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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 031006
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
606 AM EDT Sat Jun 3 2023

...COASTAL FLOODING LIKELY AROUND THE EVENING HIGH TIDE THROUGH
MONDAY...

.SYNOPSIS...
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A weak cold front will drop south through the area tonight.
High pressure returns for the first half of next week. Another
front could move through the area towards the middle of next
week.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
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No major changes were made for the sunrise update. A few showers
could brush the beaches of Charleston County over the next few
hours, but this activity will tend to dissipate as it reaches
the coast.

Today: Friday`s Rex Block will finish its transition to an Omega
Block across the CONUS today. This will keep surface features
across the Southeast U.S. fairly static with high pressure
holding firm across the Carolinas into eastern Georgia and
Tropical Storm Arlene slowing meandering south over the eastern
Gulf of Mexico while weakening. It will be another fairly quiet
day across Southeast South Carolina and Southeast Georgia.
Deeper moisture, higher mean PWATs and no capping aloft per
modified soundings could promote a bit more in the way of
convection this afternoon, but activity is still expected to
remain somewhat limited with little in the way significant
synoptic forcing mechanisms in place. Coverage should remain in
the isolated to perhaps scattered category with the better
chances for deep, moist convection holding over Southeast
Georgia, especially along/south of the I-16 corridor where a bit
more instability and a ribbon of higher quality moisture will
be found. 10-30% pops look reasonable for this afternoon into
early this evening. Areas adjacent to the southern Midlands and
CSRA may not see much, if any, shower activity as guidance shows
a sharp moisture gradient setting up in this area. Highs will
peak mid-upper 80s away from the coast with mid-upper 70s at
the beaches.

Tonight: Any lingering convection will quickly wane after sunset
with the loss of insolation. Dry conditions will prevail
overnight as an weak, ill-defined backdoor cold front/wind
shift drops south through the area and the inland high pressure
wedge is reinforced. Some clearing will occur this evening with
stratocumulus expanding inland from off the Atlantic overnight
as the front drops south. Lows will range from the mid 60s
across the far interior to the upper 60s/lower 70s along the
beaches and Downtown Charleston.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
Sunday: Weak mid-level troughing will prevail over the Southeast
U.S. in the morning. It`s expected to gradually weaken further with
time. A cold front will be located near the Altamaha River at
daybreak. It`s forecasted to continue moving south and away from our
area during the day, while drier High pressure gradually builds in
from the north. Models still indicate there`s a risk of an isolated
shower or thunderstorm along our coastal GA counties through the
Altamaha River through the afternoon, so we maintained mainly slight
chance POPs in these location. Otherwise, most locations are
expected to remain dry with partly sunny skies. Cooler air advection
within northeast winds will cause high temperatures to be several
degrees below normal. Low-level thickness values and perhaps more
clouds than sun support highs near 80 degrees across our SC
counties, and the lower to maybe middle 80s across our GA counties.
It will also be breezy in the afternoon, especially at the beaches.
The evening and overnight will be dry with decreasing clouds.
Temperatures will be noticeably below normal with lows ranging from
the mid to upper 50s far inland to the low/mid 60s along the
immediate coast.

Monday: The weak mid-level trough over the Southeast U.S. will
continue to dissipate. However, a trough over the Northeast U.S.
will strengthen, yielding NW flow over our area. At the surface,
High pressure centered just to our north in the morning will move
south with time. This will keep a front and the remnants of Arlene
well to our south. The High will dominate our weather, bringing
unseasonably dry conditions with mostly sunny skies. Highs will
remain a few degrees below normal, but still peak in the lower to
mid 80s, except cooler at the beaches. The dry conditions and mostly
clear skies continue into the evening and overnight hours. This will
lead to lows mainly in the 60s.

Tuesday: A strong trough will remain over the Northeast U.S.,
yielding NW flow over our area. Surface High pressure over the
Southeast U.S. will shift offshore in the afternoon. As it moves
away, the sea breeze could generate isolated convection in the
afternoon. But most places could end up remaining dry. Highs will
rise to above normal for a change, with most locations topping out
around 90 degrees, except cooler at the beaches.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
Mid-level troughing over the Northeastern U.S. will continue to
gradually creep southward through Friday. But most of it`s energy
should remain just north of our area. At the surface, a cold front
is expected to move south into our area on Wednesday. It should
become stationary and remain in place over or near us through
Friday. This will generate convection each afternoon. But the exact
location of the front will determine which areas have more
convection. Temperatures will be near normal.

&&

.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
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03/06z TAF discussion:
KCHS/KJZI: The risk for MVFR cigs is diminishing. VFR will
prevail. Winds could get a little gusty at KJZI by mid-
afternoon as winds veer more easterly. Some patchy MVFR cigs
could form prior to daybreak Sunday as stratocumulus moves
inland from off the Atlantic behind a weak backdoor cold front.

KSAV: VFR will prevail. Isolated showers will likely be lurking
about early-mid afternoon, but impact probabilities are too low
to justify a mention at this time.

