Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 240247

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

Issued at 843 PM MDT Sat Jul 23 2016

Hi res models still suggesting small chance of pops late tonight
into Sunday upper wave over ern UT/wrn CO tracks newd.
Have expanded pops for late tonight as well as carry pops into
Sunday morning. Rest of fcst unchanged.


.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 00Z TAFS Through 00Z Sunday Evening)
Issued At 407 PM MDT Sat Jul 23 2016

Gusty NW winds will diminish rapidly around sunset. VFR conditions
will continue through midnight. Isolated -tsra possible late
tonight/early morning with MVFR vsbys possible. Otherwise...VFR
conditions will continue.


.UNR Watches/Warnings/Advisories...


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