Spearfish, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

135
FXUS63 KUNR 261955
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
155 PM MDT Thu Jun 26 2025

.KEY MESSAGES...

- There is a chance for a few afternoon/evening storms over and
  near the Black Hills

- There is a slight risk (level 2 of 5) for severe thunderstorms
  Friday afternoon, mainly east of the Black Hills. Main hazards
  will be large hail (quarter size or larger) and damaging wind
  gusts.

- Very warm to hot on Friday and Saturday, with highs climbing
  into the 90s for most.

&&

.DISCUSSION...(This Evening Through Thursday)
Issued at 153 PM MDT Thu Jun 26 2025

Current visible satellite imagery shows clear skies over much of
the CWA with CU developing over the Black Hills and portions of
northeastern WY. Most recent mesoscale analysis depicts 1000-2000
J/kg SB CAPE over the Black Hills into northwestern SD and
portions of northeastern WY. Lack of large scale forcing will
limit convective activity today though terrain influence
convergence may provide enough lift for isolated storms to form
over the Black Hills this afternoon. Height falls ahead of an
approaching shortwave trough could support additional convection
over WY/MT, mainly over the higher terrain. Most recent CAMs show
convection over northeastern WY by 21-22z with potentially another
round of convection later tonight as an LLJ develops over western
SD into northeastern WY. Deep layer shear will be marginal at
20-30kt, which, when combined with 1000-1500 J/kg MUCAPE could
support a localized, conditional severe threat overnight.

The shortwave and attendant surface trof crosses the region
tomorrow. Thunderstorm and severe wx risk will depend on timing of
the sfc trof. Most recent NAM runs have been fairly consistent in
the trough pushing eastward across northeastern WY and far
western SD tomorrow morning, which will favor thunderstorms
developing east of the Black Hills tomorrow afternoon. Low level
southerly flow ahead of the sfc trof will advect moisture into the
western SD plains with sfc DPs reaching into the upper 50s to low
60s. This will support corridor of moderate to strong instability
(SB CAPE in excess of 2000 J/kg) across northwestern into south
central SD through the afternoon hours. 30-40kt shear, Fat CAPE
profiles, and steep low to mid-level lapse rates will favor a
large hail and damaging wind threat. Temperatures tomorrow
afternoon will climb into the 90s with very dry air west of the
sfc trof.

Another hot day on tap for Saturday as low level thermal ridge
noses back into the region. Highs will once again climb into the
90s, especially east of the Black Hills. Weak baroclinic zone will
sink into the northwestern portions of the CWA by the afternoon
hours. Low-level frontogenesis may support convection Saturday
afternoon into the overnight hours. Baroclinic zone should be
south of the CWA by Sunday, with highs slightly cooler (in the low
to mid 80s). Looking into next week, relatively high confidence
in a southeast-to- northwest oriented ridge building early in the
week, which will bring warmer temperatures but may favor at least
some isolated/scattered thunderstorms through at least the first
half of the week.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1109 AM MDT Thu Jun 26 2025

Isolated showers and storms are possible after 18-19z this
afternoon, mainly around the Black Hills where transient MVFR
conditions will be possible in any heavier showers.

Otherwise, VFR conditions are expected through the forecast
period.

&&

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

$$

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