252
FXUS63 KARX 212348
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
548 PM CST Thu Nov 21 2024

.KEY MESSAGES...

- Diminishing winds and areas of rain this afternoon will give
  way to a small chance (20%) of drizzle developing into tonight.
  Temperatures should largely stay above freezing to mitigate
  the threat of freezing drizzle.

- Active weather returns early next week with generally low to
  medium (20 to 50%) chances for minor amounts of snow with a
  couple systems Monday through Thanksgiving Day. Could be minor
  impacts to holiday travel.

- Slight warming trend into this weekend, then below normal
  temperatures next week.

&&

.DISCUSSION...
Issued at 214 PM CST Thu Nov 21 2024

Diminishing winds and drizzle potential into tonight:

Broad occluded cyclone continues to slowly depart through the Great
Lakes region. Lingering snow impacting portions of central and
southwest Wisconsin since last night switched to all rain by midday
as temperatures continue to climb into the upper 30s to lower 40s.
Winds have been gusty behind this departing system with gusts
commonly in the 30 to 40 mph range. Gusts higher than that have been
few and far between, so have canceled the wind advisory for
southwest Wisconsin and Clayton County early.

The pronounced trowal with this occluded system continues to wrap
around back through the Mississippi River valley this afternoon,
bringing a tongue of increasing low level moisture into the local
area. Forecast soundings show increasing depth of low level
saturation through this afternoon, especially along and east of the
Mississippi River. While synoptic scale forcing will gradually
weaken heading into this evening, the RAP shows a 700-600mb band of
frontogenesis developing over the region which may interact with the
1+ km deep low level saturation to produce areas of drizzle. This is
hinted at by some high resolution composite reflectivity guidance,
such as the NamNest and the HRRR. While confidence is low to medium
in drizzle potential, it does look to be more favored where minimum
temperatures tonight will be at or above freezing. Will have to keep
an eye on trends this evening, but currently not anticipating
potential for freezing drizzle.

Active, colder weather early next week for pre-holiday travel:

A drier airmass and upper level ridging will bring a break from the
breezy/windy conditions and active weather Friday through the
weekend. The next system makes landfall on the West Coast early
Saturday, with the wave(s) traversing the northern US and southern
Canada and eventually reaching the Upper Midwest by late Sunday.
Whether this arrives as a singular, stronger wave (riding the
US/Canada border) or 2 weaker split waves remains in question, but
there is ensemble agreement for some light snow potential locally.
There is about a 40 to 60% probability for at least measurable snow
(0.1") north of I-90, but only a 20% or less chance for 1" or more.

Somewhat active weather is expected to continue in the busy pre-
Thanksgiving travel days early next week. However, there are few
overall forecast details to hang one`s hat on at this time, and
ensemble guidance is split on snow potential that far out. ENS
probabilities suggest around 40% for 1" or more of snow late
Wednesday into Thanksgiving Day while GEFS is closer to 10%. There
is more confidence in the temperature pattern dropping below normal
by Monday, staying chilly through at least Thanksgiving Day.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 548 PM CST Thu Nov 21 2024

Main aviation concerns this evening continue to revolve around
winds and low ceilings across the forecast area. Gusty
winds should continue to diminish through the night tonight,
remaining from the north/northwest through the period. What
looks to stick around is the low stratus currently across the
area, with MVFR to IFR cigs forecast. There is some variability
between the different models, but there does remain some signal
for a few pockets of LIFR to develop late tonight/early Friday
morning (mainly across SE MN). Have maintained the previous
mention this issuance, but will continue to monitor trends this
evening. Otherwise, guidance would suggest ceilings will be slow
to improve on Friday, so have continued to trend that way.

&&

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

&&

$$

DISCUSSION...Kurz
AVIATION...EMS