Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 031933

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
133 PM MDT Mon Aug 3 2020

.DISCUSSION...(This Evening Through Monday)
Issued at 129 PM MDT Mon Aug 3 2020

An upper ridge builds over the Rockies, while a
shortwave pushes into the Pacific NW. Northern plains is beneath
northwest flow. With the surface high to the east and a surface low
to the west, winds across the CWA are southeasterly around 10-20
kts. A stationary boundary stretches across eastern WY. Skies are
mostly sunny, with some cumulus developing over the Black Hills
and the western SD plains. Temperatures early this afternoon are
in the 70s and lower 80s.

Pac NW wave will flatten the Rockies ridge today. As upper energy
moves over the surface boundary this evening, around 1000 J/kg
MLCAPE will support thunderstorm development across northeastern WY.
Shear of 30-40 kts could support a strong storm or two, but
expecting storms to remain sub-severe. Showers/storms will track
into western SD overnight as the wave crosses the region.

As the western CONUS ridge rebuilds Tuesday, lingering
showers/storms will continue shifting eastward as drier air moves
in. With the surface low progged to be over eastern WY/southwestern
SD in the afternoon, some additional thunderstorm development will
be possible nearby, especially around the southern Hills. MLCAPE
around 1500 J/kg could support a few strong/severe storms, but 0-6
km shear of <30 kts suggests pulsey, short-lived storms. Most of the
activity should calm down in the early evening.

Upper ridging should keep Wednesday mostly dry, but weak shortwave
energy moving across the southwestern CWA could result in some
showers/storms there. Instability and shear are expected to be
fairly minimal.

Early week highs in the 80s will begin warming back into the 90s on
Thursday, and even warmer on Friday. Mostly dry weather can be
expected during the day, with showers/storms developing both
evenings. This weekend`s weather looks similar.


.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1148 AM MDT Mon Aug 3 2020

Mainly VFR conditions are expected through the period. Scattered
thunderstorms will move into northeastern Wyoming this evening,
then continue eastward into western South Dakota late this evening
into the overnight hours.


Issued At 129 PM MDT Mon Aug 3 2020

Hot and dry conditions are expected across northeastern WY and
southwestern SD on Friday. At this time, winds are expected to
remain below Red Flag criteria; however, will continue to watch
for any changes.




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