612
FXUS62 KCHS 151959
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
359 PM EDT Thu Aug 15 2024

.SYNOPSIS...
High pressure will build in from the north through late week.
Another cold front may approach the area early next week, then
remain nearby through late week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Through this evening: Generally quite pleasant conditions for
mid August, with most dew points down in the 60s, although they
will be 70F degrees or a little higher in wake of the sea
breeze. That sea breeze boundary might allow for a couple of
stray light showers to form along a subtle theta-E axis combined
with a deep moisture convergence axis as per the SPC
mesoanalysis. Should anything occur it would be over the eastern
third of the forecast area. We have a silent 10% chance as a
result.

Tonight: The local communities will be situated between a strong
mid level anticyclone along the southern tier of the country,
with a trough in the western Atlantic. That trough will be
responsible for lifting Hurricane Ernesto off to the north-
northeast as it draws closer to Bermuda. We`ll be under the
influence of high pressure covering the eastern seaboard.
Diurnally induced cumulus will fade by sunset, leaving us with
mainly clear skies. Winds will decouple and good radiational
cooling will commence away from the coast. Based on how low
temperatures were last night/early this morning we went a bit
cooler with the 1000-850 mb thickness a bit less. This results
in min temperatures in the mid and upper 60s west of US-17, with
even some lower 60s in the Francis Marion National Forest. East
of US-17 will experience lows down in the lower and middle 70s.

Some of the statistical guidance shows some ground fog closer to
daybreak, but given unfavorable condensation pressure deficits
this shouldn`t be of any concern.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
Friday: The forecast area will remain between a mid-level ridge
centered over the Southern Plains and a long wave trough over the
western Atlantic. At the sfc, a ridge of high pressure will remain
over the Atlantic coast, providing the region with light east-
northeast winds. Forecast soundings show a strong inversion centered
at H7. The strong llvl inversion combined with sfc dewpoints in the
60s should yield little to now instability across the CWA on Friday.
The forecast will feature dry weather with highs in the low 90s.

A weak H5 ridge is forecast to ripple across the region Friday night
into Saturday. At the sfc, high pressure will remain along the coast
through the day. Given light south winds, dewpoints may increase to
around 70 degrees during the afternoon. However, lingering inversion
at H7 should provide the region with a cap, around 100 J/kg of CIN
during the heat of the afternoon. High temperatures may increase a
degree or two over values reached on Friday.

Sunday: A cold front will slowly approach from the west through the
day. Sfc winds are forecast to shift from the southwest, keeping the
sea breeze along the coast through early afternoon. The sea breeze
is expected to drift inland during the mid to late afternoon,
resulting in dewpoints to climb into the mid to upper 70s. Scattered
showers and thunderstorms are forecast to develop between the sea
breeze and the approaching cold front. High temperatures are
forecast to range in the low to mid 90s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Sunday night into Monday: The details of the forecast will be
determined by the placement and timing of the cold front. At this
time, it appears that the cold front will reach the Atlantic coast
around daybreak Monday morning. Guidance indicates that the
environment along and ahead of the cold front will feature CAPE
around 2000 J/kg and 0-6 km shear around 30 kts. This environment
could support a few organized storm clusters or lines, resulting in
strong to severe wind gusts. It is possible that a couple of severe
events may occur late Sunday night into Monday. The forecast will
feature 30-40 PoPs from Sunday night into Monday afternoon.

Tuesday and Wednesday, the sfc pattern will feature ridging high
pressure over the land as the old cold front remains stationary off
the coast. This pattern may yield light east winds, allowing a sea
breeze to develop each afternoon. Isolated to scattered showers and
thunderstorms may develop during the PM. High temperatures should
range near 90 each day.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
VFR conditions are expected to prevail at KCHS, KJZI, and KSAV
through 18z Friday. There could be a stray -SHRA near KCHS and
KJZI late this afternoon, but no impacts expected. KSAV will
also be a little gusty at times in wake of the sea breeze.

Extended Aviation Outlook: Surface high pressure will yield VFR
conditions through Saturday. A cold front is forecast to impact the
region late this weekend/early next week, bringing the risk of brief
flight restrictions.

&&

.MARINE...
This evening and tonight: Sea breeze circulations will fade
early on, but there is still a modest gradient between high
pressure inland and very distant Hurricane Ernesto. This will
create mainly E or ENE winds up near 15 kt and a little gusty
early on, dropping several knots overnight as winds back more NE
with land breeze influences. Seas will average around 3-4 feet
on the nearshore waters, and 4-5 feet on the outer Georgia
waters. Some 6 footers will move in around 6 am on the
outermost Georgia coastal zone, so we held off to starting the
Small Craft Advisory until 8 am. Some small fore-runner swells
of 13-15 second period from Hurricane Ernesto will start
reaching into the coastal waters late, an indication of things
to come on Friday into the weekend.

Friday through Tuesday: Swell wave from Hurricane Ernesto will
increase across the coastal zones on Friday, lingering into Friday
night. Wave heights are forecast to peak Friday afternoon, ranging
from 4-6 ft across the nearshore waters to 6-7 ft across the outer
GA waters. A Small Craft Advisory (SCA) has been issued for the
outer GA waters from Friday morning through Friday night to
highlight the seas. The far outer portions of the nearshore SC
waters may see some 6 ft seas, but duration and coverages appears
too limited for a SCA at this time. Otherwise, the pattern should
yield east winds between 5-10 kts Friday afternoon, becoming light
Friday night. Seas should decrease to 3-5 ft on Saturday. Sunday and
Monday, a cold front will slide across the region. Winds ahead of
the cold front may surge from the SW to around 20 kts with gusts in
the low 20s Sunday night. In addition, sea may build to around 6ft
across portions of the outer GA waters Sunday night. It is possible
that SCA wind gusts and sea could develop Sunday night. Otherwise,
wind and sea conditions may remain below SCA criteria through early
next week.

Rip Currents: Although the beaches are still not feeling impacts
of Hurricane Ernesto`s swells, there have already been reports
of 6 moderate to strong rip currents at Tybee due to local
effects. The Moderate Risk of rip currents continues on the
Georgia beaches into this evening, but we`ll keep Low Risk on
the South Carolina beaches.

Long period swell (13 to 15 seconds) from Hurricane Ernesto is
forecast to reach the forecast area on Friday. This in
combination with onshore winds will produce a high risk of rip
currents at all area beaches on Friday. The threat for rip
currents could persist into Saturday as well.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents from Friday morning through Friday
     evening for GAZ117-119-139-141.
SC...High Risk for Rip Currents from Friday morning through Friday
     evening for SCZ048>051.
MARINE...Small Craft Advisory from 8 AM Friday to 8 AM EDT Saturday for
     AMZ374.

&&

$$

NEAR TERM...
SHORT TERM...NED
LONG TERM...NED
AVIATION...
MARINE...