Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 300930
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
330 AM MDT Tue May 30 2017

.DISCUSSION...(Today Through Monday)
Issued at 329 AM MDT Tue May 30 2017

Broad upper low continues to spin just south of the Hudson Bay with
cyclonic flow over the Great Lakes/Midwest...and northwest flow on
the backside of the low across the Dakotas. A high amplitude ridge
sits across the western CONUS ahead of the next incoming trough.
Skies are clear across the region with temperatures dropping into
the 30s to mid 40s. Some locations across the western South Dakota
plains have dropped into the upper 30s...so will continue with Frost
Advisory headlines. Temps will reach the mid 60s to mid 70s today as
surface high pressure sits across the northern plains. Surface high
will push east of the CWA tonight into Wednesday morning with return
flow setting up and warmer air advecting back in from the southeast.
Overall Wednesday looks to be a dry day with highs reaching the 70s
to lower 80s. SBCAPE is expected to reach 1000-1800 J/KG along an
area from the Black Hills to southwest South Dakota. If the cap can
be broken...it looks like isolated thunderstorms could develop in
the late afternoon/evening time frame. Shear is decent enough for a
supercell to develop, so could see a couple storms become severe
with large hail and damaging winds. However widespread severe storms
are not expected given the expected isolated coverage.

In the long term...Upper ridging will remain across the western to
central CONUS through the end of the work week as the overall upper
pattern is slow to change. Isolated thunderstorms will be possible
Thursday mainly over the Black Hills and portions of the northeast
Wyoming plains. Models show the cap too strong for convection over
the western South Dakota plains. Temps will be 5 to 10 degrees
warmer than Wednesday...with some locations nearing the 90 degree
mark. A shortwave is progged to cross the northern plains Friday as
a surface low develops near the Dakotas. Will see better chances for
storm Friday. Shear doesn`t support supercell development except
perhaps a little along the Nebraska border. A cool front will cross
the area late Friday bringing near seasonal temperatures and drier
weather for the weekend.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Wednesday Morning)
Issued At 329 AM MDT Tue May 30 2017

VFR conditions will continue through the period with mostly clear
skies.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Frost Advisory until 8 AM MDT this morning for SDZ001-002-
     012>014-031-073.

WY...None.
&&

$$

DISCUSSION...13
AVIATION...7



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