-- Discussion containing changed information from previous version are highlighted. --
503
FXUS62 KCHS 230509
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
109 AM EDT Sun Jun 23 2024

.SYNOPSIS...
A weak surface trough will linger near the Georgia coast
through tonight. High pressure will then prevail over the
western Atlantic through next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Tonight: Weak low pressure currently centered near the I-95 corridor
across southeast Georgia will be slow to track north overnight due
to weak steering flow in place. Although subsidence associated with
mid-upper lvl ridging extending from the west will remain in place
for much of the night, modest instability (SBCAPE around 2000 J/kg
and PWATs near 2.0 inches) could support a few thunderstorms in
addition to moderate showers along the northern edge of the low
pressure circulation where low-lvl convergence will be greatest for
the next several hours. Otherwise, dry air to the north will likely
limit shower and/or thunderstorm coverage across much of Southeast
South Carolina into late night hours, especially as instability
wanes through the night.

Late tonight, weaker instability does remain in place as the low
pressure circulation attempts to slowly drift north. A few slowly
moving convective elements could develop near Savannah/Beaufort Co
area. Localized rainfall amounts could reach up to 3-4+ inches in
this area, but widespread rainfall amounts will likely be closer to
an inch or less. Further north (Charleston Metro), precip coverage
will remain more limited for much of the night, but latest hires
guidance does suggest an uptick in activity within a few hours prior
to daybreak. Much will depend on how far north the low pressure
circulation will track north overnight, before showing signs of
dissipating heading into Sunday.

Outside of this feature, some clearing should begin across far inland
areas of southeast Georgia late tonight and with a relatively weak
gradient in place could support radiational cooling that overlaps
lingering boundary layer moisture for a few hours. Should this
occur, patchy fog could develop across southeast Georgia, mainly
inland from coastal counties. Fog remains out of the forecast at
this time.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY/...
A weak surface low along the coast will open and be absorbed
into the approaching troughing/front well inland Sunday. Still,
ample low level moisture lingers, with showers and storms
likely to develop along the resultant sea breeze by Sunday
afternoon. Widespread cloud cover across much of the area will
limit the instability somewhat, but instability climbing to
1000-2000 J/kg of MUCAPE along the sea breeze could bring some
stronger thunderstorms, with gusty winds and lightning the
primary threats. Further inland across SE GA, dry air will work
in as the low dissipates and less cloud cover will bring warmer
temps (into the mid 90s) and lower rainfall chances. Heat index
values will climb to around 100 Sunday afternoon with warmer
temps, but less humidity inland, and greater humidity and
relatively more moderate temps closer to the coast.

A weak shortwave ridge will extend across southeast GA Sunday
night, then a shortwave trough will drop into southern SC from
the northwest on Monday. A weak surface cold front will slowly
drift into the area on Monday. Increasing thicknesses combined
with pre-frontal compression will result in toasty temperatures
in the mid to upper 90s.  The deepest moisture is forecast
to move off the coast early Monday afternoon, so afternoon
instability will not be particularly strong. A decent sea breeze
should develop and move inland in the afternoon, but there will
also be some mid-level subsidence working against buoyant
parcels. We have isolated to scattered showers and thunderstorms
in the afternoon. Heat indices will top out between 104 and
108F, just shy of needing a Heat Advisory.

A weak northwest flow will continue aloft on Tuesday while a
weak surface high is centered across inland areas. Large scale
subsidence will result in another hot day with highs in the mid
to upper 90s. Surface dewpoints should mix out across inland
southeast GA, while moisture pooling occurs closer to the SC/GA
coast. The greatest risk for Heat Advisory conditions with heat
indices above 108F will be across coastal GA and far southern
SC. The main forcing for convection will be from the sea breeze,
though a few subtle upper shortwaves are also possible.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A developing upper trough across the eastern United States and
deep tropical moisture spreading into the area is expected to
support greater coverage of mainly diurnal showers and
thunderstorms through the long term period.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
KSAV: Bands of showers and some thunderstorms along the northern
edge of surface low pressure centered near KLHW will continue
to feed up into the KSAV terminal area over the next few hours.
This will lead to a period of MVFR/IFR flight restrictions in
heavy rain/reduced vsbys at the terminal through 07Z or so.
Shower coverage will diminish thereafter, although lower MVFR
cigs will likely linger through the balance of the night into
Sunday morning with conditions improving to VFR during the
afternoon. It`s possible a sea breeze could return a few showers
and/or thunderstorm to the terminal Sunday afternoon, but
confidence in timing/occurrence remains low.

KCHS/KJZI: A few showers will pass close to the terminals
through 08Z along with periodic lower cloud cover coming off the
Atlantic. Meanwhile, a broadening area of surface low pressure
over southeast Georgia is still looking to migrate up through
southeast South Carolina late overnight through Sunday. Showers
and possibly some thunderstorms with this feature may migrate up
through South Carolina coast and through the terminals during
the early to mid morning hours resulting in MVFR and possible
IFR conditions during that time. Conditions should then slowly
return to VFR during the afternoon, but additional showers
and/or thunderstorms could bring flight restrictions
temporarily during the afternoon.

Extended Aviation Outlook: Mostly VFR. However, convection will
bring brief flight restrictions, mainly each afternoon and
evening.
-- End Changed Discussion --

&&

.MARINE...
Tonight: Weak low pressure slowly tracking north across southeast
Georgia and into southeast South Carolina late will continue to
bring moderate southeast to south winds across the waters. Some
gusts to 20 kt are possible across local waters along the
eastern edge of low pressure centered across southeast Georgia,
but conditions are expected to remain below Small Craft Advisory
levels as the pressure gradient slackens a bit overnight. Seas
will average between 2-4 ft across nearshore waters and 4-5 ft
across offshore Georgia waters this evening, then slowly show
signs of subsiding heading into daybreak Sunday.

Extended Marine: A slightly enhanced gradient is expected to
return Sunday night between an inland trough and offshore high
pressure. Wind gusts could approach 25 kt beyond 15 NM from the
coast, and seas may reach 5 ft over outer portions. Otherwise, a
fairly typical summertime pattern will occur, with the
strongest winds along the coast each afternoon as the sea breeze
develops.

Rip Currents: A moderate risk continues through Sunday due to
onshore winds and a moderate southeast swell.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

$$

NEAR TERM...DPB
SHORT TERM...CEB/JRL
LONG TERM...JRL
AVIATION...Adam/JRL
MARINE...CEB/JRL