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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
1004 PM MST Wednesday Nov 26 2014

Short term...this evening through Thursday night
issued at 153 PM MST Wednesday Nov 26 2014

Upper level analysis has a trough over the upper Midwest with a
ridge over the far SW Continental U.S.. fast northwest flow continues over
the northern plains in between these two features...with 150kt
jet across the western Dakotas. Skies are cloudy with on and off
light snow across much of the forecast area. At the
surface...Arctic high is located across southern Canada with weak
low/trough across central Wyoming. Temperatures are in the 20s to
lower 30s with generally light winds.

Tonight...NW-se oriented jet/baroclinic zone over the western
Dakotas will gradually move northeastward overnight. Light snow or
flurries over northeastern Wyoming and parts of western South
Dakota will continue...with the precipitation spreading
northeastward tonight as 500mb heights continue to rise and low to
middle level warm advection intensifies. Sref ptype probabilities
and NAM vertical profiles support a chance of snow with a slight
chance of light freezing rain/fzdz over parts of northeastern Wyoming and
northwestern South Dakota later tonight into early Thursday morning. Low
temperatures will range from the teens across the South Dakota
plains...to the upper 20s across northeast Wyoming.

On Thursday...western ridge and warmer air will continue to build
into the northern rockies and plains. There will be a wide range
of temperatures on Thursday as the colder air retreats to the east
and warmer air moves in from the southwest. Highs are expected to
range from around 30 degrees toward north central South Dakota to
around 50 degrees over parts of northeast Wyoming and southwest
South Dakota. There will be a continued chance of light snow and
light freezing drizzle across far northwest South Dakota through
the afternoon. Precipitation will finally lift north and east of the area
Thursday night...with low temperatures falling into the 20s to middle
30s.

&&

Long term...Friday through Wednesday
issued at 153 PM MST Wednesday Nov 26 2014

Upper flow will become more zonal for the end of the
week as weak ridging breaks down ahead of the next Pacific trough.
Warmer airmass over the region Friday will bring temperatures well above
seasonal averages.

The next trough will cross the Pacific northwest Saturday...bringing
a surge of cold air to the northern plains. Both the GFS and European model (ecmwf)
have slowed down the cold frontal passage from previous runs...now
having it pass through the County Warning Area Saturday night. European model (ecmwf) is still
slightly faster than the GFS. Have increased temperatures some more to
account for GFS...but confidence is low at this time...as both the
European model (ecmwf) and GFS ensembles have a 30-40 degree spread for high temperatures
Saturday. Some light snow is possible Sat night into possibly
Sunday...but minimal quantitative precipitation forecast is expected.

Sunday looks cold...with highs only in the teens. Models suggest
mainly dry conditions with moderating temperatures early next week.

&&

Aviation...(for the 06z tafs through 06z Thursday night)
issued at 959 PM MST Wednesday Nov 26 2014

VFR conditions will continue to develop across northestern Wyoming as low
stratus shift eastward. Widespread MVFR/IFR conditions expected to persist
into Thursday morning across western South Dakota along with areas of -sn. As warmer air
moves in aloft later tonight...some -fzra may develop especially
across northwestern South Dakota. All precipitation and low stratus will shift east of the
region by Thursday night.

&&

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

$$

Short term...15
long term...pojorlie
aviation...Johnson

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