Spearfish, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

257
FXUS63 KUNR 110745
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
145 AM MDT Mon Aug 11 2025

.KEY MESSAGES...

- Smoke/haze exits
- Seasonally warm/hot temperatures expected this week
- Elevated fire weather conditions developing southwest
- Marginal risk (level 1 of 5) of severe thunderstorms late
  Wednesday

&&

.DISCUSSION...(Today Through Sunday)
Issued at 143 AM MDT Mon Aug 11 2025

07z surface analysis had weak high just south of the CWA with a
cool front draped across southern SK into northern MT. Surface
observations show smoke has moved to the eastern reaches of the
CWA. The smoke will continue move out this morning per HRRR
guidance. Water vapour loop had upper trough from Hudson Bay to
the southern Plains with an upstream shortwave pushing southeast
into MT on 110kt jet streak over the Canadian Rockies.

Today/tonight, shortwave slips through the northern Plains pushing
the cool front through the CWA during peak insolation. Weak
buoyancy/shear in place with notable SBCIN over most of the CWA.
Weakest inhibition over northwest SD this afternoon, which is where
we continue to have low PoPs. Some CAMs have a weak line of
convection all the way into northeastern WY, but moisture seems
scant for that scenario. Another nice sleeping night tonight.
Temperatures will be near guidance.

Tuesday will be dry with slightly cooler temperatures.
Wednesday/Thursday, southwest flow aloft develops allowing thermal
ridge to expand into the northern plains. Weak shortwave moves
along the US/Canadian border Wednesday which will induce a weak
low along lee trough from central MT into eastern WY. Features
should encourage moisture return and low level jet Wednesday
night. Ingredients in place for isolated strong/severe convection,
especially for the northeast half of the CWA where marginal risk
(level 1 of 5) of severe thunderstorms is painted. Temperatures
will be noticeably warmer both days as thermometers soar into the
90s. Best chance of 100F readings is Thursday (LREF 30% chance).
Slightly more active pattern develops for Friday into the weekend
as southwest flow aloft spins a series of shortwaves into the
region.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1022 PM MDT Sun Aug 10 2025

Areas of smoke will continue to support MVFR vis through the
night toward central SD. Otherwise, VFR conds most places through
the period. Isolated showers and TS will be possible over far NW
SD tomorrow afternoon. A trough will move through the region
Monday afternoon, with winds shifting to the north behind the
trough.

&&

.FIRE WEATHER...
Issued At 143 AM MDT Mon Aug 11 2025

Drier weather expected through Thursday with hot temperatures
returning for Wednesday/Thursday along with minimum afternoon
relative humidities in the teens for parts of northeastern
WY/southwestern SD. Wind speeds may be sufficient for the
development of elevated fire weather conditions, particularly in
areas where seasonal fuels are drying out significantly.

&&

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

$$

DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...JC
FIRE WEATHER...Helgeson