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296
FXUS62 KCHS 120834
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
434 AM EDT Sun May 12 2024

.SYNOPSIS...
High pressure will prevail into Monday. A storm system will
affect the area by the middle of the week. Another system could
arrive later in the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
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Today: Aloft, the region will remain primarily in a northwest flow
between a trough shifting off the Mid-Atlantic Coast and a
broad/flat ridge across the Gulf of Mexico. At the sfc, a weak
trough will exit offshore north of the area while high pressure
lingers locally. The setup will favor light west/northwest sfc winds
for much of the day and should pin the seabreeze closer to the coast
until mid-late afternoon. High pressure along with a downslope wind
aloft will keep all areas dry and sunny/mostly sunny for the day and
result in slightly warmer conditions than the previous day. High
temps should range in the low-mid 80s.

Tonight: Northwest flow aloft will gradually turn more west as
modest ridging takes place overnight. The upper jet will likely
produce more cirrus across the region, followed by additional cloud
cover after midnight with the approach of h5 shortwave energy from
the west and increasing isentropic lift across southern areas closer
to daybreak. At this time, showers look to hold off until after
daybreak across southeast Georgia. Overnight lows will be noticeably
more mild given increasing cloud cover after midnight. In general,
lows should range in the upper 50s well inland to low-mid 60s across
southeast Georgia and closer to the coast across southeast South
Carolina. At the beaches, temps should remain in the upper 60s
through the night.
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&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
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Aloft, a shortwave trough will ripple across the forecast area on
Monday with a mid-level trough sweeping across the Mid-Atlantic
states Tuesday into Wednesday. At the surface a warm front will
develop to the south of the local region on Monday, lifting
northward Monday night. A cold front is then forecast to push
through the region Wednesday.

Isolated to scattered showers and possibly a thunderstorm are
possible Monday afternoon in the presence of the shortwave aloft.
Precipitation coverage will increase overnight Monday as the warm
front lifts northward and moisture surges into the region. PWATs
could approach 2", well above the daily maximum according to SPC
climatology. By Tuesday morning numerous to widespread showers are
expected to cover the forecast area. Instability doesn`t really ramp
up until later on Tuesday, so overnight Monday and Tuesday morning
only feature a chance of thunder. There are some model disagreements
regarding how much instability will be in place, with the ECMWF
showing around 1000 J/kg of CAPE, mainly focused south of the
Savannah River. The GFS keeps most instability confined to extreme
southeastern GA and the offshore waters. However, in the presence of
a forecast 40+ knots of shear, a stronger thunderstorm certainly
cannot be ruled out. SPC has outlooked the region in a Marginal Risk
of severe thunderstorms.

With PWATs forecast to reach above climatological normals there is
the threat of heavy rainfall Monday night into Tuesday. WPC has
outlooked the entire forecast area in a Slight Risk of Excessive
Rainfall on Tuesday, with generally 2 to 3 inches of rain forecast
from Monday afternoon to Wednesday morning.

Temperatures Monday and Tuesday are forecast to be in the upper 70s
to low 80s, with low to mid 80s on Wednesday. Overnight lows will be
rather mild due to the excessive cloud cover and rainfall, only
dipping into the mid to upper 60s, with around 70 along the
beaches.
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&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
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Ridging aloft will briefly build into the region on Thursday, with
another shortwave trough forecast to ripple through the southeastern
states Friday into Saturday. A surface cold front is expected to
push through the region at the end of the week, bringing the region
another chance of showers and thunderstorms. Temperatures through
the period are expected to be around or slightly above normal.
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&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
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VFR conditions will prevail at KCHS, KJZI, and KSAV through 06Z
Monday.

Extended Aviation Outlook: Showers and thunderstorms could bring
flight restrictions to the terminals Monday afternoon into the
middle of next week.
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&&

.MARINE...
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Today and Tonight: Light west/southwest winds will prevail through
morning hours while a weak sfc trough exits offshore to the north.
Winds should gradually turn south-southwest this afternoon while a
seabreeze circulation develops and high pressure remains locked in
place. However, wind speeds will generally remain around 10 kt or
less. Overnight, conditions remain quiet with high pressure lingering
across the area. South winds should range between 5-10 kt across
most waters. Seas will range between 1-2 ft through tonight for
most waters. However, seas could touch 3 feet across Charleston
County waters beyond 10 NM this morning, before subsiding this
afternoon.

Monday through Friday: A warm front will lift northward through the
marine waters Monday night, resulting in a slight surge in wind
speed from around 10 knots to around 15 knots and a shift from SE to
SW winds. Seas will average 3 to 4 ft. A cold front is then forecast
to push through the region Wednesday, with winds shifting to the NW
by Thursday morning and seas surging to 4 to 6 ft. A Small Craft
Advisory may be required for the Charleston County nearshore waters
and the 20 to 60 nm offshore GA waters. Winds and seas will diminish
Thursday night into Friday, with 2 to 3 foot seas and winds
generally around 10 knots.
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&&

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

&&

$$

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