Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 212005

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
205 PM MDT Wed Jun 21 2017

.DISCUSSION...(This Evening Through Wednesday)
Issued at 159 PM MDT Wed Jun 21 2017

Upper level analysis has broad but flat ridge across the western
CONUS with fast zonal flow across the Pacific Northwest through
the northern Plains. At the surface, a cold front extends from
western Manitoba through west central South Dakota, around KPHP at
19Z. Northwest winds of 15 to 25 mph have developed so far behind
the front under mostly sunny skies. There are a few CU developing
over the Black Hills and northwestern SD, but remain fairly flat
at this time.

For the rest of this afternoon into this evening there will be a
slight chance for a thunderstorm over the southern Hills, but
instability is fairly week. Better chances for convection will be
overnight as a weak upper level disturbance moves across the
forecast area pushing the cold front to the east. Isolated strong to
severe storms are possible near and east of the front across south
central South Dakota. Behind the front across western South Dakota,
a few rain showers will develop around midnight and continue
through the early morning hours.

For Thursday, a few ongoing showers and thunderstorms will be
possible in the morning across the South Dakota plains before
shifting east by midday. Cooler air will move into the area during
the morning, with highs Thursday afternoon only in the 70s.

The broad upper trof will settle across the northern CONUS for the
weekend, with Friday and Saturday being the coolest days. High
temperatures will only reach into the 60s to lower 70s. An upper
shortwave and Canadian cold front will slide southeast through the
area late Friday into Saturday morning, bringing a chance of showers
and a few storms. The end of the weekend into early next week looks
to be dry with another warming trend.


.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 1100 AM MDT Wed Jun 21 2017

Scattered showers/storms with MVFR conditions are possible across
the area tonight into Thursday morning, mainly after midnight.
Otherwise, VFR conditions are expected.




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