167
FXUS62 KCHS 051129
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
729 AM EDT Wed Jun 5 2024

.SYNOPSIS...
High pressure will extend across the area through today. A cold
front will approach from the northwest on Thursday, then slowly
move through on Friday. High pressure returns for the weekend,
then another cold front will move through Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, the ridge axis will be off to the east with a
shortwave approaching from the west in the morning and starting
to nudge into the forecast area in the afternoon. At the
surface, high pressure over the Atlantic will continue to be the
primary feature extending westward into the forecast area. Once
again we will be largely devoid of any real surface features to
serve as a trigger or focusing mechanism for convective
development, though the aforementioned shortwave arriving in the
afternoon should help aloft. The morning looks as though it
will be quiet with no development expected. As we get into the
early afternoon, isolated thunderstorms should start to
percolate across south-central Georgia just ahead of the
shortwave. These thunderstorms will then steadily track to the
east and into southeast Georgia during the mid to late afternoon
hours. Hi-res model runs continue to hint at this with each
run, and there is enough consensus to advertise 60 percent
chances for southeast Georgia and the counties in southeast
South Carolina along the Savannah River. Model soundings depict
an environment with CAPE values on the order of 1,500-2,000 J/kg
and DCAPE values in the 800-1,000 J/kg range. It is possible
that 1 or 2 of the developing thunderstorm clusters become
strong enough to produce damaging wind gusts. Temperatures
should continue their day- to-day gradual climb, with 88-92
degrees expected everywhere away from the immediate coast.

Tonight: As the early evening begins, there will likely be
ongoing thunderstorms that extend southward from between
Allendale and Walterboro to the entire southeast Georgia coast.
This activity could continue to spread eastward through the
evening, especially if outflow boundaries can track into
untapped area of southeast South Carolina. We will have to wait
and see how thunderstorms evolve through the afternoon, but it
is possible there could be more coverage through the evening
into southeast South Carolina than currently depicted in the
forecast. Any severe threat should steadily diminish with the
loss of heating. The focus for showers and thunderstorms should
then shift offshore for the latter part of the overnight. Look
for mild temperatures, with lows likely not falling below 70 in
most areas.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
A weak shortwave will move through Thursday afternoon and
evening, then a cold front will cross the area Friday morning.
Deep moisture will exist over the area Thursday with PWATs
around 1.75". Decent instability will develop in the afternoon
given high temps in the low to mid 90s, though some mixing out
of dewpoints inland will somewhat reduce total buoyancy. Low-
level flow out of the WSW will keep the sea breeze pinned near
the coast for much of the day, then it may move slightly inland
late in the afternoon. Weak mid-level subsidence may develop
during the afternoon as the shortwave trough axis shifts to the
coast. This may be why much of the guidance only shows scattered
convection on Thursday. We bumped PoPs down a tad, though still
anticipate at least 40-50% coverage at some point on Thursday.

Considerably drier air will move in on Friday. Downslope flow
will push highs into the low to mid 90s, but surface dewpoints
dropping into the upper 50s inland to lower 60s coastal will
make for a noticeable change in airmass. Another weak shortwave
will drop through the area Friday afternoon. Although subsidence
and drier air should severely limit the convective potential,
we could have just enough moisture across the southern half of
the area to support an isolated shower or tstm.

Saturday looks dry. Downslope flow will again push highs into
the lower 90s, though the air will feel relatively dry given
surface dewpoints mixing down into the 50s during the day.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
Another cold front will approach on Sunday, then stall near the
area Monday before eventually dissipating. Moisture will be on
the increase late weekend into early next week. This, along with
some shortwaves and decent sea breezes each afternoon, should
support scattered convection.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions are expected to prevail at KCHS, KJZI, and KSAV
through 12z Thursday. The main forecast challenge will be
afternoon and evening shower and thunderstorm activity and if it
can impact any of the terminals. KSAV seems to be the primary
candidate and we have introduced VCTS with a TEMPO for TSRA in
the 21-00z time period. For now we have kept the TEMPO MVFR, but
it is likely that if a storm directly impacts the terminal the
visibility will at least briefly drop to IFR. Gusty winds are
also a concern. This thunderstorm activity could shift eastward
into the vicinity of KCHS and KJZI later in the evening, but
confidence is too low to add anything into the TAF`s at this
time.

Extended Aviation Outlook: Aside from brief flight restrictions
in showers/tstms Thursday afternoon, VFR conditions expected.

&&

.MARINE...
Today and tonight: Southerly flow will prevail across the local
waters through the period with speeds mostly in the 10-15 knot
range. Gusts up to around 20 knots are expected along the
land/sea interface with the afternoon sea breeze. Overnight,
winds will pick up a bit thanks to modest nocturnal surging,
with speeds around a solid 15 knots or even 15-20 knots at
times. Seas are expected to average 2-3 feet.

SW winds Thursday and Thursday night will transition to W on
Friday, then a brief period of northerly flow expected Friday
night and Saturday behind a cold front. Winds return to
southerly by late weekend as Atlantic high pressure rebuilds. No
headlines anticipated.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will remain elevated today and again on
Thursday. Although the wind direction along the coast isn`t
ideal for driving large positive tidal departures, conditions
should still be sufficient to produce departures in the 0.4 to
0.6 ft. Therefore, the upcoming evening high tide and again
Thursday evening could peak right around 7.0 ft MLLW in
Charleston. Coastal Flood Advisories could be needed for
Charleston and coastal Colleton counties.

&&

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

&&

$$

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