539
FXUS62 KGSP 161830
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
230 PM EDT Tue Jul 16 2024

.SYNOPSIS...
Hot high pressure lingers above the region through Wednesday. A
pattern change begins to evolve by Thursday, as a cold front will
approach from the northwest then become stationary across our region
for several days. This will keep shower and thunderstorm chances
elevated through early next week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
Afternoon convection is ongoing and remaining relatively weak with
deep cell development. However, these storms will begin to become
stronger over the next couple hrs during max heating and additional
lift provided by incoming mlvl energy. Still, mlvl LRs are low-end
and deep shear levels below 20 kts. So, expect pulse-type storms
with some outflow enhancement possibly leading to multi-cell lines
thru the evening as they push east out of the mtns and fthills. A
few storms may become strong enuf to produce damaging outflows and
extended heavy rainfall.

Overnight, the atmos becomes rather quiet aft 02z with perhaps a few
lingering showers over the ern zones thru 06z. The sfc layer remains
a little mixed and with debris clouds hanging around, dont expect
much of a fog threat.

A wavy pre-frontal trof will push into the FA Wed afternoon and
likely produce more widespread storm activity across the mtns and
foothills. In fact, increasing shear may allow for some storm
organization and cold pool lines across the nrn fthills and NW NC
Piedmont. Highs Wed will reach a cat abv normal with td/s mixing out
into the u60s to l70s. Heat index values dont look to reach adv
criteria, but will come close across the I-77 corridor and will be
reassessed on the midnight shift for any possible product.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 200 PM EDT Tuesday: Height falls and an encroaching frontal
boundary from the northwest will be imminent as a digging upper
trough swings across the eastern half of the CONUS. Diurnal
instability and PWAT values on the order of ~2.00" will set the
stage for widespread convection across the area through much
of the forecast period, with an emphasis on coverage during
the afternoon and evening, but expect for lingering convection
during the nighttime period as well. Expect the primary threat
to be excessive rainfall as convective rainfall rates combined
with the potential for training cells along the boundary as model
guidance indicate that the boundary should sag far enough south to
hang out in the CFWA by late Wednesday into Thursday and becomes
quasi-stationary from that point on. Storm coverage for Thursday
could be in question, mainly across the mountain zones and I-40
corridor points north as the front may end up into the far southern
tier of the CFWA and allow for the continental high to filter in
drier air and thus, limit convective coverage. On the other side,
this would allow for convective coverage to become widespread across
the Piedmont zones, especially in CLT Metro, Upstate, and northeast
Georgia through Thursday, before the front sinks south of the CFWA
Thursday night. Heat indices will rise into the 90s for one more
day on Thursday, but definitely not as sweltering and should bring a
nice relief from the heat. Extensive cloud cover and elevated PoPs
will keep temperatures at bay as afternoon highs for Thursday will
be near-normal, while values drop to ~5 degrees below normal on
Friday. The frontal boundary seems like it`s going to wobble back
and forth across the CFWA and open up the door for another round
of convection Friday. Although the rain won`t be drought busting,
it will provide some relief even thought conditions will remain
very warm and muggy.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 230 PM EDT Tuesday: The upper trough from the short term
is shown being absorbed by the subtropical jet as the deep layer
flow will steadily come out of the southwest. As a result, high
PWAT values will remain in place as the quasi-stationary front
stays activated as guidance try to spin up an upper low over
the south-central CONUS. In this case, the pattern is likely
to be convectively active through the period, with a diurnal
emphasis. This will prolong an excessive rainfall threat through the
forecast period, but could become heightened in localized areas,
especially in locations that are prone to flooding. Otherwise,
temperatures will be at or slightly below normal through much
of the medium range as extensive cloud cover and elevated PoPs
continue through early next week.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Convection is getting going a little early
this afternoon with isol tstm activity already developing across the
mtns. Have adjusted the going TEMPOS up an hour or so across the NC
terminals and delayed the SC sites till 21z based on the latest
hires guidance showing a more suppressed atmos. Expect tstms to
continue to push east into the evening and clear KCLT by 02z. A
mixed sfc layer overnight and high/mid cloud cover will help offset
a fog threat thru daybreak, while low StCu is also held in check.
Winds remain aligned s/ly to sw/ly across all sites, with a nw/ly
wind shift at KAVL arnd 15z.

Outlook: An uptick in showers and thunderstorms Wednesday onward as
a cold front approaches and stalls near the region. Morning fog/low
stratus possible each morning, especially across the mountain
valleys and for areas that received heavy rainfall the day prior.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Heat Advisory until 8 PM EDT this evening for NCZ071-072-082.
SC...None.

&&

$$

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