595
FXUS63 KUNR 102029
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
129 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 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 PM MST
     this evening for SDZ001.
     Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Thursday for SDZ002-013-014-032-078.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...JC
AVIATION...Woodward