Area forecast discussion for western South Dakota and northeastern Wyoming
National Weather Service Rapid City South Dakota
243 PM MDT Wednesday Jun 19 2013
Short term...this evening through Thursday night
issued at 241 PM MDT Wednesday Jun 19 2013
Water vapor imagery shows a broad trough across the western third
of the Continental U.S. With a cut off low over the Pacific northwest.
Surface analysis shows low pressure centered over northwest
Wyoming into central Montana. Deep southeasterly flow continues
across the region...with a dry line from the big horns to
kcpr/kdgw.
Dry line will push across northeast Wyoming into this evening before
stalling on the western edge of the Black Hills. Low pressure will
swing into eastern Montana tonight with a cold front sliding across
the County Warning Area late tonight into Friday morning. For this evening...strong
instability across the area will remain largely untapped. Capping
continues to erode...but with lack of forcing...any storms that do
fire will remain isolated. In addition to cape values of over 2000
j/kg...decent enough shear for the storms that fire to become
severe. Otherwise the slightly better chances for convection will
be late tonight across central South Dakota with the frontal passage.
Upper low across the northern rockies is prognosticated to remain
stationary as more waves rotate around...with southwest flow
developing aloft across the area. Frontal boundary will stay east of
the County Warning Area along with the precipitation. Temperatures will range from the upper 70s
over northeast Wyoming to the middle 80s over the South Dakota plains east of the
Black Hills. A strong wave will round the base of the upper
low/trough crossing into eastern Montana Thursday night. This may
bring a few showers into northwest South Dakota and portions of
northeast Wyoming...but the bulk of forcing and precipitation will remain
in Montana. A few showers are also possible across south central South Dakota
as Theta-E advection increases in response to a weak surface low
developing over Nebraska.
&&
Long term...Friday through Wednesday
issued at 241 PM MDT Wednesday Jun 19 2013
Southwest flow aloft will continue Friday and Saturday as an upper
low spins over the northern rockies and an upper level ridge
remains over the Midwest. Several shortwaves will move through the
ridge. With moderate/strong instability and 0-6 km shear...looks
like an active period with the possibility of severe
thunderstorms. Highs will be in the middle-70s to mid-80s.
Sunday...upper low ejects into south central Canada...and showers
and storms should move out of the region as the low continues northeast.
Much drier air will filter in behind system.
Monday/Tuesday/Wednesday...a large scale upper level ridge slowly
develops over The Rockies and moves into the plains states. A couple
of ridge riders might bring some isolated showers and thunderstorms
to parts of the County Warning Area...but conditions are expected to be mainly dry.
Temperatures will warm into the 80s and lower 90s.
&&
Aviation...for the 18z tafs through 18z Thursday afternoon
issued at 241 PM MDT Wednesday Jun 19 2013
Gusty southeast winds will continue across much of the County Warning Area today.
Chances for thunderstorms and rain will be small this afternoon/evening ahead of a
cool front...but if any storms develop they will create local LIFR
conditions. The cool front will slowly move into the County Warning Area overnight.
&&
Unr watches/warnings/advisories...
South Dakota...Wind Advisory until 9 PM MDT this evening for sdz001-002.
Wyoming...none.
&&
$$
Short term...13
long term...pojorlie
aviation...pojorlie
