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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
1026 am MST Tuesday Jan 27 2015

Short through Wednesday night
issued at 224 am MST Tuesday Jan 27 2015

Water vapor shows large amplitude ridge over The Rockies/plains.
At the surface...high pressure has shifted into the upper Midwest with
deepening Lee trough along the Rocky Mountain front.

Today...Lee trough will advance eastward into the western Dakotas by afternoon.
Thickness ridge passing overhead along with downslope flow will
result in another warm day with plenty of record highs expected.
Thermal profiles suggest temperatures should be at least as warm as
Monday if not a few degrees warmer...but that will be dependent on
the amount of cirrus overhead.

Wednesday...the upper ridge will flatten over the northern plains as a
strong disturbance moves through. Majority of guidance suggesting
enough energy for a few -shra across northestern Wyoming...the Black Hills...and
southwestern South Dakota...although moisture will be rather limited. Gusty northwest winds
expected given cold advection and steep low level lapse rates...with
some areas on the South Dakota plains possibly reaching near advisory
criteria. Winds will decrease Wednesday evening with surface high building
in overnight.

Long term...Thursday through Monday
issued at 224 am MST Tuesday Jan 27 2015

Temperatures will gradually lower to near or below average levels
by the weekend as northwest flow brings colder air into the
region. Medium range models are in better agreement on this...but
still some issues with regard to how cold it could be and how long
the colder air remains over the region...with European model (ecmwf) still a bit
more aggressive than the GFS and Gem. Will keep trending colder
for the weekend...especially Sunday. Chances for snowfall should
hold off until Saturday into Saturday night as a stronger
shortwave moves across the region and brings in the coldest air.
Any accumulations should be light across the area...with the best
chances over the northern Black Hills. Some milder air could slide
back eastward into the region early next week...but that is very
uncertain at this point.


Aviation...(for the 18z tafs through 18z wednesday)
issued at 1024 am MST Tuesday Jan 27 2015

VFR conditions can be expected through the forecast period. A cold
front will cross the area Wednesday morning. Behind the front
across the western South Dakota plains...northwest winds will increase to 25
to 35 miles per hour with higher gusts.


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


Short term...Johnson
long term...26

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