Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 210529

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1129 PM MDT WED JUL 20 2016

.SHORT TERM...(This Evening Through Thursday Night)
Issued at 525 PM MDT Wed Jul 20 2016

mean central conus ridge will remain in place in the period as a
ridge topping impulse advects on its northern periphery. This
impulse will support a lee side low across the fa tonight, with an
associated sfc cool front. Still some potential for an isolated ts
across far nw sd along this feature this evening if capping can be
overcome. If a cell does develop, shear/cape values suggest
upscale growth into a severe cell is possible although very low
chances for this. Other high based jet streak forced convection is
possible late this evening and early thur morning across far nw
sd. Have added a low chance pop for this. Cool front will shift
south across the fa tonight, with breezy n/ne winds developing on
the sd plains.

Thur...sfc trough will stall over or just south of the fa, with
another impulse ejecting into the region per sw flow. Lingering ll
moisture over scentral sd may allow for afternoon, evening
convection there, esp if cells develop over western NE. A few
isold cells will also be possible in the central and southern BH/s
where eddy convergence and lingering ll moisture in a cond
unstable atm will be in place thu afternoon. Slightly cooler conds
can be expected as the thermal ridge shifts east, with 90s most
places and a few 100s on the SD plains. Will cont the ex heat
warning in the far east.

.LONG TERM...(Friday Through Wednesday)
Issued at 525 PM MDT Wed Jul 20 2016

By Friday, shortwave over the Pacific NW will begin to
approach the region with a 1007mb low over S-Central Montana. The
low deepens considerably during the day, and by 00z is down to 997mb
in Southeast Montana. Return flow ahead of the deepening low will
result in strong southerly winds across the CWA. Model soundings
show high LCLs and inverted-V soundings due to deep mixing across
most of the CWA except for S-Central SD, where the cap remains in
place. Regarding convection Friday, mid range guidance suggests
storms developing ahead of a dryline/surface trough during the
afternoon in Western SD and Northeastern WY. 0-6km shear will be in
the 35-40kt range and supportive of organized convection, including
supercells. Instability will be limited to around 500-1000J/Kg,
mainly due to the deep mixing expected. Expect main threat with
storms to be strong wind gusts, though some of the stronger storms
could produce large hail.

Cold front comes through late Friday night/early Saturday morning
and flow aloft through most of the long term period remains zonal.
Small shortwaves within the flow will affect the region next week
and bring chances for showers and thunderstorms. Temperatures will
be near seasonal averages.


.AVIATION...(For the 06Z TAFS Through 06Z Thursday Night)
Issued At 1124 PM MDT Wed Jul 20 2016

Isolated thunderstorms are possible across far northwest SD
overnight and then over south central SD later Thursday afternoon
and early evening. Any storm could produce brief MVFR CIGS/VSBYS.
Otherwise, VFR conditions will prevail.


.UNR Watches/Warnings/Advisories...
SD...Excessive Heat Warning until 6 PM MDT /7 PM CDT/ Friday for



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