110
FXUS63 KUNR 222329
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
429 PM MST Fri Nov 22 2024

.KEY MESSAGES...

- Weak cold front tonight with fog potential on the plains north
  and east of the Black Hills

- Elevated fire weather conditions Saturday across northeast WY

- Cold front Sunday with gusty northwest winds and small
  chance(<40%) of light snow/flurries

- Below average temperatures through Thanksgiving with slight
  chance(<20%) of snow

&&

.DISCUSSION...(This Evening Through Friday)
Issued at 1214 PM MST Fri Nov 22 2024

Water vapor shows upper ridge over the Northern Plains with Upper
low/trof over SASK/Manitoba, and strong upper low off the Pac NW
coast. At the surface, low pressure near the WY/SD/NE border with
high pressure building southeast through MT/western ND. Mainly
sunny skies with early afternoon temps in the 40s/50s.

Weak backdoor cold front will move south across the area tonight
with boundary layer flow veering more easterly (upslope) overnight
into Saturday morning. Fairly high probabilities of low
stratus/fog developing late tonight and Saturday morning across
the plains of western SD, possibly banking up against the Black
Hills. Not sure how dense the fog might become, but there are a
few HREF members that do suggest dense fog across far northwest SD
as well as parts of south-central SD.

Return flow strengthens Saturday as surface high shifts further
east. Temps will be problematic on the western SD plains depending
on quickly any stratus/fog is able to clear out. Northeast WY
into the Black Hills and southwest SD will be the warmest with
highs in the 50s, with some lower 60s possible in northeast WY as
winds shift more southwest.

Shortwave tracks across MT/ND Saturday night, with cold front
moving through the area late Saturday night into Sunday morning.
3-4mb/3hr pressure rises and robust cold advection will bring a
period of gusty northwest winds behind the front. There is a
chance of light snow/flurries (<40%) on Sunday, mainly over
northeast WY, the Black Hills, and southwest SD. Little to no
accumulation expected.

Upper flow transitions from zonal to northwesterly for the
upcoming holiday week, setting the stage for below average
temperatures. A few weak impulses move through the area bringing
small chances (<20%) of light snow.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Saturday Evening)
Issued At 426 PM MST Fri Nov 22 2024

VFR conditions will persist through this evening. Areas of fog
will develop across the western South Dakota plains after 09z
Saturday morning as a backdoor cool front settles over the area,
with a period of IFR/LIFR conds expected on portions of the
western SD plains, mainly in the far west including KRAP. Conds
will begin to improve later Sat morning. Breezy southerly winds
are expected Sat most areas, strongest on the northeast WY Plains.

&&

.FIRE WEATHER...
Issued At 1214 PM MST Fri Nov 22 2024

Elevated fire weather conditions will develop across northeast WY
on Saturday as southwest winds become breezy and RH drops to near
and below 20 percent. These elevated conditions could possibly
also develop over the Black Hills and far southwest SD.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...Johnson
AVIATION...JC
FIRE WEATHER...Johnson