Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 210528

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1128 PM MDT Sun Aug 20 2017

.DISCUSSION...(This Evening Through Sunday)
Issued at 256 PM MDT Sun Aug 20 2017

Upper air analysis shows zonal flow across much of the northern
CONUS with a series of weak waves cross the central third of the
country. One of these waves brought showers to parts of northwest SD
earlier the morning. Surface analysis shows high pressure centered
across the Dakotas with mostly sunny skies across the area with
highs in the 70s to low 80s.

An overall quiet evening is expected...with increasing clouds. Short
range models are not agreeing very well with how storms may end up
developing this evening ahead of a very weak wave...though latest
trends show storms popping up across the southern Black Hills/SW SD
area. Good theta e advection will develop tonight as southeast
return flow sets up. Storms will develop ahead of another wave late
tonight over NW SD and push into better theta e air through the
western SD plains into Monday morning...then south central SD late
Monday morning into the early afternoon. Clouds across western SD
will likely be an issue for the eclipse...most most likely closer to
central SD. It`s looking better approaching the Black Hills
area...and into northeast WY. Highs will be in the mid 70s to mid

Drier weather is expected Tuesday and Wednesday with highs pressure
across the northern plains and upper ridging building over the
northern Rockies. More active weather is expected toward the second
half of the week as the next upper trough approaches from the
northwest CONUS. Temperatures near seasonal averages will continue.


.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1124 PM MDT Sun Aug 20 2017

Isolated/scattered -TSRA will continue overnight and shift
east/southeast through Monday afternoon. Local MVFR conditions
expected with the strongest storms. MVFR/local IFR ST will
develop over south central SD overnight and push toward the Black
Hills by 12z affecting the KRAP terminal. As winds turn north
Monday morning, ST will ship back out and clear the CWA late in
the day.




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