278
FXUS63 KUNR 070459
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
959 PM MST Sat Dec 6 2025

.KEY MESSAGES...

- Light snow continues tonight through tomorrow morning

- Confidence is increasing for a High Wind Event to impact much of
  western South Dakota on Tuesday. Could see wind gusts up to 70
  mph

- Widespread precipitation expected on Wednesday. There is a low
  end chance for various precipitation types across the eastern
  plains (rain/freezing rain and a rain/snow mix)

&&

.DISCUSSION...(This Evening Through Saturday)
Issued at 106 PM MST Sat Dec 6 2025

Rest of today...Embedded in the persistent NW flow aloft a fast
moving shortwave is moving through the area this afternoon. Clouds
have increased in response with much of the region now under a low
cloud, overcast sky. Lingering moisture should be enough to
squeeze out some very light snow showers/flurries across eastern
Wyoming, western South Dakota and across the Black Hills this
afternoon and into Sunday morning. Expecting very little
accumulation with the higher peaks seeing maybe one inch, with the
valleys only seeing a trace amounts of snow. Whatever snow is out
there will diminish Sunday afternoon but with the cloud cover
sticking around, temperatures won`t warm too much on Sunday with
highs predominately in the upper 30s to low 40s across the Black
Hills and adjacent foothills. Expect the coldest temperatures out
across the easter plains where highs will be in the low 30s.
Monday will be the only quiet day as we wait on the arrival of a
fast moving cold front associated with a strong area of low
pressure diving south out of North Dakota.

Confidence is increasing for a High Wind Event to impact much of
western South Dakota on Tuesday. A fast moving and deepening low
pressure system will dive south through central North Dakota and
quickly race to the south throughout the day on Tuesday. Winds
aloft with this system are currently (latest model run) between
50-60 knots. The winds will be be backed by a fast moving cold
front with very strong cold air advection into the region and
rapid pressure rises will aid in mixing down these winds aloft to
the surface. Soundings are showing ~58 knot winds just above the
surface across NW South Dakota. If this pattern holds, High Wind
Watches will be issued potentially as soon as early Monday
morning. Current forecast calls for winds to approach 70 mph
across the NW corner of South Dakota with strong winds between
55-65 mph impacting the foothills and eastern Plains through much
of Tuesday afternoon. Additionally, strong WAA will have streamed
into the region ahead of this system and with the compressional
heating often associated with these dynamic and fast moving
fronts, and the downslope wind component, temperatures could reach
into the 60s before the front moves through.

Wednesday another wave moves through the region and this one may
be tricky in determining the P-type across some of the Black Hill
foothills and eastern Plains. CAA will be working in from the
east but surface winds out of the south and southeast will keep
low level temperatures warm with the arrival of the best QPF.
Aloft temperatures will be cooling so profiles are hinting at the
very slight chance for some freezing rain to impact portions of
the eastern Plains on Wednesday. These types of events require a
lot of parameters coming together, but there is a slight signal
and freezing rain does bring significant impacts, so this is
something we will be watching in the coming days.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 956 PM MST Sat Dec 6 2025

Light snow and patchy freezing fog are causing widespread
MVFR/IFR and LCL LIFR conditions across northeastern WY into
western SD. These conditions should continue through the rest of
tonight into early this morning. Conditions should improve to VFR
from west to east after ~16-18z.

&&

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

$$

DISCUSSION/KEY MESSAGES...Woodward
AVIATION...Wong