Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 300857
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
257 AM MDT SAT JUL 30 2016

.SHORT TERM...(Today Through Sunday Night)
Issued at 215 AM MDT Sat Jul 30 2016

Current surface map shows high pressure ridge across the upper
midwest, with weak trof across Montana into Wyoming. Isolated
thunderstorms continue across far easter portions of forecast area
in area of theta-e advection.

For today, flat shortwave ridge builds across the northern high
plains. Increasing southerly low level flow will result in MLCAPE
of 1500-2500J/KG. Forecast soundings suggest weak cap this
afternoon, especially around the Black Hills. Convective allowing
models focus thunderstorm development from the Black Hills into
south central South Dakota. Sufficient shear for a few supercells
across the Black Hills into southwest South Dakota.

Upper ridge shifts east Sunday as trof moves across western
Canada. Surface trof slides into northeast Wyoming/far western
South Dakota Sunday afternoon/evening and will be the focus for
thunderstorm development.

High temperatures will be in the 80s to around 90s today, with
some 70s in the higher elevation of the Black Hills. Warmer on
Sunday, with most locations on the plains into mid 90s.

.LONG TERM...(Monday Through Friday) Issued at 215 AM MDT Sat Jul
30 2016

Zonal upper level flow begins the period, but becomes
more southwesterly by the end of the week. On Monday, the frontal
boundary continues to slowly move through the forecast area with
models indicating a weak shortwave moving through the upper flow as
an upper low pushes across Canada. Kept some low pops in the
forecast for the hills and the eastern portions of the forecast area
due to these features. On Tuesday, another impulse is progged to
move through, if the timing of the latest GFS is correct, could see
some storms develop late in the day, especially over the hills and
western South Dakota; however,the ECMWF solution is slower. This
slower solution indicates a disconnect with the wave timing in
regards to peak heating and less of a chance of storms. For the time
being felt pops were warranted and stayed with the model consensus
solution closer to the GFS. On Wednesday and Thursday the zonal flow
becomes more west-southwesterly as the Canadian low moves east and
drags a weak cold front through the forecast area. This will limit
convection to the eastern portion of the forecast area on Wednesday
and will cool temperatures a little and bring drier conditions for
Thursday. For Friday and into the weekend, models try to deepen the
upper trough down the west coast, keeping the forecast area in
southwest flow. Moisture streaming around the upper high in the
southern plains mainly remains south of the forecast area. Thus most
of the area should be dry with low pops closer to the Nebraska
border.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Sunday Morning)
Issued At 215 AM MDT Sat Jul 30 2016

VFR conditions are generally expected across the area.
Scattered thunderstorms will develop this afternoon and continue
into the evening. Local MVFR conditions and gusty winds will be
possible near storms.

&&

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

$$

SHORT TERM...7
LONG TERM...MLS
AVIATION...MLS



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