940
FXUS63 KARX 050459
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1059 PM CST Tue Feb 4 2025

.KEY MESSAGES...

- Wintry precipitation likely (60 to 90%) late Wednesday
  afternoon through Wednesday night. Accumulating snow possible
  for many with highest accumulations in north-central
  Wisconsin where 1 to 3 inches is forecast. A glaze of ice is
  possible along and south of I-94.

- Snow chances return for Saturday (60 to 80% chance). Most
  likely now range .5" (southern part of the forecast area) to
  4" (north of I94), however there are some low-medium
  probabilities (30-50%) of greater than 6" for areas north of
  I-90. This storm system is still a ways out, thus the
  intensity and track could change.

- Colder early next week with additional light snow chances.
  Coldest wind chills 0 to -20.

&&

.DISCUSSION...
Issued at 249 PM CST Tue Feb 4 2025

Tonight - Thursday: Seasonable Temperatures and Wintry Mix
Precipitation for Midweek

As weak upper level ridging starts to break down, surface winds will
begin to shift back to the southeast through the overnight hours.
This means temperatures won`t be quite as cold overnight with
most places staying in the low teens to upper single digits as
one moves further north. Where things start to get a little more
complicated is once we move into mid-day tomorrow. The grand
ensemble continues to show a shortwave trough ejecting out of
the north Central Rockies and into the northern Plains and Upper
Mississippi River Valley through the day tomorrow. Looking at
04.12Z RAP/NAM soundings across the area, a pronounced dry layer
will be present between 750-900 mb through at least early
afternoon tomorrow which will likely work to prevent much
precipitation from forming at that time. However, as we start to
get more low level warm air advection and moisture into the
area tomorrow afternoon, we should be able to saturate through
the lower levels. A warm nose is expected to form but just how
strong is still a bit up in the air and unfortunately, this
could play a significant role in what kind of precipitation we
see on the ground. Most places in our CWA, especially areas
outside of far southwest Wisconsin, show a small and relatively
benign warm nose that just barely extends beyond the 0 degree C
isotherm. This also highlights an area that is not expected to
saturate fully. The mid levels look like they may be too dry to
tap into the ice formation at or above the DGZ, which for most
soundings is between 500-600 mb. It`s looking increasingly
likely that with the deep low level moisture in place and lack
of ice higher up, freezing drizzle may be the dominant
precipitation type across much of the area, especially along and
south of the I-94 corridor. This means that higher end
accumulations of ice have come down which is reflected in our
NBM probabilities of greater than or equal to a .10 of an inch
of ice being less than 10% for pretty much the entire area.
However, the probabilities for a glaze of ice remain very
similar to yesterday with highest probabilities (40-70%) across
southwest Wisconsin and far northeastern Iowa. Elsewhere,
probabilities for a glaze of ice remain on the medium-low side
between 10-40%.

There still looks to be a chance for snow, mainly across Taylor
and northern Clark counties where totals look to be in the 1-3
inch range. NBM probabilities of snow totals greater than or
equal to 2 inches for this area are in the 40-80% range. Nearly
all of the 04.00 GEFS/EC members are showing snowfall for this
area but totals look to have come down from previous runs as the
better forcing and snowfall looks to stay further north. This
wintry precip event is expected to be pretty short-lived as the
shortwave quickly moves off to the east with precipitation
expected to come to an end before 12Z Thursday. Winds through
the profile shift to the northwest and significantly dry things
out. This does mean that the evening commute on Wednesday and
the morning commute on Thursday may be slippery so be sure to
give yourself some extra time. As the front is expected to be
occluded by the time it moves through our area, temperatures
Thursday shouldn`t take too much of a hit with highs in the mid
20s to upper 30s.


Friday - Weekend: Second System to Bring Snow

Surface high pressure is expected to move into the area Friday which
will help to start cooling high temperatures into the teens to upper
20s. A second upper level trough is expected to swing
east/southeast through Alberta and into the Northern Great
Plains Friday into Saturday. In response, a Colorado low will
begin to move into the Central Plains and Mid-Mississippi River
Valley. As we will be on the northern side of the low,
precipitation is expected to remain all snow. 04.00 EFS members
seem to be in good agreement on the idea of snowfall with most
members agreeing on this solution. Snowfall totals are a bit
varied but that makes sense this far out. The GEFS doesn`t seem
quite as excited but the 04.12 deterministic GFS does show a
good precipitation shield across our area. Snow ratios look to
be a bit higher than climatology with 04.12Z GFS soundings
showing a deep DGZ. Areas north of I-94 could see snow ratios
in the 20:1 area with further south looking closer to 16-17:1.
Overall totals look to be in the 1-4 inch range for now. It
should be noted that there is low-medium confidence that these
totals could be higher north of I-90 with NBM probabilities of
greater than or equal to 6 inches of snowfall in the 30-50%
percent range. A lot of this will depend on how the low phases
and the overall track of the low. This far out, many changes
are likely to be made so stay tuned for forecast updates on this
system. This system will also be a quick mover with Sunday
looking dry with temperatures falling back to where they were
on Friday.


Colder for Early Next Week

Another surface high is expected to move into the area late Sunday
into Monday, which will bring a reinforcing shot of cold air into
the area. Morning lows Monday and Tuesday will range from -10 to 5
degrees with afternoon highs struggling to climb out of the teens
both days. We could see some light snow Tuesday but the main story
will be the cold as apparent temperatures will range from -20 to
near 0 at their coldest. Luckily winds should be pretty light
during this time but if this changes, we may have to look at the
possibility of cold weather headlines.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1056 PM CST Tue Feb 4 2025

Primary aviation concern is the arrival of MVFR/IFR ceilings and
associated FZDZ Wednesday afternoon into Wednesday evening.
Still looking like a good chance for this, so have highlighted a
few hours of this in the TAFs at both RST/LSE. A few flakes of
snow may mix in, but if precip occurs, it will primarily be
FZDZ. Expect MVFR/IFR conditions to then persist through the end
of the period as precip departs to the east.

&&

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

&&

$$

DISCUSSION...Barendse
AVIATION...Ferguson