Spearfish, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

597
FXUS63 KUNR 101027
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
427 AM MDT Tue Jun 10 2025

.KEY MESSAGES...

- Showers and thunderstorms this afternoon and evening, stronger
  storms could produce gusty winds and small hail.

- Active weather for the latter half of the week with daily
  chances for showers and storms.

- Smoke/haze possible through the period

&&

.DISCUSSION...(Today Through Monday)
Issued at 324 AM MDT Tue Jun 10 2025

Current upper air analysis depicts upper level ridge over the
western US while upper level trough sits over the eastern US. The
Northern Plains sits under northwest flow and mostly clear skies.
Temperatures at this hour are in the 50s to 60s. Dry weather will
persist through most of today as low level southwest flow advects
warm air into the region. Temperatures will climb into the upper
80s to 90s across much of the CWA with wildfire smoke aloft
advecting into the region from Canada causing hazy skies. East-
west oriented sfc trof/weak frontal boundary descends into western
SD by early afternoon with narrow corridor of 500-1500 J/kg SB
CAPE developing along it. This may be enough to support isolated
to scattered high based convection in northwestern SD into the
Black Hills and northeastern WY later this afternoon. Moisture is
going to be a limiting factor as while lobe of Pac moisture
progged to advect over the region later this evening, deep layer
moisture is looking meager. However, if deeper convection does
manage to form, forecast soundings depict a well mixed and deep
boundary layer which will be supportive of strong wind gusts.
Storms will push to the east through the night.

Frontal boundary stalls out just to the south of the CWA, with
weak subsidence in place over the region Wednesday, which should
keep things dry for much of the day. Another impulse moves into
northeastern WY by late Wednesday afternoon and evening, which
will support convection over northeastern WY. Corridor of 500-1500
J/kg CAPE progged to develop over northeastern WY which will
support storms with better lower to mid level moisture supporting
deeper convection. Shear isn`t great, around 30-40 kt bulk shear,
but it will be enough to support a marginal severe threat.
Inverted-V profiles in the forecast soundings indicative of a
damaging wind threat with the stronger storms.

Frontal boundary pushes further south Thursday with cooler
airmass moving into the region. A marked temperature gradient will
set up over the CWA with highs in the mid 60s across the northern
half of the CWA and highs in the 80s across the southern half.
Things will gradually dry out as the wave moves to the east,
though diurnal instability over the Black Hills may support some
afternoon showers on Thursday. Forecast confidence diminishes
after Thursday as precip chances will hinge on location of stalled
front, wave timing, and moisture recovery. Best chances for
convection will be in and around the Black Hills as temperatures
recover and warm back up for the weekend.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Wednesday Morning)
Issued At 426 AM MDT Tue Jun 10 2025

VFR conditions are expected to prevail through the TAF period.
Convection may form on the higher terrain in Wyoming and move
east possibly impacting both TAF sites, though intensity is not
likely to significantly reduce visibility. Lightning is possible
but probability at either TAF sites is low.

&&

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

$$

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