842
FXUS63 KUNR 102331
AFDUNR

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

.KEY MESSAGES...

-Mixed precip expected across the area tonight, with some icing
 across portions of NW SD

-Warm Thurs ahead of an arctic front

-Cold and snowy Thur night into Sat with some snow accums,
 heaviest across NW SD where a few inches are possible

-Warm and dry next week

&&

.DISCUSSION...(This Evening Through Wednesday)
Issued at 128 PM MST Wed Dec 10 2025

Active northern stream will continue to bring wild swings in
temps along with precip chances through the end of the week.
Massive western CONUS ridge will support another CP front into the
region tomorrow as a clipper system tops the ridge. This system
is supporting strong WAA over the region today, with high centered
upglide supporting a developing band of precip over the region
this afternoon. Precip is fighting a very dry layer in the lower
atmosphere, indicated by the 18Z UNR raob. However, this layer
will eventually saturate with precip reaching the ground this
evening on the Plains. Still expecting a good chance of icing
across portions of NW SD, esp from Lemmon to Dupree where a tenth
or so of ice is expected. Did trim back the adv in the far west
given staunch WAA, which now supports a very narrow window of
mixed precip across Harding and esp Butte Counties. Temps there
should rise above freezing this evening and remain above freezing
through the night. The other question mark will be Haakon County
where precip chances look more limited with marginal profiles.
Most places will see warm temps Thur ahead of the clipper with
westerly flow supporting decent mixing. Expecting highs in the 50s
and 60s across the southern half of the FA, warmest in SW SD.
Coolest locations will be in NW SD. Cold front will settle into
the region Thur afternoon/evening with temps falling through the
night. Baroclinic zone will setup over the region and stall with
several weak impulses agitating the flow and supporting rounds of
light snow. Accums will range form 1 to 2 inches in the SW half to
third with 2 to 4 inches across the NE half. Easterly upslope
flow may allow for some enhancement in the BH foothills, esp given
cold profiles supporting higher snow ratios. In addition, some
upslope fog will also be possible Friday into Sat. Upper ridge
begins to shift east Sunday with things warming back up next week,
along with breezy conds as the nearby active northern stream
supports traversing impulses, which could eventually bring another
round of cold air toward the end of the week.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Thursday Evening)
Issued At 426 PM MST Wed Dec 10 2025

A band of mixed precipitation will move from northwest to
southeast across the area tonight as the band slowly lifts
northeast. Areas MVFR/IFR conditions will be associated with the
strongest echoes over the Black Hills into northwestern SD through
11/12z. Mainly VFR conditions expected for a short period
Thursday morning/early afternoon, but then MVFR/IFR conditions due
to snow will develop late in the period and affect the entire
area after 12/00z.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until 11 PM MST this evening for SDZ001.
     Winter Weather Advisory until 11 AM MST Thursday for SDZ002-013-
     014-032-078.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...JC
AVIATION...Helgeson