Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 182031
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
231 PM MDT THU AUG 18 2016

.SHORT TERM...(This Evening Through Friday Night)
Issued at 229 PM MDT Thu Aug 18 2016

Water vapor imagery shows cyclonic flow across cntrl Canada into the
nrn Plains...with zonal flow across the cntrl Plains. A series of
weak upper waves are crossing WY/SD at this time...while a strong
wave is diving into the nrn Rockies. Surface analysis shows a cold
front across nrn Neb into scntrl SD with temps in the mid 90s ahead
of it at KICR...and mid 80s behind it at KPHP. A second cold front
is stretching from nw SD into ne WY with 70s across the far wrn SD
plains and upper 50s toward KGCC. Regional radar mosaic showing
showers stretching across nw SD into ne WY along the second
front...and storms developing along the front farther south. Storms
will continue to fire into scntrl SD this afternoon/evening as the
front progresses southeastward. Cape ranging from 1-3kJ/kg across
scntrl SD and effective bulk shear of 30-40kt will support some
strong to severe storms...but that threat will quickly end toward
the mid evening as cooler air pushes in. The secondary front will
push through into wrn SD tonight into cntrl SD Friday. Band of
precip associated this boundary continue eastward into wrn SD...then
into scntrl SD overnight. Behind the boundary...models are showing a
lull in precip before the aformentioned stronger wave pushes in from
the west. This wave will bring a band of precip across the CWA
during the day Friday which could bring half an inch or so of QPF by
Fri evening. Temps will be much cooler with highs in the upper 50s
to upper 60s across most areas. Precip will clear out from west to
east Fri afternoon and evening. Temps Fri night will drop into the
40s across the plains...and mid to upper 30s across the higher BH.

.LONG TERM...(Saturday Through Thursday)
Issued at 229 PM MDT Thu Aug 18 2016

Progressive fairly amplified flow is expected through the period.
Upper trough will shift into the Great Lakes Saturday into Sunday
as Fall-like surface high moves through the CWA. Temperatures
Saturday will be 10-15F below normal and Sunday 5-10F below.
Transient upper ridge builds in for the first part of next week
with well-defined return flow and warming temperatures. Small TSRA
chances return Tuesday afternoon into the middle of next week as
an upper trough moves across the Rockies into the northern Plains.
As the trough settles in, cooler weather will return for the
second half of next week.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 229 PM MDT Thu Aug 18 2016

Showers and thunderstorms will increase in coverage through the
period with widespread precipitation expected over the area by
late tonight into Friday. Areas IFR/MVFR conditions over northeast
WY will spread across the western South Dakota plains tonight into
Friday.

&&

.UNR Watches/Warnings/Advisories...
SD...None.
WY...None.
&&

$$

SHORT TERM...13
LONG TERM...Helgeson
AVIATION...Helgeson



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