844
FXUS63 KARX 091036
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
536 AM CDT Mon Mar 9 2026

.KEY MESSAGES...

- Widespread precipitation likely (50-70%) for Tuesday and into
  Wednesday with rain transitioning to snow overnight Tuesday
  night and into Wednesday. A brief period of freezing rain
  (10-20%) will be possible during this rain to snow transition.

- Clipper system brings precipitation (60-90% chance) for
  Thursday evening through Friday morning with a rain/snow mix
  favored.

- Accumulating snow potential (40-70%) for the upcoming
  weekend.

&&

.DISCUSSION...
Issued at 211 AM CDT Mon Mar 9 2026

Today - Wednesday: Rain Changes to Snow Overnight Tuesday

Zonal flow today will keep our temperatures fairly pleasant for
this time of year with minimal moderation in the ambient
airmass over the region. As a result, NBM percentiles for high
temperatures respond accordingly for today with highs in the
upper 50s to upper 60s across the local area. This changes as
Tuesday comes around though as an upper-level trough swings
through the Rockies into the Great Plains on Tuesday evening
ushering in some low-level cold advection into the region and
establishing a fairly pronounced baroclinic zone across the
Upper Midwest. As this occurs, deterministic models generally
agree on some level of surface cyclogenesis with the vicinity of
the IA/IL/MO triple point and a slight northerly push of the
warm sector. As a result, will have multiple different types of
precipitation modes to address as this low-level cold advection
interacts with the warm conveyor processes of the developing
surface cyclone across the area.

Initially, rain will likely be the predominate precipitation type
across the local area on Tuesday evening as surface temperatures
remain above freezing. Cannot rule out some thunderstorm potential
in far southwestern WI as the warm sector push attempts to bring
some MUCAPE into Grant County, this coupled with fairly steep mid-
level lapse rates could result in some hail risk with the elevated
instability atop the warm nose from the aforementioned warm
advection aloft, however this would be an incredibly brief window.
Otherwise, as surface temperatures cool into the overnight, rain
will transition to snow from northwest to southeast. There remains
some caveat to this though, initially the warm nose from the
aforementioned warm advection aloft shown in the 09.06z NAM
does not cool right away as the low-level cold advection moves
in. As a result, there is some probabilities in the NBM (10-20%)
for measurable ice accumulations as this thermodynamic profile
would support at least a brief period of freezing rain. However,
this appears to be an interplay of how quickly the developing
surface low ejects east as the upper-level trough moves overhead
to cool this warm nose down. Consequently, any icing impacts in
the local area remain very low confidence. Otherwise, as the
entire thermal profile cools below freezing, a transition to
snow ensues with a band of snow moving through the area during
the morning hours on Wednesday associated with a weak band of
600-800mb frontogenesis.

Overall, probabilistic guidance is not overly enthusiastic
about snowfall amounts on Wednesday morning with the 09.01z NBM
having medium probabilities (30-60%) for amounts over 1 inch
north of I-90. Furthermore, probabilities for amounts in excess
of 3 inches are even less north of I-90 (10-30%). This overall
seems to fit the current conceptual model as this system is
fairly progressive with the bulk of precipitation pushing east
of the local area by noon on Wednesday. So confidence seems
respectable for some snowfall accumulations into Wednesday
morning but unclear as to exactly if more impactful
accumulations will occur.

Thursday - Friday: Cooler with Rain/Snow Chances

As we head into the second half of the work week, a secondary
clipper system in the form of a shortwave trough will descend out of
the Canadian Plains into the Upper Midwest Thursday night and into
Friday morning in a newly establish northwesterly flow pattern.
Overall confidence is fairly high for precipitation with this wave
with the NBM having precipitation chances generally in the 60-90
percent range across the local area. However, with southerly surface
flow present throughout the day on Thursday, this will allow some
warmer surface temperatures to be present which should favor rain
for a sizable portion of this system for areas south of I-94.
However, as some cold air advection works in overnight and into
Friday morning, could see a changeover to snow or a rain/snow
mix. In any case, probabilities for QPF over 0.25" with this
system in the grand ensemble (GEFS/EC/Canadian ensemble) are
fairly low (10-30%). That being said, there are some medium
probabilities (30-50%) north of I-94 for snowfall amounts of an
inch or greater in this same dataset. Regardless, temperatures
will likely be near normal with highs in the upper 30s to 40s.

This Weekend: Accumulating Snow Potential

By the time this weekend rolls around, zonal to somewhat
northwesterly flow is in place which will likely keep our
temperatures slightly cooler than normal with highs in the 30s
to lower 40s. The next feature that we will need to watch very
closely will be a shortwave trough that originates from the
Pacific Northwest and works east way east/southeastward Saturday
evening and into Sunday. The conceptual model painted in
deterministic guidance shows a deepening surface low somewhere
in the Upper Midwest (however there remains fairly significant
differences in where this occurs) that has a fairly pronounced
deformation band with it, with snow being the favored
precipitation type north of the surface low. What is remarkable
within the cluster analysis of the 09.00z grand ensemble
(GEFS/EC/Canadian ensemble) is the general agreement in the
synoptic pattern with only subtle difference between each
cluster group, not something you see all that often 5-6 days
out. In any case, the EC Extreme Forecast Index paints an area
of 50% probabilities for exceeding model climatology snowfall
amounts into Sunday with a shift of tails of 0 to 1 across the
region. This shift of tails is being driven by several members
within the EC ensemble of amounts over 6". This can be noted in
the NBM which has medium probabilities (30-50%) for 6 inches or
greater north of I-90. What is also important to note is when
looking at the 50 individual members of the EC ensemble, the
vast majority have this axis of heavy snow amounts this weekend
somewhere in the region, the question is exact location. Will
certainly be a period to watch as the position and intensity of
the developing surface low with this upper-level wave will be
critical. Given that this is still 5 to 6 days away,
predictability with this system remains low, so be sure to
monitor the forecast over the coming week as details will
certainly change!

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 536 AM CDT Mon Mar 9 2026

VFR conditions are expected throughout much of the TAF period with
wind speed and direction changes driving much of the aviation
forecast. Have opted to hold onto a brief period of LLWS early this
morning as the RAP/HRRR holds onto winds of 40-45 kts at 2kft until
around 13-14z. Otherwise, a frontal passage this afternoon will
shift winds from west/southwesterly to northerly but will remain
steady from around 6-12 kts. Cigs may decrease around 09z to low-VFR
levels however the probability in the HREF is low (20-40%) for MVFR
cigs at this time so opted to leave out any MVFR mention.

&&

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

&&

$$

DISCUSSION...Naylor
AVIATION...Naylor