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000
FXUS62 KCHS 110056
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
856 PM EDT Wed Apr 10 2024

.SYNOPSIS...
A storm system will impact the region late tonight into
Thursday. High pressure should build over the region on Friday
and persist into early next week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Convoluted pattern evolving across the region. Strong short-
wave energy is progressing out of eastern Texas with an
attending surface low over central Mississippi. Ongoing complex
of showers and severe thunderstorms is advancing through
southeast Alabama into southwest Georgia and along the Florida
Panhandle with a muddied surface pattern across the Gulf Coast.
Northern side of the MCS precip shield is already progressing
into south-central Georgia and already just a few counties
west/southwest of the forecast area.

Meanwhile, southeasterly flow off the Atlantic has/is kicking
off a couple narrow bands of light showers that are moving
through parts of southeast South Carolina. We have updated the
forecast to account for the showers off the Atlantic.

Will see how well the MCS precip shield holds together over the
next several hours as the system encounters increasing stable
conditions downstream and should steadily weaken in time. But
per forward momentum and regional radar trends we have sped up
the timing of precip into the forecast area, now spreading into
the western part of the forecast area around or shortly after
midnight and largely to the coast by sunrise.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
Thursday will feature the most impactful weather of the stretch. Mid
level low initially over the Lower Mississippi River Valley will
lift northeastward while getting absorbed in the larger scale trough
as it approaches the East Coast. Surface low will take a similar
track, with the associated cold front sweeping through the local
area later in the day. Models continue to show a band of showers and
thunderstorms moving through ahead of the front, primarily in the
morning through mid afternoon. Area wide rainfall totals average in
the 1-1.5 range, with locally higher amounts possible.

Attention then turns to the severe weather potential. Shear of 50+
knots is certainly supportive of storm organization though
instability progs remain rather meager - a few hundred J/kg at best
with poor mid level lapse rates. Radar will certainly bear watching
however with strong storms possible, capable of producing damaging
wind gusts and also isolated tornadoes given hodographs and
associated SRH values.

Even outside of convection, it will be a breezy day as a 50-60 kt
LLJ translates across the area. Wind gusts upwards of 40-45 mph will
be possible, highest along the coast and over the Charleston tri-
county. A Wind Advisory has been issued for the entire area.
Motorists should especially use caution on bridges and overpasses.

Rain chances decrease rapidly early Thursday evening as the line of
storms shift offshore. While the strongest winds will have ended,
winds will remain fairly gusty through the night with tight pressure
gradient remaining in place. The Wind Advisory will likely need to
be replaced by a Lake Wind Advisory for Lake Moultrie.

Quieter and dry weather anticipated for Friday and Saturday as the
surface low finally pulls away and high pressure expands across the
region. Gusty west winds will linger on Friday, but otherwise no
significant weather concerns. Highs in the lower to middle 70s on
Friday will gain a couple degrees for Saturday in the upper 70s
across most locations.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
High pressure will remain in control for the early to middle of next
week. No significant weather concerns with a rain-free conditions
expected. Temperatures will be on a warming trend through the
period.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Unsettled conditions overnight through the day Wednesday.

Surface low pressure over Mississippi will progress into the
western Carolinas through Thursday. Ahead of the system, one
area of showers and some thunderstorms may reach the terminals
during the late overnight hours in a weakened state. But we have
sped up timing of precip and conditions trending MVFR during
the overnight hours, particularly at KSAV where showers may
reach that terminal as early as 06Z.

Additional showers and possibly some thunderstorms will follow
through the day Thursday as a warm front surges up through the
region followed by a trailing cold front late day.

Meanwhile, gusty southerly to southeasterly winds will develop
later overnight and further increase through the day Thursday
with peak gusts in excess of 30 knots possible Thursday
afternoon.

Extended Aviation Outlook: VFR. Gusty west winds may remain
across the terminal Thursday night into Friday.

&&

.MARINE...
Tonight, the marine zones will remain between deepening sfc low
pressure over the Deep South and high pressure centered over the
western Atlantic. This pattern will provide the region with
strengthening south winds tonight. Winds will develop gusts in
excess of 25 kts across the outer GA waters this evening, then the
nearshore waters (outside the CHS Harbor) after midnight. In
addition, wave heights will build through tonight, reaching 5-8 ft
late. Small Craft Advisories have been issued for all zones outside
the CHS Harbor tonight.

Thursday through Monday: Hazardous marine conditions are expected to
overspread the waters on Thursday ahead of an approaching cold
front. Wind gusts are forecast to reach 35-40 knots which has
prompted a Gale Watch across all waters, including the Charleston
Harbor. Seas also build, peaking in the 7-10 ft range. There will be
some improvement later in the day and overnight Thursday, however
Gale Watches will need to be replaced by Small Craft Advisories for
some period of time, likely continuing into Friday for portions of
the waters. The pressure gradient finally eases as we move into the
weekend and early next week, with no additional concerns.

High Surf: Large breaking waves are expected to develop at the
beaches on Thursday, highest along the Charleston county coast. A
High Surf Advisory has been hoisted there.

Rip Currents: On Thursday, breaking wave heights exceeding 5 ft with
very gusty winds will yield a High Risk for rip currents at all
beaches. An increased risk of rip currents will likely last through
the end of the week.

&&

.TIDES/COASTAL FLOODING...
For the upcoming evening high tide (~10:30 pm): The astronomical
high tide for Charleston is 6.56 ft MLLW. The observed tidal
departure is currently running about 0.7 ft, which would again be
sufficient to produce minor coastal flooding if it maintains into
the evening. Onshore southeasterly flow will be a bit stronger than
the past few days and this should keep the tidal departure around
this level. It appears we are again in line for a peak tide value
somewhere in the 7.1-7.3 ft MLLW range. A Coastal Flood Advisory is
in effect for Charleston and coastal Colleton Counties from 9 PM to
midnight.

The threat for coastal flooding will decrease after this evening`s
high tide as we move further away from the new moon and perigee and
winds eventually turn offshore with a cold front.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Wind Advisory from 8 AM to 8 PM EDT Thursday for GAZ087-088-
     099>101-114>119-137>141.
     High Risk for Rip Currents from Thursday morning through Thursday
     evening for GAZ117-119-139-141.
SC...Wind Advisory from 8 AM to 8 PM EDT Thursday for SCZ040-
     042>045-047>052.
     High Risk for Rip Currents from Thursday morning through Thursday
     evening for SCZ048>051.
     Coastal Flood Advisory until midnight EDT tonight for SCZ049-
     050.
     High Surf Advisory from 8 AM Thursday to 8 AM EDT Friday for
     SCZ050.
MARINE...Gale Watch from Thursday morning through Thursday evening for
     AMZ330-374.
     Small Craft Advisory from 2 AM to 8 AM EDT Thursday for AMZ350-
     352-354.
     Gale Watch from Thursday morning through late Thursday night
     for AMZ350.
     Gale Watch from Thursday morning through Thursday afternoon
     for AMZ352-354.
     Small Craft Advisory until 8 AM EDT Thursday for AMZ374.

&&

$$

NEAR TERM...Adam
SHORT TERM...ETM
LONG TERM...ETM
AVIATION...ETM/Adam
MARINE...ETM/NED