984
FXUS63 KARX 222309
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
505 PM CST Fri Nov 22 2024

.KEY MESSAGES...

- Clouds likely holding through Saturday morning

- Rain/snow chances (20-50%) return Sunday night into Monday
  with minor wet snow accumulation possible in Taylor and
  northern Clark counties

- Turning much colder in the coming week, especially around
  Thanksgiving; not much active weather locally to impact
  holiday travel

&&

.DISCUSSION...
Issued at 204 PM CST Fri Nov 22 2024

Clouds likely holding through Saturday morning:

North to northwest flow persists over the region behind a deep
departing cyclone east of the Great Lakes and an upper ridge over
the Plains. Shallow moisture and weak low level flow has led to a
persistent widespread low stratus shield over the region, though the
clearing line is not far off in south-central Minnesota and
central Iowa. The cloud cover is expected to hold in place
tonight, based on a plan view of RAP 950mb RH and also RAP/HRRR
forecast soundings. In fact, partial clearing looks unlikely to
arrive until closer to midday Saturday when the 850mb ridge axis
finally arrives. Thus, with more cloud cover tonight than
originally expected, have nudged tonight`s minimum temperatures
up by generally a couple degrees.

While the weekend still looks to trend dry overall, there are some
signals suggesting weak warm air advection and fgen forcing could
try to interact with a bit of incoming mid-level moisture. Forecast
soundings are rather dry through roughly 950mb to 700mb, so this may
be more of a virga setup, or perhaps a few sprinkles at most. Will
maintain a dry Saturday forecast for now, but something we`ll be
monitoring.

Rain/snow chances return Sunday night into Monday:

Sunday night into Monday brings our next main chance of
precipitation as the upper ridge exits. A digging upper trough in
the lee of the Rockies will encounter a favorable plume of moisture
extending northward from the Gulf. It looks likely that there will
be an open shortwave that advances overhead on Monday, along with a
closed low riding Minnesota`s northern border. Some solutions try to
phase these two features as they approach the Great Lakes, while
others keep them separate. Regardless, precip chances are
increasing, ranging from 50% in Taylor and Clark counties to 20% in
our far southern/western counties. GEFS members are a little more
aggressive with a southwestward trail of light QPF extending back
into central Iowa Monday between 6am and noon, whereas ENS and GEPS
ensembles cut off precip chances more along our southern border.
Depending on temperatures (which should climb above freezing for
much of the area), much of the precip may fall in the form of rain
before mixing with or changing to all snow. Any accumulating snow
potential, though minor, looks to be mainly favored across north
central Wisconsin where we currently have 0.5 to 1.5" across Taylor
and northern Clark counties.

Holiday travel and Thanksgiving outlook:

The rest of the coming week doesn`t look to be quite as unsettled as
it had been looking earlier. A couple weak shortwaves with limited
moisture could clip northern areas Thanksgiving Day into Friday, but
otherwise the more robust storm system looks to pass just south of
the Ohio Valley with impacts likely to stay south of our area.

The bigger story for next week will be an intrusion of colder air,
with a glancing blow Monday and Tuesday before we get deeper in the
cold 850mb blob around Thanksgiving. By Friday, ensemble guidance
keeps highs below 30 degrees area wide with lows heading into the
weekend in the teens to single digits.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 505 PM CST Fri Nov 22 2024

CIGS: persistent low stratus expected to hang around into Sat with
RAP/HRRR bufkit soundings scattering the low deck out west of the
Mississippi river between 12-18z, and west of there 18-00z. Expect a
break with vfr scattered conditions for a few hours but a VFR mid
deck of clouds slated to return with warm air advection/upper level
shortwave Sat evening, and could drop into MVFR/IFR by 18z Sun.

WX/vsby: southeast MN developed mostly MVFR fog late night/early
this morning and short term guidance favors that again tonight.
Latest HREF places a 60% for sub 4sm at KRST...and will continue to
lean forecast this way. Lesser probs for IFR (35%) but will monitor
and adjust if these look like they will be realized. Expect
improvement by 12z Sat.

Next chance for light pcpn (likely rain) will come later Sunday
afternoon into the night, with continued chances into Monday.
Amounts and impacts look relatively minor at this time.

WINDS: northwest to west tonight with some variability/decrease in
speeds as high pressure builds in Sat. Expect a swing to the
southeast for Sat night.

&&

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

&&

$$

DISCUSSION...Kurz
AVIATION.....Rieck