189
FXUS62 KCHS 300742
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
342 AM EDT Tue Apr 30 2024

.SYNOPSIS...
High pressure will prevail through much of the week. A weak
disturbance will move through today and Wednesday, then a weak
cold front will stall in the vicinity this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Early this morning: We`re starting off a bit warmer than
yesterday morning, but there are still a number of places down
in the mid and upper 50s far inland. Closer to the coast it`ll
be about 5-10F degrees warmer. Nothing more than a little light
fog and patchy stratocumulus and cirrus.

Today: The ridge aloft is forced east in advance of a short
wave that crosses the Appalachians during midday, then moves
into the local vicinity the second half of the afternoon.
Meanwhile at the surface, a lee side trough will develop, as the
western periphery of Atlantic high pressure originally over the
area pulls to near the coast this afternoon. There will be some
showers and storms in the ocean within the southerly flow on
the back side of the offshore high. But the main convergence
that generates this convection stays offshore, maybe coming
close to the Charleston County coast for a brief time late
morning /early afternoon.

There`s a weak cap that holds in place into the early
afternoon, before we reach our convective temperatures around
80F degrees. So there is little to no chance of any rain through
2 or 3 pm. However, with the approaching short wave, and PWat
climbing to between 1.25 to 1.50 inches, we do look to get our
first chance of rain in more than a week. While lapse rates are
decent, the CAPE and shear isn`t anything significant. That
along with the greater buoyancy staying to our west, suggests
that convection will likely remain disorganize. Thus the severe
risk is basically non-existent. However, it is non-zero, given
dry air between about 700 and 500 mb, and the resulting DCAPE of
600-800 J/kg. So maybe a few strong wind gusts can occur where
incoming convection collides with the sea breeze late in the
day. There might also be a little hail in the stronger updrafts
with WBZ less than 10K feet. The highest chances for convection
will be near and west of I-95, where we have 30-40% PoPs late
day. It is also those places that might see a couple of stronger
storms.

Despite increasing cirrus this morning, which lingers into the
afternoon, there is good warm advection to allow for max
temperatures to hit 80-85F degrees away from the beaches, where
the sea breeze holds coastal communities down in the 70s.

Tonight: the short wave passes through the forecast area,
reaching near the coast or offshore by Wednesday morning. the
lee side trough remains in place, while the western side of the
Atlantic ridge pulls a bit further out to sea. There is just
enough instability and ample moisture for the short wave to work
with, so we do maintain chance PoPs much of the night. Although
with the passage of the short wave, probabilities drop off
across Georgia late. The nocturnal environment is not conducive
for any severe storms after the early evening.

There are indications of some fog forming across parts of
Georgia after midnight. But with perhaps too much lingering
cloud cover, we refrained from including in the forecast at this
time.

Given the cloud cover and dew points in the lower and middle
60s, that`s about as cool as it`ll get.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
A few showers could move through the Charleston Tri-County area
Wednesday morning in association with the tail end of the upper
shortwave. Weak upper level subsidence will develop during the
afternoon as shortwave ridging occurs. However, moderate
moisture will remain in place during the afternoon, and a decent
sea breeze will develop, potentially popping isolated showers.

Deep layered ridging Thursday into Friday should maintain dry
weather with above normal temperatures. A shortwave could
approach far western areas late Friday afternoon so it`s
possible some convection could drift into those zones late in
the day. Highs will reach the mid to upper 80s both days.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...

A relatively zonal flow will develop Friday night and continue
into early next week, with occasional shortwaves rippling
through. A weak cold front is forecast to stall across far
inland areas over the weekend. Tropical moisture will spread
into the area with PWATs hovering around 1.7" much of the
period. Isolated to scattered mainly diurnal convection is
expected, along with above normal temperatures.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
KCHS/KJZI/KSAV: VFR will prevail at all sites through 06Z
Wednesday. There will be a few showers off the coast of KJZI
during the late morning and early afternoon, as they remain
offshore. Upstream from all terminals, scattered SHRA/TSRA will
occur during the mid and late afternoon, eventually progressing
east tonight. While flight restrictions are possible should any
directly impact a terminal, probabilities are too low to show
anything in the latest TAFs. All airfields will experience some
wind gusts of 15-20 kt in wake of the sea breeze after 18-19Z.

Extended Aviation Outlook: VFR will generally prevail.

&&

.MARINE...
Today and tonight: While an inland trough develops and remains
in place, it keeps the western edges of Atlantic high pressure
close to the local waters through the period. This in turn
causes southerly winds of 15 kt or less. The exception might be
Charleston harbor this afternoon, where some gusts approach
hing 20 kt will be possible at times. Seas in the Atlantic will
be no more than 3 or 4 feet. Mariners should be alert for a few
t-storms here and there, with a few potentially resulting in
gusty winds and frequent lightning strikes.

Wednesday through Sunday, no marine concerns expected. 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 in 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...