097
FXUS63 KARX 101157
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
557 AM CST Fri Jan 10 2025

.KEY MESSAGES...

- Scattered snow showers expected today. Accumulations around a
  dusting to a few tenths of an inch.

- Accumulating snow likely from Saturday Night into Sunday.
  Highest probabilities (50 to 60%) for snowfall in excess of 2
  inches remains along and to the NE of I94.

- Colder Monday through Wednesday. Morning wind chills 10 to 20
  below zero.

&&

.DISCUSSION...
Issued at 315 AM CST Fri Jan 10 2025

Today into Tonight: A Light Dusting to a Few Tenths of Snow

As light snow continues to trek eastward this morning, upstream
observations support increasing NW flow to bring in cooler air. As
this cooler air begins to work in from the northwest, model
soundings suggest boundary layer saturation through roughly 5kft.
There still appears to be an hour or so window for freezing drizzle
potential as saturation is deep enough to support precipitation if
lift is present, but there is a lack of saturation in the DGZ
initially before colder air cools the lower-levels. There isn`t too
much lift in the low-levels initially until the cooler air moves in
and steepens the low-level lapse rates and instability increases.
Upstream observations near Grand Forks support this idea as the pcpn
initially showed on ons as UP before transitioning to -SN. Opted to
keep freezing drizzle from the gridded forecast at this time given
the disconnect in forecast lift between NW Minnesota and our local
area, but will monitor this morning for any indications of ice.

Previous forecasts mentioned only flurries in the forecast, but have
collaborated with neighboring offices this morning to go with
prevailing scattered snow showers after 15Z or so initially before
these chances drift to the SE through the rest of the day. Model
soundings show an inverted V type look as the day progresses, which
would favor limited accumulations of a light dusting to a few
tenths. Will continue to watch upstream conditions through this
morning as a vortmax is progged to drop SE from Manitoba today.

Saturday night through Sunday: Increasing Chances for 1 to 3 Inches
of Snow

Ridging begins moving in tonight, with a ridge of surface high
pressure expected to translate across the area. Another trough is
forecast to move across the Rockies today into Saturday, before
slowing down and moving across the Upper Mississippi Basin on
Sunday. Latest round of forecast ensembles show continued higher
probabilities of accumulating snow across the area, highest along
and north of I90. Snowfall probs over the last 24 hours have
remained consistent in magnitude, however the location has shifted
north a bit and the speed of the system is a little faster. This
will bring local snow amounts down south of I90, with slightly
reduced probabilities along and north of I90. Probabilities for 1+
inch of snowfall across the area range from roughly 30% in Charles
City to 70% in Medford. Much of NE Iowa and SE Minnesota now have
these chances in the 25 to 50% range, with locations east of the
river near 50 to 80%. Chances for 2+ inches of snowfall range from
5% in Charles City to 50% in Medford. A widespread 20 to 50% chances
exist between the two locations. Canadian members favor the highest
snowfall accumulations, with GEFS coming in 2nd, and EC the lowest
in our local area at this time. A combination of all of their
members puts the high-end snowfall amounts (99th percentile) around
4 inches to the northwest of I94 using a SLR of 10:1. Given a fcst
SLR of around 16:1, we will need to add 60% to that amount bringing
that high-end closer to 6-6.5 inches of snow. Winds will be in the
teens, so not expecting any blowing/drifting snow, but accumulating
snow Sunday could pose minor difficulties in travel, especially
along the I94 corridor.

Next Week: Colder, Especially if a Snow Pack Develops

Modeled 850mb temps fall to around -20C Monday afternoon behind the
exiting low pressure system. The pressure gradient remains tighter
as surface high pressure drops into the Upper Midwest from the
Canadian Prairies Tuesday. With a favored fresh snowpack,
temperatures are expected to fall to around 0 Monday morning and
into the single digits below zero Tuesday morning. With a pressure
gradient remaining, wind chills in the -10 to -20 range will be
possible each morning Monday through Wednesday.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 543 AM CST Fri Jan 10 2025

One area of light snow has pushed off to the east and there has
been some spotty freezing mist or a mix of mist and snow in its
wake. This mix should give way to snowshoer as a trough moves
in with reinforcing cold air. A mix of VFR/MVFR ceilings this
morning, however forecast soundings try to show more of a
prevailing MVFR with the snow moving in. With the more vigorous
snow showers, some visibilities may be reduced to MVFR/IFR for
a brief time. The snow showers exit the area this evening. West
to northwest winds 5 to 15kts. Some stronger gusts 10 to 20kts
in open areas in southeast MN.

&&

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

&&

$$

DISCUSSION...JAW
AVIATION...Zapotocny