Spearfish, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

781
FXUS63 KUNR 261118
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
518 AM MDT Tue May 26 2026

.KEY MESSAGES...

- Warmer temperatures continue this week, with highs mainly in the
  80s

- Chances of showers and thunderstorms will increase Tuesday night
  and continue through the rest of the week

&&

.UPDATE...
Issued at 1002 PM MDT Mon May 25 2026

No major changes to the forecast. Breezy southerly flow will
develop tomorrow with advsy level gusts (45+ mph) possible over
portions of the western SD plains. The limited coverage of these
gusts will preclude any issuance of wind advisories at this time.
In addition to the gusty winds, very warm weather with highs in
the upper 80s to upper 90s and minimum afternoon humidities
ranging from 15 to 20 percent will lead to elevated to near
critical fire weather conditions across much of the area with
locally critical fire weather conditions possible where fuels are
receptive.

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 1203 PM MDT Mon May 25 2026

Current upper-air analysis and water vapor imagery depict large-
scale ridging over the Rockies and troughing along the PAC NW coast.
A surface low remains positioned just off the coast. WV imagery
indicates increased moisture over south-central SD, where isolated
thunderstorms are possible this afternoon and evening, though
conditions are more favorable farther east. Radar currently shows a
few weak returns associated with possible developing convection over
the northern Black Hills. Surface observations show temperatures
mainly in the 80s with light and variable winds across the region.

As the trough propagates eastward, increased southerly/southeasterly
low-level flow will bring higher dewpoints into the area this
afternoon and evening, especially across south-central SD. HREF
guidance shows dewpoints rising into the 50s and lower 60s along
with 0-6km bulk wind shear values of 25-35kts. Current CAM guidance
continues to favor convective initiation over north-central NE
before storms move into southeastern SD. However, an isolated
thunderstorm or two can`t be ruled out for south-central SD. Similar
to the last couple of days, pop-up showers and an isolated
thunderstorm or two may develop over and around the Black Hills
through the afternoon and into the evening hours. High temperatures
will range from the 80s to lower 90s today and persist through the
week under continued ridging across the region.

By Tuesday afternoon, ensemble guidance shows the trough evolving
into a cut-off low over OR/northern CA. This pattern will support a
more active and unsettled weather regime across the region with near-
daily thunderstorm chances through much of the week. Current SPC
outlooks maintain general thunderstorms through Wednesday with no
organized severe weather expected. This more active pattern is
expected to continue through the weekend and into next week.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Wednesday Morning)
Issued At 515 AM MDT Tue May 26 2026

VFR conditions are expected through the forecast period. Gusty
southerly winds (25-40kt gusts on the open plains) will develop
this morning and continue through the period, although some
reduction is expected after sunset. Isolated shra/TS over south-
central SD will dissipate by 15z. Then, isolated TS may develop
over northeastern WY after 26/21z.

&&

.FIRE WEATHER...
Issued At 1203 PM MDT Mon May 25 2026

Even with green-up occurring across the region, relative humidity
values over the next couple of days will fall into the mid-teens
to low-20s across much of the area south of I-90. In addition to
low RH values, gusty southerly/southeasterly winds are expected to
develop Tuesday morning, leading to elevated fire weather
conditions south of I-90.

&&

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

$$

UPDATE...Wong
DISCUSSION/KEY MESSAGES...Schultz
AVIATION...Helgeson
FIRE WEATHER...Schultz