238
FXUS62 KGSP 130502
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
102 AM EDT Tue Aug 13 2024

.SYNOPSIS...
Dry high pressure gradually builds in from the north through
Thursday, pushing a stalled front further south of the area. The
high will drift east off the East Coast Friday, as a cold front
approaches from the west over the weekend. The front will bring
a return of better chances of shower and thunderstorms.

&&

.NEAR TERM /THROUGH TODAY/...
As of 100 AM EDT Tuesday: Main change needed was adding slight
chance PoPs where isolated showers are located this morning, along
the southern Blue Ridge Escarpment and the northern NC Foothills.
The 00Z HRRR shows convection gradually increasing in coverage over
the next few hours so maintained chance PoPs through daybreak.
Otherwise, the forecast remains on track.

A quiet night is planned through 4 or 5 AM, with some mountain
valley fog and enough high clouds to keep temps a few degrees above
climo. The situation gets more interesting after this time as a weak
wave is expected to drop down in the broad eastern mid/upper trof
toward daybreak. At the same time, the low level flow will come back
around from the south, providing some weak upslope near the Blue
Ridge. Some of the CAMs begin to respond near the Escarpment right
around daybreak, but all of the CAMs show unusual early initiation
near/east of the Escarpment. Precip probs start ramping up
accordingly and then fan out from there through the early afternoon.
Relatively strong mid/upper flow for this area for mid-August will
move overhead in the afternoon, elongating hodographs and pushing
the deep layer shear into the 40-45 kt range. If not for relatively
warm mid levels that keep lapse rates and sfc-based CAPE modest
(like maybe 1500-2000 J/kg at best), we might be in business.
However, because of those limiting factors, the severe weather
potential might be held in check for the afternoon. Can`t argue with
the Marginal Risk on the Day 2 Outlook from SPC and will watch for
the changes. We will also have to mind the potential for training
storms, given the recent rainfall. High temps should have quite the
gradient SW-to-NE because of high pressure bridging over the central
Appalachians by afternoon, which will keep highs below normal over
the northwest Piedmont, and near normal over northeast Georgia.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
As of 226 PM EDT Monday: The short term forecast picks up tomorrow
night with flat upper ridging extending from the Desert Southwest to
the Lower Mississippi Valley. Broad and perturbed northern stream
flow will be draped on the poleward side of the ridge from the
central Rockies to the Mid-Atlantic. A shortwave trough embedded
within broad northwest flow is progged to be located over the
Appalachians tomorrow night with a few showers and thunderstorms
possibly lingering into the early evening hours. This activity
should be short lived, however, as the progressive nature should
shift any tailing storms into the Midlands. Thereafter, dry air is
forecast to filter into the region from the northeast and will bring
an end to most diurnal convection. The one exception will be over
the mountains were a handful of isolated to scattered showers will
be possible both Wednesday and Thursday. Temperatures will be below
average with highs in the low to mid 80s and lows in the low to
upper 60s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 246 PM Monday...Heading into late week, the overall synoptic
pattern will remain relatively unchanged with several shortwave
troughs embedded in northern stream flow spilling over the southern
US subtropical ridge. A rather well defined trough is progged to
approach the Appalachians on Friday with an associated cold front
sweeping into the area on Saturday. This will bring an uptick in
PoPs with at least scattered to potentially numerous showers and
storms expected along and ahead of the frontal boundary. Guidance
diverges thereafter with respect to the eastward progression of the
frontal boundary and whether it clears the area or stalls. This is
well depicted in ensemble clustering with three distinct camps
apparent. Will thus keep the forecast in line with the national
model blend until better agreement is realized. Either way, a
northwest flow regime will likely remain entrenched over the area
which will keep temperatures in line with climatology, if not a tick
or two below.

&&

.AVIATION /05Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Interesting TAF period expected this evening.
KAVL can expect another round of mountain valley fog / low stratus
toward dawn, but the bigger story will be predawn showers and
thunder, which the hi-res guidance depicts breaking out as early
as 06-08z across the Blue Ridge Escarpment, then expanding eastward
through and after dawn, continuing well into the afternoon. PROB30s
were maintained at all TAF sites, along with VCSH.  Prevailing MVFR
was added to the Upstate sites before dawn and into the mid-morning
hours, as the latest guidance has doubled down on the appearance of
a deck of upslope stratocu in response to deepening moisture there.

Outlook: Expect generally isolated to scattered diurnal convection
across the region each day through the work week. Patchy fog and
low stratus will be possible each night in the mountain valleys
and in locations that receive rainfall.

&&

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

&&

$$

SYNOPSIS...ARK
NEAR TERM...AR/MPR/PM
SHORT TERM...TW
LONG TERM...TW
AVIATION...MPR