Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 281053
AFDUNR

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

.SHORT TERM...(Today Through Sunday Night)
Issued at 208 AM MDT Sat May 28 2016

08z surface analysis had low pressure over northeast NE with
frontal boundary into OK. Another frontal boundary was located
from southern SK to northwest WY, where a weak low was located.
Water vapour had upper low over south central NE / north central
KS. This upper low will move northeast today taking a shield of
showers and thunderstorms mainly east of the CWA save for far
eastern portions of south central SD. Another upper low over
western AB will swing a shortwave at the base of it`s trough
through WY / MT into southern SK today. The shortwave will push
the frontal boundary into the CWA with about 500J/kg MLCAPE
pooling along it. 0-6km bulk shear weak. Expect showers to develop
this morning across western WY and then move east over CWA into
this evening, expanding in coverage with embedded thunderstorms.
Have increased pops over the Black Hills to account for terrain
interaction. Went below guidance for highs today given increased
cloud cover.

Tonight, frontal boundary moves east and dissipates as synoptic
forcing shifts into Canada. Diurnal trend in convection expected
with activity waning after sunset. Temperatures will be near
guidance.

Sunday, weak shortwave ridge expected, but next shortwave rotating
around southwest Canada upper low will drop into MT inducing weak
low development over WY. Models differ on extent of return flow
ahead of this system with NAM showing enough CAPE / shear for
isolated severe thunderstorms but GFS much less aggressive. SPC
favoring weaker solution, so will follow. Temperatures will be near
guidance.

.LONG TERM...(Monday Through Friday)
Issued at 208 AM 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. Instability and shear will be sufficient for strong to severe
thunderstorms to develop in the afternoon, which will shift
eastward in the evening as drier air and a cold front push through
the CWA.

Chances for precip continue Tuesday as upper low passes through the
Dakotas. Cooler temperatures in the 60s, along with some 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 12Z TAFS Through 12Z Sunday Morning)
Issued At 452 AM MDT Sat May 28 2016

Isolated to scattered showers/storms will redevelop
across the CWA late this morning into this evening, most numerous in
the hills. MVFR conditions will be possible in showers/storms.

&&

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

$$

SHORT TERM...Helgeson
LONG TERM...Pojorlie
AVIATION...Pojorlie


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