Extended Aviation Outlook: A cold front could bring flight
restrictions and gusty NE winds on Sunday. Mainly VFR will
prevail afterwards. There will be low probabilities of flight
restrictions during the middle of next week due to
afternoon/evening convection.
-- End Changed Discussion --

&&

.MARINE...
Through Tonight: Northeast winds will average around 15 kt
through the day with seas 2-4 ft, building to 3-5 ft. Overnight,
a northeast wind surge will work south behind a backdoor cold
front. By daybreak, northeast winds will reach 20-25 kt with
gusts to 30 kt over the South Santee-Edisto Beach nearshore leg
with 15-20 kt with gusts to 25 kt elsewhere. Seas will build
4-6 ft over the South Santee-Edisto Beach nearshore leg to 3-5
ft in the Edisto Beach-Savannah nearshore and Georgia offshore
legs with 2-3 ft in the Savannah-Altamaha Sound nearshore leg. A
Small Craft Advisory has been issued for all legs except
Charleston Harbor beginning at 4 AM.

Sunday: A cold front will be located near our extreme southern GA
waters at daybreak. It`s forecasted to move south, away from our
area during the day. Meanwhile, High pressure will gradually build
in from the north. The combination of an elevated surface pressure
gradient and cooler air advection over the waters will yield gusty
NE winds and steep, wind-driven waves. Small Craft Advisories will
be in effect for all of the ocean waters. Additionally, Charleston
Harbor may need an advisory for wind gusts during the day. Winds and
seas will start to trend lower overnight as the pressure gradient
levels off and the cool advection wanes. But conditions will remain
high enough for the advisories to continue.

Monday: High pressure will approach from the north, while a front
and the remnants of Arlene remain well to our south. The High will
be the dominant feature for our area, causing elevated NE winds in
the morning to ease during the day, with seas subsiding as well. The
Small Craft Advisories for the waters within 20 nm should end by
late afternoon. However, the advisory for the GA waters beyond 20 nm
should persist until around midnight. Wind and seas will continue to
trend lower during the evening and overnight.

Tuesday and Wednesday: High pressure is expected to be centered
to our south on Tuesday, then shifting away by midweek. At that
time, another front could approach from the north, possibly
bringing elevated winds and seas.

Rip Currents: Persistent, strong NE winds will be generating
elevated seas, with a somewhat onshore component, more notably
for our GA beaches. A Moderate risk of rip currents is in effect
for all of our beaches on Sunday. It`s not out of the question
this risk may need to be raised if winds/seas are higher than
expected. The risk of rip currents persist on Monday.

&&

.TIDES/COASTAL FLOODING...
Charleston/Coastal Colleton: Tide levels in the Charleston
Harbor will make a run for the 8.0 ft MLLW major flood threshold
for this evening`s high tide. A Coastal Flood Watch has been
posted to account for this possibility. The watch will be
upgraded to a Coastal Flood Advisory or Coastal Flood Warning
later today as the total water forecast is further refined
based on this morning`s tide trends. Significant saltwater
flooding can be expected at this level across much of the coast
of Charleston and Colleton Counties, including areas around
Charleston Harbor. Road closures are likely across much of
Downtown Charleston at this level and saltwater will approach or
even flood the lower levels of some structures. Similar
conditions will be experienced elsewhere up and down the coast.
The backside of Edisto Beach along Big Bay Creek is especially
vulnerable at 8.0 ft MLLW. Levels will peak near or just above
major flood thresholds for Sunday evening and possibly again
Monday evening. Additional Coastal Flood Watches and Warnings
may be needed.

Beaufort County south to McIntosh County: Tide levels at Fort
Pulaski are expected to peak well into the minor flood level
for this evening`s high tide and could even approach moderate
flood stage. At the upper portion of the minor flood level,
water will approach or even encroach onto portions of Highway 80
heading to Tybee Island. Some saltwater flooding could also
occur along the backside of Tybee Island and Fripp Island and in
parts of Darien along Darien Creek. Moderate flooding is
possible with the Sunday evening high tide and again Monday
evening. Right now, it appears levels will remain below major
flooding thresholds. A Coastal Flood Advisory will likely be
issued for this area later today. Additional Coastal Flood
Advisories will be needed Sunday and possibly Monday.

Tidal Berkeley: Minor flooding typically occurs across parts of
southern Berkeley County, especially in Daniel Island, when tide
levels reach 8.0 ft MLLW in the Charleston Habor. A Coastal
Flood Advisory may be needed for this area this afternoon and
possibly again Sunday and Monday evenings.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
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GA...None.
SC...Coastal Flood Watch from 6 PM EDT this evening through this
     evening for SCZ049-050.
MARINE...Small Craft Advisory from 4 AM Sunday to 3 PM EDT Monday for
     AMZ350-352-354.
     Small Craft Advisory from 4 AM Sunday to midnight EDT Monday
     night for AMZ374.
-- End Changed Discussion --

&&

$$