429
FXUS63 KUNR 040344
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
944 PM MDT Wed Sep 3 2025

.KEY MESSAGES...

- Smoke expected to continue overnight in the forecast area.

- Strong dry cold front passes through Thursday, bringing gusty
  northwest winds and elevated fire conditions.

&&

.DISCUSSION...(This Evening Through Wednesday)
Issued at 141 PM MDT Wed Sep 3 2025

Current surface analysis shows high pressure just north of North
Dakota, while a low sits over central MT. Water Vapor and upper
air models show narrow ridge stretching from the four corners
region into the PAC NW, with northwest flow over our region. Still
some areas of patchy light fog and low ceilings over the western
SD plains this afternoon. Temperatures sit in the upper 50s and
60s with winds generally out of the north to northeast.

Main forecast concern for the near-term will be Thursday as a
shortwave and associated strong dry frontal boundary comes down
out of Saskatchewan through the Dakotas. Limited moisture should
temper any precipitation chances, though a light upslope shower
over the Black Hills is not out of the question Thursday
afternoon. Temperatures should warm up into the mid 70s to low 80s
before the frontal boundary brings strong northwest winds into the
forecast area during the day. Deterministic models show the
strongest pressure rises behind the cold front (5-7 mb/3hr) east
of our forecast area. However good mixing and 2-5 mb/3rd pressure
rises in our CWA will still bring strong northwest winds 45 to 60
mph late Thursday morning through the afternoon. HREF continues to
show very low (0-10%) probabilities of exceeding 55 mph Thursday,
so have opted for a widespread wind advisory over any potential
high wind warning headlines.

Cooler temperatures will be in store for Friday and Saturday
following this cold front, with highs in the 60s both days. Late
weekend into early next week, PAC NW upper ridge slides over the
Rockies and into the northern and central plains, sparking a
gradual warming trend, with highs by Monday back into widespread
80s. Model guidance continues to show minimal precipitation
chances through the forecast period

&&

.AVIATION...(For the 06Z TAFS Through 06Z Thursday Night)
Issued At 943 PM MDT Wed Sep 3 2025

Smoke will linger through the overnight hours, while conditions
should remain VFR for most of the area, LCL MVFR conditions are
possible. Winds variable overnight around 5 kts pick up from N/NW
by late morning with gusts up to 40kts. LLWS possible during
morning transition period, mainly over northeastern WY.

&&

.FIRE WEATHER...
Issued At 141 PM MDT Wed Sep 3 2025

A dry cold front will move through Thursday. Minimum relative
humidities will dip into the 20s with gusty northwest winds from
40-55mph. Elevated fire danger is expected, especially for the
fine fuels of the grasslands. The Grassland Fire Danger is
forecast high to extreme for Thursday afternoon on the western SD
plains.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from 10 AM MDT /11 AM CDT/ to 8 PM MDT /9 PM CDT/
     Thursday for SDZ001-002-012>014-025-026-030>032-041>044-046-
     047-049-072>078.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...Dye
AVIATION...Wong
FIRE WEATHER...Dye