846
FXUS62 KCHS 030213
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1013 PM EDT Tue Jul 2 2024

.SYNOPSIS...
A weak area of low pressure will linger across Southeast
Georgia through Wednesday. Through the rest of the week, a hot
and humid air mass will build over the region. A weak cold
front could approach the region by early next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Late this evening: No change to the forecast thinking for the
overnight. Previous discussion continues below.

Early this evening: Surface analysis shows high pressure wedged
in across Georgia and the Carolinas with the remnant boundary
down to the south near the FL/GA state line. The effect of the
surface high has been to finally drive some drier air into the
area, with a tight gradient on display in precipitable water.
Portions of interior Dorchester and Berkeley counties likely
have precipitable water values of 1.5 inches or less, while the
coast from around Beaufort south to the Altamaha has
precipitable water values on the order of 2.1-2.3 inches.
Overall, we have had minimal shower activity over the last few
hours, though radar imagery shows increasing activity offshore
across the coastal waters. For the overnight, model guidance
generally paints a similar picture. The idea is that subtle
convergence within the deeper moisture (mostly offshore) will be
the focus for increase shower and thunderstorm activity.
However, within the low-level northeasterly flow, this activity
will likely try to bleed onshore along the Georgia coast, up
through Beaufort County and into the Edisto area. We have rain
chances mostly focused over the waters (in the 50-70 percent
range) but do show 40-60 percent chances right along the coast
from Tybee up through Edisto/Seabrook/Kiawah. Given the degree
of available moisture and slow moving nature, some heavy
rainfall will be possible along the coast in these areas,
perhaps up to an inch.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Wednesday: A weakening stationary front or surface trough will
remain across southeast GA through the afternoon. The HREF
indicates a pool of 1500 to 2000 J/kg of CAPE will remain along
and south of the trough. At the surface, the center of a 1020 mb
high will remain off the mid-Atlantic coast, resulting in broad
east flow across the forecast area. As temperatures warm into
the upper 80s to lower 90s, a seabreeze should develop and
advance inland during the afternoon hours. Scattered to numerous
showers and thunderstorms are expected to form over the coastal
waters of GA early Wednesday morning, the convention is
expected to spread onshore generally south of the Savannah River
from midday through the afternoon.

Independence Day: A large H5 ridge will expand across the Deep
South and Southeast US region. Forecast soundings indicate a
subsidence inversion centered at H75. This inversion should
maintain at 30 to 50 J/kg of CIN through the heat of the
afternoon. In addition, PW values should remain limited to 1.5
inches across the region. As a result, the forecast will feature
dry conditions through much of the day. However, a SCHC PoPs
are possible across portions of southeast GA, and the far inland
counties of SC. Little to no QPF is expected. Given the
position of the mid-level ridge, and expected partly sunny
conditions, temperatures are forecast to peak in the mid to
upper 90s with heat index values between 100 and 105.

Friday: GFS indicates that the center of the +590 DM ridge will
remain over the Deep South. Forecast soundings indicate that
the subsidence inversion will remain centered at H75, resulting
in at least weak capping. However, given the passage of a weak
late afternoon sea breeze, isolated showers and thunderstorms
may develop during the afternoon. High temperatures should range
in the mid to upper 90s for most areas. In addition, dewpoints
along and behind the sea breeze may increase into the mid to
upper 70s, with a few spots reaching the low 80s. Heat index
values may exceed 108 in spots, especially across portions of
the SC Lowcountry.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The mid-level pattern through the long term will be very
interesting. The ridge will generally remain across the
Southeast U.S. as a closed low associated with TC Beryl enters
the western Gulf of Mexico. To the east, GFS and ECMWF indicate
that a closed low south of Bermuda will drift toward the
Southeast coast. As a result, moisture will gradually build
across the region under the ridge, especially as the closed low
over the Atlantic approaches from the east. At the sfc, a weak
cold front will approach from the west, expected to become
nearly stationary east of the Appalachians early next week. This
pattern should support generally diurnal showers and
thunderstorms, greatest coverage expected on Monday and Tuesday.
Conditions will remain hot across the CWA, high in the mid to
upper 90s with heat index values around Heat Advisory values.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
The 00z TAF period begins with VFR conditions at KCHS, KJZI, and
KSAV. Through the overnight, the main issues will be the
potential for another round of MVFR ceilings and showers trying
to approach mainly KSAV and KJZI. Guidance favors keeping KCHS
and KJZI both VFR, with MVFR ceilings at KSAV for a period of
time from roughly 05-12z. Any overnight showers and
thunderstorms should be mainly confined to the coast but could
be in the vicinity of KSAV and KJZI from the early morning hours
through just after sunrise. Overall, the chances of Wednesday
afternoon convection appear low.

Extended Aviation Outlook: Brief flight restrictions are
possible in showers and thunderstorms, mainly in the afternoon
and evening through the period.

&&

.MARINE...
Tonight: Winds continue to frequently gust 25-30 kt across
South Carolina nearshore waters and the Savannah River Entrance
this afternoon as pinched gradient conditions persist. Models
have not handled the evolution of the pinched gradient well at
all today. Given the current trends, the advisory has been
extended until 6 PM. Winds should diminish after this the front
begins to buckle north and resulting pinched gradient relaxes a
bit. Seas will diminishing to 2-4 ft through the night.

Wednesday through Sunday: Winds are forecast to remain from the
northeast on Wednesday, generally between 10 to 15 kts. Seas
will range between 2 to 3 ft. Thursday through this weekend,
south winds are forecast to remain less than 15 kts. Seas will
favor values between 2-3 ft.

&&

.TIDES/COASTAL FLOODING...
Another round of minor coastal flooding will be possible at
Charleston with the Wednesday evening high tide cycle.

&&

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

&&

$$

NEAR TERM...BSH
SHORT TERM...
LONG TERM...
AVIATION...BSH
MARINE...