Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 210758
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
158 AM MDT Mon Aug 21 2017

.DISCUSSION...(Today Through Sunday)
Issued at 156 AM MDT Mon Aug 21 2017

A weak wave moving through zonal flow is helping to create some
scattered thunderstorms across northwestern SD. Satellite shows
some low clouds developing across Nebraska and portions of the
western SD plains. Surface high is over eastern ND/northern MN,
and with low pressure over eastern WY, winds across the CWA are
southeasterly around 10-15 kts. Temperatures are in the lower 60s.

Upper wave will slide through the northern plains today, and winds
across the CWA will become northerly as the surface trough shifts
east. Southeasterly flow and theta-e advection will continue across
south central SD through the morning. Hi-res models are showing
thunderstorms over south central SD late morning/early afternoon,
and with MLCAPE around 2000 J/kg and 0-6 km shear of 30-40 kts, some
strong to severe storms will be possible. Although morning fog/low
clouds across south central/southwestern SD should dissipate by the
time of the eclipse, skies across central SD are still expected to
be mostly cloudy. However, far western SD and especially
northeastern WY should see some clearing. Highs today will be in the
lower 80s.

An upper ridge will keep weather warm and dry through the middle of
the week. Chances for showers and thunderstorms will increase
towards the end of the week as a Canadian low pressure system
flattens the ridge. This system should shift east of the region by
the weekend, and another ridge is expected to build over the
western CONUS, potentially persisting through early next week.
Near average temperatures in the 80s are expected through the
week.


&&

.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1124 PM MDT Sun Aug 20 2017

Isolated/scattered -TSRA will continue overnight and shift
east/southeast through Monday afternoon. Local MVFR conditions
expected with the strongest storms. MVFR/local IFR ST will
develop over south central SD overnight and push toward the Black
Hills by 12z affecting the KRAP terminal. As winds turn north
Monday morning, ST will ship back out and clear the CWA late in
the day.

&&

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

$$

DISCUSSION...Pojorlie
AVIATION...Helgeson



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