Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 212100

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
300 PM MDT Mon Aug 21 2017

.DISCUSSION...(This Evening Through Monday)
Issued at 300 PM MDT Mon Aug 21 2017

Current surface analysis shows low pressure and cold
front now southeast of the CWA, with high pressure over southwest
SK. Upper level analysis shows trough over south central Canada with
west-northwest flow over the Northern Plains. Skies have become
mostly sunny across much of the area. Temps are in the 70s to around
80 across the area. Much drier air is slowly filtering in from the
north and west, with dewpoints ranging from the mid 30s to lower 40s
over northeast WY and far western SD, to the low to mid 60s over
south central SD. Brisk northerly winds continue across portions of
the western SD plains.

Dry northwesterly flow aloft will develop across the area into
midweek, with mainly dry conditions anticipated through Wednesday.
High pressure will move over the area tonight with cool
temperatures, lows in the 40s and lower 50s. As the high moves east
of the area on Tuesday, south to southeast winds will develop. Ridge
over the west coast now will slowly move east into the Rockies
region through Wednesday. Frontal boundary to the southwest of the
region will move northeast into the area as a warm front. Temps will
be back to near to above average levels on Wednesday.

Weather will become more unsettled for the latter part of the week
as weak upper level disturbances interact with the boundary that
will stall over the area. Chances for showers and thunderstorms will
increase across western portions of the CWA on Thursday and then
across much of the area on Friday. Instability forecast for late
week looks favorable for at least isolated strong to severe storm
potential, especially on Friday with approaching cold front from the
northwest. The cold front is progged to move through early in the
weekend, with mostly dry weather and seasonable temperatures
Saturday through Monday.


.AVIATION...For the 18Z TAFS Through 18Z Tuesday
Issued At 300 AM MDT Mon Aug 21 2017

VFR conditions through tonight. Gusty north winds this afternoon
will decrease, then switch to the south early Tuesday morning.




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