Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 270728

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
328 AM EDT Tue Jun 27 2017

A weak upper level system will bring a few showers to western
NC today, but otherwise dry and cooler weather will continue through
Wednesday. High pressure moves off the East Coast on Thursday with
warm and moist air moving north from the Gulf through next weekend.
This brings back the daily chance of afternoon and evening showers
and thunderstorms through the weekend.


As of 320 AM Tuesday: the near-term fcst is mostly dry with notably
cool temps for late June. Broad upper-lvl trofing will remain over the
Eastern CONUS thru the period with ridging over the west. An embedded
shortwave will round the backside of the trof and move over the fcst
area later this morning/afternoon. It will lift to the NE by the end
of the period early Wed as heights begin to recover over the southeast.
At the sfc, Canadian high pressure will steadily slide SE today and
tonight and should be centered just to our north by early Wed. As the
upper shortwave approaches aloft, a weak cold front will move thru the
CWFA later this morning bringing some slight chances for precip, mostly
over the higher terrain. The latest model soundings are looking pretty
dry and lack any notable instability as the front moves thru. The only
things going for it will be the favorable upper-lvl support from the
shortwave and some better/deeper moisture upstream that could allow
showers to translate across the NC/TENN border and into the CWFA.
With the sfc high building in behind the front, the afternoon should
see skies clearing and high temps well below normal for late June,
especially over the northern zones.


As of 230 AM EDT Tuesday: Weak northwest flow aloft will be in place
at the start of the short term in the wake of the shortwave trough
axis. Cool high pressure will be centered over the Appalachians on
Wednesday, leading to another day of below-normal temperatures. The
high will move offshore late in the day, with moist return flow
ensuing. A shortwave and associated moisture will drift up from the
Gulf, and weak isentropic upglide ahead of this will bring a return
of diurnally-driven thunderstorms to the mountains and portions of
the Upper Savannah Valley on Thursday. While temperatures will
remain below seasonal normals, the increase in low level moisture
will bring humidity levels up with a return to more muggy
conditions. This Gulf moisture advection will continue to propagate
east and toward the Carolinas as the surface high pushes farther out
to sea. Meanwhile a stronger shortwave will push out of the Canadian
Rockies underneath a longwave trough over central Canada. This will
push a weak front through the center of the country which will be
approaching the Ohio Valley toward the end of the period. By
Thursday night, should see lows pretty much near seasonal normals
with dewpoints continuing to rise.


As of 300 AM EDT Tuesday: Warm moist advection will continue as we
start the period with southerly flow around the western periphery
of an Atlantic high, with surface low pressure working its way
across the Great Lakes and an attendant front pushing toward the
Ohio Valley. Should see a fairly diurnal trend to convection on
Friday with highs still a few degrees below seasonal normals, but as
the front approaches on Saturday, pops trend up to likely in the
mountains with continued increasing dewpoints resulting in a return
to above-normal overnight lows (with highs still hovering a couple
of degrees below). The front will become quasi-stationary, hanging
around the area through the weekend, with another enhancement to
diurnal pops on Sunday. Minimal shear associated with the upper
trough will be in place so could see some slight organization to the
convection, but generally expect pulse convection, with sbCAPES
generally between 1500-2000 J/kg (certainly not unusual for this
time of year). Do not see a significant reason for increased severe
potential other than the fact that convection itself, severe or not,
may be slightly more widespread. The front pushes south by Monday
but as an upper ridge builds into the Lower Mississippi Valley, it
will lift the SW portion of the front back north as it connects with
yet another shortwave diving through the Upper Midwest, so expect
near-normal temperatures and a continued enhancement in diurnal pops
through the pend of the period.


At KCLT and elsewhere: expect VFR conditions to prevail thru the
taf period. Broad sfc high pressure will remain centered to our
NW and slide closer to the fcst area over the next 24 hours. Winds
will be calm to light and vrb overnight, and then shift to a NLY
and then NELY direction and pick up in speed as a reinforcing, but
mostly dry cold front, moves over the area. Isolated SHRA are possible
across Western NC with this front between daybreak and midday, however
the only site that could be impacted is KAVL, and it is not expected
to see any restrictions.

Outlook: light winds and VFR conditions should continue through
mid week. Moist, southerly return flow will develop around the
offshore ridge on Thursday. As a result, typical summertime conditions
will return by the end of the work week, with mainly late afternoon/
evening SHRA/TSRA causing possible restrictions.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
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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