201
FXUS63 KUNR 101722
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1022 AM MST Wed Dec 10 2025

.KEY MESSAGES...

- Snow will transition to rain this afternoon and evening.
  Freezing rain expected across northwest/central South Dakota
  tonight and Thursday morning.

- Long duration snow expected Friday through Saturday. Moderate
  accumulations possible.

- Dry and warmer early next week.

&&

.DISCUSSION...(Today Through Tuesday)
Issued at 320 AM MST Wed Dec 10 2025

Upper air analysis continues to show stubborn northwest flow across
the western to central CONUS. Behind the departing compact low over
the Midwest, weak ridging is approaching from central/eastern
Montana. The next wave is just behind it, crossing the northern
Rockies to near central MT. At the surface...high pressure is
quickly moving in from eastern MT. Winds will continue to weaken
early this morning from west to east. Mostly clear/sunny skies
across the majority of the CWA will make for a quiet morning. Highs
today will range from near 30 over NW SD to upper 40s over NE WY.
The next wave approaches later today. Warm H80-70 flow will increase
from the W/SW, providing warm air advection, leading to overrunning.
H70 frontogenesis/isentropic lift will support rain (or snow
transitioning to rain) through the afternoon and evening. Most areas
will warm to above freezing as the warm front works through
CWA...but it will fail to reach NW/Central SD. This will lead to a
freezing rain event. This icy precip will begin late this afternoon
as snow, transition to light freezing rain in the evening, then
continue overnight until the precip slides east of the CWA border.
Ice accumulation up to a tenth of an inch is expected. There is a
second resurgence of precip in the late Thursday morning as a
weak cold front pushes into NW SD. Guidance from 00z model runs
show CAA lacking with this front, allowing temps to warm above
freezing and end the threat of icing. A stronger secondary front
will cross the area in the late afternoon/early evening. NBM 25/75
percentiles show max temps at Hettinger ND ranging from 37 to
48...and at Faith 40 to 53 degrees. That is promising for melting
of the ice and ending any impacts to travel. Will that in mind,
see no need to make changes to the Winter Weather Advisory area
and timing. Chances for rain will linger across NE WY and far
western SD through the day on Thursday...and a rain/snow mix over
the Black Hills. The Thu evening cold front will drop temps back
below freezing overnight. As previous shift astutely
mentioned...this could result in wet roads icing up overnight in
time for the Friday commute as temps drop 30-40 degrees in 18
hours. Overnight snow will linger through Friday over NE WY/NW
SD/Black Hills, with good agreement on 1 to 4 inches of
accumulation...the highest over the Black Hills. Models show a
strong wave crossing ND on Friday, bringing another round of snow
to NW/Central SD...and 1 to 4 inches. Models are having difficulty
with the placement of overlapping snow totals from both events.
Am going middle of the road with totals in the 2 to 6 inch range
through a 48 hour period. The beginning of next week could finally
bring a pattern change...and with it dry weather and above
average temperatures.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 949 AM MST Wed Dec 10 2025

Main weather concern will be for the possible development of MVFR
conditions across the terminals with the onset of -RA/-RASN
occurring at the terminals between 18-00z. Conditions across the
terminals will gradually improve with VFR conditions prevailing at
the terminals by 06z. Winds will be light out of the south today
but will shift to the WSW across the KGCC terminal and to the NW
across the KRAP terminal by 11z and 16z respectively. Winds at
these terminals will be in the 15-20 knot range with gusts up to
30 knots possible.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Thursday for SDZ001-002-012>014-032-078.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...13
AVIATION...Woodward