Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 250913

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
313 AM MDT Tue Jul 25 2017

.DISCUSSION...(Today Through Monday)
Issued at 312 AM MDT Tue Jul 25 2017

09Z vapor shows an upper low over eastern Saskatchewan/western
Manitoba, a small wave moving through northwestern South Dakota,
and southwest flow across the forecast area. At the surface, a
boundary is draped across northwest South Dakota with another
boundary along the South Dakota/Nebraska border. Latest radar
imagery has convection across southern Montana, southwestern North
Dakota, and northwestern South Dakota.

Showers and storms across northwestern South Dakota will dissipate
this morning. However, additional storms are expected after 18Z
today. The multiple surface boundaries combined with a well defined
shortwave, will lead to widespread showers and storms tonight. By
00Z PW values will rise to 150-200% of normal as moisture pools
along the southwestern boundary creating 2000 J/kg MLCAPE and little
MLCIN. Could see some training storms and/or locally heavy rain,
especially with light steering winds. 0-6km bulk shear will be
sufficient for isolated severe storms this afternoon and evening
with a decent chance of a MCS overnight for south central South

On Wednesday and Thursday, the upper ridge will begin to rebuild
over the western CONUS. Temperatures will be slightly cooler with
the chance for showers and storms, mainly over northeastern Wyoming
and far western South Dakota.

Friday through Sunday, the upper ridge will build over the high
plains with warmer temperatures and small chances for thunderstorms.


.AVIATION...(For the 06Z TAFS Through 06Z Tuesday Night)
Issued At 1054 PM MDT Mon Jul 24 2017

Isolated thunderstorms expected overnight across far northeast
Wyoming and far northwest South Dakota. Scattered thunderstorms
will develop across the area Tuesday afternoon and evening. Local
MVFR conditions possible with thunderstorms, otherwise VFR
conditions expected.




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