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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
218 PM MST Friday Feb 27 2015

Short term...this evening through Saturday night
issued at 214 PM MST Friday Feb 27 2015

Broad upper trough spans the Continental U.S....with Arctic air plunging
into the southeastern states. Skies are mostly clear over the
northern plains...with the exception of far southwest South Dakota and the
Southern Hills...where some light upslope snow has been reported.
Surface high to the southeast of the region is producing some
breezy southerly winds across the area...bringing in some warmer
air. Temperatures are generally in the 20s.

Surface trough crosses the region tonight...causing winds to become
northwesterly. Clouds will increase...and more chilly air will move
into the region as another cold surface high slides in. Lows tonight
will be in the single digits.

Cold air and clouds will continue to advect into the area on
Saturday. Lowered high temperatures across the northwestern half of the County Warning Area
for these reasons. Expect highs to range from the upper teens across
northeast Wyoming and far northwest South Dakota to the lower 30s across south
central South Dakota. Upper flow begins to split Saturday night as low cuts
off over California and northernmost energy pushes into the northern plains.
The southern part of the County Warning Area may see some light snow on Sunday night
as this wave passes through...but kept chances slight as best
forcing stays south and high pressure remains over the area. Single
digits are again expected for lows Saturday night.

Long term...Sunday through Friday
issued at 214 PM MST Friday Feb 27 2015

Cold temperatures and northwesterly flow will continue
through Sunday as an upper level trough moves out of the County Warning Area. A
1035mb high will slide southeast of the County Warning Area during the day Sunday...
gradually switching surface winds from northwest to southeast by Monday morning.
Monday is looking to be mild as warmer air advects into the region
from the west ahead of a longwave trough. The warmth will be short
lived...as an Arctic front will push through the region late Monday
night into Tuesday morning. Temperatures will decline during the
afternoon Tuesday as strong cold air advection takes place...and
overnight lows will drop below zero for all of the County Warning Area. There will
be some moisture behind the Arctic front...but snow amounts will
generally be light...around 1 to 3 inches for the County Warning Area.

The GFS and European model (ecmwf) are in agreement of a strong ridge building into
the western US by midweek and persisting beyond the end of the
forecast period. As a result...expect generally dry conditions past
Wednesday with a warming trend for the County Warning Area. By Friday...afternoon
highs could be well into the 50s...about 10 degrees above
climatology for this time of year.

&&

Aviation...for the 00z tafs through 00z Saturday evening
issued at 214 PM MST Friday Feb 27 2015

An area of MVFR/near-MVFR ceilings over southwestern South Dakota was moving
northeast and spreading into west-central South Dakota. Short-term guidance has been
poor in handling this...but given the upstream clouds/moisture would
expect the area to continue its northeastward motion...affecting west-central and
parts of scntrl South Dakota into early evening. Otherwise...VFR conditions will
prevail across the County Warning Area until late tonight when a weak upper-wave will
bring increasing MVFR ceilings over parts of northestern Wyoming and far northwestern South Dakota.

&&

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

$$

Short term...pojorlie
long term...mckemy
aviation...bunkers

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