Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 280752

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
152 AM MDT Fri Jul 28 2017

.DISCUSSION...(Today Through Thursday)
Issued at 112 AM MDT Fri Jul 28 2017

Current surface analysis shows a frontal boundary stretching
across eastern Montana and northeastern Wyoming with high pressure
off to the east over western Minnesota. Upper level analysis
has weak ridging over the high plains with a shortwave trough off
the Pacific Northwest Coast. Westerly flow continues to bring
impulses across the Rockies and into portions of the Northern
Plains. GOES-16 Water Vapor bands and surface dewpoints in the mid
50s to mid 60 indicate abundant moisture in all levels of the
atmosphere. Precipitable water values are above average, some
areas 150 percent or so of average.

A few showers may linger though mid morning with scattered storms
developing by mid day across the Black Hills and northeastern
Wyoming. CAPE values today will be around 1000 j/kg, especially
across the southwestern portion of the area. Some heavy rainfall
is likely again today with the stronger convective activity. The
threat for strong to severe storms should be limited, with the
best chances across southwest SD where 0-6 km shear is 35 to 40
kt. High temperatures today will be in the 80s with gusty
southerly winds over the western South Dakota plains.

High pressure will continue to build over the western CONUS for
most of next week, resulting in northwest flow across the area.
Unsettled weather will continue with a daily chance for afternoon
and evening storms. Near to slightly above average temperatures
will continue with highs in the 80s and 90s and lows in the 60s.

.AVIATION...(For the 06Z TAFS Through 06Z Friday Night)
Issued At 1110 PM MDT Thu Jul 27 2017

Leftover isolated to scattered -TSRA will move across northeast WY
through south central SD overnight with local MVFR conditions.
Looks like some IFR ST/FG may develop over northeast WY overnight
due to narrow band of high dew points and recent precipitation.
Mainly dry weather Friday morning will be replaced by additional
TSRA Friday afternoon and evening with local MVFR conditions.




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