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747
FXUS63 KUNR 150324
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
924 PM MDT Fri Jun 14 2024

.KEY MESSAGES...

- Isolated/scattered showers and thunderstorms expected into
  tonight, with a marginal risk for severe storms through the
  evening.

- Very warm and breezy Saturday with chances for PM showers and
  thunderstorms across a good portion of the area, some possibly strong
  to severe. Gusty winds developing Saturday night behind a
  passing cold front.

- Unsettled weather continues through a good portion of next week, with
  occasional chances for showers and storms as well as cooler
  temperatures.

&&

.DISCUSSION...(This Evening Through Friday)
Issued at 252 PM MDT Fri Jun 14 2024

Current surface analysis shows a developing warm front from
eastern MT to the Black Hills area and across the central high
Plains. Upper level analysis shows a shortwave ridge passing over
the Plains, with a trough off the Pacific NW coast. Skies are
variably cloudy with isolated/scattered showers and thunderstorms
over much of the area. Extensive cloud cover in many areas is
helping to inhibit stronger storm development so far, but
potential still exists over the next several hours for a few strong
to marginally severe storms over the forecast area. Temps are
generally in the 70s to mid 80s, with some 60s over the Black
Hills. Winds are breezy from the south to southeast in many areas.

Isolated to scattered showers and thunderstorms are expected to
continue developing and persist into tonight as the warm front
settles over western SD and weak energy aloft passes through the
ridge. Increasing moisture and steep mid-level lapse rates near and
ahead of the warm front will result in MUCAPE values of mostly 800
to 1500 j/kg across a good portion of western SD into the evening
hours. Shear looks to be marginally strong enough for at least short-
lived supercells and more organized storm development across most of
the area. Large hail and strong wind gusts would be the primary
threats from any stronger storms into this evening. Activity should
gradually shift east of the area overnight.

Warm front will set up generally from northwest to central and
southeast SD on Saturday, with very warm temperatures anticipated.
Highs will reach the mid 80s to mid 90s in most areas, warmest over
southern portions of northeast WY into southwest SD. South to
southwest winds will increase, possibly becoming rather gusty from
the west to southwest across northeast WY by late in the afternoon
as a pre-frontal trough moves east of that area. Upper trough will
track into the Pacific NW, with flow aloft becoming southwesterly
from the Rockies to the Plains. Some showers and storms should
develop during the afternoon, especially over far northeast WY, far
western SD, and the Black Hills near the surface trough. The higher
CAPE values, 1000 to over 2000 j/kg, will be near and north/east of
the warm front later in the afternoon and early evening, mainly from
northwest SD to central SD. Approaching cold front from the
northwest will arrive across northeast WY and far northwest SD
during the early to mid evening hours, then swing through the rest
of the forecast overnight. The best chance for stronger storms still
looks to be across far northeast WY to northwest SD late in the day
and evening, but slightly later timing of the front could lower
potential. Gusty northwesterly winds will accompany the front, for
at least a brief period, as 4-6 mb/3 hr pressure rises take place in
many areas. The potential for at least for a couple/few hours of 40
to 50+ mph wind gusts is fairly high (40 to 70 percent) across a
good portions of the plains later Saturday night.

Sunday will be much cooler and drier with highs in the 70s and lower
80s. Sunday looks to be the one dry day of the period across the
forecast area as Pacific NW upper trough tracks northeast into south
central Canada. However, chances for showers and thunderstorms will
likely increase again Sunday night and Monday as another upper
trough moves through the Pacific NW and into the northern Rockies.
Depending on the track of upper energy moving through the Plains
east of the trough, some strong to severe storms are possible later
Sunday night and Monday as moisture returns from the south and
southeast. Better chances look to be toward south central SD at this
time. This upper trough will track north-northwest of the region as
well on Tuesday as a cold front passes across the northern Plains,
with the better chances for showers likely across northwest SD.
Midweek looks drier, but at this point can`t rule out at least
isolated showers and thundershowers in some areas Wednesday and
Thursday. Temperatures Monday through Thursday look to be at least
slightly below average, with Monday the coolest day in many areas. A
more unsettled pattern could return at the end of the week and into
next weekend.

&&

.AVIATION...
-- Changed Discussion --
(For the 06Z TAFS Through 06Z Saturday Night)
Issued At 922 PM MDT Fri Jun 14 2024

Isolated to scattered thunderstorms will occur through much of
tonight across western SD, but ending shortly after midnight
across northeast WY. Brief MVFR conditions in stronger storms.
IFR CIGS due to low stratus may develop over central SD after 06Z
tonight. Isolated to scattered thunderstorms will again develop
Saturday afternoon, with brief MVFR conditions in stronger storms.
-- End Changed Discussion --

&&

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

$$

DISCUSSION/KEY MESSAGES...26
AVIATION...Johnson