132
FXUS63 KUNR 061131
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
531 AM MDT Sat Jun 6 2026

.KEY MESSAGES...

- Hot on Saturday. High-based storms with strong winds are
  possible over portions of northeast Wyoming and far northwestern
  South Dakota.

- A cold front moves through Sunday with showers and
  thunderstorms and cooler temperatures on Monday.

&&

.UPDATE...
Issued at 528 AM MDT Sat Jun 6 2026

Wind gusts were increased based on latest ensemble data and hi-
res models. Issued Wind Advisory for NW SD due to enough
confidence in wind gusts around 40 to 50 mph.

UPDATE Issued at 912 PM MDT Fri Jun 5 2026

No major changes with this forecast update. Main concern over the
next 24 hours is the high temperature forecast for tomorrow
(Saturday). Widespread highs in the mid to upper 90s across the
Wyoming and South Dakota plains; can we push close to 100 in spots
given the recent rains and green-up? Despite the recent
precipitation, expect elevated to near-critical fire weather
conditions, especially across northeastern Wyoming where RH will
fall into the single digits to around 10 percent. Otherwise,
overall forecast remains on track through the weekend.

&&



.DISCUSSION...(This Evening Through Friday)
Issued at 1245 PM MDT Fri Jun 5 2026

Upper level analysis has mostly zonal flow over the Northern Plains
with a shortwave ridge on the east side of the Rockies. At the
surface high pressure is centered over the area with an area of low
pressure in northeastern Washington and a trailing cold front into
northern California. Visible satellite indicates a cu field over
northeast Wyoming, around the Black Hills, and across southern and
easter portions of the forecast area.

Mostly sunny skies will continue through the afternoon with a slight
chance of a diurnally, terrain driven shower or storm this
afternoon. Dewpoints are in the 50s to low 60s over the hills could
produce brief heavy rain.

On Saturday it will be hot. NBM has highs in the 90s with upper 90s
over northeast Wyoming and southwestern South Dakota. HREF spreads
are between 90 degree and 94 degrees for KRAP whereas the NBM is
much higher at 98 degrees. With all the recent rain and greenness
around, it appears the NBM is running to high. Therefore, I bumped
down temperatures about 5 degrees over the South Dakota Plains to
fall more in line with the HREF 25-75th percentile highs.

A few high-based showers and storms are possible Saturday afternoon
and evening over northeast Wyoming, the Black Hills, and far
northwestern South Dakota ahead of a deepening lee cyclone. Strong
diurnal heating combined with height falls and steep lapse rates in
the afternoon will bring the potential for afternoon showers and
storms. The more favored environment is over eastern Montana and
western North Dakota, but ample shear within the forecast area could
result in a few storms with strong wind gusts of 60+ mph.

A cold front moves through on Sunday and Sunday night, entering the
forecast area around 12Z before exiting around 12Z Monday. Energy
ahead of a shortwave trough aided by a jet streak and strong surface
heating could result in some terrain driven storms. Additional
storms will be possible during the evening along the surface front
as the strong boundary-layer heating erodes the capping. Thus expect
some isolated severe storms.

Monday will be cooler across the entire forecast area behind the
cold front. Surface high pressure will slide across the CWA through
the day with upper level southwest flow. Another hot day is ahead on
Tuesday with prefrontal warming before a deep upper low and another
cold front impact the area on Wednesday and Thursday. Overall, this
pattern will result in daily chances for showers and storms.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Sunday Morning)
Issued At 528 AM MDT Sat Jun 6 2026

VFR conditions are expected throughout the forecast period.

Main changes through the TAF period will be centered around wind
speed changes. Speeds will slowly increase this morning with
strongest winds this afternoon. Winds decrease this evening.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from noon today to 11 PM MDT this evening for
     SDZ001-002-012>014-078.
WY...None.
&&

$$

UPDATE...GS
DISCUSSION/KEY MESSAGES...MLS
AVIATION...GS