Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 181757
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1157 AM MDT Tue Jul 18 2017

.DISCUSSION...(Today Through Monday)
Issued at 254 AM MDT Tue Jul 18 2017

Current surface map shows cold front across south
central/southwest South Dakota, with high pressure building into
the northern plains. Scattered thunderstorms over northwest into
south central South Dakota. Thunderstorm activity will shift east
of the forecast area this morning as upper level shortwave moves
into the eastern Dakotas. High pressure shifts into the eastern
Dakotas. With cooler northeast to east low level flow, highs will
be 10 to 15 degrees lower than yesterday. Lack of instability
and/or strong cap in place for much of the forecast area. May be
an isolated thunderstorm over the Black Hills into northeast
Wyoming late this afternoon and early evening, then shifting into
northwest South Dakota in area of weak theta-e advection.

Warm front lifts back into western South Dakota Wednesday with
weak low across southwest South Dakota. Moisture pooling across
western South Dakota pushes MLCAPE to 2000-3000J/KG. Decent cap in
place and weak forcing may limit coverage of convection Wednesday
afternoon. Better chance of thunderstorms Wednesday night as low
level jet increases. Sufficient shear for a few severe
thunderstorms.

Area will remain under flat upper ridge through the end of the
week with above average temperatures. Strong wave topping the
ridge late Saturday/Sunday will allow for some cooling as cold
front moves through. Ridge builds back early next week.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1155 AM MDT Tue Jul 18 2017

Isolated thunderstorms may redevelop late this afternoon and
evening over the Black Hills and portions of the surrounding
plains. VFR conditions expected through Wednesday morning outside
of any thunderstorm development.

&&

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

$$

DISCUSSION...7
AVIATION...13



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