Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 212146

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
546 PM EDT SAT MAY 21 2016

Dry high pressure builds into our region from the Mississippi and
Ohio valleys from Sunday into the start of the week as low pressure
lingers over the mid Atlantic.  A moist southerly flow develops by
mid week and continues into the weekend.


As of 530 PM...Only minor tweaks were made to the last update. The
latest radar imagery shows a broken line of showers and a couple of
sub-severe tstms, extending from the Triad to the southern NC
foothills. This line should track east across the I-77 corridor and
Charlotte metro area early this evening. The latest HRRR and 18z NAM
agree that the activity within this line will struggle to maintain
strength, despite over 1000 J/kg of CAPE and 35-40 kt of bulk shear.
So I expect cloud-to-ground lightning and brief gusty winds to
remain the primary threats. A couple cells in the Yadkin/Davie areas
produced some small hail. Outside this line, just a few isolated
showers can be seen. Later this evening...only a few cells will
linger along/near the TN border, as the rest of the activity wanes.
Lows tonight are forecast to range in the low 50s across the mtns to
upper 50s east.

Sunday...High pressure will build in across the the high
remains centered over the Mississippi River Valley. However...H5
closed low centered over VA will continue to support generally moist
NW flow across the west facing mtn slopes. Clouds and iso showers
will remain in the forecast through Sunday. Elsewhere...dry
conditions with gusty NW winds will be featured in the forecast.
High temps should range from upper 60s within the mtn valleys to mid
to upper 70s across the upper Savannah River Valley.


As of 200 PM Saturday...the early part of next week will be
dominated by an upper low that should move off the Mid-Atlantic
coast Sunday night and Monday, then slowly rotate up to the New
England Coast on Tuesday. The western Carolinas will be under the N
flow part of the circulation into Tuesday, so other than some
lingering showers on the TN border Sunday evening, it should be dry.
The plume of better moisture rotating around the upper low is
expected to be just east of the fcst area on Monday. A few showers
may nick part of the NW Piedmont on Monday as some of the lingering
instability underneath the mid-level cool pool will be close by.
After that, think it should be dry as the low moves away Tuesday and
a flattening upper ridge builds in from the west Tuesday night.
Temps should moderate through the period...back to just below normal
on Monday...and then a few degrees above normal on Tuesday.


As of 235 PM Saturday, 500mb flow has a ridge axis from Mobile Al
to KY on Wednesday with surface high pressure shifting to the east
and off the east coast.  Moisture will be increasing slowly from the
west on south to southwesterly low level flow. Instability is rather
low Wed PM with 600 CAPE near Fontana Lake on the GFS model and
lower on ECMWF.  Moisture and instability will increase Thursday
into Friday as the much higher CAPEs remain near and west of
Mississippi River.  CAPE of 1000 to 1500 across our area Thursday PM
and even a bit higher Friday PM on GFS. Best CAPE on ECMWF on Thurs
PM with around 1600 late day.  Not much change in grids from
previous forecast. Low level flow becomes more SE going into next
weekend as ridge will be centered off the mid Atlantic Coast. This
would introduce an upslope component.

Max Temps a few degrees above normal with Highs in the 80s for all
elevations below 2500 feet. Mins mostly in the 60s.


At KCLT and elsewhere east of the 1730z...low ceilings
across the foothills and Piedmont were finally showing signs of
dissipating. However...ceiling may linger for another or two before
becoming VFR across KCLT...KGSP...KGMU. Showers have developed along
the east facing slopes...perfectly timed and located to latest
forecast. This band should strengthen into thunderstorms as steer
flow transports the storms east. I will forecast TSRA at KHKY
between 19z-21z and KCLT 20z-22z. Elsewhere I will highlight with
VCSH or VCTS. Winds will favor a SW wind during the afternoon...then
NW with the passage of the boundary. VFR with gusty NW winds during
the daylight hours on Sunday.

KAVL...convection will remain close to the terminal this
afternoon...then dry out. Wet soil will favor a period of IFR late
tonight...I will highlight with a TEMPO from 5z-10z. Winds will
strengthen from 340 degrees and gusts to 25 kts.

Outlook: Conditions should gradually dry out Sunday and Monday. AFTN
showers and TSTM chances may return on Wednesday.

Confidence Table...

            21-03z        03-09Z        09-15Z        15-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High  96%     Med   63%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High 100%     High 100%

The percentage reflects the number of guidance members agreeing
with the schedule TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:




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