Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 261035

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
635 AM EDT Fri May 26 2017

Weak, dry high pressure will settle into the region today, then
drift east off the Florida coast by Saturday. Moisture and unstable
conditions will return to the region over the weekend, as a cold
front slowly approaches from the northwest.


As of 635 AM EDT: Sat pix show NW flow stratocu beginning to
dissipate this morning. Expect this trend to continue through the
morning. Any lingering mountain valley fog will dissipate as well.
Although gusty winds will continue across the mountains, any strong
gusts will be limited to locations above 5000 feet.

Heights rise today as upper ridging builds into the area then
flattens tonight. A relatively tight pressure gradient and lee
trough this morning slowly relaxes this afternoon. Still, expect
gusts to linger across the mountains and low end gusts develop with
mixing elsewhere. However, winds will not be as strong as Thursday.
Winds will taper off this evening as high pressure builds in and lee
trough dissipates. Cirrus will move in from the west today and
thicken overnight. Highs will be near or slightly below normal with
lows up to 5 degrees above normal.


As of 300 AM Friday: a flat upper ridge axis will slowly cross the
forecast area on Saturday, shifting to the East Coast on Sunday. The
flat flow will keep a swath of decent bulk shear across the Midwest
to the southern Appalachians. At the surface, a relatively flat
Bermuda High will bring warmer and more humid air back north into
the region, while a zonally oriented front stalls out across the
Tennessee Valley to the central Appalachians. Guidance is in good
agreement on moderate to high instability along and south of this
front. This combined with the shear and deep layer westerly flow may
support one or two rounds of organized convection, with the CWFA in
the track. However, models are not in agreement on the details, so
PoPs were not changed much from previous forecast. Saturday looks
fairly capped thru at least early to mid-aftn, but the highest peaks
of the NC mountains will probably see deeper convection, so chance
PoPs will be carried there. Highs will be a couple categories above
normal, mainly in the upper 80s across the Piedmont.

Saturday night thru Sunday night, PoPs should gradually increase, as
the upper ridge shifts east and CIN weakens. The NAMnest and GFS
hint at a weakening MCS pushing into the NC mountains before
daybreak Sunday. However, the better chance of an MCS pushing into
and possibly crossing the mountains will likely be Sunday aftn/eve.
At the very least, strong convection may develop across the area
with less CIN and still plenty of CAPE in the 2000-3000 J/kg range.
PoPs ramp up to likely in the west and low-end chc in the far east.
Temps will continue to be above normal.


As of 330 AM EDT Friday: not much change to the medium range with
this morning`s forecast package. A large upper low will slowly drift
east just north of the Great Lakes, keeping a trough axis across the
Ohio Valley. A cold front should push thru the area on Monday,
bringing another day with diurnal convective chances. Models seem to
be in a little better agreement on pushing the front completely thru
the area and stalling to our south for Tuesday. Wednesday also looks
relatively quiet with temps near normal.

The upper low will wobble to the north and allow a subtropical ridge
to start building back in across the Southeast states for Thursday.
This will lift the front back north across the region as a warm
front and bring back moisture and instability with chc PoPs


At KCLT and elsewhere: VFR conditions will continue through the
period. Northwest upslope flow stratocu and any mountain valley fog
will dissipate this morning. Cirrus moves in from the west and
thicken through the period. W to SW winds continue outside of the
mountains and NW wind at KAVL. Expect low end gusts to develop with
mixing and continue through the afternoon. Winds taper off and
become light this evening.

Outlook: Continued VFR into the day on Saturday. Thunderstorms and
associated restrictions may develop across NC Saturday afternoon,
but will be more likely Sunday. Scattered thunderstorms and
associated restrictions are expected Monday and Tuesday.

Confidence Table...

            10-16Z        16-22Z        22-04Z        04-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     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 scheduled 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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