390
FXUS63 KUNR 201118
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
418 AM MST Thu Nov 20 2025

.KEY MESSAGES...

- Areas of fog this morning and again Friday morning
- Mild and dry through the weekend
- Pattern change with colder air expected next Tuesday through
  Thanksgiving


&&

.DISCUSSION...(Today Through Wednesday)
Issued at 221 AM MST Thu Nov 20 2025

Upper level analysis shows low pressure centered over NW
Manitoba/NE Saskatchewan with trough axis extending through the
Upper Midwest. A shortwave trough is evident on water vapor
imagery pushing through the Northern Plains. Another upper low is
evident across the SW US with southwesterly flow aloft through the
Rockies into the Central Plains along with mid-level and upper-
level moisture streaming northward. A surface trough has pushed
east of the forecast area and stretches from northern MN through
eastern SD with high pressure settling into eastern MT.

Scattered showers have developed across the area early this
morning. These showers will push eastward and weaken around
daybreak as upper level forcing shifts east. Areas of low stratus
and fog have developed across NW SD and south-central SD;
additional fog may develop into SW SD into NE WY and along the
eastern foothills under upslope flow. Low clouds will linger
across these areas into the late morning and early afternoon
before some improvement is expected.

The upper level trough currently situated over the SW US will
eject into the central/southern Plains later today into Friday
morning with surface cyclogenesis occurring across KS/OK/MO.
Precipitation will develop along the northern periphery of the
low, pushing into central NE. While no precipitation is forecast
for our area, another round of fog and low stratus is expected
Thursday night into Friday morning as easterly, upslope flow
develops.

Split flow will persist into the weekend - another disturbance
will dig into the SW US and develops into a closed low while brisk
west-northwest flow stretches from the Pacific NW into the Upper
Midwest. This will result in generally mild and dry weather for
the forecast area through Monday. A quick moving upper trough will
drop through the Northern Plains late Monday into early Tuesday
bringing much colder air to the region Tuesday through the latter
half of next week. Considerable differences remain among both the
deterministic models and the ensembles regarding the evolution of
the surface low next Tuesday into Wednesday. As such, confidence
in precipitation chances and amounts are low. Regardless,
conditions look colder (highs <35-40F) and breezy Tuesday through
Thanksgiving.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Friday Morning)
Issued At 417 AM MST Thu Nov 20 2025

Local MVFR/IFR/LIFR conditions in low clouds and fog will persist
this morning through 14-16z across NE WY and portions of western
SD. Conditions will improve Thursday afternoon, but might linger
on the eastern slopes of the Black Hills.

&&

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

$$

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