Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 182021

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
221 PM MDT WED MAY 18 2016

.SHORT TERM...(This Evening Through Thursday Night)
Issued at 219 PM MDT Wed May 18 2016

20z surface analysis had high over the Midwest with moderate
pressure gradient / return flow over the CWA. CU field over parts
of the CWA, but vertical extent limited. Water vapour had upper
low over four corners region with westerly flow aloft over the CWA
ahead of upper trough diving into western Canada / northwest US.

Tonight through Thursday night, upper trough moves into CA / OR as
it closes off and turns upper flow distinctly southwest over the
CWA. Warm air advection will continue ahead of it with moisture
return in response to lee trough and southerly flow. CU will die off
tonight with temperatures near guidance. Modest low level jet
develops over the SD plains, but moisture will be limited. 0.5-
1KJ/kg MLCAPE foreseen over the CWA Thursday afternoon with 25-
50J/kg MLCIN. Forecast shortwave energy hard to come by, but terrain
rooted convergence may be enough to tap into instability. Any storms
that form will have trouble moving off the Black Hills. Shear looks
to be weak. Low PoPs continue for the Black Hills later Thursday to
account. Highs Thursday should be 5-10F than today given forecast
soundings. Better low level jet develops Thursday night with more
robust moisture return -- may see elevated TSRA Thursday night over
central SD.

.LONG TERM...(Friday Through Wednesday)
Issued at 219 PM MDT Wed May 18 2016

Upper low settles over the Pacific NW and stalls out late in the
week, with ridging over the plains. Still can`t rule out a few
showers and thunderstorms over the Black Hills and northeast WY
late Friday if cap erodes enough as southwest flow aloft edges
into the area.

Chances for showers and thunderstorms will gradually increase
through the weekend and into early next week as the upper trough
eventually moves across the Northern Rockies and into the Northern
Plains. Medium range models still having difficulty with timing,
track, and strength of trough as it approaches. Best chances for
pcpn still look to be across western portions of the CWA Saturday
afternoon/evening...then more widespread activity likely Sunday into
Monday. However latest model runs showing the main forcing farther
east across the cntrl/ern Dakotas which would mean less precip
overall across the CWA Sunday. There is certainly some potential for
strong to severe storms over the weekend as the front slowly crosses
the region. Chances for showers and storms will persist into the
middle of next week as another trough likely develops over the
western states. Temperatures will remain above average through the
weekend, with some highs in the 80s across the plains. More
seasonable temperatures should return early next week behind the


.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 219 PM MDT Wed May 18 2016

VFR conditions are expected through the forecast period.


.UNR Watches/Warnings/Advisories...


SHORT TERM...Helgeson
AVIATION...13 is the U.S. government's official web portal to all federal, state and local government web resources and services.