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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
142 PM MST Tuesday Feb 9 2016

Short term...this evening through Wednesday night
issued at 135 PM MST Tuesday Feb 9 2016

1930z surface analysis reveals a north/S oriented baroclinic boundary
draped across western South Dakota...with temperatures in the 40s
and 50s across northeastern Wyoming and western South Dakota...and
30s on the cool side of the boundary in central South Dakota.
Radar reveals some light echoes over the eastern-most counties in
the County Warning Area...though the bulk of the precipitation has not been
reaching the ground with only a few stations recording trace
amounts.

Tonight...baroclinic boundary gradually moves eastward out of the
County Warning Area. Could have a few lingering snow showers and some patchy
freezing drizzle before 06z. Otherwise...drier air moves into the
area and we will see gradual clearing from west to east.

Temperature forecast on Wednesday could be a bit tricky...as warmest
air aloft is over the region early in the day...and models indicate
decent cold air advection at 850mb and 700mb during the day. Current thinking is
areas across northeast Wyoming and western South Dakota will
probably mix out the inversion in the morning and easily reach into
the 50s for highs...while the South Dakota plains may take a bit
longer to mix down and will only see highs in the 40s.

By Wednesday night...models forecast a weak backdoor cold front moving
into eastern and central portions of the County Warning Area with surface winds
switching from the northwest to the east. Some model forecast
soundings are showing a stratus deck just off the surface a couple
of thousand feet in depth...so it is possible there may be some
fog in areas late Wednesday night into Thursday morning. Will hold
off on putting it in the grids given some model differences on
moisture in low levels...but will monitor for future forecasts.

Long term...Thursday through Tuesday
issued at 135 PM MST Tuesday Feb 9 2016

Amplified active northwest flow will persist in the period. Western noam
positive middle level height anomaly will remain centered just west
of the region...with active northwest flow to the east. This will result
in a ll baroclinic zone wavering across the region with mild conds
over the western half of the forecast area....and much cooler conds over
eastern areas. Middle/level impulses passing to the east of the forecast area
will fluctuate this boundary across the region with some bouts of
light wintry precipitation eastern half. A stronger wave will advect
through the ridge Sat-sun...supporting better chances for
rain/snow over area...especially NE Wyoming and the northern Black Hills.
However...mild northwest flow looks to persist behind this wave as Arctic
air will remain bottled to the north per flow blocking over
central Canada while Pacific flow spreads further east into the
Midwest.

&&

Aviation...(for the 18z tafs through 18z wednesday)
issued at 135 PM MST Tuesday Feb 9 2016

VFR conditions will prevail over most of the area today.
Scattered rain/snow showers are expected over parts of central
South Dakota through the afternoon. MVFR ceilings are possible with
any showers. There is a slight chance of freezing drizzle over
central South Dakota overnight tonight...mainly from Lemmon to White River
and east.

&&

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

$$

Short term...mckemy
long term...jc
aviation...jc

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