Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 140441

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1041 PM MDT Thu Jul 13 2017

.DISCUSSION...(This Evening Through Thursday)
Issued at 135 PM MDT Thu Jul 13 2017

The upper ridge is building over the western CONUS, and a surface
high sits over the Dakotas. Other than a few cumulus over the
Hills, skies are sunny. Temperatures are in the 80s, and winds are
southeasterly around 10 kts.

Thunderstorms will be possible over the Hills this afternoon, with
marginal instability and moderate shear supporting a few strong to
severe storms. A couple CAMs show showers over northeastern WY, and
with the cap slightly weaker there, have added slight chance PoPs.
Showers/storms will dissipate early this evening, and lows will be
in the 60s.

With the upper ridge in place, temperatures will climb into the 90s
and near 100 Friday into early next week. Mostly dry weather is
expected through the weekend; however, a band of thunderstorms will
develop along a weak surface trough Friday evening. MLCAPE is
expected to be about 500-1000 J/kg across northeastern WY,
northwestern SD, and the Black Hills, and shear will be weak.
There may be a couple strong to severe storms initially where
instability is better, but at this point it looks like storms will
be moving into a less favorable environment and should weaken as
the evening progresses.

A Canadian low pressure system will begin to flatten the ridge
Monday, placing the northern plains in more active zonal to
southwest flow. Chances for showers and thunderstorms will increase
through midweek. Hot temperatures will continue into Monday, but
then a gradual cooldown is expected.


.AVIATION...(For the 06Z TAFS Through 06Z Friday Night)
Issued At 1040 PM MDT Thu Jul 13 2017

A front will bring isolated to scattered thunderstorms mid Friday
afternoon through mid evening over northeastern Wyoming and
northwestern South Dakota. Gusty outflow winds are expected from
these storms. Otherwise VFR conditions expected through the


Issued At 135 PM MDT Thu Jul 13 2017

Hot conditions will return to the area Friday and persist into
early next week. Minimum relative humidity values will drop to the
upper teens and lower 20s across much of the area each afternoon.
Winds do not look strong over the next few days, but periods of
elevated fire weather conditions are possible, especially later in
the weekend into early next week if humidities are lower.




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