Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 292328
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
728 PM EDT MON AUG 29 2016
A weak tropical system will approach the North Carolina Outer Banks
tonight and tomorrow before moving back out to sea on Wednesday.
A cold front will approach the region from the north Wednesday night
with another tropical system emerging from the Gulf of Mexico on
Thursday. This system is expected to remain just to our south and
move offshore over the weekend.
.NEAR TERM /THROUGH TUESDAY/...
As of 725 PM: Water vapor imagery shows several tropical features in
the western Atlantic and Gulf of Mexico. The GSP forecast area
appears to sit between all of them. A break in the large ridge of
high pressure, from Missouri to Bermuda, was noted off the North
Carolina coast - via aforementioned water vapor imagery.
The threat of convection has diminished with the loss of heating
this evening. Mainly high level clouds will spread west into the
area from the system off the Atlantic coast through the night. There
will be some lower stratocu developing near the blue ridge however.
Patchy dense mountain valley fog should develop again overnight then
dissipate relatively quickly after daybreak in most locations.
On Tuesday, as lower theta e air continues to advect into our
forecast area, any precipitation prospects should be minimal. That
said, best chance will be across the NC mountains, so have retained
minimal PoP there favoring climatologically normal locations.
Despite the clouds, temperatures continue to edge up. We plan to
follow the suite of temperature guide tonight, and then perhaps a
degree or two (above the coolest high temperatures Tuesday).
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 200 pm EDT Monday: By Tuesday evening, tropical depression 8
will be moving northeast of the Outer Banks and well outside of
having any direct impacts on the GSP CWA. Meanwhile, tropical
depression 9 will gradually organize over the Gulf before tracking
across northern Florida late on Thursday. 9 is also not expected to
have direct impacts on the CWA, being too far south and eventually
southeast of the area; at least through Thursday. POPs, though,
will increase Wednesday and Thursday as deep upper trough over the
northeast CONUS with a surface cold front approaches the area on
Wednesday and Thursday with a FROPA expected around 18Z on
Thursday. FROPA will bring a significant chance for showers
Thursday afternoon through Friday morning, with some showers
possible Wednesday afternoon over higher terrain in advance of the
system. Airmass is dryer than recent weeks and we will see CAPE
below 1000 j/kg at most Tuesday and Wednesday afternoons, and precip. amounts
are not expected to be particularly generous. Front is followed by
significantly cooler and dryer conditions leading into the end of
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 210 PM EDT Monday, the medium range fcst picks up at 00Z on
Friday with a positively tilted upper trof axis passing to our
north and a very steep upper ridge spreading over the central
CONUS. In addition, a tropical disturbance that is currently
located north of Western Cuba is expected to be moving across
Northern Florida by early Friday. As we move into the weekend,
the trof axis will translate offshore while the upper ridge
spreads farther east eventually encompassing the eastern half
of the CONUS.
At the sfc, a tropical low associated with the upper lvl disturbance
mentioned above is expected to be moving over North Central Florida
and then off the southeast coast on Saturday. The long range models
appear more consistent with the system overall, however the ECMWF is
still quite a bit faster moving the low off the southeast coast over
the weekend compared to the GFS. The Canadian model remains the farthest
west and slowest wrt the storm track. Regardless, by early Sunday all
the models agree that the low will be moving well offshore and Canadian
high pressure will spread back over the region and persist into early
next week. As for the sensible fcst, the guidance has been trending
drier overall with most of the precip associated with the tropical
system likely remaining to our south and east. The best chances for
widespread precip will be early Friday over the SE zones with only
scattered slight chance POPs for Saturday. The rest of the period
should be dry. Flooding should not be a concern over the CWFA with
total QPF on Friday expected to be less than 0.5 inches. Temps will
start out near or slightly below climatology on Friday and remain
in that range for the rest of the period.
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
At KCLT: Mainly high level cloudiness will move in from the east
through the night. Cannot rule out a few lower VFR clouds from time
to time, but no lower cigs are expected. FEW VFR CU develops after
daybreak and becomes SCT for the afternoon with continued high level
clouds. ENE to NE winds continue through the period diminishing
overnight then picking up in speed during the morning and continuing
through the day.
Elsewhere: Non-mountain sites will be similar to KCLT, but could see
more in the way of low VFR near or just after daybreak. KAVL should
see another round of LIFR and possibly VLIFR fog and clouds by
daybreak with a relatively quick return to VFR after daybreak. Any
convection will be limited to the mountains, but chance to low to
include in the TAF for now.
Outlook: We will remain in-between many systems surrounding the
sites Wednesday, with convection tied into mostly higher terrain.
Mountain valley fog possible again. A cold front will enter the
region Thursday and Thursday night, with a potential uptick in
showers and thunderstorms. Depending on the track of any of the
various tropical features, we might be favoring a drier weekend
23-05Z 05-11Z 11-17Z 17-18Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 100% High 100% Low 39% 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: