975
FXUS62 KCHS 122359
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
759 PM 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 /UNTIL 6 AM SATURDAY MORNING/...
Early evening analysis reveals surface low pressure inland over
southeast Georgia...roughly over the Tattnall County area with
an inverted trough that extends northeastward up through
Berkeley County, and a myriad of smaller scale boundaries out
there. 23Z SPC mesoanalysis page shows >2K J/Kg of MLCAPE
across the forecast area although convection has diminished
greatly over the last couple of hours.

Weak surface low will be migrating very slowly westward through
the night along with slowly weakening low level convergence
anticipated across the region. Some additional showers/storms
could continue or develop off the Charleston coast throughout
the night, some of which could skirt the Charleston County
coastal areas. Inland, a few more showers may yet bubble up
over the next few hours until we see some increase in CINH.
Thus, forecast will feature some lower end precip chances
through the balance of the evening

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Saturday: Aloft, a mid-lvl ridge will gradually strengthen across
the Southeast United States. At the sfc, weak low pressure across
southern areas should gradually nudge west during the day while a
weak front/stalled boundary lingers nearby. The pattern will favor a
slightly weaker onshore wind compared to the previous day, but will
continue to advect moisture characterized by PWATs in excess of 2.0
inches across a large portion of the area. An afternoon sea breeze
interacting with a the nearby front/boundary should become the main
focusing point for afternoon convection, with greatest precip
coverage across the Tri-County Area away from the beaches mid-late
afternoon. Coverage and intensity of rainfall should be less than
the previous day with subtle forcing in place, and precip totals
should generally average around 1/2 inch or less. However, a few
locations could see slightly higher precip amounts during a
thunderstorm. Expect precip coverage to quickly diminish during
evening hours with the loss of diurnal heating.

Outside/before precip, warm and humid conditions are anticipated
across the area, with a few locations potentially experiencing heat
index values between 105-109 for an hour or two along and east of
the I-95 corridor, mainly across Southeast South Carolina early to
mid afternoon. Some uncertainty in the duration of highest heat
index values comes into question given precip developing across the
same area by peak diurnal heating hours. However, sfc temps should
still peak in the mid-upper 90s away from the coast alone, warmest
across Southeast Georgia. Overnight lows will remain mild, generally
in the mid 70s inland to upper 70s/lower 80s near the coast.

Sunday and Monday: Aloft, mid-lvl ridging will persist, but show a
slightly weaker signal while a series of subtle h5 shortwave pass
along the base of a low amplitude trough across the Mid-Atlantic
states. At the sfc, what is left of weak sfc low pressure and a
nearby front dissipates with the pattern becoming more summerlike in
nature with lee troughing across the Midlands and high pressure
extending across the western Atlantic. These features should provide
sufficient forcing and/or a focusing mechanism for afternoon
convection in a moist environment (PWATs around 2 inches) just
inland to the area, before a westerly flow between the mid-upper
trough to the north and a ridge to the southwest nudges activity
across the local area. Some enhancement along a sea breeze shifting
inland is possible each day, at least in regards to carrying chances
of showers and thunderstorms across the entire area. A stronger
thunderstorm can not be ruled out, but overall organized severe
weather potential remains low. Outside of precip, conditions will
become quite warm, with afternoon highs in the mid-upper 90s away
from the coast. A few locations could even touch 100 degrees far
inland each afternoon. The combination of a weak downsloping wind
aloft and low-lvl mixing during the afternoon should lower sfc
dewpts across areas experiencing the warmest temps well inland, but
many areas could experience heat index values that support Heat
Advisories each afternoon, mainly along and east of the I-95
corridor. Overnight lows will remain mild, generally in the mid 70s
inland to upper 70s/lower 80s near the coast.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Ridging will gradually build across the Southeast United States,
while weak shortwave energy ripples 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 into mid week. Heat Advisories could
be required Tuesday through Thursday, until a front approaches the
area late week with greater shower/thunderstorm coverage locally.
Heat Index values could even approach Excessive Heat Warning
criteria (113F) across portions of the forecast area on Tuesday and
Wednesday.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Showers and thunderstorms have diminished greatly across the
region, although showers may continue to percolate through the
evening hours. Also, there could be some additional showers and
thunderstorms that persist or develop off the Charleston coast
that make a run toward the coast overnight through early
Saturday. However, chances are too low to include in the
terminal forecasts at this juncture.

Saturday will see another round of showers and thunderstorms
develop in the afternoon and the latest forecast will feature
VCSH from 18Z onward.

Extended Aviation Outlook: Scattered afternoon showers/thunderstorms
could produce tempo flight restrictions at CHS/JZI/SAV terminals
each afternoon through early next week.

&&

.MARINE...
Tonight: South to southeast winds are favored through tonight
as weak low pressure and an associated surface boundary shifts
further inland. Speeds will be in the 10-15 kt range. Seas will
average 2-4 feet, with some 5 footers across the outer portions
of the Charleston County nearshore waters.

Saturday through Tuesday: A pinched gradient could develop over the
marine waters through early next week as high pressure persists
across the western Atlantic and a trough lingers inland. However,
conditions are expected to remain below Small Craft Advisory
criteria. In general, southerly winds will be in place with
temporary increases to around 15 kt, mainly near the coast where sea
breeze circulations develop, then shift inland. Seas will range
between 2-4 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...Adam/ETM
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...Adam/DPB
MARINE...DPB/ETM