295
FXUS62 KGSP 080739
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
339 AM EDT Wed May 8 2024

.SYNOPSIS...
A summerlike weather pattern lingers through mid-week leading to
mainly diurnal showers and thunderstorms and above normal
temperatures. Showers and thunderstorm activity will become more
numerous ahead of a strong cold front tonight into Thursday, with
severe storms possible. The cold front pushes east early Friday
morning but another system approaching out of the south may bring
shower and thunderstorm chances back again on Friday. Drier
conditions and below normal temperatures return just in time for the
weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 330 AM EDT Wednesday: Dry conditions continue across most of
the forecast area this morning, although a few isolated showers are
tracking east across the southwest NC mtns and NE GA. Shower
activity is expected to gradually blossom through mid-morning,
especially across the NC mtns and Foothills, and isolated embedded
thunder cannot be entirely ruled out. Some activity may push all the
way into the NC Piedmont and northern SC. Have the highest PoPs
confined to the western half of the forecast area, with lower PoPs
elsewhere. Thick upper cloud cover continues across the eastern half
of the area this morning, with scattered to broken mid to high level
cloud cover across the western half of the area. Cloud cover may
limit fog formation somewhat across the NC mtns and Foothills
through daybreak. Lows this morning will end up around 15 degrees
above climo thanks to cloud cover and SW`ly flow.

Upper ridging will remain over the Southeast this morning before
pushing east this afternoon. A vort lobe embedded within the upper
flow will track overhead western NC this afternoon and early
evening, leading to another round of scattered shower and
thunderstorm development. Coverage is expected across mainly western
North Carolina, although some convection may spill into the eastern
SC Upstate. The HRRR shows better coverage of diurnal storms today
while the NAMNest shows more isolated coverage. Thus, capped PoPs to
low-end likely across much of western NC for today. SW`ly flow will
lead to the continued influx of Gulf moisture across the region
today, allowing dewpoints to climb back into the mid 60s and lower
70s east of the mtns. Plentiful low-level moisture combined with 30-
40 kts of deep shear and SBCAPE values from 2,000-3,000 J/kg during
peak heating, will allow any storms that develop to become strong to
severe. The main hazards with any severe storms that develop will be
large hail and damaging wind gusts. An isolated tornado or two
cannot be entirely ruled out, but the limiting factor will be 0-1 km
shear generally being less than 20 kts. So, the tornado threat looks
low today, but certainly not zero. With all of this in mind, The Day
1 SPC Severe Wx Outlook expansion of the Slight Risk (across most of
the forecast area) and addition of and Enhanced Risk ( across the
western NC mtns, mainly along the southern and central NC/TN border)
seems reasonable. High temperatures this afternoon are expected to
be the warmest of the week, climbing into the mid to upper 80s in
the mtn valleys and east of the mtns. Areas near the Charlotte Metro
may even see highs reach the lower 90s! Thus, it will be another
humid day with highs remaining around 9-12 degrees above climo.

Meanwhile, a strong cold front will continue to creep eastward
through this evening before pushing into the TN Valley overnight.
So, another round of overnight convection may be in order. However,
confidence on convection for tonight remains low as the HRRR and RAP
show widespread convection while the NAM and NAMNest only shows
isolated activity over the western half of the forecast area. With
CAMs not in good agreement, capped PoPs to low-end likely overnight
across the NC mtns overnight, with chance PoPs elsewhere. If
convection develops, the strong to severe storm threat would return
overnight. The WPC Excessive Rainfall Outlook has the western zones
in a Slight Risk for excessive rainfall, with a Marginal Risk across
the eastern zones today into tonight. The flash flood threat would
be more of a concern overnight if convection develops. Lows tonight
should remain around 13-15 degrees below climo.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 255 am EDT Wednesday: Pre-frontal, organized strong-to-severe
convection is likely to be ongoing in or very close to the forecast
area at the start of the period, with damaging downburst winds and
possibly brief, isolated tornadoes being of concern. How the
environment evolves beyond the morning is subject to a great deal of
uncertainty at this point. With surface front expected to be
west-through-north of the area through the day, low level moisture
will be more than adequate for diurnal destabilization. However, the
magnitude of insolation/heating depends upon how quickly morning
convection is able to clear the area, how quickly clouds are able to
thin (if at all), and how quickly any lingering cold-pool air mass
is the air mass is able to modify. Convection-allowing model
guidance is virtually unanimous in suggesting that the atmosphere
will be unable to recover sufficiently to support afternoon
redevelopment of convection. If a few storms are able to initiate in
the afternoon, deep layer shear of around 50 kts will support
organized convective structures, with any severe storm threat
dependent upon how much instability is realized.

The frontal zone is expected to sag slowly southeast across the
region Thu night and Friday...and won`t pick up much speed until a
short wave trough digs from the southern Appalachians to the
Carolina coast during the day Friday. As such, the front may not be
able to completely clear our area before diurnal destabilization
occurs. A consensus of short term guidance suggests scattered
convection will develop along/south of the I-85 corridor Fri
afternoon. Once again, there is considerable uncertainty as to how
much instability will be available Fri afternoon, but deep layer
shear is expected to be very strong, so at least a marginal severe
storm threat could evolve. The front is expected to finally push
southeast of the area Fri evening, allowing cooler and much drier
air to filter into the area. In fact, min temps Sat morning are
expected to end up a category or so below normal.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 315 am EDT Wednesday: A broad upper trough is expected to
progress across the East through the weekend, with dry air/pleasant
surface dewpoints supporting wide diurnal temp ranges...max temps
averaging around normal and min temps a category or so below climo.
By early in the work week, a split flow regime is expected to be in
place across the eastern Conus, with a short wave ridge developing
across the Southeast...downstream of a southern Great Plains upper
low. Global models are at odds regarding the evolution of this
feature, namely its interaction with the northern stream, and
eventual impacts on sensible weather across the Southeast. For now,
there`s enough of a signal to include chance PoPs across much of the
CWA by Mon night/Tue. Temperatures are forecast to be very close to
normal through the period.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Some spotty showers have developed over the
western half of the forecast area this morning, but these are not
currently impacting any of the terminals. Shower coverage is
expected to increase through daybreak, especially across western NC,
so have a TEMPO at KAVL with VCSH at KHKY to account for this
activity blossoming in the next few hours. Embedded thunder cannot
be entirely ruled out with these showers overnight, but confidence
was too low for a thunder mention at this time. Patchy fog may
develop across the NC mountains and Foothills this morning in
association with the showers. VFR conditions remain in place and
will continue through much of the forecast period, outside of
diurnal convection today. Have PROB30s everywhere except KAND for
TSRA this afternoon and early evening. Afternoon cumulus will
develop once again today thanks to daytime heating. Winds will
generally remain SW through the period, although KAVL`s winds look
to be variable at times. Low-end gusts are possible this afternoon,
mainly for the SC Upstate terminals. However, low-end gusts cannot
be entirely ruled out at KCLT and KAVL. Shower and thunderstorm
chances may return again overnight, along with restrictions, but
confidence on this is low as the high-res guidance sources are not
in any agreement regarding this potential. Thus, maintained a dry
forecast through the end of the TAF period for now.

Outlook: A cold front will approach out of the west on Thursday
before tracking over the terminals Thursday evening into early
Friday morning. This will lead to better convective chances, as well
as restrictions. A system lifting out of the south my increase
shower and thunderstorm chances again on Friday, but confidence on
this remains low. Drier conditions can be expected this weekend.

&&

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

&&

$$

SYNOPSIS...AR
NEAR TERM...AR
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...AR