220
FXUS62 KCHS 121144
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
744 AM EDT Fri Jul 12 2024

.SYNOPSIS...
A weak front will meander across the area through Saturday.
Atlantic high pressure will then rebuild across the area while
a surface trough exists inland Sunday through the middle of
next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A coastal low is expected to track WNW over the western
Atlantic this morning. Near term models indicate that the center
of the low may make landfall around the mouth of the Savannah
River during the mid-day. Circulation around the low should
result in SE winds across the SC coastal waters early morning.
However, winds over land may remain from the north through
daybreak. Given the winds, instability should remain over the
coastal waters early this morning, building gradually over the
coastal areas. Showers and thunderstorms are forecast to
increase off the coast before daybreak this morning, with
convection expected to gradually weaken as it pushes onshore.

Early this morning, temperatures should rapidly warm into the
80s, with values reaching around 90 degrees before noon. High
temperatures are forecast to range from the mid 90s across SE GA
to the upper 80s across the Charleston Tri-county. As
temperatures warm, winds should shift from the SE, producing a
sea breeze along the SC coast. Instability in the wake of the
sea breeze should increase to 1500- 2000 J/kg of MLCAPE across
the SC Lowcountry. In addition, PW values should increase to 2.2
to 2.4 inches with K-index increasing into the upper 30. At
least numerous showers and thunderstorms are forecast to develop
across portions of the SC Lowcountry, with scattered to
numerous showers and thunderstorms along and east of the I-95
corridor. In fact, the period of greatest thunderstorm coverage
may occur of Charleston County shortly after sunrise, just prior
to the sea breeze formation. The period between 9 AM until
noon, storms may feature very slow motions, back-building, with
torrential downpours between the Edisto and Santee Rivers. After
noon, forecast soundings indicate that storm motions may
increase above 10 mph. The HWO will continue to feature a
mention of flooding today.

Tonight, the sfc low is expected to drift inland and weaken to a
trough. Isolated to scattered showers and thunderstorms may linger
well into the overnight hours, especially across the SC Lowcountry.
Low temperatures are forecast to range in the mid to upper 70s.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
Saturday: Ridging will begin to build into the southeastern states,
while a weak front will remain stalled in the vicinity at the
surface. PWATs will remain slightly elevated, around 2.0 inches,
with showers and thunderstorms possible across the Charleston Tri-
County in the morning hours. Thereafter, precipitation will likely
take a turn towards a typical summertime pattern with scattered to
widespread showers and thunderstorms in the afternoon. With the
ridging building aloft and plentiful sunshine, temperatures are
forecast to reach into the mid to upper 90s across the region. Head
Indices are currently forecast to be 104 to 106F, just shy of the
108F Heat Advisory criteria. Conditions will need to be monitored
closely, and Heat Advisories may be required. Overnight lows will
remain rather mild, only dropping into the mid to upper 70s.

Sunday and Monday: The ridging aloft will weaken as a mid-level
trough swings across the eastern CONUS. The local forecast area will
likely be positioned at the far southern periphery of this trough,
while at the surface a weak front will drift towards the local
forecast area. With the slight extra forcing aloft and the weak
front in the vicinity the region will likely see enough extra
forcing to spur scattered showers and thunderstorms. Some local
enhancement from the afternoon sea breeze could aid these showers
and thunderstorms, with precipitation possibly reaching all the way
to the coast. Temperatures will be quite hot each day, with heat
indices around 105 to 110F. Heat Advisories will likely be required
for roughly along and east of I-95. Overnight lows will remain mild,
with lows only in the mid to upper 70s.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
Ridging will gradually build into the southeastern states, while
shortwave energy will ripple across the Mid-Atlantic states along
the southern periphery of a mid-level trough. At least scattered
showers and thunderstorms will be possible each afternoon, typical
of a summerlike pattern. Outside of precipitation, hot and humid
conditions are forecast early in the week. Heat Advisories may be
required Monday through Wednesday. Head Index values could even
approach Excessive Heat Warning criteria (113F) across portions of
the forecast area on Tuesday.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
Prior to the 12Z TAFs: KCLX detected increasing shower and
thunderstorm coverage across the coastal waters of SC and GA.
The center of a coastal low will track west, expected to move
over the nearshore waters by mid-morning. The low is expected to
slide over SE GA/SC by mid-day, drifting inland through the
rest of the afternoon. Convection across the region will
increase as the low approaches and tracks on shore today. Peak
coverage of showers and thunderstorms is expected at KCHS and
KJZI between 13Z and early this afternoon. The KCHS and KJZI
TAFs will feature a mention of VCSH or VCTS through much of the
daylight hours. Both TAFs will feature a TEMPO from 13-17Z for
MVFR conditions during TSRA. Convection will start a bit later
at KSAV, with peak coverage expected during the mid afternoon.
The KSAV TAF will feature a TEMPO from 19-22Z for MVFR
conditions during a TSRA. Convection should gradually decrease
this evening, with the greatest coverage expected north of KCHS
and KJZI.

Extended Aviation Outlook: Scattered afternoon showers/tstorms could
produce brief flight restrictions at all terminals through early
next week.

&&

.MARINE...
Today: A coastal low will track across the marine zones this
morning, pushing onshore near the mouth of the Savannah River during
the mid-day. The weak low should continue to drift inland through
this afternoon. Winds across the marine zones should favor a
direction from the SE through the day, speeds between 10-15 kts.
Seas this morning should favor values between 2-3 ft, building to 2-
4 ft this afternoon. A few 5 ft waves are possible across the outer
portions of the Charleston County nearshore waters this afternoon.

Saturday through Tuesday: A pinched gradient could develop over the
marine waters through early next week as high pressure persists
offshore and a trough lingers inland. However, conditions are
expected to remain below Small Craft Advisory criteria. Generally S
winds are forecast, 10-15 knots. Slightly stronger wind speeds are
possible along the direct coastline in association with the
afternoon sea breeze. Seas should average 3 to 4 ft.

Rip Currents: Moderate SSE swell directed mainly north of Cape Fear
will work into Charleston County coast today. The modest increase in
swell will bump the rip current risk to Moderate for the Charleston
County beaches.

&&

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

&&

$$

NEAR TERM...NED
SHORT TERM...CPM
LONG TERM...CPM
AVIATION...CPM/NED
MARINE...CPM/NED