000
FXUS63 KARX 282038
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
238 PM CST Mon Nov 28 2022

.DISCUSSION...(This evening through Monday)
Issued at 230 PM CST Mon Nov 28 2022

Key Messages:

 - A mixture of snow and freezing drizzle along and northwest of
   an Austin to Wabasha line during the day on Tuesday. Several
   inches of snow and a glaze of ice expected, but amounts hinge
   on the exact mixture of snow and freezing drizzle.

 - Wintry mix spreads eastward Tuesday night with light snow and
   possibly a brief period of freezing drizzle expected area-wide.
   Colder air rushing in may also turn wet roads slick overnight
   into Wednesday morning.

 - Cold and blustery on Wednesday, warming for Friday, with a
   passing system and cooler temperatures for the weekend.

TONIGHT - TUESDAY NIGHT: Wintry Mix Details

A lee cyclone ejects off the Front Range in Kansas tonight and
curves to the east/northeast over the ensuring 24 hours, tracking
across southeast Iowa and eastern Wisconsin before reaching Lake
Superior by 06Z Wednesday. A leading vort max lifting along the
eastern flank of the parent upper level trough has already pushed
a surface cold front across the MN/Dakota border, which meanders
eastward into southeast Minnesota after midnight tonight.
Increasing low-level moisture rides over the low-level baroclinic
zone tonight as the main upper wave/surface low approach from the
west. A solid wedge of 280-290K isentropic ascent becomes
established by 12-15Z Tuesday with a narrow, sloped Fgen band
proving to be the focus for the highest QPF/snow totals. The
surface cyclone passes southeast of the forecast area between
21-00Z Wednesday, with the strongest forcing waning quickly in its
wake. Light synoptic lift lingers for another 6 hours ahead of
the upper wave, with the snow ceasing by 00-06Z for most locales.

The general model consensus is locking in on the main snow band
taking shape to the northwest of the forecast area along the Fgen
corridor, running through the Twin Cities metro area from southwest
to northeast. Snowfall amounts taper off quickly south of this
band as the combination of warmer surface temperatures and an
increasing risk of losing ice introduction aloft complicates the
forecast. All of the models are showing this 100-200-mb mid-level
dry wedge impeding on the southern flank of the snow band, the
question just becomes where exactly this sets up with about 50-100
miles of spread still noted in the deterministics/ensembles. With
most deterministic profiles showing the colder air undercutting
the dry slot, have introduced freezing drizzle/ice accumulations
to the forecast along this snow/rain transition zone for much of
the forecast area.

Snow and ice amounts will be very sensitive owing to the
previously discussed factors and therefore it remains tough to pin
down exact values for any one location. Have hoisted a winter
weather advisory for parts of southeast Minnesota where confidence
is highest for both snow and ice accumulations that could impact
travel. However, there is a modest likelihood that this advisory
will need an eastward expansion with later updates as we hone in
on the impacts resulting from the wintry mix transition and
freezing of wet road surfaces as much colder air arrives Tuesday
evening/night.

WEDNESDAY - WED NIGHT: Cold and Blustery with a Few Flurries Possible

As Tuesday`s cold front and low pressure system continue to lift to
the NE across Lake Superior into James Bay, a surface high pressure
ridge shifts in from the west. The result will be blustery NW winds,
with gusts in the 25 to 30 mph across much of the area. With colder,
polar air across the area behind Tuesday`s cold front, wind chill
values fall into the single digits above zero across most of the
area--a few locations in SW Wisconsin and NE Iowa will have wind
chills in the low teens above zero. Slick spots are expected on any
untreated surfaces Wednesday morning. By Wednesday night, winds
begin to slacken as the surface ridge moves further overhead -
warmer air begins to move in as the ridge axis shifts east of our
area, though temps remain fairly steady through the night with wind
chills in the single digits above zero.

THURSDAY - FRIDAY: Trending towards Normal, Cold Front Friday Night

Southwest winds bring in warmer air aloft through the day Thursday
into Friday. Temperatures Thursday rise to slightly below normal and
near normal on Friday with highs in the mid-30s across central
Wisconsin and mid-40s to the south across SW Wisconsin and NE Iowa.
Enough wind lingers Thursday for wind chills to be in the teens.
Late in the day on Friday, a cold front approaches from the NW.
Predictability on the timing of this front remains low, as
temperature spread between the NBM 25th and 75th percentile is well
into the teens Friday evening as GEFS guidance remains much faster
than EPS.

WEEKEND/EARLY NEXT WEEK: Another System Saturday, Cooler Temps

Predictability in the details heading into the weekend and early
next week remains low at this time. Clustered ensemble guidance
suggests GFS, GEM, and EC ensembles are not favoring any solution
over another - ensemble means show near-zonal flow Saturday as a
potential wave and low pressure system pass to our north along the
US/Canada border and Lake Superior. Sunday into Monday, ensemble
means suggest cooler air across the Upper Midwest as GEFS and EPS
show a signal for a leeside low pressure system developing across
the Central Plains and lifting NE into the Great Lakes region -
something to monitor in the days ahead.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1136 AM CST Mon Nov 28 2022

VFR conditions persist for the rest of the day today, with
MVFR/IFR ceilings spreading from south to north after 06Z tonight
and lowering to IFR/LIFR for the day on Tuesday. A band of snow,
possibly mixed at times with freezing drizzle, develops along an
AEL to MDZ line during the day on Tuesday with light rain south of
this band.

Winds will be from the south at 10-20kts through this afternoon,
lessening tonight and backing to the north/northeast along the
front from AEL/MDZ for Tuesday morning. The threat for sustained
LLWS this evening has decreased and have removed from the TAFs,
but cannot completely rule it out for a few hours.

Looking ahead, the front pushes southeast Tuesday evening,
causing precipitation to switch to light snow (possibly mixed
briefly with freezing drizzle) Tuesday evening area-wide. Winds
also switch to the northwest and remain in the 10-20G 30 kt range
into Wednesday.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...Winter Weather Advisory from 4 AM to 9 PM CST Tuesday for MNZ079-
     086-087-094.

IA...NONE.
&&

$$

DISCUSSION...Skow/JAW
AVIATION...Skow

NWS ARX Office Area Forecast Discussion