Scientific Forecaster Discussion

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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
321 am MDT Friday Apr 18 2014

Short term...today through Saturday night
issued at 320 am MDT Friday Apr 18 2014

Current surface analysis shows low pressure across southern
ab...with a warm front stretching southeastward across eastern Montana
into western South Dakota. Main cold front tails back westward from the low
across southwestern Canada. Upper level analysis shows shortwave
ridge moving east over The Rockies...with trough moving quickly east
across the Pacific northwest. Scattered to broken middle and high clouds are
passing over the area at this time...most abundant over northern
portions of the County Warning Area. Temperatures are in the lower 30s to middle 40s with
breezy southerly winds over portions of southwestern into central
South Dakota.

A warm day is on tap across the region...ahead of the approaching
cold front that will pass late in the day and this evening. Pressure
gradient will tighten over the Dakotas today ahead of low pressure
that will slowly move east along the Canadian/Montana border. The
strongest winds will be across central South Dakota and eastward late this
morning and afternoon. Across south central South Dakota...southerly winds
will likely approach low end advisory criteria at times this
afternoon...but should mainly stay in the 20 to 30 miles per hour range...with
gusts to around 40 miles per hour. Warm advection will continue across the area
this morning as warm front drifts north and east into northern South Dakota by
this afternoon. Highs will mostly be in the 70s across the
area...with some 60s over the higher Black Hills and lower 80s
likely in some locations to the south and east of the Black Hills.

The cold front will push into northwestern portions of the County Warning Area by
middle afternoon and then track southeast across the County Warning Area through the
evening hours. The main push of colder air and associated winds
behind it will remain to the north of the County Warning Area as our area gets more
of a glancing blow. Though winds could be rather gusty for an hour
or two behind the frontal passage across the South Dakota plains. The main
upper level forcing with the fast moving trough will remain to the
north of the County Warning Area as well. However...there should be sufficient lift
and instability for at least isolated showers and storms to develop
along and behind the front late today into tonight. Will keep the
best chances generally across northwestern South Dakota for very late today
and this evening. There looks to be potential for gusty winds and
possibly some small hail with any storms that develop into the
evening hours. Activity should dissipate or move east of the County Warning Area by
late tonight. Lows early Saturday will generally be in the middle 30s
to middle 40s.

Saturday looks to be partly cloudy and a bit cooler across the area.
Highs will still be above average...60s to around 70 degrees.
Breezy northwesterly winds will develop across the South Dakota plains during
the late morning and afternoon.

&&

Long term...Sunday through Thursday
issued at 320 am MDT Friday Apr 18 2014

An upper level/thermal ridge will dominate Sunday and Monday
bringing dry weather and above normal temperatures. A strong upper
level trough will push precipitation chances into the area later
Tuesday through Thursday. Rain showers/thunderstorms and rain will be possible...especially
Tuesday/Wednesday. Most guidance is in decent agreement pushing
main upper low/shortwave associated with upper trough north of
County Warning Area...which would result in a mostly liquid event. Can/T rule out
some slushy snow Thursday night...but moisture availability behind
system in question.

&&

Aviation...for the 12z tafs through 12z Saturday morning
issued at 320 am MDT Friday Apr 18 2014

VFR conditions will prevail most areas through tonight.
There is a chance of thunderstorms and rain this afternoon/evening with localized MVFR
visibilities. Gusty southerly winds are expected ahead of a cold front
today...with the cold front moving through this evening...leading to
northwest winds.

&&

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

$$

Short term...26
long term...helgeson
aviation...helgeson