Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 152315
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
515 PM MDT Sun Jul 15 2018

.DISCUSSION...(This Evening Through Sunday)
Issued at 150 PM MDT Sun Jul 15 2018

Main upper trough that brought the cold front through the region
is pushing away across southern Canada, with a southern periphery
shearing impulse supporting waning precip over scentral SD. NW
unsettled flow will remain as small scale upper trough slides
under a building ridge over the NW CONUS. Jet streak associated
with this feature coupled with ejecting impulses will support
chances for TS the next two days as capping remains weak over the
area. Steep mid level lapse rates coupled with positive theta-e
advection, upslope flow, and increased LL SE flow may support an
isolated storm or two tonight, at first over NE WY, then further
east into far western SD by Monday morning. Diurnal heating
coupled with increasing flow, ample LL moisture, and the advancing
impulse will support TS tomorrow afternoon, first over the Black
Hills then over much of NE WY by evening. A couple supercells will
be possible over the Black Hills given SE upslope flow regime,
AOA 2 KJ/KG of CAPE and increasing bulk shear. Given the setup,
felt a severe mention was warranted from the BH SE and over parts
of NE WY, with large hail the main threat. Convection will shift
SE into Mon night with perhaps some elevated ISOLD TS late as the
main impulse advances east. Better coverage for storms expected
Tue as most of the remaining NW CONUS impulse pushes east. Decent
shear values with ample LL moisture will again support a severe
threat, esp from NE WY into scentral SD. Good chances for precip
expected Tue night into Wed for much of the FA as the upper trough
shifts east. Warmer/drier weather expected by the end of the week
as flow becomes less unsettled. Still expect some ISOLD TS at
times though, esp around the Black Hills. Temps are expected to be
seasonal, warmest toward next weekend.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Monday Evening)
Issued At 513 PM MDT Sun Jul 15 2018

Leftover MVFR CIGS in/near the Black Hills will dissipate this
evening leaving mainly VFR conditions through Monday afternoon.
Isolated thunderstorms may develop later tonight over northeast WY
and then spread into western SD Monday with local IFR conditions
in the strongest storms.

&&

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

$$

DISCUSSION...JC
AVIATION...Helgeson



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