Spearfish, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

896
FXUS63 KUNR 020512
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1012 PM MST Sun Feb 1 2026

.KEY MESSAGES...

- Patchy dense fog will develop across western SD tonight.

- Breezy northwest winds across northwestern and southwestern SD
  Monday

- Above average temperatures and mostly dry weather through next
  week

&&

.DISCUSSION...(This Evening Through Sunday)
Issued at 115 PM MST Sun Feb 1 2026

Some sunshine is filtering through mid- and high-level stratus
over most of the area this afternoon. Far eastern reaches of the
area have dealt with a thicker and lower cloud deck. A back- door
cold front is draped across the SD plains, coming to rest against
the eastern elevations of the Black Hills. West of the boundary,
a few locations have snuck up to 50F.

.TONIGHT...

A mesoscale surface high settles into western South Dakota
overnight, backing the northerly winds and making them easterly.
Though relatively light, they should be enough to produce some
patchy fog as the moist boundary layer is subjected to widespread
orographic lift. Greatest threat for the patchy fog will be west
of the Missouri River but east of the Black Hills and east of a
line from Buffalo, SD to Pine Ridge, SD. Current HREF
probabilities suggest about a 50% probability of visibilities less
than a mile and about a 35% chance of visibility slipping under
1/2 mile in this same area. Fog development looks likely (90%+).
Low temps will range from the low 30s in northeast Wyoming to low
20s in south-central South Dakota.

.MONDAY...

Breezy winds may be the most consequential weather on Monday with
northwestern South Dakota experiencing wind gusts of up to
35-45mph as another mid-level shortwave traverses the area. The
northwest flow of the polar jet will push the vorticity lobe of
the shortwave through central South Dakota by sunset. AM showers
of rain/snow are possible in eastern Montana / western North
Dakota before crossing into central/eastern South Dakota in the
evening. Have maintained some 20% PoPs on the eastern fringe of
the forecast area for Monday eve. Were the precip to fall, some
raindrops could be mixed in with the flakes. No accumulation is
anticipated.

.TUESDAY...

The busy northwesterly flow at H5 continues. The active pattern
brings a cold front dashing through the area on Tuesday
afternoon/evening. Ahead of the front, expect highs to plateau in
the 40s. The strong northwesterly winds behind the front should
be enough to produce some upslope snow in the Black Hills. Current
guidance suggests a reasonable 1-3" with a rain/snow mix in the
foothills and surrounding plains.

.SECOND HALF OF THE WEEK...

Currently Wednesday and the remainder of the forecast is dry and
mild. Temps will generally be about 20 degrees warmer than
seasonal norms. Thursday brings the week`s warmest temps with the
negatively tilted *ridge* overrunning this CWA. Highs in the 60s
should threaten some warm high records and warm min temp records
are also in danger.

Confidence in the extended forecast is lower than normal due to
the proximity of the polar jet and its attendant baroclinic zone
in eastern South Dakota. Any unforeseen wiggle of the jet could
bring drastic changes in the temperature forecast. That`s the bad
news. The good news is that the GFS, outlier as it was, has backed
away from it`s cold solution for next week.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1010 PM MST Sun Feb 1 2026

Patchy fog and low clouds are expected to develop across the NW
SD plains after 06Z, resulting in localized MVFR-IFR cigs/vsbys.
Otherwise, VFR conds are expected throughout the TAF period with
gusty northwest winds developing Monday afternoon.

&&

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

$$

DISCUSSION/KEY MESSAGES...Nicolaisen
AVIATION...JC