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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
319 am MDT Friday Oct 9 2015

Short through Saturday night
issued at 248 am MDT Friday Oct 9 2015

Upper level analysis has longwave trough shifting east of the
northern plains...with ridge building in the west. Weak shortwave
topping the ridge across southwest Canada at the moment...producing
some high thin clouds across the northern plains. At the
surface...high pressure is present across the Dakotas with a Lee
trough across central Montana. Some patchy fog is present along the
western and southern flanks of the Black Hills...extending into
the Pine Ridge area. Temperatures at 3 am are mainly in the
40s...with a few 30s in the Black Hills and southwest South Dakota.

Today...western upper level ridge will shift east across the
northern rockies. Warmer air will push back into the area as a
weak surface warm front moves slowly east across the County Warning Area. Patchy
morning fog across parts of northeast Wyoming and southwest South
Dakota will mix out quickly this morning as warmer air moves in.
Highs will mostly be in the low to middle 70s across the
plains...with 60s over the Black Hills. High cloud cover will
accompany the front as it moves east this morning...but should
dissipate some into the afternoon. Skies will become mostly clear
by this evening as the warm front moves east of the area...setting
up for a very warm Saturday. Lows tonight will be in the middle 40s
to middle 50s.

Saturday...upper ridge axis slides across the northern plains with
very warm air moving through the area. 850mb temperatures of 20-22c will
translate to surface temperatures well into the 80s across the
area. Would not be surprised if a few locations approach 90
degrees Saturday afternoon under sunny skies. Many locations will
approach record highs for the day. Upper flow becomes more zonal
Saturday night as ridge begins to flatten. Boundary layer flow
will remain westerly overnight...with very mild temperatures
expected through the night. Lows will only fall into the
50s...with lower 60s possible along the eastern foothills of the
Black Hills.

Long term...Sunday through Thursday
issued at 248 am MDT Friday Oct 9 2015

The upper level ridge will break down Sunday as a fast
moving upper level trough races across the US/Canadian border. It
will drag a cold front through the County Warning Area with 30-45kt 850mb winds
behind it and modest cold air advection. Windy/very windy spots
expected on the northwest South Dakota plains...headlines will likely be
needed later. Moisture will be left forecast dry.

Dry weather will continue next week with west/northwest flow aloft
and several weak/dry shortwaves/cool fronts. Temperatures will
remain somewhat above normal.


Aviation...for the 12z tafs through 12z Saturday morning
issued at 248 am MDT Friday Oct 9 2015

Patchy fog across portions of northeast Wyoming into
southwest South Dakota will result in local IFR visibilities early this
morning. Otherwise...VFR conditions will dominate through tonight.


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


Short term...15
long term...helgeson

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