Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 191704

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1104 AM MDT Thu Sep 19 2019

.DISCUSSION...(Today Through Wednesday)
Issued at 310 AM MDT Thu Sep 19 2019

Current surface map show high pressure across the Dakotas, with
lee trof over Montana/Wyoming. Plenty of sunshine expected across
the area today with shortwave ridging aloft ahead of western CONUS
trof. Return flow on back side of surface high will result in
gusty south winds across much of the forecast area. With increasing
low level moisture, MLCAPE climbs above 1500J/KG this afternoon.
Strong cap in place (MLCIN 100-200J/KG) and lack of forcing will
limit thunderstorm development this afternoon. Theta-e advection
associated with nocturnal low level jet and weak mid level impulse
should bring a few thunderstorms overnight. CAMs suggest two areas
of area over northeast Wyoming and Black Hills
area and the other over central South Dakota east of the forecast

West CONUS trof moves over the Rockies on Friday and into the
western Dakota Friday night. Widespread convection expected Friday
afternoon/evening. Instability/shear favorable for severe
thunderstorms, especially east of the Black Hills. A few showers
will linger into Saturday.

Next trof digs across the western CONUS early next week.
GFS/ECMWF/GEM in decent agreement with upper low cutting off
across the southwest...resulting in zonal/split flow across the
Northern Plains. Dry weather expected for much of the week with
near average temperatures.


.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1059 AM MDT Thu Sep 19 2019

VFR conditions and breezy southeasterly winds will continue
through this afternoon and early evening. Later this evening and
into Friday morning, showers and isolated thunderstorms with MVFR
conditions will be possible. Some patchy fog across northwestern
SD could also result in MVFR conditions early Friday morning.




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