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000
FXUS62 KGSP 112329
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
729 PM EDT Thu Apr 11 2024

.SYNOPSIS...
A cold front moves east and off the Carolina coast tonight as drier
air filters into our region from the west and northwest. Very windy
conditions develop Friday into Saturday. Dry and warm weather
returns for the weekend into the middle of next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
545 PM Update...The fcst is in pretty good shape. Still having a
hard time seeing deep cells and lightning across the FA. Mid-level
lapse rates have been meager, which is limiting the updraft
potential. Strong gusts are developing within the diff heating zone
as stout winds at the top of the mixed layer are efficiently
transferring to the surface, so made some tweaks to gusts in the
grids. Expect the ongoing convec activity to become a little more
organized over the next couple hours as it shifts east into an area
of 1500 J/kg sbCAPE and effShear on the order of 70 kts. With low-
level helicity quite high and backed sfc winds downstream, the
potential exists for rotating supercells to develop if updrafts can
become stronger and deeper.

As of 230 PM EDT Thursday: Showers continue lifting northward across
much of the forecast area this afternoon thanks to a low pressure
system lifting northeast across the TN/OH Valley. No lightning is
currently present in this activity, but some stronger storms are
noted in eastern TN as of the writing of this AFD. Mostly cloudy
skies continue across most locations, but breaks in cloud cover are
noted across the western North Carolina mountains and the southern
SC Upstate and portions of northeast Georgia. Any breaks in cloud
cover will allow for destabilization thanks to temps ranging from
the mid to upper 60s and dewpoints ranging from the low to mid 60s
across much of the forecast area. The latest SPC mesoanalysis shows
500-1000 J/kg of SBCAPE in place as of 2pm, and projects a plume of
1500 J/kg of SBCAPE across the southern and eastern zones later this
afternoon. A plume of DCAPE is also noted from 800-1000 J/kg across
the southern and eastern zones this afternoon. The mesoanalysis also
shows 60-70 kts of bulk shear over the area, with 0-1 km shear at 30
kts over the eastern half of the CWA this afternoon. All this to
say, any areas that see breaks in cloud cover will have the
potential to see isolated strong to severe storms develop. The main
threat with any storm that manages to become severe may produce
damaging wind gusts. However, an isolated, brief tornado cannot be
entirely ruled out this afternoon, especially over the NC Piedmont
along/near I-77. Thus, SPC`s Day 1 Marginal Risk looks well placed.
The severe threat will end by the early evening hours with the loss
of daytime heating and as the bulk of activity pushes east of the
forecast area. Highs this afternoon will climb a few degrees above
climo. Breezy S/SW winds will continue through this evening.

Rain chances will linger this evening into late tonight, especially
across the western North Carolina mountains thanks to a secondary
cold front tracking across the region. Thus, maintained chance PoPs
through midnight east of the mountains, with likely to categorical
PoPs across the western North Carolina mountains. Have Pops ramping
down to chance after midnight across the western North Carolina
mountains. Winds will gradually increase across the mountains
overnight becoming gusty while gusts east of the mountains will
gradually decrease throughout the overnight hours. With gusts
expected to reach advisory criteria (45-55 mph), a Wind Advisory was
issued for most of the North Carolina mountains starting midnight
tonight. Cloud cover will gradually diminish east of the mountains
overnight into early Friday morning becoming clear to mostly clear.
Lows tonight will end up a few degrees above climo despite the
decreasing cloud cover.

Cloud cover will linger across the western North Carolina mountains
through Friday while mostly sunny skies prevail elsewhere. Shower
and thunderstorm chances should return along the NC/TN border Friday
afternoon thanks to NW flow. Some of this activity may break
containment of the mountains, per the HRRR and NAMNest, but
confidence on this is low at this time. Thus, have highest PoPs
confined to the NC/TN border with lower PoPs elsewhere. Highs on
Friday will end up a few degrees below climo behind the departing
cold front. Winds will once again increase on Friday thanks to a
tight pressure gradient so the Wind Advisory will remain in place
for portions of the North Carolina mountains through Friday evening.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 155 pm Thursday: Long wave trough axis will be in the process
of moving east of the area at the start of the period. Persistent,
rather strong/deep NW flow acting on lingering low level moisture
across the TN Valley into the western slopes of the southern
Appalachians to yield continued potential for upslope showers near
the TN/NC border. However, chance PoPs will steadily ramp down
through Fri night, as flow (finally) steadily weakens and moisture
depletes. However, conditions will remain gusty over the mountains
Fri night into at least the first half of Saturday. While critically
low RH is expected to be primarily confined to the Piedmont and
foothills, fire danger will nevertheless be enhanced across much of
the CWA during the daylight hours Saturday.

As trough progresses away from the East Coast during the latter half
of the weekend, the surface gradient will finally relax and winds
become tame. While RH is again expected to be quite low Sunday
afternoon, winds will be well below critical levels. The bigger
story will be the rather dramatic warm-up resulting from height
falls and return SW flow. After near-normal conditions that are
expected Fri night through Sat night, temps are expected to soar to
around 10 degrees above climo Sun afternoon, with widespread lower
80s expected across the Piedmont and foothills, while even the major
mountain valleys are expected to push the 80 mark.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 210 pm Thursday: An upper ridge will build strongly across the
central Conus during the extended period...downstream of the next
major West Coast storm system. This will result in continued very
warm conditions through the period, with temps expected to range
from 10-12 degrees above climo...making it feel more like
mid-to-late May than mid-April. Conditions will otherwise remain
inactive over our area, with slowly moistening conditions expected
through the week. The western storm system is expected to kick out
across the Great Plains early in the week, but the strong ridge is
forecast to deflect this feature into the Great Lakes and Ontario
during mid-week. This may drag an occluding frontal system toward
our area for days 6/7, but indications in the global models is that
this will have little-to-no effect on our sensible weather, and only
token 20-30 PoPs are featured along the TN/NC border during this
time frame.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Convective activity continues across the area
this evening, yet only isol cells are producing lightning. Have
included thunder mention at KCLT and KHKY thru 02z. Confidence
remains low across the other terminals for a much more than a rain
or vicinity shower mention this evening. Expect lowering CIGS likely
into the MVFR range, with passing activity this evening into the
early overnight, them a return of VFR conds thru the TAF period
across all sites thru the period. Southwesterly to westerly winds
remain gusty and increase in strength later in the period. Winds at
KAVL will begin the period sw/ly then shift nw/ly arnd midnight.

Outlook: Wind gusts will gradually taper off Friday night east of
the mountains, but will remain gusty across the North Carolina
mountains through Saturday. VFR conditions will persist this weekend
and early next week as high pressure builds across the terminals.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Wind Advisory from midnight tonight to 9 PM EDT Friday for
     NCZ033-048>050-052-053-059-063>065-501-503-505-507-509.
SC...None.

&&

$$

SYNOPSIS...DEO
NEAR TERM...AR/SBK
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...SBK