Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 270226

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1026 PM EDT Mon Jun 26 2017

A weak upper level system will bring a few showers to western
NC on Tuesday, but otherwise dry and cooler weather continues
through Wednesday.  Cool 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.


1020 PM update: Made adjustments, the best I could, to min temps
tonight. Radiative cooling has outpaced guidance in many locations,
with heat island effect evident from analysis. No source captures
this well so I improvised hourly values and mins based on GLAMP
trends and the current obs. The result is a tad cooler, but
confidence is not exceedingly high.

A broad ulvl trof will dominate the pattern thru the period with a
Canadian sfc high beginning to build in this evening. The upper trof
will become a little more acute as an embedded s/w dives across the
base, this one being appreciably stronger than the one impacting
the Appalachian region now. The best model timing consensus has
this wave reaching the NC mtns around daybreak. Revised PoPs are a
bit lower overall, owing to a drier trend seen in 18z models and
also the paltry nature of moisture profiles. However, it looks
reasonable to expect isolated showers will survive downstream of
the mtns acrs WNC, so the new values are a tad higher there. Due
to the dry llvls and mixing airmass...sbCAPE will be hard to come
by thru the day. The thunder chance appears too small to include in
the fcst. With a sfc high building in behind the upper energy...the
afternoon will see clearing skies. A lower sfc theta-e airmass
builds in and this will hold max temps a couple categories or so
below normal...especially north.


As of 230 PM EDT Monday: The aforementioned upper level trough and
short wave feature will be exiting our forecast area (FA) Tuesday
night. Skies should clear as a subsidence pattern shifts into the
region and high pressure settles in.

The high will bring quiet weather conditions Wednesday, but it will
be on the move. By Wednesday night the high will be off the east
coast, and our flow will gradually start to turn to the south.

The suite of short term guidance remains insistent on allowing some
isentropic upglide to reach about the western half of our FA late
Wednesday night and Thursday morning.

As a result dewpoints will be on the rise, clouds increasing, and
small or chance POPS will be featured in the west, mainly Thursday
afternoon. Our eastern FA should stay dry Thursday. Meanwhile,
SBCapes in the west reach between 1000-1500 J/kg. There appears to
be enough evidence to add thunder in those areas where instability
levels will be on the rise.

Minimum temperatures Tuesday might be darn well comfortable, with
some 40s in the higher terrain, to the upper 50s and lower 60s in
various parts of the piedmont.

From that point forward, the model thermal pattern depicts a gradual
increase, which is noted by the MOS guidance. Therefore, our
temperature forecast will show and upward trend into Thursday.


As of 140 PM EDT Monday: A pattern change will be well underway
by Thursday night with surface high pressure located near Bermuda
going into the start of the weekend with low level southerly flow
developing and continuing for days.  A weak cold front slides south
from the Great Lakes then stalls out near or just north of our area
through the weekend. PM instability increases from not much at all
Thursday evening to around 1000 CAPE Friday evening to just less
than 1500 Sat evening to above 1500 CAPE Sunday evening.  The
greatest coverage of convection expected over the mountains being
closer to the front and better source of moisture and instability.
Coverage to the likely range for portions of the mountains during
the late day hours. Low chance of severe especially if sunshine
creates greater instability in localized areas. Although 925mb level
wind through most of this period will be SW, 850mb wind on Friday is
forecast to be SW then become mostly from the west into early next

Max temps will gradually rise from about a category below normal
Friday to only a degree or two below on Monday. These max temps held
down a bit by cloud cover.  Min temps near normal Friday morning
then 2 to 5 degrees above normal into early next week.


At KCLT and elsewhere: Under a weak pressure pattern winds will
be very light tonight, initially favoring southerly across
the Piedmont. These will shift to NW-N in the early morning
as a reinforcing but mostly dry cold front pushes acrs the
Appalachians. Isolated SHRA are not out of the question across
western NC with this front between daybreak and midday. However,
they are unlikely to have any aviation impact. Winds will remain
N and perhaps even veer NE as high pressure builds in behind the
front during the late aftn.

Outlook: Light winds and VFR conditions should continue through
mid week. Moist, southerly return flow will develop around the
offshore ridge Thursday. As a result typical summertime conditions
will return by week`s end, with mainly late-day SHRA/TSRA causing
ocnl restrictions.

Confidence Table...

            02-08Z        08-14Z        14-20Z        20-00Z
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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