Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 181723

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1123 AM MDT Fri Aug 18 2017

.DISCUSSION...(Today Through Thursday)
Issued at 212 AM MDT Fri Aug 18 2017

Upper level analysis shows a wave pushing through the
northern plains, with a ridge building over the western CONUS, and
northwest flow over the CWA. Storms have moved into the eastern
Dakotas and Nebraska, leaving partly cloudy skies over western SD
and northeastern WY. At the surface, winds are generally light and
westerly, and temperatures are in the mid 50s to lower 60s.

As the upper ridge shifts over the region, weather will become dry
and warm. Under mostly sunny skies, highs today will be in the 80s.
Lows tonight will be in the 50s.

The thermal ridge axis will cross the CWA Saturday, and temperatures
will warm into the 90s. At the upper levels, a Canadian trough will
begin to flatten the ridge, placing the northern plains in zonal
flow. A cold front will push into northwestern SD during the
afternoon, creating some breezing winds there. Some weak storms will
be possible across the Black Hills in the afternoon.

Zonal upper flow will continue on Sunday. Highs will be in the 80s
and lower 90s, slightly cooler farther north. Surface low over
eastern WY will result in breezy, moisture-advecting easterly winds
across the western SD plains. By 00Z, models are showing MLCAPE of
3000+ J/kg across south central SD. Storms are expected to develop
as a weak wave crosses SD during the late afternoon and evening,
although models differ on location and timing of the storms. Best
chances look to be across central SD and eastward.

Chances for showers and thunderstorms will continue on Monday with
another shortwave. Skies are looking partly cloudy around midday
Monday. An upper ridge is expected to bring drier weather for much
of next week, with just some isolated storms possible. Temperatures
next week look near average, in the 80s.


.AVIATION...(For the 18Z TAFS Through 18Z Saturday)
Issued At 1122 AM MDT Fri Aug 18 2017

VFR conditions are expected through Saturday morning.




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