925
FXUS62 KCHS 232007
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
407 PM EDT Thu May 23 2024

.SYNOPSIS...
High pressure will persist through tonight. Diurnal convection
and hot temperatures are expected during the holiday weekend. A
cold front might bring impacts to our area on Tuesday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Into this evening: The CAMs continue to show isolated
convection developing on microscale boundaries, and as of this
writing the KCLX radar was showing a couple of showers trying
to form. Given a decent cap remaining in place, we prefer to
keep things rainfree. We`ll carry 10% chances just in case
someone experiences a stray shower. Temperatures will peak in
the upper 80s to near 90F away from the coast, dropping to the
upper 70s and lower 80s by sunset, as sea breeze circulations
eventually fades.

Tonight: The mid and upper ridge axis over the Atlantic has
given way to westerly flow across the Deep South and Southeast
as a couple of convectively induced waves ripple east out of
the lower and middle Mississippi River Valley. Convection
associated with one of these waves over and near the southern
Appalachians will move east or east-northeast through the night.
The steering flow is expected to keep it outside the forecast
district, although the remnants of the activity could skirt
Berkeley County closer to daybreak. We`ll keep PoPs at less than
15%, so no mention is required in the forecast. It`s possible
that this decaying convection might leave an outflow boundary
nearby into Friday.

It`ll be a warm night with temperatures around 5F above climo
since the dew points are higher within a south-southwest
synoptic flow.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
Friday: Interesting setup across the forecast area by Friday
afternoon. Using a blend of MOS, high temperatures are forecast to
favor values in the low 90s across SE GA/SC. Forecast soundings
indicate by Friday afternoon, SBCAPE values along and ahead of sea
breeze will pool between 2500-3000 J/kg with little to no CIN.
Guidance indicates that a MCV, sourced from the Deep South, is
expected to pass over the forecast area Friday afternoon. The
combination of the mid-level disturbance and sea breeze should
concentrate thunderstorm coverage over the CHS Tri-county. PW values
around 1.7 inches with SRH 0-3 km around 100 m2/s2. These
thunderstorms should develop into loosely organized clusters. In
addition, DCAPE values are forecast to range between 900-1000 J/kg,
likely supporting long lasting cool pools of outflow air, serving as
areas for thunderstorm development. These thunderstorms should
produce swaths of torrential downpours, yielding pockets of 1.5 to 2
inches with a general area of .5-1 inch of rainfall. In addition,
one or two storms may produce damaging wind gusts. These hazards
will be added to the Hazardous Weather Outlook.

Saturday: The broad mid-level trough will ripple over the Atlantic
during the morning, with heights beginning to rise during the
afternoon. Surface conditions should once again feature high
temperatures in the low 90s with dewpoints in the low 70s. Model
guidance indicates that a field of CAPE of 1500-2000 J/kg with
shallow CIN should develop by the heat of the afternoon. Isolated to
scattered thunderstorms should develop along a sea breeze, but less
coverage that expected on Friday.

Sunday: GFS indicates that a broad H5 ridge will build across the
region. Conditions should become hot and humid during the
afternoon. High temperatures are expected to range in the mid 90s
with dewpoints in the low 70s along the coast. Heat index values may
exceed 100 degrees across the coastal counties, especially across SE
GA. Given poor mid-level lapse rates, convection will be limited to
a SCHC.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The H5 ridge axis will shift east on Memorial Day, with heights
slowly falling from west to east during the afternoon. Temperatures
should peak within a degree or two from values reached on Sunday.
Tuesday appears to be an active day, with the approach and passage
of a cold front. The forecast will feature solid CHC PoPs at this
time. However, if upstream MCS activity arrives over the CWA from
upstream, PoPs will need to be increased. High temperatures are
forecast to range around 90 degrees. Drier air should spread across
the forecast area on Wednesday and Thursday. High temperatures
should favor values in the upper 80s.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
VFR conditions are expected at the CHS/JZI/SAV terminals
through 18Z Friday. Cumulus will continue into the early
evening, with skies BKN at times around 5K feet. There might be
a stray pop-up on the sea breeze through 22-23Z at KSAV and
maybe KCHS. But little or no impacts would occur.

Any risk for convection on Friday looks to not occur until
after 17-18Z Friday.

Extended Aviation Outlook: Brief flight restrictions are
possible due to showers/thunderstorms each afternoon/evening.

&&

.MARINE...
Into this evening: Southerly winds will reach 10-15 kt with the
sea breeze influences, before they gradually diminish after
sunset.

For tonight: The local waters will be positioned on the western
side of Atlantic high pressure that is centered to the east of
Bermuda. The gradient is fairly relaxed, so S or S-SW winds
will be no more than about 10 or 12 kt. Seas will be just 2
feet.

Extended Marine: The forecast area will remain between high pressure
across the western Atlantic and Gulf of Mexico and a series of low
pressure tracking over the Mid West. This pattern should result in a
sea breeze to develop each afternoon. A cold front should sweep
across the coastal waters on Tuesday. Wind and sea conditions should
remain below Small Craft Advisory conditions.

Rip Currents: The combination of astronomical influences from
the Full Moon, modest onshore winds, and a small swell will
lead to an enhanced risk of rip currents into this evening at
all of our beaches.

At this time the risk looks low for Friday.

&&

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

&&

$$

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