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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
1110 PM MDT Sat Sep 20 2014

Short term...this evening through Sunday night
issued at 225 PM MDT Sat Sep 20 2014

20z surface analysis showed tight gradient over the South Dakota plains
with winds peaking so will keep advisory going until expiration at
23z.

Tonight...high pressure builds into the County Warning Area with clear skies and
decreasing winds. Temperatures should fall off nicely with readings
near guidance by morning.

Sunday...transient upper ridge moves from The Rockies into the
northern plains as surface anticyclone moves from the County Warning Area to the
Midwest. Return flow will develop on the back side over the west
with weak warm air advection. Temperatures will be seasonal.

Sunday night...upper low moves into ID/WY/UT...pinching off upper
ridge. Latest guidance suggests slower return of moisture so have
backed off on probability of precipitation until very late Sunday night over the far
southwest. Lows near guidance expected.

&&

Long term...Monday through Saturday
issued at 225 PM MDT Sat Sep 20 2014

Models are still in agreement about a cut-off low crossing the
region through first half of next week. Return flow will set up
with moisture advecting in the deep southerly flow. This combined
with some minimal instability will allow for showers and
thunderstorms Monday and Tuesday. Drier air will return Wednesday
as a ridge builds...however now both the ecm and GFS show a
secondary upper low developing and retrograding back over the northern
plains. Models showed a similar solution two or three days ago
before quickly abandoning it...but now its back again. Either
way...see no reason to add probability of precipitation. Highs will be near to slightly
above average for the second half of the week.

&&

Aviation...for the 06z tafs through 06z Sunday night
issued at 1109 PM MDT Sat Sep 20 2014

VFR conditions will continue tonight and on Sunday.

&&

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

$$

Update...10
short term...10
long term...13
aviation...10

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