849
FXUS63 KUNR 211959
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1259 PM MST Fri Nov 21 2025

.KEY MESSAGES...

-Mild and dry through the weekend

-Turning colder Tuesday with some light rain/snow possible

-Colder pattern sets up next week and will persist into early
 December with chances for snow

&&

.DISCUSSION...(This Evening Through Friday)
Issued at 1255 PM MST Fri Nov 21 2025

Mild westerly Pac flow will continue this weekend with dry
weather. However, a pattern change is in store as northern Pac
ridging shifts the core of lower heights and cold temps southeast
into the CONUS next week. This will all ensue Monday night into
Tues. Split flow pattern currently in place with weak dry troughs
progressing through the flow locally. WAA ahead of a weak impulse
has allowed temps to rise into the 50s on the Plains where fog and
low clouds have cleared. Expect the remaining clouds to clear out
this afternoon. Weak trough will move through the region Sat,
with temps about the same as today, mainly in the 50s, maybe a tad
cooler across the north. Another round of WAA Sat night into
Sunday with another pleasant mild day. Expect highs in the 50s and
60s, warmest on the Plains east of the Black Hills. Southern
stream system will clip scentral SD early Monday with some light
rain possible there. After another slightly cooler, but mild
Monday, the first in a series of impulses will then move into
region supporting a stronger cold front by Monday night. Some
light rain and snow will possible post frontal Monday night into
Tuesday, mainly across the far west (northeast WY and the northern
Black Hills). Expected precip to possibly start as rain and
change to snow as CAA ramps up. The main impact from this system
will be gusty northwest winds, with adv levels possible across
western SD. Tues highs will be in the morning with falling temps
through the day. Baroclinic zone will be over or near the region
through the rest of the week with impulses riding SE along the
frontal zone. This will support chances for rain/snow, with the
warmest temps over western areas. A stronger/deeper longwave
trough will begin to shift east into the central CONUS next
weekend with the potential for a winter storm system somewhere in
the middle CONUS. This will hinge on how the trough progresses
east, with a split trough offering more progressive flow with less
chances for snow locally, while a longwave trough would support a
decent chance for widespread accumulating snow. Something to
watch. One thing for sure is that much colder weather will arrive
by late next weekend into early the following week.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Saturday)
Issued At 1020 AM MST Fri Nov 21 2025

Patchy fog and low clouds will continue across portions of
northeast Wyoming and western South Dakota through 20Z. Otherwise,
VFR conditions are expected.

&&

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

$$

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