Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 250546
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
146 AM EDT WED MAY 25 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 TODAY/...
As of 145 AM: After clearing skies, mid clouds are on the increase
outside of the mountains due to moisture trapped under a subsidence
inversion. High clouds will spread into the mountains from the west.
The increasing mountain clouds should keep most valley fog at bay
but with the best chance of fog in the southwest mountain valleys.
Weak southerly flow around the periphery of the western Atlantic
surface high will continue to bring moisture into the area through
Wednesday. This will help push max temps a couple of degrees warmer
on Wednesday afternoon. Enough deep-layer moisture and weak lift
will also arise over the mountains for slight to low chances of
thunder Wednesday afternoon. Given the increase in afternoon
cumulus, SBCAPE should be limited with generally less than 500 J/kg
with slightly higher amounts localized over the peaks. The main
threat would be with cloud-to-ground lightning.
.SHORT TERM /TONIGHT 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 /06Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: mid clouds trapped under a subsidence
inversion are spreading out across the area outside of the
mountains. Expect the BKN mid clouds to scatter out near daybreak as
cirrus moves in from the west. Cannot rule out some mountain valley
fog, but chance will increase if the high clouds move in slower than
expected. Expect cumulus to develop with heating after daybreak.
Isolated to scattered mountain ridge top convection will develop
through the afternoon then taper off during the evening. Confidence
too low for any mention at KAVL or the other airfields. SW winds
will increase in speed through the day, then taper off during the
Outlook: Mainly VFR conditions will prevail through the period, but
patchy morning fog chances continue at KAVL. Scattered afternoon
SHRA/TSRA coverage will increase Thursday through Friday - with more
uncertainty on Sat.
05-11Z 11-17Z 17-23Z 23-00Z
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 schedule TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link: