049
FXUS63 KUNR 152009
AFDUNR

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

.KEY MESSAGES...

-Daily chances for thunderstorms, some possibly severe, through
 Tuesday.

-Wet and cooler mid-week

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


&&

.DISCUSSION...(This Evening Through Sunday)
Issued at 122 PM MDT Sun Jun 15 2025

.Severe Risk Today...

Satellite and water vapor analysis shows the main forcing
continuing to move westward through central Montana. The most
active area for convective activity has been to our southwest
across the higher terrain over eastern Wyoming along the heating
differential boundary. Across the Black Hills we had some agitated
CU (Cumulus) develop this afternoon but this turned into failed
initiation as the main updraft tower encountered some stronger
shear and got sheared apart with only the orphan anvil remaining.
In the wake the CU field along the Black Hills looks meager at
best. We could continue to see the CU field expand but it looks
like our show will be dependent on the arrival of the upper level
forcing as it approaches northeastern Wyoming. Atmospheric
parameters again show large instability but as evident with
yesterdays limited convective activity, this afternoon`s sounding
continues to show a drier boundary layer, which should limit
convective activity prior to the upper level forcing progged to be
over our area by the early evening. CAM models continue to show
two small liner/bowing segments one skirting across the South
Dakota/Nebraska border while the other and stronger of the two,
pushes out of southeastern Montana and scrapes across the South
Dakota/North Dakota border. These segments will pose a damaging
wind threat as these clusters move east through the overnight
hours.

Severe weather remains a threat on Monday as a cold front pushes
through the region. Timing of this front will shift where the
greatest magnitude threat as the prefrontal environment will
continue to yield ~3000 J/kg of CAPE and have an environment for
severe storms. Environment post-frontal may still yield ~1500 J/kg
of CAPE but high 0-6km shear may again shred weaker convection
that tries develop during the afternoon hours. The severe threat
in the post-frontal sector will occur when main shortwave trough
approaches eastern Wyoming. This aforementioned trough continues
to progress through our region on Tuesday which will lead to
scattered to widespread showers and thunderstorms across much of
western South Dakota along with some cooler temperatures.

By mid-week increasing heights return as a ridge axis moves into
the Intermountain West which should bring drier conditions and
warm to hot temperatures to the region.



&&

.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 1113 AM MDT Sun Jun 15 2025

Low clouds and fog continue to dissipate across NW SD, with
MVFR/IFR conditions transitioning to VFR after 18z. 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...Woodward
AVIATION...SE