122
FXUS62 KCHS 010741
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
341 AM EDT Wed May 1 2024

.SYNOPSIS...
A weak disturbance will move off the coast this morning. High
pressure will then prevail through Friday. A series of
disturbances will move through Saturday through Monday, then
high pressure will rebuild.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: A well defined short wave that is easily observed on
water vapor imagery will pull off the South Carolina coast
early this morning. This is replaced by ridging that approaches
from the west. The surface pattern is rather nebulous, with the
western edges of the Atlantic high staying over the ocean, and a
subtle surface trough nearby.

Patchy fog will be around early this morning due to calm winds
and plenty of low level moisture. This is generally inland, and
will mix out by 9 am.

With the passage of the short wave, showers during the pre-dawn
will come to an end. NVA in wake of that feature, subtle height
rises, and a weak cap will keep things rainfree into early
afternoon. However, once we reach our convective temperature in
the lower 80s, which will be reached around 1-2 pm, convection
will start initiating along almost pure sea breeze. While there
is good low level lapse rates, the mid level lapse rates are
only so-so, and CAPE and shear is on the weaker side. These
conditions along with limited buoyancy will only be able to
produce isolated to scattered showers and a few t-storms. This
is mainly over the eastern half of the forecast counties, tied
to the sea breeze inland motion.

It`ll be another unseasonably warm day, and utilizing the low
level thickness forecast with the MOS consensus and NBM, we
arrive at highs in the mid and upper 80s away from the immediate
coast.

Tonight: Ridging aloft builds overhead, while a weak pressure
pattern is found at the surface that shows Bermuda high pressure
offshore, another high near the Appalachians and a broad, but
weak trough in the local vicinity. The loss of heating will
quickly allow for convection along the sea breeze to come to an
end, and the rest of the night will be rainfree. The biggest
concern will be in regards to fog. Light to calm winds,
subsidence with a fairly strong inversion trapping moisture
underneath, and favorable condensation pressure deficits will
produce at least patchy coverage to the fog. However, some
guidance is hitting it harder, and shows not only greater
coverage, but also some potential for dense fog. There,s a
little cooler air that moves in as skies clear, allowing for
lows to get a few degrees cooler than it was this morning.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
Deep layered ridging will prevail Thursday into Friday. Despite
a robust afternoon sea breeze both days and decent moisture
advection, strong mid-level subsidence should maintain dry
conditions. Above normal temperatures expected with highs in the
mid to upper 80s.

The upper ridge axis will shift just off the coast Saturday
morning, allowing upper shortwave energy to move into the area
from the west. Prevailing onshore flow should allow a sea breeze
to develop fairly early in the day and progress inland. The best
convergence and forcing for convection will exist inland.
Greater sky cover will knock a few degrees off high temps, with
low/mid 80s expected.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
A quasi-zonal flow will exist Saturday night through Monday,
with a series of upper shortwaves moving through. Fairly deep
moisture will be in place, and a good sea breeze will develop
each day. Isolated to scattered showers and thunderstorms
expected during the period. Broad upper ridging Monday night
through Tuesday will bring mainly dry conditions with
temperatures climbing into the 90s in many areas.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
KCHS/KJZI/KSAV: A short wave moving through the area will result
in scattered SHRA and isolated TSRA at or near the KCHS and KJZI
terminals through the pre-dawn hours. This might result in a
TEMPO group of MVFR conditions at both sites. Convection will
not impact KSAV, so we have them as VFR. And early morning
fog/stratus will occur inland from all three airports.

Light offshore winds will develop early this morning, than gives
way to a light sea breeze during the early and mid afternoon
(first at KJZI, then at KCHS, then at KSAV). Isolated showers
and t-storms will form along this boundary between about 18Z and
23Z. But confidence is low of any direct impacts at the
airfields, so no mention at this time.

Extended Aviation Outlook: Flight restrictions possible in
overnight/early morning fog and stratus. Scattered showers and
thunderstorms Saturday through Sunday.

&&

.MARINE...
Today and tonight: The local waters will lie under or near the
western periphery of Bermuda high pressure, while a subtle
trough is found over nearby land areas. The resulting pressure
pattern is relaxed, and even with sea breeze circulations this
afternoon and evening, wind speeds will mainly be no higher than
10 or perhaps 15 kt. Seas will be just 2 or 3 feet. Late
tonight there will be the formation of some fog over land
areas, some of which could move into the Charleston Harbor and
the Atlantic waters very close to shore.

No marine concerns expected Thursday through Monday. Atlantic
high pressure will remain the dominant feature with a relatively
weak gradient in the area. Wind speeds will generally stay
below 10 kt except right along the coast with the afternoon sea
breeze, and seas will mostly run 2-3 ft.

&&

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

&&

$$

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