Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 301116
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
516 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 515 AM MDT Sat Jul 30 2016

(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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