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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
959 am MST Friday Jan 30 2015

Short through Saturday night
issued at 236 am MST Friday Jan 30 2015

Water vapor shows short wave crossing the northern rockies and flattening
the upper ridge in place. At the surface...associated trough is advancing
into eastern Montana/eastern Wyoming.

Today...short wave will cross the northern plains and push the surface
boundary through the Dakotas. This will allow thermal ridge to
nose into the County warning forecast area and help push temperatures into the 50s on the South Dakota
plains...a little cooler further west. Very little moisture with
this system so dry conditions expected.

Saturday...a stronger disturbance embedded in the northwest flow aloft
will shift through the northern rockies into the northern plains. Temperature forecast
will be tricky as Arctic air attempts to back into the South Dakota plains
while inverted surface trough over northestern Wyoming keeps temperatures warmer in the
west. As 140kt jet streak on back side of trough enters the western
zones late on Saturday/Saturday night...Arctic will plunge southward
through the entire County warning forecast area. Large scale ascent associated with jet
streak and low level cold air advection with result in widespread light snow across western
South Dakota...with less of a chance in northestern Wyoming. Accums should be light in
most areas...generally 2 inches or less...given lack of moisture.
Temperatures Saturday night should settle in the single digits on the South Dakota
plains and slightly warmer in the western zones.

Long term...Sunday through Thursday
issued at 236 am MST Friday Jan 30 2015

An unsettled and colder pattern will persist through at least
the first half of next week. Shortwave energy will cross the
northern plains in northwest flow...bringing light snow to parts
of the area from time to time. Best chances for light snow will be
Monday night into Tuesday morning across northern portions of the
forecast area. An upper ridge is prognosticated to build across The
Rockies late next week...with dry weather expected.

The temperature forecast for the first half of next week remains
tricky as surface frontal boundary meanders across the County Warning Area at times.
A brief warmup is still expected on Monday ahead of the shortwave
Monday night. Cooler air will again dive southward Tuesday into
Wednesday...although models disagree on exactly how far west the
coldest air will reach. The GFS and European model (ecmwf) both have warmer air
moving back into the region towards the end of next week.


Aviation...for the 18z tafs through 18z Saturday
issued at 956 am MST Friday Jan 30 2015

VFR conditions are expected through Saturday morning.


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


Short term...Johnson
long term...15

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