807
FXUS63 KUNR 091045
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
345 AM MST Tue Dec 9 2025

.KEY MESSAGES...

- Strong winds expected today. A High Wind Warning continues for
  most of western SD.

- Snow expected on Wednesday, turning to rain. Light freezing
  rain possible Wednesday night.

- Turning colder with chances for snow Thursday through Saturday.


&&

.DISCUSSION...(Today Through Monday)
Issued at 338 AM MST Tue Dec 9 2025

Upper air analysis shows obstinate northwest flow across the
western/central CONUS. Water vapor shows a strong wave crossing the
northern Rockies, quickly approaching the northern High Plains.
Surface analysis indicates low pressure just north of MT, quickly
heading toward ND. As the low approaches this morning, winds will
increase, gusting to over 60 mph through the day. The best chance
for strong winds will be across most of the western SD plains.
Locations across the NE WY zones will also see gusty winds. Some
models show the potential for gusts over 50kt, but overall consensus
is that it will stay below that threshold. There are newer
indications that +50kt gusts could develop over the eastern half of
the Black Hills. Will have dayshift take a closer look with 12z runs
to see if a late update is needed with headline adjustments.
Otherwise, the High Wind Warning looks to be in good shape. A cold
front will cross the area late this afternoon or early evening. Low
level mixing w/ CAA will keep wind momentum going after sunset. This
system will also bring light rain to the area, especially ahead of
the frontal boundary. Snow is expected across the Black Hills, but
temps will be above freezing except over the highest terrain. QPF
will be light. Winds will gradually decrease overnight as surface
high pressure builds across the Dakotas. The next system is
following closely behind...and could bring interesting weather for
Wednesday. Low pressure over the MT Rockies on Wednesday will slide
SE, arriving to the CWA on Thursday. Strong overrunning will support
700mb frontogenesis/isentropic lift on Wednesday, bringing
widespread light snow in the morning, then becoming rain through the
day as warmer air advects in from the west. The broad band of snow
over central South Dakota could become freezing rain as warmer air
aloft noses in. Overall QPF amounts look to be light...under a tenth
of an inch, which will limit ice accumulation. But will keep an eye
on this for potential impacts. A cold front is then expected to push
through Thursday, then another reinforcing cold front Thursday
night. Though it looks like snow will hang around on Thursday and
into Friday, it`s still a bit uncertain what snow amounts will look
like. There does seem to be better agreement between the ECM and
GFS...bringing light to somewhat moderate amounts over NE WY/Black
Hills late Thursday, then moderate or heavy amounts over NW SD
through Friday and Saturday. There is a lot to track over the next
few days.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Wednesday Morning)
Issued At 338 AM MST Tue Dec 9 2025

Areas of MVFR/IFR conditions due to lower clouds/ra/sn will
affect northeast WY/northwest SD today. Otherwise VFR conditions
expected over southwest into south-central SD. Strong winds
gusting to +50kt are expected across much of the western SD plains
today.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...High Wind Warning from 8 AM MST /9 AM CST/ this morning to 2 AM
     MST /3 AM CST/ Wednesday for SDZ001-002-012>014-025>027-
     030>032-041>044-046-047-049-072>078.
WY...High Wind Warning from 8 AM this morning to 2 AM MST Wednesday
     for WYZ060.
&&

$$

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