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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
223 am MDT Sat may 30 2015

Short through Sunday night
issued at 207 am MDT Sat may 30 2015

Upper analysis shows a broad upper ridge to the west of the region
this morning. Latest surface analysis shows a narrow band of high
pressure over the Dakotas.

The surface high will shift eastward today. Breezy southerly return
flow developing on the west side of the high will help to increase
ll moisture over northestern Wyoming again this afternoon. A weak shortwave
combined with 850-700mb Theta-E advection will create a slight
chance of thunderstorms over parts of far northeastern Wyoming
late this afternoon with the chance of thunderstorms spreading
eastward into mainly northwestern South Dakota this evening.

On Sunday the upper ridge will increase in amplitude over the
western third of the Continental U.S. And high temperatures will warm to
around the average for this time of year. Instability due to ll
moisture and diurnal heating will combine with another weak
shortwave to produce a chance of thunderstorms on Sunday afternoon over
northestern Wyoming...the Black Hills and far southwestern South Dakota late Sunday afternoon with a
slight chance of thunderstorms over much of the rest of the area
on Sunday afternoon.

Long term...Monday through Friday
issued at 207 am MDT Sat may 30 2015

Ridge axis moves over the northern plains
Monday...allowing above average temperatures to return to the area.
A weak wave will pass through the ridge Monday afternoon and
evening. With MLCAPE values near 2000 j/kg over western South Dakota...some
strong to severe storms may be possible...although best shear will
be farther east. Chances for showers and thunderstorms are expected
for the remainder of the week as a western trough redevelops and
upper flow over the northern plains becomes southwesterly. Highs
next week will be near seasonal averages...warmest Monday and


Aviation...for the 12z tafs through 12z Sunday morning
issued at 207 am MDT Sat may 30 2015

Fog/low stratus with MVFR/IFR ceilings/visibilities over the
southern/eastern foothills and into northeast Wyoming will persist into
this morning before dissipating. VFR conditions are expected from
midday through the forecast period.


Unr watches/warnings/advisories...
South Dakota...none.


Short term...10
long term...pojorlie

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