Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 271055
AFDGSP

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

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 640 AM Tuesday: sct mid to high clouds continue to stream across
the region from the west this morning. Temps have bottomed out 1 to 2
categories below climatology for late June, with dewpts below climo as
well. I kept some slight chance PoPs in the fcst over the next 6 to 8
hrs as the weak cold front pushes thru the CWFA, however it`s doubtful
that most locations will see any measurable precip. Otherwise, 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
and 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.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
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.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: expect VFR conditions to prevail thru the
12Z taf period. Broad sfc high pressure will remain centered to our
NW and slide just to our north over the next 24 hours. Winds remain
calm or near calm so far this morning, but should shift to a NLY
and then NELY direction and pick up in speed as a reinforcing cold
front moves over the area. Isolated SHRA are possible across Western
NC with this front over the next 6 to 8 hrs or so, however the only
site that could be impacted is KAVL, and any restrictions are
unlikely.

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...

            11-17Z        17-23Z        23-05Z        05-06Z
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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$
SYNOPSIS...TDP
NEAR TERM...JPT
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...JPT



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