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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
1020 PM MST Friday Dec 26 2014

Update...
issued at 720 PM MST Friday Dec 26 2014

02z surface analysis and regional radar loops show -sn has
developed over south central South Dakota ahead of upper low spinning over
northeast Colorado. Accumulations should be minor as the lift slides
eastward overnight. Update to push likely probability of precipitation/minor accumulations.

&&

Short term...this evening through Saturday night
issued at 223 PM MST Friday Dec 26 2014

Upper level analysis has large trough from the northern rockies to
The Four Corners area...with nearly closed low centered in northwest
Colorado. Weak upper shortwave ejecting out of the trough is
bringing cloudy skies to much of the area with some light snow
across Nebraska and into far south central South Dakota. At the
surface...Arctic high in place across the Dakotas with light
northerly winds. Temperatures at 2 PM are in the teens to middle 20s.

Tonight...cloudy and cold conditions will persist as Arctic high
settles into the area. Light snow will continue across far south
central South Dakota during the evening...with little accumulation
expected. This shortwave will shift east overnight with mostly
cloudy skies expected there. Further west...skies will slowly
clear from west to east overnight...with temperatures falling into
the single digits across much of the area.

Saturday...skies will start off mostly sunny in the morning...with
some increasing clouds from the northwest in the afternoon. Upper
trough and surface high pressure will shift east...with westerly
boundary layer flow taking over. Highs will be in the 20s with
winds from the west to southwest in most areas. Clouds will
increase further Saturday night as the next system begins to
approach the region from the west-northwest. Lows will be in the 5
to 15 degree range.

Long term...Sunday through Friday
issued at 223 PM MST Friday Dec 26 2014

Next upper wave embedded in persistent northwest flow digs
through the northern rockies and into the region by late
Sunday/Monday. This will bring another round of light snow to the
area with a few inches of accumulation likely across much of the
County warning forecast area. Significantly colder air slips into northern plains
Monday/Tuesday...with 1055mb high centered across northeast
Wyoming/western South Dakota by Tuesday afternoon. Temperatures
Monday/Tuesday will be in single digits above zero...and well
below zero both Tuesday and Wednesday mornings. Wind chills will
drop to -15 to -30f...especially Monday night. Slow moderation in
temperatures middle to late week...although next cold front may drop
into the northern plains on Friday bringing more cold air and a
chance of snow.

&&

Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1013 PM MST Friday Dec 26 2014

The back edge of an area of MVFR ceilings will move east and exit
southwest into central South Dakota by morning. Another narrow band of MVFR
ceilings will cross far northwest Wyoming and northwest South Dakota late
tonight/early Saturday morning...possibly affecting the kgcc/krap
tafs. Mainly VFR conditions are then expected Saturday
afternoon/evening.

&&

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

$$

Update...helgeson
short term...15
long term...Johnson
aviation...helgeson

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