120
FXUS62 KGSP 262354
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
754 PM EDT Sun May 26 2024

.SYNOPSIS...
Temperatures remain above normal through Monday.  There is a risk of
strong to severe thunderstorms from this evening until the cold
front passes Monday evening.  Cooler and drier conditions return
tuesday through Friday.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 749 PM EDT Sunday: Severe storms are ongoing across the area
with a line of storms moving across the mountains and into the
foothills. Farther south, across the Upstate, several discrete
supercells, including left splits, have produced reports of hail and
wind damage. A severe threat will continue through the evening as
these storms gradually make their way east across foothills and into
the Piedmont. The main hazards will be for damaging winds, large
hail, and isolated tornadoes.

Previous discussion: Embedded shortwaves residing within the mean
flow of flat upper ridging will provide the upper forcing for ascent
needed to carry multiple waves of potential severe weather across
the area. A digging upper trough over the Midwest will swing an
attendant cold front towards the region, but won`t reach the area
until the end of the forecast period. PWAT values ~1.50" with height
falls and increasing deep layer shear will support the chance for
multiple chances of severe weather as the CFWA resides within a warm
sector as stout southwesterly WAA filters into the region. Here is
the current forecast as far as how the next 24-36 hours will evolve:

Ongoing MCS continues to truck through the OH Valley and the
northern extent of the TN Valley. The trends continue to support the
southern flank of the bowing segment to graze the northern zones
of the CFWA, mainly locations along and north of I-40. Outflows
ahead of the line of convection will be the driving force for more
thunderstorms to develop south of I-40. The environmental parameters
support 2000+ J/kg of sbCAPE, increasing mid-level flow (35-40 kts)
allowing effective bulk shear (0-6 km) to keep the bowing segment
organized, while allowing for supercells to develop away from the
segment, which will most likely impact the NC mountains through
the Charlotte Metro. A few CAMs have a few developing across
the Upstate, where more instability is available. Large hail and
damaging winds will be the primary threat with any supercell that
forms. An isolated tornado can`t be ruled out, but low-level shear
doesn`t support strong tornadogenesis. The hail threat won`t be
present with the southern flank of the bowing segment, but will have
a higher straight-line wind threat with DCAPE >1000J/kg, with a few
quick spin ups possible, especially if embedded supercells can
survive along the line. Expect this threat to begin within the next
hour or two across the northern mountains and push east through the
area by sunset, maybe a little later. In this case, the bowing
segment should survive all the way through the area despite dealing
with terrain as MCS Maintenance upticks through the evening.
Temperatures will be in the upper 80s to near 90 ahead of the
expected convection, making it one of the hottest days of the year
so far. One thing to note, a second bowing segment is developing
across west-central TN, behind the first and CAMs are struggling to
pick up on it. Worried this might be a surprise in the area, but
will need to monitor its evolution over the next few hours.

The aforementioned bowing segment is just one of possibly three
rounds of severe weather during the near term. A second round is
likely to occur overnight as the ongoing convection over the Midwest
currently travels eastward and maintains itself as it encroaches the
region late overnight through mid-morning Monday. The environment
doesn`t support a persistent MCS through the CFWA, especially
east of the mountains. Deep layer shear will increase slightly and
elevated instability will be available when the second MCS moves
across the area. If a strong cold pool can be generated, then
there will be a surprise run across the CFWA Monday morning, with
straight line damaging winds being the primary threat. The one good
thing is that most of this activity is rather progressive and will
lower the hydro threat, but localized flash flooding can`t be ruled
out. With convective debris and another round of storms overnight,
expect overnight lows to remain 5-10 degrees above normal.

Last, but not least, the third round that`s possible during peak
heating on Monday, but will need a few factors to come together
for it to reach its full potential. This one will be dependent
on how much the environment recovers from the second round of
convection and if the atmosphere regenerate more instability. As
of now, CAMs do exactly that, with dewpoints in the uppers
60s to near 70 and instability quickly redeveloping by peak
heating, ahead of an incoming cold front. Deep layer shear will
remain elevated (35-45 kts) and curved hodographs would support
rotating supercells on Monday. The question will be if we can tap
into any surface instability to take advantage of the otherwise
really good kinematics in place. If instability becomes realized
Monday afternoon, all three hazards will be possible (large hail,
damaging winds, tornadoes) with upscale growth by the time the
storms get into the eastern zones and east of the CFWA. The only
thing about this forecast is that it will remain uncertain until
we see what happens with the second round of convection that`s
expected overnight. Decided to lower temperatures slightly for
Monday as convective debris will be hard to shake off, especially
during the morning hours. As a result, afternoon highs on Monday
will be at or slightly above normal.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 135 PM Sunday...Upper heights remain nearly zonal Tue which
will help maintain dry conds and temps warming about 5-7 degrees abv
normal. Surface td/s will mix out deeper than Mon and expect lower
RH values making for a rather nice feeling day. Heights and
thicknesses begin to drop Tue night thru Wed and with a cP airmass
mixing in, don`t envision a good chance of precip associated with
incoming mlvl s/w Wed afternoon. So, kept the fcst dry and again
another nice feeling day with low RH and highs closer to normal. Dry
conds continue thru the overnight periods and really no good chance
of dense fog as sfc tdd/s generally average arnd 10 F across the
fcst area.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 145 PM Sunday...No sigfnt changes were made to the ext range
fcst. Still expect a mostly dry period as the mean h8-h5 flow aligns
w/ly to nw/ly and continues to reinforce a cP airmass building down
the east coast. The latest GFS swings a rather strong h5 s/w thru
the pattern Fri, but moisture looks too limited to introduce precip.
The going showery activity was maintained Sat as another ulvl wave
approaches from the west which will have a better llvl GOM
connection. Deep convection looks limited with this system, however,
as the wave runs into a strong ridging aloft possibly subduing tstm
development. Temps will remain arnd normal levels each and a limited
fog potential continues each night due mainly to sfc dryness.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Showers and thunderstorms continue to impact
the area with temporary restrictions possible at all terminals
through the evening hours. A break in the storms is expected
overnight before a second line of convection moves through the area
during the early to mid morning hours. Associated visibility and
ceilings restrictions can be expected. Thereafter, gusty winds are
expected through the afternoon. A final round of storms will be
possible during the afternoon hours, but confidence is low as to
whether this activity will be able to develop.

Outlook: Drier weather is expected by midweek.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...CAC/TW
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...TW