983
FXUS62 KCHS 151430
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1030 AM 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 /THROUGH TONIGHT/...
Hurricane Ernesto was located well east of the Bahamas and
heading north, caught in a deep trough over the western
Atlantic. Our area is strongly under the influence of high
pressure, and with a dry northwest flow aloft, PWat is down to
just 70-80% of normal for many places. The KCHS sounding shows
PWat 2/3 inches less than yesterday morning, with a tremendous
dry layer between about 650 mb and 450 mb, where RH is down less
than 5% through that layer.

Rain chances are limited to just slight chance through the day,
mainly over southeast Georgia over McIntosh and Long County
where there is some higher theta-E air. There could be a stray
shower along the sea breeze along the coastal corridor where
there is an axis of better moisture convergence. But the vast
majority of the forecast area will stay dry with a strong
inversion around 10K-12K feet. We maintain d a forecast free of
t-storms with the HREF with their 1-hour thunder probabilities
less than 10% and MLCAPE only about 100-200 J/kg. Being the time
of year it`s possible that an isolated t-storm could form, but
odds are strongly against such an occurrence.

Dew points for most locations will be in the 60s through the
day, making for more tolerable humidity levels than we`re
accustomed to in summer. Max temperatures will be similar to
Wednesday, and mainly in the 80s to around 90F degrees.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Friday: Aloft the region will remain along the eastern periphery of
high pressure centered over Texas. A mid-level low pressure center
will be positioned just to the west of the Great Lakes, while to the
east Tropical Cyclone Ernesto remains well off of the SE coastline.
Surface high pressure will be directly overhead on Friday, yielding
a dry forecast with highs in the upper 80s to around 90. Overnight
temperatures will be a little cooler, with upper 60s in many
locations and around 70 at the beaches.

Saturday and Sunday: Slight ridging aloft will develop along the
southeastern coastline through the weekend as the region becomes
pinched between the low pressure over the Great Lakes and Tropical
Cyclone Ernesto. High pressure will remain the dominant synoptic
feature at the surface, however a weak cold front will approach from
the west on Sunday. Dry conditions are forecast on Saturday, however
rain chances increase into Sunday as the weak cold front approaches.
High temperatures both days are forecast to reach into the low 90s,
with overnight lows in the low to mid 70s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
Broad troughing aloft will develop late Sunday and into early next
week along the Eastern Seaboard as the aforementioned area of low
pressure over the Great Lakes pushes towards the NE. At the surface
a weak cold front is progged to impact the region early in the work
week. Even with the weak cold front, PoPs are limited to around 30-
40% each afternoon. Temperatures are forecast to remain right around
normal through the period.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
VFR conditions are expected to prevail at KCHS, KJZI, and KSAV
through 12z Friday.

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...
Today: Surface high pressure will center across the coastal
plain of SC/NC with winds out of the E/NE up near 15 or 15-20
kt. Seas will average 3-4 feet, with some 5 footers on the
outer Georgia waters.

Friday through Tuesday: Surface high pressure will begin to shift
away from the local marine waters on Friday, with winds shifting
from the NE in the morning to the E/SE by the evening hours. Swell
from Hurricane Ernesto will begin to impact the region on
Friday, with seas reaching 5 to 6 ft out to 20 nm, and 6 to 7 ft
out to 60 nm in SE GA. Small Craft Advisories will likely be
required for all marine zones outside of the Charleston Harbor.
These Small Craft Advisories may linger into Saturday as swell
continues to impact the region. By Sunday the region should be
clear of all advisory conditions, with winds generally around 10
to 15 knots, increasing in speed along the coastline in the
afternoon hours with the sea breeze circulation.

Rip Currents: Although the beaches are still not feeling impacts
o Hurricane Ernesto`s swells, based on numerous reports of rip
currents from Tybee Beach yesterday, the Rip Current MOS
showing a solid Moderate Risk, and WFO JAX with a High Risk at
their Georgia beaches, we opted to go with Moderate Risk from
Tybee to Sapelo today. Low Risk is maintained elsewhere.

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...None.
SC...None.
MARINE...None.

&&

$$

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