622
FXUS63 KARX 041143
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
543 AM CST Tue Nov 4 2025

.KEY MESSAGES...

- Warm weather continues for today with highs around 60,
  slightly cooler for the latter part of the week, then much
  colder by early next week--highs in the 30s and lows in the
  teens Sunday and Monday.

- Breezy Wednesday morning and again Thursday with gusts up to
  30-35 mph. Otherwise dry weather until Thursday evening.

- The potential for accumulating snow remains on the table for
  Saturday and Saturday night, though confidence remains low on
  the specifics with amounts or the exact location of the snow
  band.

&&

.DISCUSSION...
Issued at 305 AM CST Tue Nov 4 2025

Today: Warm and Dry

Surface ridging currently transiting the Driftless Region
progresses eastward this morning with increasing southerly flow
today. Weak warm air advection in the lower troposphere (3 C
increase in 850-mb temps over 24 hours) nudges temperatures a
few degrees warmer compared to yesterday with many locales
touching 60 degrees. A ribbon of 700-mb theta-e advection may be
able to saturate enough to produce light sprinkles northeast of
I-94 this evening, but otherwise the forecast for today is dry.


Wed & Thu: Breezy Periods, Seasonal Temperatures, Dry

A zonal pattern brings the next vort lobe across the Rockies
tonight, which amplifies Wednesday morning as it tracks along
the U.S./Canadian border and then into the Great Lakes in the
afternoon. A lee trough across the Northern High Plains shifts
to the mid-Missouri River Valley this evening with the low
center contracting as it also moves into the Great Lakes early
Wednesday morning. The isallobaric wind increases as upstream
high pressure rapidly builds in the wake of the cyclone with the
associated pressure gradient tightening from 20 ubar/km to
nearly 40 ubar/km in 12-18 hours.

Lower tropospheric cold air advection in the wake of the
attendant cold front will aid to funnel these stronger winds to
the surface for a 6-9 hour period in the morning before the
pressure gradient relaxes in the afternoon. The 04.00Z HREF 35
mph wind gust probabilities top out around 80-90 percent between
09-15Z (focused on southeast Minnesota into northeast Iowa and
southwest Wisconsin), tapering off quickly thereafter. Higher
wind gust probabilities fall off quickly above the 35 mph
threshold, with values of 30-50% for 40 mph gusts and <10% for
45 mph gusts.

The progressive pattern brings high pressure through Wednesday
night with cyclonic flow amplifying for Thursday and the end of
the week. Gusty southerly winds are expected for Thursday
during the day ahead of the next cyclone approaching from the
Dakotas. This low and the bulk of the forcing passes to the
north Thursday night, with any precipitation that manages to
form along the trailing cold front being light in nature. Only
about 50% of the LREF members develop any measurable
precipitation over the area, mainly east of the Mississippi
River, with only a 10-20% chance that rainfall amounts exceed
0.10".


Cooler and More Active to End the Week

A secondary cold front blasts through the region on Friday,
sending temperatures falling through the afternoon/evening and
setting the stage for a colder weekend and start to next week.
There exist a 10-15 degree interquartile spread for high
temperatures on Friday (mid-40s to mid-50s), indicative of the
timing discrepancies in when this front slides through.

A PV lobe breaks off a negatively-tiled trough lifting up along
the Pacific NW coast Friday night, racing ESE and reaching the
region Saturday into Saturday night. Accompanied by favorable
kinematic forcing, the system has the potential to produce the
first measurable snow for the region. Questions still linger as
to whether the thermal profiles will support snow and the
placement of the accompanying mesoscale frontogenesis forcing.

Given the fast translational motion of the wave and the rapid
surface cyclone development Friday night/Saturday morning, it is
understandable that the medium range ensembles still differ
substantially with snow amounts and placement. It is worth
noting that the deterministic EC/GFS solutions are settling down
on a snowfall band setting up in southern Minnesota/northern
Iowa and then spreading east into southern Wisconsin/northern
Illinois, and hopefully the ensemble members reflect this trend
soon.

The timing of this system on Saturday morning plays a key role
in the amount of snow that falls during the day. Members that
bring in snow earlier in the morning and limit the degree of
daytime heating bring notably more snowfall compared to those
that arrive later in the morning or midday. Whether snow rates
can overcome warmer ground temperatures (2 inch temps still in
the mid-40s) is another question that remains unanswered. For
now, while confidence is increasing that there will be snow in
the region, the predictability of the forecast remains low. The
EC Extreme Forecast Index sums this concept well--depicting a
shift of tails corridor through the region with the actual EFI
values of less than 50%.

Of much higher confidence (>95%) is the cold snap lurking for
the latter half of the weekend into early next week as polar air
surges southward in the wake of our Saturday system. High
temperatures should stay confined in the 30s with lows in the
20s to even teens Monday morning.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 542 AM CST Tue Nov 4 2025

Light southerly winds increase later this morning with gusts
approaching 20 to 25 mph west of the Mississippi River. These
winds diminish later this afternoon then gradually turn
southwest this evening ahead of a weak cold front. The
northwest wind shift is expected between 08Z and 11Z across the
region. With this wind shift, sustained winds of 10 to 20 mph
with gusts of 20 to 25 mph expected for much of the region with
some areas west of the Mississippi River approaching 30 mph for
gusts as we head towards the end of the TAF period. VFR
conditions will continue through the TAF period as there will be
some mid level clouds between 15kft and 20kft for much of the
day.

&&

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

&&

$$

DISCUSSION...Skow
AVIATION...Cecava