Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 171800
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1200 PM MDT Mon Jul 17 2017

.DISCUSSION...(Today Through Sunday)
Issued at 255 AM MDT Mon Jul 17 2017

Current surface map shows cold front creeping through western
South Dakota. There are a few showers lingering across northwest
South Dakota. For today, cold front makes it into central South
Dakota this afternoon. Low level moisture pooling along front will
result in MLCAPE of 1500-2000J/KG. May be a few strong storms with
damaging winds. If storms can obtain some rotation with the
marginal shear, then some larger hail will be possible. Slower storm
movement may result in locally heavy rain. While the main focus
will be along the front this afternoon, a few thunderstorms are
also possible around the Black Hills. Better chance of
thunderstorms tonight into Tuesday morning with increasing
850-700mb theta-e advection in response to right entrance region
of jet streak tracking across the Dakotas.

Front will be stalled out in northern Nebraska Tuesday afternoon
as weak high pressure slides through the Dakotas. Return flow on
back side of high will bring increasing low level moisture in to
northeast Wyoming and Black Hills area, with 1500-2000J/KG MLCAPE.
Thunderstorms will develop across northeast Wyoming and Black
Hills late Tuesday afternoon.

Area will be under flat upper ridge through the remainder of the
week. GFS/ECMWF then amplify ridge over the Rockies over the
weekend with digging trof over the Great Lakes. Forecast area will
be on western edge of northwest flow, allowing for slight cooler
temperatures with back door fronts. Isolated to scattered
thunderstorms possible each day.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1138 AM MDT Mon Jul 17 2017

Scattered thunderstorms will form this afternoon over the Black
Hills and south central SD, with better chances for thunderstorms
later this evening and overnight. Storms this evening will begin
in northeastern Wyoming before moving across western South Dakota
overnight. Expect gusty winds in and around storms. A few mid
levels clouds will remain over the Black Hills and Foothills in
the morning, before clearing by afternoon.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION...7
AVIATION...MLS



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