854
FXUS63 KUNR 231744
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1144 AM MDT Sat Aug 23 2025

.KEY MESSAGES...

- Mild temperatures into next week.

- Mainly dry. A few showers/storms possible over the Southern
  Hills and far southern areas through early next week.

- Higher chances for showers and storms Thursday through Friday.

&&

.DISCUSSION...(Today Through Friday)
Issued at 121 AM MDT Sat Aug 23 2025

Upper level analysis has a low over the northern Great Lakes/
southern Canada with an area of high pressure over the Four
Corners and a negatively tilted ridge extending into the Pacific
Northwest. At the surface, high pressure centered over central
Montana is building into the northwestern portion of the forecast
area. A few showers/storms have formed over the southwestern
portion of the forecast area -- from south of Gillette to
Newcastle to Custer to Pine Ridge. These showers look to be
interacting with residual moisture convergence, some theta-e
advection and boundary layer convergence.

For today, expect showers/storms to dissipate early this morning,
leaving behind some mid-level clouds over the southwestern half
of the forecast area and clear skies across the northwestern
portion of the area. Temperatures will be mild, as drier and
cooler air pushes southward in response to the surface high
pushing eastward through the day.

A weak wave will round the upper ridge tonight as subtropical
moisture advects into the far southern potions of the forecast
area. Warm air advection combined with a strengthening low-level
jet may result in a few showers/storms over the far southern
portion of the area.

For Sunday, mild and dry conditions are expected as the upper
ridge locks into place over the Desert Southwest and northwest
upper flow continues. Any convective activity Sunday night should
stay just south of the area.

Ensemble model consensus for the first half of the week keeps the
area in northwest flow with occasional energy rounding the ridge,
bringing slight chances for showers/storms to the southwestern
potions of the area, leaving the northwestern half dry. 850 temps
are near normal for the end of August, so the mild conditions will
continue.

By midweek, the ridge looks to break-down and shift east, bringing
a surge of monsoonal moisture into the area. A weak shortwave
looks to move through the area Thursday/Friday. Higher (but near
normal) precipitable water values would indicate this would be
our next shot for appreciable moisture from showers/storms.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 1141 AM MDT Sat Aug 23 2025

Good flying conditions expected with VFR ceilings and
visibilities. Cloud deck around 5kft at the beginning of the TAF
sites will dissipate over the next couple hour. Additional mid
cloud development may approach the TAF sites overnight, but kept
SCT coverage with lower confidence in northward extent. Winds are
expected to remain light.


&&

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

$$

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