Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 181504

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
904 AM MDT Sun Jun 18 2017

Issued at 900 AM MDT Sun Jun 18 2017

Fast northwest flow continues over the region, with a 110 kt upper
jet moving over the CWA. Hi-res convective models continue to show
some showers and isolated thunderstorms developing across the area
this afternoon and into this evening, which is supported by some
weak instability, an area of Q-vector convergence, mid-level
moisture influx, and some positive vorticity advection. Forecast
soundings show dry low levels, and so some showers may end up
being virga, but decided to add some slight chance PoPs for much
of the CWA this afternoon and evening.


.DISCUSSION...(Today Through Saturday)
Issued at 331 AM MDT Sun Jun 18 2017

Upper level analysis has broad trof continuing to shift east into
the Great Lakes region, while western ridge shifts onto the West
Coast. In between, fast northwest flow remains across the northern
Plains. Skies are mostly clear to partly cloudy across the area.
At the surface, high pressure resides across the northern Rockies.
Temperatures are cool at 3am, with readings in the 40s to lower

Today...Western CONUS upper ridge will build into the Great Basin,
and a warming trend will begin across the area. Highs will be in
the 70s, with mostly dry conditions. Hi-res convective models are
hinting at a few afternoon showers, supported by some weak
instability across the Black Hills and far northwest South Dakota.
Upper ridge will continue to build tonight, with mostly clear
skies expected. Lows will fall into the 50s, with some 40s across
the Black Hills.

For the upcoming week, strong upper ridging will keep weather
mainly warm and dry. Highs will be in the 80s and 90s by midweek,
with a slight cooldown expected towards the end of the week. Low
temperatures will warm back to the 50s and 60s for much of the
week. Some weak shortwave energy will cross the region late in the
week as the upper ridge begins to weaken. This will lead to some
small chances for shower and thunderstorms by Thursday and


.AVIATION...(For the 12Z TAFS Through 12Z Monday Morning)
Issued At 514 AM MDT Sun Jun 18 2017

VFR conditions expected through the period. Some isolated showers
and thunderstorms will be possible over the Black Hills and far
northwestern SD during the afternoon.




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