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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
518 PM MDT Monday Oct 20 2014

Short term...this evening through Tuesday night
issued at 121 PM MDT Monday Oct 20 2014

An upper ridge was dominating our weather today per water vapor
satellite images...while a large-scale trough was moving toward
the western Continental U.S.. skies were clear over the County Warning Area with temperatures 10-15f
above average. Surface pressure falls and a tightening mslp gradient
was supporting southerly winds of 10-20 miles per hour across much of the plains.

For tonight the mild and dry weather will continue as the upper ridge
moves over the eastern Dakotas and a low-level thermal ridge moves
across the County Warning Area. South/southwest 850mb winds of 15-40 knots will help
keep the blyr mixed...with occasional gustiness at the surface.

On Tuesday the strongest 850-mb winds will be across the South Dakota plains
east of the Black Hills...with speeds of 25-40 knots. May hit borderline
Wind Advisory conditions across scntrl South Dakota from 15-24z. Across northestern Wyoming
the winds will be southwest behind a surface trough. Also on Tuesday
afternoon the surface dewpoints should increase to 45-50f across much of the South Dakota
plains (ahead of the surface trough) as lapse rates reach 7.5 c/km. This
will produce MLCAPE of 100-250 j/kg with mlcin almost as high. Even
though a short-wave trough will be moving across the northern rockies...
large-scale ascent will be lacking. Thus...do not expect any deep
moist convection during the day.

On Tuesday night the short-wave trough moves across Montana with a surface
trough and cold front moving through western South Dakota. Again...lift and
moisture will be lacking...thus very little in the way of precipitation
expected. However...some small probability of precipitation are warranted across parts of
southern South Dakota where convergence along the surface trough/front and MUCAPE of
250-500 j/kg may help initiate a few shra/tsra.



&&

Long term...Wednesday through Monday
issued at 121 PM MDT Monday Oct 20 2014

Weak upper trough will cross the region on Wednesday and usher
slightly cooler air into the area. Moisture will be limited with
this system with the best chance for any precipitation over scntrl
South Dakota. The upper ridge will then rebuild over the central Continental U.S. And
bring dry weather and much above average temperatures into the weekend. Next
trough approaches late in the weekend.

&&

Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 515 PM MDT Monday Oct 20 2014

VFR conditions expected through the period. Pressure falls ahead
of an approaching upper level wave will support strong ll
flow...with a low level jet expected over the South Dakota plains tonight. Areas of ll
wind shear in excess of 30 knots will be possible there through
tonight...mainly where surface winds completely decouple.

&&

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

$$

Short term...bunkers
long term...Johnson
aviation...jc

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