102
FXUS63 KUNR 272043
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
143 PM MST Thu Nov 27 2025

.KEY MESSAGES...

- Light snow will begin tonight across much of western SD into
  northeastern WY. Minor accumulations and travel impacts
  expected.

- Cold temperatures this weekend with highs 10 to 20 degrees below
  normal.

- Light snow is possible for the middle of next week in the late
  Tuesday/Wednesday time frame

&&

.DISCUSSION...(This Evening Through Thursday)
Issued at 143 PM MST Thu Nov 27 2025

Main forecast concern for the next couple days will be light snow
across much of western SD into northeastern WY. Closed upper low
off the coast of WA will transition to an open wave as it
traverses the Northern Rockies tonight. Mid-level frontogenesis
and modest Q-vector convergence ahead of the shortwave will
facilitate the development of a snow band across northwestern into
south central SD early Friday morning. In terms of snow totals,
there`s still some uncertainty as to where the strongest forcing
will be and thus where the band will develop. This would have
impacts on snow totals, especially across northwestern SD. As of
now, it`s looking like far northwestern SD could see 3+" of snow,
therefore have hoisted a Winter Weather Advisory for Harding,
Perkins, and Ziebach Counties. Additional winter weather headlines
may be needed if the band ends up further west.

The other area of concern is the Northern Black Hills as boundary
layer flow shifts to the north through Friday afternoon into
Saturday. Upslope snow is possible for the northern Black Hills
with Froude numbers >1 and 0-2km RHs of >80%. Snow totals here may
exceed 4" with up to 6" possible. Therefore have hoisted a Winter
Weather Advisory for the Northern/Wyoming Black Hills and
northern foothills zones. Developing sfc low slides to the south
of the forecast area late Friday night into Saturday. Precip wraps
around the north side of the low and brings an additional round
of light snow to the forecast area overnight with much of the CWA
seeing minor snow accumulations by Saturday morning. Tightening
sfc pressure gradient across the CWA in the wake of the low will
support breezy northerly winds Saturday morning. Winds of 15 to 25
mph with gusts up to 40 mph combined with falling snow could
cause some patchy blowing snow across northeastern WY and western
SD early Saturday morning, which may cause minor travel impacts.

Arctic airmass pushes into the Northern Plains behind this system
with temperatures of 10 to 20F below normal. Highs on Saturday
and Sunday will struggle to climb out of the 20s with lows
Saturday and Sunday night plummeting into the single digits.
Another shortwave skirts the far southern portions of the CWA
Sunday evening which could bring a few snow showers to
southwestern SD, though not anticipating much, if any, impacts.

Region remains under northwest flow through the middle of next
week. Temperatures will slightly warm for Monday into Tuesday,
with highs in the 30s to 40s instead of the 20s. Another shortwave
sweeps through the Northern Plains late Tuesday into Wednesday.
This could bring the next chances of light snow to the forecast
area.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1006 AM MST Thu Nov 27 2025

Areas MVFR CIGS across northwestern South Dakota will dissipate
through the afternoon. Otherwise, VFR conditions will prevail
through the 28/06z, including the KRAP/KGCC terminals. After
28/06z, a band of light snow may develop over the area leading to
local MVFR conditions.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory from 5 AM Friday to 11 AM MST Saturday
     for SDZ001-002-014-078.
     Winter Weather Advisory from 2 PM Friday to 11 AM MST Saturday
     for SDZ024-025.
WY...Winter Weather Advisory from 2 PM Friday to 11 AM MST Saturday
     for WYZ057.
&&

$$

DISCUSSION/KEY MESSAGES...Wong
AVIATION...Smith