this weekend. To illustrate how anomalous
this event is in the EC, the current EC Extreme Forecast Index
with the 26.00z run has our area seeing a 70 to 90 percent
chance to exceed model climatology with a shift of tails
suggesting the highest snowfall members exceeding the 99th
percentile of guidance. What this shift of tails effectively
means in the context of the ensemble is there are several
members in the 12"+ range, especially south of I-90 in northeast
IA and southwest WI where the EC favors the heaviest snow at
this point in the local area.

THE BOTTOM LINE WITH THIS! It is very important to note though that
there is still some degree of uncertainty in the exact track of this
low and how far north its deformation zone extends, so a shift in 50
miles one way or another may shift the axis of heavy snow further
into or out of the local area. Currently, the main point of
disagreement in the 26.13z NBM vs the 26.12z GEFS/EC would be on the
northern periphery of the highest totals based on where the surface
low is. The 26.13z NBM is the more aggressive solution by far as
opposed to the GEFS/EC which keeps the highest totals south of I-90
and the larger potential for 6" totals restricted to south of I-94.
Regardless, the bottom line to consider regardless of how this
system inevitably evolves is that this will impact post-Thanksgiving
travel for the weekend and you will want to consider alternate plans
and delay travel as needed as the forecast continues to get
refined.


Next Week: Very Cold Start to Next Week

As we head into next week, reinforced northwesterly flow will allow
for sharp cold advection to knock out temperatures down even further
with median high temperatures falling into the teens across much of
the area beginning on Friday and overnight lows falling to near or
even below the zero degree mark. Exactly how cold we get will depend
somewhat on what our snow cover looks like into next week, if we
establish a robust snowpack our temperatures will likely skew
colder. Regardless, the grand ensemble (GEFS/EC/Canadian ensemble)
has respectable probabilities (30-60%) for wind chills of colder
than -10F on Monday morning, certainly the coldest air we have seen
thus far and a reminder that winter is in fact here.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 505 PM CST Wed Nov 26 2025

CIGS: the area will remain under the influence of upper level
troughing/northwest flow into Thu evening. RAP/HRRR soundings
suggest KRST/KLSE hover between 2.5-3.5 kft through this period.
Should finally scatter out the deck later Thu night into Friday as
the area as high pressure moves in.

WX/vsby: a bit of upper level energy along with favorable low level
lapse rates/instability could pop a few -shsn Thu afternoon, mostly
across WI. A lot more miss than hit. Won`t add to the forecast yet.

WINDS: winds will be on a decreasing trend for the early evening
hours but still expected to hold in the low/mid teens sustained from
around 310 through the period. Gusts also likely to persist in the
low to mid 20 kts.  Winds will finally lighten up overnight Thu into
Friday as the region comes under the influence of high pressure.

&&

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

&&

$$

DISCUSSION...Naylor
AVIATION.....Rieck