693
FXUS63 KUNR 061911
AFDUNR

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

.KEY MESSAGES...

- High-based storms capable of gusty winds are possible over
  northeast Wyoming, far western South Dakota, and the Black Hills
  through the overnight hours.

- A cold front moves slowly through the area Sunday and Sunday
  night, bringing showers and thunderstorms, severe storms are
  possible.

&&

.DISCUSSION...(This Evening Through Saturday)
Issued at 110 PM MDT Sat Jun 6 2026

Upper level analysis has a shortwave ridge centered over the Eastern
Dakotas with a low dropping into the Pacific Northwest. At the
surface a cold front extends from northeastern Montana into
southwestern Idaho, with a weak lee trof developing near the
Bighorns. Visible satellite indicates a few mid level clouds ahead
of the front with the lower portions of the UNR 18Z sounding
showing very dry air off the surface.

For tonight, a high-based storm or two could get going over the
Black Hills or northeastern Wyoming due to daytime heating and the
forcing of the lee trof. Hi-res models are indicating a broken line
of strong showers and storms along the trof, extending along the
WY/SD border by 02Z-ish. With limited low-level moisture, the
primary threat would be gusty winds.

The cold front approaches the area around 06Z tonight, reaching
the SD/WY border near 12Z. From there, it is expected to stall-
out. This stalled boundary will be the primary focus for
convection during the afternoon and evening. Supercell development
is possible with 0-6 km shear estimated to be 40-50 kts, steep
lapse rates, MLCAPE of 1700 J/kg, and MUCAPE 2400 J/kg. With drier
air still expected off the surface and dewpoints ranging from 35
to 55 degrees, expect LP supercells capable of producing
significant hail and very strong winds. A tornado could also be
possible.

Monday will be cooler behind the cold front, with highs only in the
70s and 80s. Surface high pressure will slide through the CWA,
resulting in increasing southeasterly winds of 10-25 mph during the
afternoon. Another hot day is ahead on Tuesday with prefrontal
warming back into the 90s. Once again the NBM is probably running
too, due to the greenness. A deep upper low and another cold front
impact the area on Wednesday and Thursday, resulting in a chance for
scattered storms.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 1123 AM MDT Sat Jun 6 2026

VFR conditions are expected through most of the forecast period.
Isolated high-based thunderstorms are possible across portions
of northeast Wyoming and the Black Hills where transient MVFR
conditions are possible, along with gusty/erratic winds.
Widespread, gusty (~30kts) south/southeasterly winds will persist
into the late afternoon before weakening during evening hours.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory until 9 PM MDT this evening for SDZ001-002-012>014-
     078.
     Wind Advisory until 6 PM MDT this evening for SDZ031-072-073.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...MLS
AVIATION...Schultz