Area forecast discussion for western South Dakota and northeastern Wyoming
National Weather Service Rapid City South Dakota
213 PM MDT Sat may 25 2013
Short term...this evening through Sunday night
issued at 157 PM MDT Sat may 25 2013
Water vapor shows distinct short wave moving through far eastern Wyoming
into the western Dakotas...with convection beginning to intensify from
the northern Black Hills into northwestern South Dakota. Convective parameters remain in place
for continued development/intensification of storms through this
evening with very large hail a possibility...and just enough low
level shear and low lcl's to include a threat for tornadoes...and
a Tornado Watch in effect for all but Tripp County until 04z.
Straight line winds could become more of an issue later as storms
possibly merge into a large scale complex turning into a squall
line/mesoscale convective system over far eastern reaches of the County warning forecast area...especially as low
level jet increases.
On Sunday...depending on where today/S convection ends
up...leftover Lee trough/warm front/surface boundary will be
stretched across County Warning Area. Southwest flow aloft will continue. Daytime
insolation will result in 2-3kj/kg MLCAPE...but shear won't be
quite as pronounced as today. Slight risk of severe thunderstorms
looks reasonable given thermodynamics present. Temperatures will
be near guidance.
&&
Long term...Monday through Saturday
issued at 157 PM MDT Sat may 25 2013
Persistent trough across the Pacific northwest will keep
the northern plains under active southwest flow through next
week. Daily chances for thunderstorms will continue as light east to
southeast boundary layer flow continues to bring moist air into
the region...and weak energy ejects out of the western trough into
the northern plains. A stronger shortwave is prognosticated to cross the
area on Monday...leading to the potential for strong to possibly
severe storms during the afternoon and evening hours. Longer range
guidance is still suggesting a strong negatively tilted upper trough
working through the northern plains middle to late next week...which
could provide widespread significant rainfall. Temperatures will
remain above average with some cooling expected towards the end of
the week as the upper trough moves into the northern plains.
&&
Aviation...for the 18z/00z tafs through 18z/00z Sunday afternoon
issued at 157 PM MDT Sat may 25 2013
Scattered/numerous thunderstorms and rain are expected this after/evening with some lingering
overnight bringing MVFR/IFR visible in heavier precipitation. Some ts may
become severe with large hail/strong gusts. Some low ceilings may
develop overnight over portions of the South Dakota plains...bringing areas of
MVFR/IFR ceilings. Otherwise...VFR conditions are expected.
&&
Unr watches/warnings/advisories...
South Dakota...none.
Wyoming...none.
&&
$$
Short term...Johnson
long term...77
aviation...77
