Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 171110
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
510 AM MDT Thu Aug 17 2017

.DISCUSSION...(Today Through Wednesday)
Issued at 336 AM MDT Thu Aug 17 2017

Upper level analysis has broad trof over western Canada with
compact shortwave moving east across Minnesota and weak ridging
sliding into the northern Plains. Skies are mostly clear across
the central and western Dakotas back into eastern Montana and
Wyoming. At the surface, high pressure resides across the Dakotas
with a weak trof of low pressure extending from eastern Montana
into central Wyoming. Temperatures across the area at 3am are in
the 50s, with some 60s and breezy south winds across northeast
Wyoming.

A warmer and drier airmass will move over the area for the rest
of the week and most of the weekend as near zonal flow develops
over the region. The best chance for showers and storms through
this period will be this afternoon and evening as a weak shortwave
and surface trof quickly cross the area. With drier airmass
across the area, instability will be relatively weak, with the
threat for severe storms looking to be minimal. However, some
gusty winds will be possible with any stronger storms.
Temperatures over the next few days will be near to above average
after temperatures mostly below average for the last 2+ weeks.

A more active flow is likely to return by the end of the weekend and
early next week. Chances for stronger thunderstorms are forecast
for late Sunday and continue into Sunday night as a shortwave
disturbance crosses the area. Another weak disturbance may produce
a few thunderstorms over the Black Hills area during the afternoon
and evening, with some cloud cover possible across at least parts
of the area Monday morning/midday. Model differences are fairly
large at this point, so level of certainty is rather low.

A ridge is expected to build over the Rockies during the middle part
of next week, with at least some slight chances for showers and
storms. Temperatures look to be near average levels for early to mid
week.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Friday Morning)
Issued At 509 AM MDT Thu Aug 17 2017

A few thunderstorms will move across the area this afternoon into
tonight. Local MVFR conditions with the thunderstorms, otherwise
VFR conditions expected.

&&

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

$$

DISCUSSION...15
AVIATION...7



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