978
FXUS63 KUNR 091954
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
154 PM MDT Thu Oct 9 2025

.KEY MESSAGES...

- Breezy southerly winds Friday and Saturday; gusty northwest
  winds Sunday behind a cold front.

- Periodic chances for rain showers through the weekend, with
  minimal overall precipitation.

- Mild temperatures through Saturday, turning cooler Sunday and
  into early next week.

&&

.DISCUSSION...(This Evening Through Thursday)
Issued at 150 PM MDT Thu Oct 9 2025

Upper level analysis has a ridge of high pressure centered over
the central CONUS, flanked by a deep upper low offshore over the
Pacific Northwest and a compact low tracking from Saskatchewan
into Manitoba. This setup is producing southwest flow across the
western portions of the forecast area. At the surface, a weak
frontal boundary stretches across south central South Dakota.

Tonight: The Canadian upper low shifts southeast into the Great
Lakes Region while the Pacific Northwest low remains nearly
stationary. This pattern amplifies the central CONUS ridge, with
its axis extending from the Texas/Oklahoma Panhandle through the
Black Hills into Alberta. Surface pressure rises from high
pressure over Saskatchewan will spread across the CWA, promoting
a chilly night under clear skies and light winds. NBM temperatures
align well with deterministic guidance, generally ranging from
the upper 30s to mid 40s. Given the warmer trends in recent
guidance, frost headlines will be withheld for northwest South
Dakota.

Friday: As the surface high shifts east of CWA, southerly to
southeasterly winds will develop. Strengthening pressure gradients
and falling pressures will lead to breezy conditions. Cloud cover
and the eastward shift of the thermal ridge may result in
slightly cooler highs, though still but near guidance values.

Saturday: The offshore upper low moves inland across Oregon and
Washington, while remnants of Tropical Storm Priscilla lift
northeastward through eastern Utah and western Colorado into
Wyoming. Although the associated energy will be weakening and the
strongest forcing remain south of the area, the combination of
moisture and instability could support isolated showers and a
thunderstorm late in the day. A tight surface pressure gradient
will maintain gusty southerly winds.

Saturday night and Sunday: The western upper low evolves into a
broad trough that sweeps through the Rockies into the Northern
Plains. A cold front will advance through the forecast area early
Sunday, bringing cooler temperatures, gusty northwest winds, and
scattered showers. The system will move quick, with the strongest
forcing remaining north of the CWA.

Monday and Beyond: Another upper low deepens over the Pacific
Northwest, this time digging southward along the California Coast
and ejecting energy into the broader flow. While model solutions
diverge significantly next week-especially regarding timing-
ensemble trends favor continued southwest flow with embedded
impulses. This pattern supports ongoing unsettled conditions,
periodic shower chances, and cooler but seasonally appropriate
temperatures.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1118 AM MDT Thu Oct 9 2025

VFR conditions will prevail through the forecast period.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

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