Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 241847
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
247 PM EDT TUE MAY 24 2016
High pressure will prevail over the Southeast most of this week. A
moist southerly flow will develop in mid week, which will
lead to warmer temperatures and mainly afternoon chances of showers
and thunderstorms each day through Friday.
.NEAR TERM /THROUGH WEDNESDAY/...
As of 230 PM EDT Tuesday: Upper ridging will continue to build into
the area through the short term with corresponding height increases,
naturally resulting in temperature increases as well. Southerly,
albeit weak, flow around the periphery of the western Atlantic
surface high will continue to bring moisture into the area, so most
notably we will see an increase in overnight low temperatures
tonight, a good 5-10 degrees warmer than what we saw this morning.
Highs Wednesday will climb a couple of degrees warmer than those
today (currently 79 at GSP at AFD time).
However, a weak shortwave will lift over the ridge tonight into
early tomorrow, tracking up the Ohio Valley. This will bring enough
deep-layer moisture and weak lift for slight to low chances of
thunder across the mountains Wednesday afternoon, with of course an
increase in afternoon Cu. sbCAPE is limited, generally less than 500
J/kg with slightly higher amounts localized over the peaks where
topography comes into play. Main threat would be with cloud-to-
ground lightning, and without even being in General Thunder for the
Day2 SPC Outlook, any other threats would be very minor.
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 230 PM Tuesday: The short term fcst period initializes
Wednesday evening amidst a broad, yet slowly weakening upper ridge
centered over the southeast states, while a large H5 trof digs over
the desert southwest. At the surface, high pressure over the
western Atlantic will continue to promote weak southerly waa across
the southern Appalachians as cyclogenesis gets underway ahead of the
a fore mentioned H5 trof atop western KS/OK/TX. Closer to home, a
weak shortwave impulse riding through the apex of the upper ridge
combined with ample llv destabilization will have resulted in
iso/sct shra and tsra over the NC high terrain by 00z Wednesday.
With that, profiles are indicative of pulse type convection amidst
weak flow throughout the column and ever improving deep layer
moisture. Pwats aren`t all that impressive, generally 1.25-1.5
inches at best, however given the weak flow and modestly elevated
lcls, think the primary convective concern will be wet microbursts
as well as isolated flash flooding amidst any slow moving
Moving along through the period, not much change synoptically on
Thursday and Friday as the subtropical ridge persists over the
southeast CONUS, with continued southerly waa at the surface.
Precipitation chances remain elevated over the high terrain where
any inhibition will be weakest each day allowing for more widespread
initiation with heating. As for the remainder of northeast GA and
the western Carolinas, precipitation chances will be lower through
the period relative to the mtns given proximity to the ridge center,
however said chances do increase with time as guidance favors
generally unstable and uncapped profiles both Thursday/Friday with
improving pwats and weak flow aloft. All said, the threat for pulse
convection induced flash flooding will increase over the NC mtns
given degrading antecedent conditions each day. Antecedent
conditions over the piedmont regions will also be degraded with
time, however relatively less than that of the mtns, yet still
presenting a non zero threat for hydro issues. Lastly, guidance
continues to indicate, although with some discontinuity regarding
the details, that a weak tropical low is to form/strengthen over the
western Atlantic and eventually approach the southeast coast on
Friday evening. Although any specific impacts from this feature are
beyond the scope of this fcst time frame, it should be noted that
flow over the southeast does look to back as the system approaches.
This could yield improving upslope flow conditions along the blue
ridge for Friday.
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 2 PM Tuesday: An upper ridge east of the Mississippi and
broad upper trough to the west on all models at 00z Saturday. The
ridge broadens over the weekend and into the first half of next week
as tropical moisture moves toward the Carolinas from the Bahamas.
Diurnal convection is expected each PM but so much depends on where
this tropical moisture ends up. The GFS is still bringing the weak
low more to the west than the ECMWF. The GFS gives the western
Carolinas and NE GA tropical rains late Sunday into the first half
of the week while the ECMWF has us mostly dry. National guidance
remains of opinion that organized tropical development has low
chance. 7 day rain total guidance are now showing upslope
enhancement rainfall of at least 1.5 along eastern Escarpment. GFS
now takes the weak tropical low up I-26 from Sunday evening to the
NC Mtns on Tuesday. Whenever there is a named TC, the first one
will be named ALEX and secondly BONNIE. That may take a while though.
Low level wind flow will depend greatly on the track of the
counterclockwise circulation of low pressure. The ECMWF has mostly
light and variable on Saturday then east and NE Sunday into Tuesday
with a projected low center crossing the NC coast. ECMWF and GFS has
less than 500 CAPE Saturday PM. Instability generally 1000 to 1500
CAPE are forecast by the models each PM.
Max temps well into the 80s on Saturday, Gradually cooling off to
70s Mtns and 80 to 84 foothills and piedmont Mon and Tuesday due to
the increased clouds and tropical saturation. MINs in the 60s.
.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: VFR through the period for the TAF sites,
though cannot rule out some brief fog in the southwest mountain
valleys toward sunrise Wednesday. Generally light SW winds (5kt or
less) through the period, near calm overnight. Will see intermittent
cirrus passing through the area, but otherwise SKC until Wednesday
midday when some low VFR Cu should develop across the area.
Outlook: Mainly VFR conditions will prevail through the week, but
patchy morning fog chance continues at KAVL. Scattered afternoon
SHRA/TSRA may return Wednesday afternoon, with daily coverage
increasing Thursday and Friday.
18-24Z 00-06Z 06-12Z 12-18Z
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 schedule TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link: