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402
FXUS62 KCHS 150836
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
436 AM EDT Wed May 15 2024

.SYNOPSIS...
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A cold front will move through late today, followed by high
pressure into Friday. A storm system will affect the area this
weekend, followed by high pressure from the north next week.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Early Morning: A southwest flow will maintain a fair amount of low-
lvl moisture early, supporting a marginally unstable environment
capable of producing a few showers and/or thunderstorms across far
inland zones of southeast South Carolina. Just upstream ongoing
convection has persisted through the night across parts of the
Midlands and north of Lake Moultrie. This activity is expected to
drift north-northeast with time, likely remaining out of the area,
but given the lingering environment have maintained 15-20 POPs
across the Tri-County Area a few hours after daybreak.

Today: Southwest flow this morning will gradually turn more westerly
along the base of a mid-upper lvl trough slowly advancing toward the
Mid-Atlantic States this afternoon. The setup will tend to favor a
bit of subsidence within a downslope wind by late morning, keeping
most if not all areas dry into mid afternoon while stronger sfc
heating promotes low-lvl mixing into drier air aloft. Afternoon
highs will become warmer than the previous day, peaking in the mid-
upper 80s across most areas away from the beaches. For much of the
day, forcing will be lacking and moisture limited well ahead of a
weak front approaching from the northwest. However, there should be
an uptick in shower/thunderstorm chances heading into late afternoon
as weak h5 shortwave energy along the leading edge of the mid-upper
trough advances across the local area and encounters an environment
characterized by SBCAPE around 2000-3000 J/kg, mid-lvl-lapse rates
around 7 C/km and potentially a fair amount of DCAPE at a time when
wind fields support 0-6km bulk shear around 35-40 kt. A few
thunderstorms could become strong and/or severe in this setup, with
the best chances of occurrence across the Tri-County Area late
afternoon into early evening when larger scale forcing interacts
with a somewhat pinned seabreeze circulation near the South Carolina
coast.

Tonight: Showers and/or thunderstorms will likely weaken
considerably and/or shift offshore with a weak sfc front shortly
after sunset, ending precip across the entire area for the rest of
the night. Dry high pressure will then settle in for the night with
temps dipping into the low-mid 60s inland to upper 60s/around 70
near the coast.
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&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
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The local forecast area will be positioned along the southern
periphery of a mid level trough situated off the Mid-Atlantic coast.
A nice day is expected on Thursday, owing to the NW flow aloft and
high pressure briefly building in at the surface. High temperatures
will reach into the mid to upper 80s, with mostly clear skies and
dry conditions forecast. Overnight lows Thursday will be in the mid
60s inland with 70 along the beaches.

The flow aloft will briefly transition to a zonal flow on Friday,
with surface high pressure retreating out into the Atlantic waters.
To the west a mid level trough and associated surface cold front
will begin trekking towards the Deep South. Ahead of the approaching
cold front isolated showers and thunderstorms are possible across
the far inland zones late Friday. Otherwise, another rain-free
forecast with high temperatures again reaching into the mid to upper
80s. Overnight lows will be rather mild, given the increasing cloud
cover ahead of the approaching cold front. Low temperatures are
forecast to only dip into the mid 60s inland with low 70s along the
coastline.

Saturday is expected to be another active weather day as a low
pressure system impacts the forecast area. A warm front is forecast
to lift northward early, with a cold front pushing through later.
PWATs are forecast to reach 1.5+ inches Saturday afternoon.
Additionally, both the GFS/ECMWF show a decent amount of instability
across the region (around 1000 J/kg of CAPE). Given the favorable
environment, numerous showers and thunderstorms will be possible.
Showers and thunderstorms as well as thick cloud cover will likely
hinder high temperatures on Saturday, only reaching into the low to
mid 80s.
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&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
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The aforementioned mid level trough will slip offshore Saturday
night/Sunday morning, with broad ridging building in behind it. High
pressure will also build in at the surface and dominate through the
remainder of the weekend and into early next week. Apart from Sunday
afternoon which could see a greater coverage of showers and
thunderstorms due to lingering dynamics from the departing trough,
rain chances through early next week remain minimal as subsidence
builds into the region. Under plentiful sun, ridging aloft, and
surface high pressure temperatures each day will reach into the
upper 80s with some locations across southeastern GA possibly
touching 90.
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&&

.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
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KCHS/KJZI/KSAV: VFR conditions are expected at CHS/JZI/SAV terminals
through 09-10Z Wednesday, but low stratus should develop across the
terminals for a few hours thereafter, resulting in MVFR cigs between
10-13Z at CHS/JZI and 09-13Z at SAV. A brief period of IFR cigs can
not be ruled out during this same time frame, but confidence remains
too low to include in the latest TAF issuance. VFR conditions are
expected to return at all terminals by late morning Wednesday, but
gusty west-southwest winds around 20 kt are anticipated during much
of the afternoon.

Extended Aviation Outlook: Showers and thunderstorms could bring
flight restrictions to all terminals on Saturday as a low pressure
system impacts the region.
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&&

.MARINE...
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Today and Tonight: A Small Craft Advisory remains in effect across
Charleston County waters early this morning, mainly due to lingering
6 ft seas beyond 15 NM from the coast. Sea conditions should improve
by mid morning, resulting in conditions that remain below advisory
levels.

A somewhat enhanced pressure gradient will persist across local
waters today ahead of a weak cold front advancing toward the
coast late day and early night. The pattern supports southwest
winds generally up to 15-20 kt by late morning and through
afternoon hours, before stronger wind fields shift to the north-
northeast and the pressure gradient weakens post fropa. Cold
air advection behind the front will be somewhat marginal,
suggesting marine conditions to remain below advisory levels
through the night. Seas should generally range between 3-5 ft by
late morning, highest across offshore Georgia waters and
Charleston County waters. Overnight seas will subside to 2-4 ft.

Thursday through Monday: Conditions through the period are expected
to remain below Small Craft Advisory criteria. High pressure will
briefly build in at the surface on Thursday, with winds generally
around 10 knots and seas averaging 2 to 3 ft. A cold front will push
through the region on Saturday, shifting winds more to the W and
surging slightly to around 15 knots with gusts to 20 knots. Seas are
expected to build on Saturday as well, increasing to 3 to 4 ft. By
Monday winds will shift to the NW, generally around 10 knots with
seas diminishing to around 1 to 2 ft.
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&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 6 AM EDT early this morning for
     AMZ350.

&&

$$

NEAR TERM...DPB
SHORT TERM...CPM
LONG TERM...CPM
AVIATION...CPM/DPB
MARINE...CPM/DPB