214
FXUS62 KCHS 181110
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
710 AM EDT Fri Oct 18 2024

.SYNOPSIS...
Dry high pressure will prevail through the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
For today: A closed low about 300 miles east of the Delmarva
will shift east-southeast through the day. This allows for an
amplified ridge extending from near Hudson Bay in Canada, south
through the Great Lakes, and into the southeast states to push
slowly east. In turn this generates small height rises across
the local area. At the surface, low pressure is underneath the
closed low aloft, with robust high pressure covers much of the
eastern half of the country.

Once again there isn`t any rain in the forecast, with just some
of those stratocumulus offshore to brush through parts of the
coastal counties of Georgia. This is where the low level flow is
most directly onshore, aided by perhaps very subtle isentropic
ascent and a little low level moisture.

Our temperatures were derived from the various MOS guidance and
NBM, and also relying heavily in the 1000-850 mb thickness
forecast. This supports afternoon highs in the upper 60s and
lower 70s, which is about 6-8F below climo.

Tonight: Low pressure surf ace and aloft in the ocean heads
southeast toward Bermuda, while strong high pressure surface and
aloft covers the forecast counties and much of the eastern U.S.
Although there will be some marine based stratocumulus heading
toward the shore late, it`ll generally be a clear/mostly clear
night. Winds do decouple in many areas, setting the stage once
again for good radiational cooling, especially inland. We leaned
toward the cooler side of guidance, and then even "knocked off"
a couple of degrees from there. It won`t be as cold as the past
two nights with continued air mass modification. Bu still around
10F below normal. And even these values might still be a little
"warm".

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
Cool and dry high pressure will prevail Saturday through Monday.
Low-level thicknesses will steadily increase during the period,
leading to a gradual warming trend. Highs in the mid 70s on
Saturday will rise to the upper 70s Sunday, then upper 70s to
lower 80s on Monday. Good radiational cooling expected Saturday
night and Sunday night, with lows dipping into the 40s inland,
and 50s elsewhere.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
Dry weather expected through late week as an upper ridge builds
from the west and high pressure remains in place at the surface.
Temps will remain a few degrees above normal.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
VFR conditions will prevail at KCHS, KJZI, and KSAV through 12Z
Saturday.

Extended Aviation Outlook: Prevailing VFR.

&&

.MARINE...
Today: The coastal waters will be positioned on the southeast
side of a strong and humongous continental high pressure system,
with low pressure about halfway between Long Island and
Bermuda. There`s a decent gradient in place as a result, which
will favor N and NE winds as high as 15 or 20 kt. Seas will
average 3-4 feet within 20 nm from shore, but up to 5 feet on
the outer Georgia waters.

Tonight: The synoptic pattern isn`t much different, with a
continuation of the expansive high over the eastern states, as
the Atlantic low draws closer to Bermuda. NE winds will again be
near 15 or 20 kt, but with this continued fetch, seas will be
able to build at least a foot. As a result we have 6 footers
entering the outer Georgia waters this evening, and raised the
Small Craft Advisory flags for those waters at 8 PM. This will
be the beginning of a long duration advisory.

Saturday through Wednesday: With surface high pressure remaining
over the eastern United States, a steady NE flow will prevail
over our marine area. Wind gusts could occasionally reach 25 kt.
The primary concern is building seas. 6 ft seas are expected to
be ongoing across the offshore GA waters by Saturday morning. We
expect some 6 footers to move into the nearshore SC/GA waters
later Saturday night into Sunday. For now we have a Small Craft
Advisory through Tuesday night for the offshore GA waters. But
we`ll likely need advisories for the nearshore waters with the
next forecast package.

Rip Currents: The locally produced Rip Current Calculator and
the Rip Current MOS both point to a moderate risk for rip
currents along the Georgia beaches today. This is where we have
the slightly stronger onshore winds. The risk is low elsewhere,
but any higher wind could prompt a greater risk.

&&

.TIDES/COASTAL FLOODING...
Today: It`s a given that we`ll have minor or even moderate coastal
flooding this morning for coastal Charleston and Colleton County,
as the astronomical tide is 7.2 ft MLLW. We expect at least
some positive anomaly on top of that, so we issued a Coastal
Flood Advisory valid from 7-11 AM.

Th rest of the coast from Beaufort to McIntosh County will be
close to achieving shallow coastal flooding, and we could yet
require an advisory there as well. But since latest levels are
trending down, and are actually below astronomical levels, we
opted not to issue the advisory.

Elevated tide cycles are expected through the first part of
next week. Minor to moderate coastal flooding is currently
forecast for the entire southeast South Carolina and Georgia
coast with the morning high tide cycles this weekend. It`s not
out of the question to see tide levels approach major flooding
threshold of 8 ft MLLW in the Charleston Harbor with the
Saturday morning high tide. Although not all guidance is in
agreement regarding this potential.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Coastal Flood Advisory until 11 AM EDT this morning for SCZ049-
     050.
MARINE...Small Craft Advisory from 8 PM this evening to 6 AM EDT
     Wednesday for AMZ374.

&&

$$

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