Scientific Forecaster Discussion

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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
1006 am MDT Wednesday Apr 23 2014

issued at 956 am MDT Wednesday Apr 23 2014

Surface low has moved into northwest South Dakota. Winds are
starting to increase across northwest South Dakota and northeast
Wyoming...and still expect them to become windy this
afternoon behind the cold front. Clouds cover most of the County Warning Area...with
some clearing skies working into northeast Wyoming. Rain showers
continue to move eastward through west and central South Dakota.
Tweaked probability of precipitation and sky grids...but rest of forecast looks fine.


Short through Thursday night
issued at 325 am MDT Wednesday Apr 23 2014

Current surface analysis shows low pressure over southeast
Montana...with cold front approaching our northeast Wyoming zones. Warm
front stretches eastward across northern South Dakota. Upper level analysis
shows trough moving into the northern rockies...with upper low
developing over southeast British Columbia. Southwest flow aloft over the region
is bringing plenty of clouds...with remaining shower activity from
earlier over central South Dakota now. Temperatures are very mild this
morning...with 50s to around 60 degrees across the area. A strong
southerly low level jet is centered across the central Dakotas and
Nebraska...with breezy to windy conditions near and east of a line from
Perkins to Shannon counties.

Models remain in good agreement on upper low remaining well north of
the it moves along the Canadian/US border over the next
couple of days. This will keep US on the drier and windy side of the
system. Windy conditions will continue over the next couple of
days...switching to the northwest today as the cold front to the
west pushes through. The strongest winds will generally be across
the northwest and west central South Dakota plains each day. A Wind Advisory
is in effect for much of this area today and will likely be needed
for the same areas tomorrow as well. There will be a few showers in
the vicinity of the front when it moves through northeast Wyoming and
western South Dakota this morning. The front will then move through south
central South Dakota early in the afternoon. The chances for any thunder will
be mainly confined to far eastern portions of the County Warning Area during the
midday and afternoon hours...with the the threat for severe storms
staying south and east of the County Warning Area late today as the front approaches
those areas. Highs today will range from the 50s over northeast Wyoming
and the Black the 70s over south central South Dakota.

Drier air will move into the area from the west during the afternoon
and evening...with mainly dry conditions through the rest of the
short term. Will keep slight chances for showers or sprinkles across
northeast Wyoming this evening and far northwest South Dakota early Thursday as
shortwave energy on the southern edge of the system clips these
areas. As previously mentioned...Thursday will be a windy day as
well...especially across northern portions of the County Warning Area. A tight
pressure gradient will remain in the vicinity of secondary low that
passes north of the area. Winds will decrease late in the day. Mild
air will remain across the area...with highs in the 60s...50s over
the Black Hills. The dry airmass will be place across the area into
Thursday night...allowing temperatures to fall into the upper 20s and 30s


Long term...Friday through Tuesday
issued at 325 am MDT Wednesday Apr 23 2014

Upper ridge axis crosses the region Friday bringing mild and dry
conditions to the area.

Focus then turns to a strong upper trough working through the west
early in the weekend...and into the plains later in the weekend and
early next week. Cooler air will begin to filter into the northern
plains on Saturday...with widespread precipitation working into the region late
Saturday and Sunday and continuing through Monday. Latest 00z runs
of the GFS/ECMWF/Gem are now shifting the main upper low further
south...with the consensus taking the low across Kansas. Under this
scenario...temperature profiles would not be quite as cold for our area and
would result in more of a rain event versus snow. However...should
the models trend back further north with the upper low then snow
chances would increase. Stay tuned as model shifts are likely over
the next few days.


Aviation...for the 12z tafs through 12z Thursday morning
issued at 325 am MDT Wednesday Apr 23 2014

A cold front will cross the area this morning...bringing gusty
northwest winds to the area through the afternoon. The strongest winds
will occur over northwestern and west-central South Dakota where gusts to 40kts are
expected. A few high based showers/thunderstorms are possible today
bringing local MVFR visibilities...but mainly VFR conditions are expected.


Unr watches/warnings/advisories...
South Dakota...Wind Advisory until 6 PM MDT this evening for sdz001-002-012-013-



short term...26
long term...Johnson