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657
FXUS63 KUNR 221823
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1223 PM MDT Sat Jun 22 2024

.KEY MESSAGES...

-- Changed Discussion --
-Much warmer to start the week with warm conds continuing through
 most of the work week.

-Mainly dry to start the week, although isolated thunderstorms
 will be possible at times. Becoming more unsettled later in the
 week.
-- End Changed Discussion --

&&

.DISCUSSION...
-- Changed Discussion --
(This Evening Through Saturday)
Issued at 1222 PM MDT Sat Jun 22 2024

Upper level ridge will breakdown in the eastern CONUS, and build
over the western/central CONUS this week. However, active northern
stream with several passing shortwaves will support more of a
flat ridge across the Northern Plains as sfc troughs pass through
the flow on a 1-1.5 day period. Morning upper wave has shifted
into the eastern Dakotas with backside subsidence spreading over
the region. Drier BL than the last few days, although ESE winds
will support an uptick in BL moisture. Subsidence should limit
convection on the Black Hills until later in the afternoon when
capping erodes. In addition, the next shortwave will advect into
the region by then and help decrease any inhibition. Bulk of
forcing with this wave will pass north of the FA, with only
isolated convection expected in the FA, mainly NW SD. There is
plenty of shear (40-50 knots) and decent CAPE (1000-2000 J/kg),
enough of each to support isolated supercells if convection can
sustain. The most likely place would be across NW SD. TS chances
will linger into the evening across NW SD and diminish overnight.
Large scale ridging will ensue Sun with hot temps in NE WY where
westerly flow will ensue. Otherwise, much warmer across western SD
as well, but easterly flow should limit temps to the upper 80s
lower 90s. Dry conds expected Sunday, with perhaps an isolated TS
in the evening over NE WY as another weak impulse traverses the
region. Associated sfc trough will settle over the region Monday
and may actually support somewhat cooler conds across NW SD as
easterly flow becomes established. However, the far SW FA will see
continued hot conds with ongoing LL westerly flow, with a few
lower 100s not out of the question there. Another impulse will
advect through the flow later Monday, supporting chances for TS in
the afternoon and evening, with convection likely initiating over
the higher terrain along/south of the trough. The region will
then remain on the northern edge of the ridge for the remainder of
the week with temps on the warmer side of normal most days. There
will also be continued slight chances for TS at times as impulses
skirt along the northern periphery of the ridge. A deeper upper
trough will then progress through the flow by the end of the week,
supporting more widespread chances for showers/storms, along with
a brief cool down next weekend.
-- End Changed Discussion --

&&

.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 1208 PM MDT Sat Jun 22 2024

VFR conditions will prevail through the forecast period. There is
a slight chance of showers and thunderstorms this
afternoon/evening, over and near the Black Hills and northwestern
South Dakota.

&&

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

$$

DISCUSSION/KEY MESSAGES...JC
AVIATION...JC