Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 232010

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
210 PM MDT SAT JUL 23 2016

.SHORT TERM...(This Evening Through Sunday Night)
Issued at 158 PM MDT Sat Jul 23 2016

Current surface map shows cold front for Sunday/Sunday night
outside of the Black Hillsmoving through central South Dakota.
Gusty northwest winds across western South Dakota. Winds will
decrease this evening. High pressure builds into the western
Dakotas overnight. Latest runs of HRRR/RAP/NAM indicate some
potential for accas/ts development late tonight as shortwave
passes north of the forecast area. Forecast soundings have
250-500J/KG uncapped CAPE above the increasing 850-700mb theta-e
advection. Have added small pops overnight for portions of
northeast Wyoming into western South Dakota. Isolated
thunderstorms possible over the Black Hills Sunday afternoon/early
evening, otherwise dry conditions across the forecast area.

.LONG TERM...(Monday Through Saturday)
Issued at 158 PM MDT Sat Jul 23 2016

Main fcst challenge facing the extended fcst is timing
of pcpn chances through the period. Upper flow takes on a zonal to
slightly amplified zonal flow. Models show quick moving waves
traveling over cwa...with GFS20 highlighting convective feedback
at the 500hpa level Tuesday evening and again Wednesday evening.
Being able to discern which wave will be responsible for
convection...and to nail down exactly where it will fire are
difficult at best. Looking at 850hpa-700hpa spec humidity...decent
amount of moisture returns with over 10+ g/kg moisture readings
noted...along with impressive 700hpa theta-e ridges developing
with moisture plumes.

Temp wise...first part of week appears to be warmer with zonal
flow...with cooler readings slipping in from middle to end of week
as wrn CONUS ridge builds.


.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 158 PM MDT Sat Jul 23 2016

look for winds to gust as high as 40kts through 23z across the
krap terminal as gusty nw winds will be found on the backside of
an exiting cold front. Winds will begin to diminish
afterwards...with winds under 10 kts for both krap and kgcc
expected by 03z. Look for good vfr conds with unrestricted vsbys
through valid portion of terminal forecast.


.UNR Watches/Warnings/Advisories...
SD...Red Flag Warning until 9 PM MDT this evening for SDZ260>262-264.

WY...Red Flag Warning until 9 PM MDT this evening for WYZ259-297>299.



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