232
FXUS63 KARX 061941
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
140 PM CST Sat Dec 6 2025

.KEY MESSAGES...

- Some shift southward of the winter storm track, with subsequent
shift south of the heavier snow band. Amounts trending a bit less
than previous forecasts, and mostly from along and south of I-90.
Highest amounts locally still look to fall across parts of northeast
IA into far southwest WI (3 to 6", 20-40% chance to exceed 6").
Advisories/Warnings continue, but if southward shift of band
continues, expect some revisions as the evening wears on.

- Below normal temperatures persist throughout the next week with
Tuesday being the "warmest" day with highs rising into   the 30s.

- Additional snow chances continue into next work week. Rain will
likely mix in with snow late Tuesday for areas south of  I-94.

&&

.DISCUSSION...
Issued at 140 PM CST Sat Dec 6 2025

> WINTER STORM TONIGHT: taking a shift southward which would move
the bulk of the local snowfall along/south of I-90.

HRRR/RAP morning runs coming in with a distinct shift southward with
the winter storm track, more aligned with the very persistent,
consistent GFS and EC, which never wavered much from this southern
track. The HRRR remains even more aggressive with late morning/early
afternoon runs - pushing the snow farther south. RAP has been more
steady.

Ample lift in the projected snowband with sloping Fgen, isentropic
upglide on the 280:295K sfcs, favorable low level QG convergence,
and the parent shortwave itself. Some upper level jet support too.

DGZ mostly under 100 mb thick per RAP/HRRR soundings, but the SREF
suggests a decent shot (over 30%) for 1"/hour rates within the heart
of the band. EFIs are in the 0.7 to 0.8 range with a non-zero SoT in
the band. Still confident that 6+" amounts will be reached in the
band, less so in where that lays out.

With the CAMS aligning more with the global models...will shift the
snowband a bit farther south. HREF/REFS still painting a 20-40%
chance for 6+" of snow in the warning area of northeast IA across to
far southwest WI. Amounts less around I-90, more 1 to 3" range now,
but advisory still appropriate for this early season snowfall - and
higher impact area (interstate travel). PLan to "stand pat" with
current outlay of headlines for now. But, if the aggressive HRRR
trend looks like reality, some adjustments to the headlines will be
needed later this evening.



> NEXT WEEK: active pattern continues with periodic shots for
precipitation. Still trending cold for the most part, but Tue still
looking like a day many will warm above freezing.

Busy, progressive northwesterly flow a loft promises to spin a
multitude of shortwave troughs across the upper Mississippi river
valley. Some weak, some potentially strong.

On Mon/Mon night the GEFS and EPS continue to shift a couple weak
perturbations across the region, one more south, one more north. THe
northward shortwave looks a bit stronger and has a better chance to
lay down minor accumulations of snow Mon night. Favored track has
kept these chances across northern WI - and mostly away from the
local forecast area.

The next shortwave should pack more of a "punch" as it drives across
the northern plains Tue, spinning east/southeast across the region
Tue night. While the GEFS and EPS have been in good agreement with
relative strength and timing, positioning varies quite a bit -
between and within the model suites. Some keep the related pcpn band
across northern MN/WI. Others paint it across the local area. A few
push it even farther south into northern IA. On the whole though,
more favor a northern track.

There is surge of "milder" air ahead of the system which will
complicate ptypes. GEFS and EPS have inched up expected highs for
Tue over their last several runs with mid 30s now looking more
likely (60 to 80% chance to warm above freezing). Of course, these
temps reflect a more northward storm track. If it shifts south, so
will the milder air. The low level warming looks like a rain or snow
question at this time - not icy. Will let the model blend take the
reigns for ptype for now. Where it does snow, plenty of forcing with
deep QG convergence and sloping Fgen that a several inch band could
be realized.

Colder air surges in post the Tue night system and should hold temps
well below normal through the weekend. Other shortwaves will also
bring more snow chances here and there.


&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1131 AM CST Sat Dec 6 2025

Incoming snow seen on radar imagery traversing the Missouri River
Valley from eastern South Dakota through western Iowa early this
afternoon. Accompanying impacts likely drop into IFR visibilities
per local climatology. IFR to MVFR ceilings linger post snowfall
overnight with low level cold air advection saturating the lowest
levels.

Drier air within this colder airmass suggests VFR potential Sunday
morning as cold air advection weakens. Low confidence situation
given model bias to remove impacts at longer forecast hour as well
as select model biases in sustaining low level saturation.

Subsequent aviation impacts frequent the longer term forecast:
accompanying small show chances Sunday night through Monday morning
and again Monday through Thursday.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 6 PM this evening to 6 AM CST
     Sunday for WIZ041>043-053>055-061.
MN...Winter Weather Advisory until 6 AM CST Sunday for MNZ086-087-
     094-095.
     Winter Weather Advisory from 6 PM this evening to 6 AM CST
     Sunday for MNZ088-096.
IA...Winter Storm Warning until 6 AM CST Sunday for IAZ008-018-019-
     029.
     Winter Weather Advisory until 6 AM CST Sunday for IAZ009-010.
     Winter Weather Advisory from 6 PM this evening to 6 AM CST
     Sunday for IAZ011-030.

&&

$$

DISCUSSION...Rieck
AVIATION...JAR