841
FXUS63 KUNR 152308
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
508 PM MDT Wed Oct 15 2025

.KEY MESSAGES...

-Good chance of rain and a few TS tonight, esp far Western SD,
 with some hail possible in stronger storms, mainly far SW SD

-Some fog and drizzle continuing tonight, mainly on the SD Plains

-A cold front will bring rain/snow chances Friday night with cool
 and breezy weather for Saturday

-After a mild Sunday, semi-unsettled and cooler to start next
 week

&&

.DISCUSSION...(This Evening Through Wednesday)
Issued at 113 PM MDT Wed Oct 15 2025

Deep upper trough in the central Rockies will eject northeast
into the region, supporting a good chance of showers and a few
thunderstorms tonight. ESE moist flow ongoing with low clouds,
patchy fog, and drizzle continuing on the SD Plains. Main area of
lift and associated jet streak will shift toward the region this
evening. This will support a cluster of elevated showers and TS
over mainly far western SD. Given dynamic forcing from the jetlet,
ample deep layer moisture, sufficient effective shear, and
steepening mid-level lapse rates, a few stronger cells will be
possible with hail, possible quarter size or larger. PW`s will be
over an inch in many areas, which will also support locally heavy
rain although cells will be moving fairly quick. Showers and
isolated TS will linger through tonight as few weaker impulses
traverse the flow, although the bulk of activity will shift toward
NW SD. Sfc trough will shift through the region early Thur
morning, with any fog or drizzle ending with the wind shift. Dry
slot will push into the region later Thur morning and afternoon
with things drying out and winds shifting westerly. Best chances
for rain rain will be over the far NW where the system deformation
zone will be in place. Outside of this area, shower chances will
be mainly scattered to isolated. Some thunderstorms will also be
possible over scentral SD ahead of the sfc trough where sufficient
instability will be in place. Dry for Fri with warmer temps most
places, but breezy winds are expected. NW flow impulse will drop
into the region Friday night, supporting chances for rain with
some snow possible across the western third if temps drop quick
enough. This system will also force a cold front into the region,
with much cooler and windy weather for Sat. Another deep trough
will move into the western CONUS by Sunday, with downstream
ridging supporting much warmer weather Sunday as 60s and few 70s
are expected. Semi-unsettled NW flow can be expected for the
first part of next week with some chances for rain/snow, and
breezy and cooler weather, but still seasonal. Mean ridging is
currently progged over the region toward the end of next week,
which would support a warming trend and dry weather for the second
half of the week.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Thursday Evening)
Issued At 506 PM MDT Wed Oct 15 2025

Areas of fog, some drizzle, and low clouds will persist through
the forecast period with IFR/LIFR conditions. Showers and
thunderstorms have formed over central WY and far western NE.
This storm system will bring chances for rain and storms to the
area after 02-04z with hail and gusty winds possible with any
stronger cells.

Precipitation chances and low clouds will persist through the
forecast period with gradual improvement after 18-20z Thursday.

&&

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

$$

DISCUSSION/KEY MESSAGES...JC
AVIATION...SE