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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
528 PM MDT Tuesday may 5 2015

Short term...this evening through Wednesday night
issued at 243 PM MDT Tuesday may 5 2015

Water vapor imagery shows an upper low across The Four Corners with
increasingly active southwesterly flow over the northern plains. A second trough
is moving onshore the Pacific northwest. Regional radar shows rain showers/thunderstorms and rain
moving north across the lbf County Warning Area. The Pacific northwest trough will deepen
and cut off tonight as the four corner low begins its phase in
transition. This wave will lift north/NE across the Central Plains tonight
and northern plain Wednesday/Wednesday night. Abundant moisture and large scale
forcing will bring is precipitation to the area tonight through Wednesday night.
Showers...and perhaps a few isolated thunderstorms...will move into scntrl
this evening...and work its way into the rest of the County Warning Area late
tonight or Wednesday morning. As the low swings by the Dakota Wednesday...cooler
air will wrap around and push across the County Warning Area mainly during the
afternoon hour tomorrow. This frontal passage will bring the best
chance of precipitation for this event as heavier showers and some
thunderstorms are expected along and ahead of the front. Precipitation will
gradually decrease Wednesday night as the open wave lifts north into
ND/can. When its all said and done it looks like most areas will see
one half to one inch of rain...with perhaps some areas getting more
than this.

Long term...Thursday through Tuesday
issued at 243 PM MDT Tuesday may 5 2015

As the upper low spins over California...weak energy will eject
into the northern plains and will keep chances of showers around
for Thursday and Friday. Precipitation chances increase on Saturday as
California closed low moves into the Central Plains. Both the ecm
and GFS are wrapping cooler air around the low into the County Warning Area
Saturday night into Sunday morning...with 850mb temperatures around 0c.
This could mean some precipitation falls as snow across the higher
elevations of the Black Hills...but still much uncertainty exists
with the track of this storm.

Temperatures from middle week into the weekend will be near to slightly
below average...in the 50s and 60s with the ample cloud cover and
precipitation chances.

&&

Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 525 PM MDT Tuesday may 5 2015

Scattered/numerous -shra/isolated -tsra will move northwest
across southern South Dakota this evening. Widespread -ra will develop
overnight and persist Wednesday across the majority of the area
resulting in MVFR ceilings/visibilities on the plains and IFR ceilings/visibilities over
the higher terrain.

&&

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

$$

Short term...13
long term...15
aviation...helgeson

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