889
FXUS63 KUNR 151004
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
404 AM MDT Sun Jun 15 2025

.KEY MESSAGES...

-Daily chances for thunderstorms, some possibly severe, through
 Monday

-Wet and cooler mid-week

-Mostly dry and much warmer weather for the second half of the
 week

&&

.DISCUSSION...(Today Through Saturday)
Issued at 359 AM MDT Sun Jun 15 2025

Upper air analysis continues to show a stalled upper low off the Pac
NW/Canadian coast, with active WSW flow across the western CONUS.
Weak ridging sits across the northern Plains. At the surface/lower
levels, deep Gulf moisture continues to stream in from the south,
with dewpoints in the upper 50s to mid 60s. The next shortwave will
push in from the WSW later this afternoon. Models are continuing to
show the stronger wave across SE MT/NE WY/NW SD, which is where the
strongest forcing will be. Latest HRRR shows SBCAPE generally around
2500-3000 J/kg and bulk shear of 45-55kt (across the majority of the
CWA). The best chance of severe storms over the area will thus be
over portions of NE WY and NW SD. CAMs shows a squall line with the
potential for over 65 kt wind gusts, but 06z model runs do hint at
this being slightly farther north, perhaps barely clipping the NW
edges of the CWA. Will keep an eye on these trends. Eroding CIN late
this afternoon/early evening across NE WY, the Black Hills area, and
far western SD plains will support supercells with large
hail/damaging winds, though more widely scattered than the
aformentioned storms over SE MT. Storms are expected to organize
into a line and advance eastward into the western SD plains. Like
the past few nights, once storms move into the plains, the main
threat will transition more toward wind than hail. As the wave
crosses ND late tonight, a cold front will cross the CWA on Monday.
The best theta E will be ahead of the frontal boundary across
SW/SCentral SD, with SBCAPE of 2500 to 3000 J/kg. Behind the front,
there will still be 1000 to 2000 J/kg of SBCAPE and 6k bulk shear
over 55kt. Additionally, the next strong wave is expected to cross
the region Monday afternoon and evening. This will support the
potential for another round of severe weather, with large hail and
damaging winds. A larger shortwave trough will cross the central to
northern Plains on Tuesday. This will bring continued chances for
showers and thunderstorms, though the severe potential is much less.
Models are trending more southerly with the strongest forcing, which
keeps the bulk of QPF near the Neb border or farther south. Upper
ridging builds in for the second half of the week, bringing warmer
and drier weather to the region. Some areas may see highs in the mid
to upper 90s by Friday.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Monday Morning)
Issued At 400 AM MDT Sun Jun 15 2025

IFR conditions will be possible early this morning across far
northwestern SD as fog/low clouds develop. Otherwise VFR
conditions are generally expected through the forecast period. The
next round of strong thunderstorms will develop this afternoon
across NE WY and spread north/east across western SD this evening.

&&

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

$$

DISCUSSION/KEY MESSAGES...13
AVIATION...13