671
FXUS63 KUNR 120828
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
228 AM MDT Sun Oct 12 2025

.KEY MESSAGES...

- Two cold fronts moving through today will bring very windy
  west/northwest winds, colder weather, and some showers
- Freezing temperatures possible Monday morning
- Unsettled weather next week

&&

.DISCUSSION...(Today Through Saturday)
Issued at 222 AM MDT Sun Oct 12 2025

08z surface analysis had low over western ND with warm front into
eastern NE and cold front into central WY. Secondary cold front
lurking along the Canadian/MT border. Water vapour loop had upper
trough across the Rockies with 110kt jet streak on the front side
creating narrow band of shra/TS west of the CWA. Downslope winds
starting on schedule in the KSPF area with gusts near 50mph over
the past hour, which should spread across localized areas on the
eastern slopes of the Black Hills for the next few hours. Main
concern this forecast is upper trough.

Today/this evening, 110kt jet streak transports upper trough
east/northeast as it wraps into slightly negatively tilted upper
low over southeast SK. This will propel first cold front through
the CWA this morning with 3-5mb/3hr pressure rises leading to very
windy west/northwest wind gusts over northwestern SD. Quick shot
of post frontal moisture is whipped through the northwest half of
the CWA this morning where a blob of QG-forcing zips through. As
upper low wraps up, it slings the secondary cold front into the
CWA this afternoon with well-defined q-vector
divergence/subsidence/drying. Result will be waning
precipitation, well-mixed boundary layer, modest cold air
advection, and 2-4mb/3hr pressure rises. 30-40kt 800mb winds
behind both fronts give credence to wind advisory level winds
(25-35g55 mph) through early this evening over northwestern SD.
Have added the Wall-Philip area to the current Wind Advisory.
HREF barely shows support for >45mph wind gusts, but NBM has
50-90% chance of 45-55mph wind gusts, which better matches
subjective pattern recognition. NBM chance of >50kt gusts <20%.

Tonight, surface anticyclone slips into the CWA with decreasing
winds and increasingly supportive conditions for frost/freezing
temperatures for some folks. Latest guidance/probabilistic trends
has been for MinT to be a bit warmer over southwest to south-
central SD. Will let day shift take final look at headlines need
to cover susceptible vegetation impacts Monday morning.

Monday/Tuesday, southwest flow aloft develops per upper
low/trough over the western CONUS. Embedded shortwave will support
a few showers Monday night/Tuesday. Upper low lifts northeast as
upper trough translates eastward for Wednesday/Thursday. It will
bring increasing chances for QPF over the CWA. Temperatures next
week will be near guidance with cloud cover/precipitation
modulating expected highs significantly, especially east of the
Black Hills.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1054 PM MDT Sat Oct 11 2025

A cold front will move through the region between 09Z and 18Z.
Gusty northwest winds, up to 35-45kts, will be found behind this
cold front. Additionally, a stratus deck accompanying the cold
front could create localized MVFR conditions and rain showers over
northeastern Wyoming, the Black Hills, and northwestern South
Dakota.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory until 7 PM MDT this evening for SDZ001-002-012>014-
     025-072-073-078.
     Wind Advisory from 6 AM this morning to 7 PM MDT this evening
     for SDZ031-032-043.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...Smith