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FXUS63 KUNR 131117
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
517 AM MDT Tue Oct 13 2026

.KEY MESSAGES...

- Cooler weather prevails with precipitation chances through
  Thursday.

- Near-freezing temperatures overnight tonight and Tuesday and
  Thursday nights.

- Breezy Thursday with warmer weather for the weekend.

&&

.UPDATE...
Issued at 958 PM MDT Mon Oct 12 2026

Light rain showers are pushing into southwestern SD courtesy of a
weak upper wave ejecting over the Northern Plains. This light
precip should continue to move northeastward through tonight as
upper trof moves east. The cloud cover overnight should keep temps
from dropping off too much, though we`ll still see some chilly
temps with lows dropping to the upper 30s across much of the area.
Another chilly night on tap for Tuesday night into Wednesday with
many areas approaching freezing. Some spots could see their first
frost of the season early Wednesday, mainly across northwestern
SD where cloud cover will be less.

Looking ahead to wind potential on Thursday, NAM progs 3-hr
pressure rises of 3-4 mb, which will support breezy conditions.
Though the stronger cold air advection and stronger 850-700 mb
winds still looks to be displaced to the north and east of the
forecast area.

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 1235 PM MDT Mon Oct 12 2026

Closed upper low is centered over southeastern OR with deep
trough axis extending southward off southern CA coast. Water vapor
imagery shows shortwave trough pushing north of the forecast area
into ND with additional moisture and embedded vort maxes to our
west along the eastern periphery of the low. A surface cold front
stretches from southern MN through northeastern NE back into
southwestern NE. Low clouds with mist/fog persist across the
forecast area early this afternoon, although breaks in the clouds
are becoming more numerous and expansive. Cold tonight with many
areas falling into the mid to upper 30s.

The upper low is forecast to dig into the southwestern US with the
trough axis shifting further east overnight tonight into Tuesday as
broad upper level ascent overspreads the region. Light rain possible
overnight tonight into Tuesday morning with ample cloud cover.
Additional chances of light precipitation arrive early Wednesday
through Thursday morning, with the best chances for widespread
precipitation along the SD/NE border and southward.

Northern stream trough is forecast to drop out of Saskatchewan and
Manitoba into the Upper Midwest early Thursday, swinging a strong
cold front through the Northern Plains and Upper Midwest. A strong
belt of 850-700 mb wind (~40-60 knots) will push into ND and central
SD, sideswiping the forecast area. The strongest cold air
advection will remain displaced east of the forecast area, where
strongest winds can be expected. Deterministic NBM guidance
continues to forecast 60+ mph wind gusts across portions of NW SD
and the western SD plains Thursday afternoon. However, an
ingredients-based approach coupled with ensemble guidance does
not support winds this strong. The current forecast has Wind
Advisory level winds (~45 mph) for portions of NW SD into the
western SD plains Thursday afternoon and evening, although there
is low confidence that this solution verifies; certainly, the High
Wind (>60 mph) potential looks unlikely (probability < 15%).

Western ridging returns next weekend with above average temperatures
forecast and dry conditions.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Wednesday Morning)
Issued At 509 AM MDT Tue Oct 13 2026

Widespread MVFR to local IFR conds will linger into the afternoon,
slowly trending up northeast to southwest. Light rain will move
out the area this morning, with dry conds expected this afternoon.
MVFR to IFR conds in mainly low clouds may linger over portions
of the northeast WY Plains, the Black Hills, and SW SD through
much of the period given weak flow and lingering low level
moisture.

&&

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

$$

UPDATE...Wong
DISCUSSION...SE
AVIATION...JC