637
FXUS63 KUNR 211722
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1022 AM MST Fri Nov 21 2025

.KEY MESSAGES...

- Seasonable temperatures and dry through the weekend.
- Turning colder with light snow possible next week.

&&

.DISCUSSION...(Today Through Thursday)
Issued at 143 AM MST Fri Nov 21 2025

Upper level analysis shows split flow across the US with
northwestern flow from southern Canada into the Great Lakes. Water
vapor imagery shows upper shortwave ejecting into the Central
Plains and Midwest with a surface low deepening across southern
KS. Further upstream, a closed upper low is located across central
CA with active northwest flow across the Pacific NW.

East-southeasterly surface flow will continue this morning with
areas of low clouds and fog, primarily across northeastern WY and
southwestern SD, including the foothills. Low clouds will erode
this morning with gradually clearing skies expected through the
evening.

Dry westerly flow will persist across the Northern Plains through
the weekend as the closed low over the southwestern US slowly
ejects into the Southern/Central Plains late Sunday. Expect high
temperatures 5-15F+ above normal today through Monday. The
aforementioned closed upper low is forecast to eject into the
Central Plains as an open wave by 12z Monday, with a chance of
rain showers across south-central SD early Monday. A northern
stream shortwave will immediately follow with much colder air
spilling into the region Monday night into Tuesday. Light
rain/snow is possible with the cold frontal passage late
Monday/early Tuesday with the best chances across the western
third of the forecast area and Black Hills. Chances for light snow
will persist through Thanksgiving although low predictability in
the evolution of the synoptic pattern precludes higher forecast
confidence in precipitation potential for the latter half of next
week. Active flow will continue Thanksgiving into the following
weekend.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Saturday)
Issued At 1020 AM MST Fri Nov 21 2025

Patchy fog and low clouds will continue across portions of
northeast Wyoming and western South Dakota through 20Z. Otherwise,
VFR conditions are expected.

&&

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

$$

DISCUSSION/KEY MESSAGES...SE
AVIATION...Smith