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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
1040 PM MST Wednesday Jan 28 2015

issued at 1039 PM MST Wednesday Jan 28 2015

Forecast updated to drop remainder of Wind Advisory.

Update issued at 901 PM MST Wednesday Jan 28 2015

Winds continue to decrease across northwest South Dakota as best
pressure rises shift into south central South Dakota. Dropped Wind
Advisory across the northwest.


Short term...this evening through Thursday night
issued at 205 PM MST Wednesday Jan 28 2015

Primary upper level shortwave and associated surface
trough continues to advect east across the area this
afternoon...with a trailing secondary wave over eastern Montana
associated with the main cold front. Weak ascent coupled with a ll
moisture ridge is supporting a few rain showers over the SW half of the
forecast area...with a waning trend in coverage expected into early evening.
Main story is the winds across the South Dakota plains. Strong ll
flow/pressure rise couplet/and cold air advection will combine to support near or
at wind advection winds through much of the evening. Did extend the wind
advection to cover scentral South Dakota...and in time through the evening.
Otherwise...mainly benign weather in the period as the region
remains on the warm side of fast northwest flow aloft. Weak surface ridge will
advect through the area Thursday...with a another weak fast moving
system expected by Friday. Mild weather will continue.

Gusty northwest winds will persist on the South Dakota plains into the evening.
Secondary pressure rise/cold air advection push will with steep ll laps rates will
support good mixing of fast flow down. This will allow winds of 25
to 35 miles per hour with gust to 50 to continue on much of the South Dakota plains
through most of the evening. Winds will begin to wane late this
evening into early Thursday morning. A pocket of cold air advection low clouds will
push into western South Dakota this evening and cover most of the eastern forecast area
Thursday morning. The NAM is certainly the most aggressive per low
clouds...keeping them in place over the South Dakota plains through much of
Thursday. However...feel this is a little overdone given lack of
appreciable snow cover...which will support better mixing and
subsequent mix out of clouds Thursday afternoon. Thus...sided with the
warmer side of guidance for Thursday per highs. Warm air advection will develop Thursday
afternoon and spread west to east across the region. This should
keep temperatures up overnight Thursday in the favored downsloping areas as
pressure falls rev up and SW flow increases.

Long term...Friday through Wednesday
issued at 205 PM MST Wednesday Jan 28 2015

One more above average day is expected on Friday...with
highs in the 40s to around 50 degrees. A cool down is still in store
for this weekend and early next week...though GFS ensemble still
shows a fairly large spread of possible temperatures through the period.
Northwest flow will bring a Canadian cold front across the area
early on Saturday. High temperatures will be near average on
Saturday...then generally near to below average from Sunday through
Tuesday as the baroclinic zone wavers back and forth across the
area. Shortwave energy behind the front will bring a chance
for snow Saturday into Saturday looking a little later
than previous runs. Any accumulations look to be light across the
area. Northwest flow aloft will continue to bring weak disturbances
across the area through the rest of the extended...with considerable
cloud cover and at least some low chances for probability of precipitation across portions
of the area...mostly far northeast Wyoming...the Black Hills...and far
northwest South Dakota.


Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1014 PM MST Wednesday Jan 28 2015

Widespread MVFR/local IFR ceilings across western South Dakota and
portions of northeast Wyoming will persist through Thursday
morning. Conditions will improve late Thursday morning for
northeast Wyoming/far western South Dakota...with MVFR ceilings
lingering across central South Dakota into Thursday afternoon.


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


short term...jc
long term...pojorlie

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