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107
FXUS62 KCHS 222021
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
421 PM EDT Sat Jun 22 2024

.SYNOPSIS...
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A weak surface trough will linger near the Georgia coast
through tonight. High pressure will then prevail over the
western Atlantic through next week.
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&&

.NEAR TERM /THROUGH SUNDAY/...
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Through Tonight: Weak low pressure currently centered near I-95
in Liberty County will continue to slowly trek up the coast
overnight as it weakens. Though strong upper ridging/subsidence
will limit the growth of most updrafts, 1000-1500+ J/kg of CAPE
through the rest of the afternoon and into the evening could be
sufficient to spawn a few short lived thunderstorms. Otherwise,
mainly scattered showers across eastern GA, and only isolated
showers across the Low Country expected to prevail through the
evening.

Late tonight, modest destabilization as the top of
stratus/strato-cu near the center of the low circulation
radiates could provide some convective enhancement, and a few
slowly moving convective elements could develop near
Savannah/Beaufort Co area. Localized rainfall amounts could
reach up to 3-4+ inches in this area, but widespread rainfall
amounts will likely be closer to an inch or less. Further north
toward the Charleston Metro will see more limited rainfall
coverage with prolonged heavy rainfall unlikely.

Elsewhere across inland southeast GA some clearing could occur
late tonight with the gradient relatively weak. There could be
enough time for some favorable radiational cooling to overlap
with lingering BL moisture, and some patchy, light fog could
develop mainly along and west of the US Hwy 301 corridor.

Sunday: Weak surface low along the coast will open and be
absorbed into the approaching troughing/front well inland.
Still, ample low level moisture lingers, with showers and storms
likely to develop along the resultant sea breeze by the
afternoon. Widespread cloud cover across much of the area will
limit the instability somewhat, but instability climbing to
1000-2000 J/kg of MUCAPE along the sea breeze could bring some
stronger thunderstorms, with gusty winds and lightning the
primary threats. Further inland across SE GA, dry air will work
in as the low dissipates and less cloud cover will bring warmer
temps (into the mid 90s) and lower rainfall chances. Heat index
values will climb to around 100 for most tomorrow afternoon,
with warmer temps but less humidity inland, but greater humidity
and relatively more moderate temps closer to the coast.
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&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
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A weak shortwave ridge will extend across southeast GA Sunday
night, then a shortwave trough will drop into southern SC from
the northwest on Monday. A weak surface cold front will slowly
drift into the area on Monday. Increasing thicknesses combined
with pre-frontal compression will result in toasty temperatures
in the mid to upper 90s.  The deepest moisture is forecast
to move off the coast early Monday afternoon, so afternoon
instability will not be particularly strong. A decent sea breeze
should develop and move inland in the afternoon, but there will
also be some mid-level subsidence working against buoyant
parcels. We have isolated to scattered showers and thunderstorms
in the afternoon. Heat indices will top out between 104 and
108F, just shy of needing a Heat Advisory.

A weak northwest flow will continue aloft on Tuesday while a
weak surface high is centered across inland areas. Large scale
subsidence will result in another hot day with highs in the mid
to upper 90s. Surface dewpoints should mix out across inland
southeast GA, while moisture pooling occurs closer to the SC/GA
coast. The greatest risk for Heat Advisory conditions with heat
indices above 108F will be across coastal GA and far southern
SC. The main forcing for convection will be from the sea breeze,
though a few subtle upper shortwaves are also possible.
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&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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A developing upper trough across the eastern United States and
deep tropical moisture spreading into the area is expected to
support greater coverage of mainly diurnal showers and
thunderstorms through the long term period.
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&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
Very weak low pressure slowly riding up the Georgia coast
through tonight will continue to bring ample low level moisture
advection across the area. Scattered to broken ceilings will
continue this afternoon, with MVFR ceilings prevailing mainly
across southeast Georgia, but at least occasional MVFR still
possible across parts of the Low Country.

Tonight, BL cooling and continued moisture advection will
result in increasing coverage of MVFR ceilings, and all TAF
sites will prevail MVFR late this evening through Sunday
morning. Scattered showers continue through this evening, with
a few thunderstorms possible mainly along the GA coast. Rainfall
coverage overnight will be more limited, but isolated to
scattered showers still possible mainly along the coast. Though
brief visibility reductions and locally higher wind gusts
are possible at all terminals overnight, confidence in
timing/coverage is too limited to justify even a TEMPO group for
vis restrictions overnight.

Extended Aviation Outlook: Mostly VFR. However, convection will
bring brief flight restrictions, mainly each afternoon and
evening.

&&

.MARINE...
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Weak low pressure slowly moving up the Southeast coast will
continue to bring mainly moderate southeast winds across the
waters tonight and Sunday. Some gusts to near 20 kt are possible
near the low center on the east and north sides, and near any
showers or storms, but SCA conditions are unlikely to be
reached. Seas remain 3-4 ft overnight and Sunday as easterly
medium period slowly diminishes while southerly windswell begins
to build.

Extended Marine: A slightly enhanced gradient is expected
Sunday night between an inland trough and offshore high
pressure. Wind gusts could approach 25 kt beyond 15 NM from the
coast, and seas may reach 5 ft over outer portions. Otherwise, a
fairly typical summertime pattern will occur, with the
strongest winds along the coast each afternoon as the sea breeze
develops.

Rip Currents: A moderate risk continues through Sunday due to
onshore winds and a moderate southeast swell.
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&&

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

$$

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