853
FXUS62 KCHS 231739
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
139 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 /THROUGH TONIGHT/...
The CAMs continue to show isolated convection developing this
afternoon on microscale boundaries. But until we actually see
something forming we prefer to keep things rainfree given the
cap remaining in place. Temperatures are on track to reach the
upper 80s to near 90F away from the shoreline now that the sea
breeze in aligned near Route US-17.

Today: As the ridging aloft moves further into the Atlantic,
there are several very subtle impulses in the westerly flow
aloft that pass on through. There is a little more moisture
compared to recent days, and there is even some MLCAPE that will
reach near 1000 J/kg this afternoon. Perhaps these conditions
allow for some pop up showers on the sea breeze, similar to what
the CAms are showing. But since there remains a decent cap
around 5-8K feet, and lapse rates are rather paltry, we do
maintain a forecast free of convection. We`ll update the
forecast as necessary should anything actually occur.

Temperatures at 850 mb are forecast to reach 16-17C this
afternoon, an increase of about 2-3C from this morning. If this
is realized, and with a southwesterly synoptic flow we will be
able to attain max temperatures in the upper 80s to near 90F.
Due to sea breeze influences the coastal locations will be held
to the lower and middle 80s.

Tonight: Upper ridge axis will flatten out across the Deep South and
southeast CONUS courtesy of a couple of convectively induced waves
rippling out of the central and lower Mississippi River Valley and
through the southeast and mid Atlantic region. There may be a
surviving cluster of showers/thunderstorms working across the
Carolinas during the course of the night, although all recent
guidance runs and blended guidance probabilities suggest convection
remains just north of the forecast area...from the SC Pee Dee region
into North Carolina and Mid Atlantic. Our inclination is to have a
dry forecast through the overnight period into early Friday
morning. Temperatures will continue to run mild, in the upper
60s to lower 70s for lows and a touch warmer along the coast.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Friday: The mid-levels will consist of zonal flow over our region,
with a weak disturbance just passing to our north during the evening
and overnight. At the surface, High pressure will be centered in the
western Atlantic, with it`s periphery trying to reach into the
Southeast. A front will stay well to our north and northwest.
Meanwhile, weak surface troughing should develop near our area
during the day and persist into the overnight. Flow around the
western Atlantic High will usher moisture into our area, with PWATs
rising to almost 1.85" during the afternoon. Temperatures peaking in
the lower 90s will cause instability to increase. Models remain in
good agreement indicating isolated to scattered thunderstorms
forming along the sea breeze in the afternoon, especially across our
SC counties. Locally heavy rainfall is possible along with gusty
winds, especially in the stronger storms. Convection should
gradually decrease into the evening and overnight. Lows will be
mild, ranging from the upper 60s far inland to the lower 70s just
about everywhere else.

Saturday: Weak troughing will form off the Southeast coast in
response to weak ridging forming over the Southeast U.S. Surface
High pressure will remain in the western Atlantic while troughing
persist over a portion of the Southeast. Low level winds will
continue to usher a decent amount of moisture into our area. Though,
it`s still uncertain how high PWATs will get. High temperatures
peaking in the lower to middle 90s away from the beaches will
generate a decent amount of instability. Therefore, scattered to
maybe numerous convection is expected to form along the sea breeze
in the afternoon. Rising DCAPEs point to some marginally severe
storms with damaging wind gusts being the main concern. But there
will also be locally heavy rainfall. Convection will gradually
decrease into the evening and overnight. Lows will remain mild,
ranging from the upper 60s far inland to the lower 70s just about
everywhere else.

Sunday: The mid-levels will consist of a weak ridge over the
Southeast. It should shift offshore as time progresses. The surface
pattern will be similar to previous days with High pressure in
the western Atlantic while troughing persist over a portion of
the Southeast. Low level winds will continue to usher a decent
amount of moisture into our area. High temperatures are expected
to reach the lower to middle 90s away from the beaches, which
will generate a decent amount of instability. Another round of
pulse convection is expected to form along the sea breeze in the
afternoon. Some storms could be marginally severe with damaging
winds being the main concern, followed by locally heavy
rainfall.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
West southwest mid-level flow will be over our region Sunday night.
A longwave trough will gradually develop over the eastern half of
the U.S. Monday into Tuesday, then prevail into Wednesday. Surface
High pressure will remain in the western Atlantic through Monday,
with surface troughing over portions of the Southeast. Expect
convection along/near the sea breeze each afternoon/evening,
decreasing during the overnight hours. A cold front should move
through our area on Tuesday, bringing more numerous convection. High
pressure is expected to bring drier conditions on Wednesday.
Temperatures will remain above normal through Tuesday, then drop to
near normal on Wednesday.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
VFR conditions are expected at the CHS/JZI/SAV terminals
through 18Z Friday. Cumulus will continue into the early
evening, as cloud cover becomes BKN at times around 5K feet.

Any risk for convection 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...
Surface high pressure along and off the southeast coast will
yield winds becoming southerly across the coastal waters
through tonight, with a sea breeze push anticipated along the
coast during the afternoon/evening hours. Speeds will run 10
knots overall with some increase during the afternoon (10 to 15
knots) with the sea breeze. Seas of 2 feet or less anticipated
through tonight.

Extended Marine: High pressure will persist in the western Atlantic
while surface troughing prevails over the Southeast U.S. This will
lead to a typical summer wind pattern. Each day, winds will back and
be stronger along the land/sea interface with the formation of the
afternoon sea breeze. Gusts could approach 20 kt across the
Charleston Harbor with the passage of the sea breeze. Each night,
winds should veer as the low level jet sets up along the coast.
Additionally, convection is expected to return this weekend and
persist into next week.

Rip Currents: The combination of astronomical influences from
the Full Moon and a small swell will lead to an enhanced risk of
rip currents today at all of our beaches. The in-house Rip
Current Calculator continues to indicate a Moderate Risk, while
the Rip Current MOS points to a Low Risk. For consistency, we
have maintained the Moderate Risk. Rip currents are most likely
at Tybee Island.

&&

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

&&

$$

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