Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 290506
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1106 PM MDT SAT MAY 28 2016

.SHORT TERM...(This Evening Through Sunday Night)
Issued at 235 PM MDT Sat May 28 2016

The latest upper analysis showed low pressure centered over far
southeastern South Dakota. Bands of showers and thunderstorms
rotating around that upper low have been occasionally brushing the
eastern parts of Tripp county in south central South Dakota. To
the west, shortwave energy rotating around an upper trough
extending from a British Columbia low and an associated sfc front
have combined to produce a N-S oriented band of showers and
thunderstorms over far western South Dakota and parts of
northeastern Wyoming this afternoon. That band will continue to
shift slowly eastward during the rest of the afternoon and into
the evening with showers and thunderstorms gradually dissipating
around sunset.

On Sunday, subsidence associated with a weak shortwave ridge will
work to keep a cap on any convection through most of the day, but
late in the afternoon the next shortwave rotating around
southwestern Canada upper low will drop into Montana inducing
weak low development over Wyoming. Models continue to differ on
extent of low and mid level moisture return flow ahead of this
system with NAM showing enough CAPE / shear for isolated severe
thunderstorms but GFS is still much less aggressive with
convective development. Temperatures will be warmer than average.
The chance of showers and thunderstorms will continue on Sunday
night.

.LONG TERM...(Monday Through Saturday)
Issued at 235 PM MDT Sat May 28 2016

As a trough over the Pacific Northwest crosses the
northern Rockies early next week, an upper low will deepen. Surface
low over western SD will cause southerly winds to bring warm and
moist air to western and central SD on Memorial Day, resulting in
temperatures in the mid 70s to lower 80s and dew points in the 50s.
A strong cold front will push in through the afternoon behind the
low. Thunderstorms will develop ahead of the front...mainly across
central SD. Forcing...instability and shear will be sufficient for
storms to become strong to severe. Gusty NW winds are expected
behind the front as precip ends.

Chances for precip are again expected Tuesday as upper low passes
through the Dakotas...though best chances now appear to remain
across NW SD. Cooler temperatures in the 60s, along with breezy
northwest winds, are expected for Tuesday into Wednesday. A ridge
develops over the western CONUS behind the low, and with northwest
flow over the Northern Plains, the second half of next week looks
drier. A warming trend is also expected into next weekend.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1104 PM MDT Sat May 28 2016

VFR conditions expected through Sunday morning. Isolated
thunderstorms expected Sunday afternoon and evening with local
MVFR visibility.

&&

.UNR Watches/Warnings/Advisories...
SD...None.
WY...None.
&&

$$

SHORT TERM...10
LONG TERM...13
AVIATION...7


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