Mystic, South Dakota Weather Forecast Discussion

213
FXUS63 KUNR 181114
AFDUNR
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
514 AM MDT Thu Sep 18 2025
.KEY MESSAGES...
-Showers shifting east through tonight and ending by Friday
-Drier and warmer this weekend
-Seasonal and mainly dry next week
&&
.DISCUSSION...(Today Through Wednesday)
Issued at 113 AM MDT Thu Sep 18 2025
Mean trough over the Northern Plains will slowly shift east
through today with showers waning. Main deformation band situated
over central SD will continue to support decent rains there
through morning. Further west, isolated showers with some upslope
drizzle is ongoing. Clear skies and light winds can be found on
the backside of the system over northeast WY, with a good chance
for fog to develop through the night. Have added this to the
forecast through morning, including portions of far western SD.
Upper low will shift east today with lingering low level
instability and moisture allowing for scattered to isolated
showers over much of western SD through the day. Phasing northern
stream upper low will pinwheel around the the backside of the main
upper low tonight, potentially supporting a few showers over the
southwest third of the FA. Have added some low pops for this.
Otherwise, patchy fog will be possible over much of the region
late tonight. Diving Pac northeast upper trough will support
downstream ridging into the region this weekend, with warm and dry
conds expected Friday through Sunday. Compact but potent upper
trough will then move into the region by later Sunday, supporting
a cool front into the region Sunday night. Decent lift and
sufficient Pac moisture will be in place to support some post
frontal showers Sunday night into Monday across much of the area.
Otherwise, dry weather expected through most of next week attm as
another ridge builds into the Rockies and Northern Plains and the
flow looks to become blocked as an upper low stalls in the
Midwest. This will also allow temps to warm to seasonal values
with highs in the 70s and few 80s.
&&
.AVIATION...(For the 12Z TAFS Through 12Z Friday Morning)
Issued At 509 AM MDT Thu Sep 18 2025
MVFR/IFR conditions with rain will continue this morning in
central SD. Patchy fog can be expected through mid morning across
northeast WY and portions of far western SD, with vis down to a
half mile at times. Conditions will gradually improve west to east
today with conds trending VFR to MVFR (MVFR cigs may linger
through the day in central SD). MVFR to IFR conds are possible
early Friday in patchy fog. In addition, there is a chance of
showers across the southwest third late tonight into Friday
morning.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&
$$
DISCUSSION/KEY MESSAGES...JC
AVIATION...JC

NWS UNR Office Area Forecast Discussion