116
FXUS62 KCHS 170257
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1057 PM EDT Fri Aug 16 2024

.SYNOPSIS...
High pressure will remain over the area through most of this
weekend. A cold front will push across the area Sunday night,
then remain nearby through late week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
A mid-upper lvl trough will dig across the Great Lakes region, while
an extensive mid-upper lvl ridge extends across the Deep South and
into the local area. At the sfc, high pressure will prevail while
Hurricane Ernesto impacts Bermuda well offshore. The pattern will
set up a dry and stable air mass locally, and maintain rain-free
conditions across all zones through the night. While there could be
a few mid-upper lvl clouds drifting through at times overnight,
skies will generally remain clear. Light/calm winds and a dry air
mass will favor a decent amount of radiational cooling tonight, with
low temps falling below normal. However, with a southerly boundary
flow to develop and slight air mass modification, lows will trend a
bit warmer than the last two nights. In general, lows should range
in the upper 60s to lower 70s, but locations along the beaches are
expected to stay in the mid-upper 70s.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Saturday: H5 ridge will build across the deep south, with a subtle
ridge across the forecast area. At the sfc, weak high pressure will
remain across the western Atlantic as a broad trough remains across
the Foothills of the Carolinas. This pattern will support light
south-southwest across the forecast area. However, as temperatures
warm into the low to mid 90s, a weak sea breeze should develop
Saturday afternoon and evening. Forecast sounding across the sea
breeze indicate that the environment will remain weakly capped.
Guidance does support some convection sourced from inland GA
reaching inland SE GA during the afternoon, highlighted with SCHC
PoPs. Saturday night, guidance indicates that a vort max will
accompany the approaching H5 trough. The forecast will highlight
SCHC across portions of the SC Lowcountry late Saturday night into
Sunday.

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. Heat index values will peak
near 108 across portions of the GA coast and the southern SC coast.

Interesting setup across the region Sunday evening. Models indicate
that an MCS will develop across the western Carolinas Sunday
afternoon, then tracking east. The MCS is expected to reach the
forecast area Sunday evening, pushing over the Atlantic Sunday
night. Forecast soundings show CAPE values ranging from 1500-2000
J/kg, with modest values of DCAPE. Hodographs indicate a deep curved
profile, with 0-6 km bulk shear around 30 kts and 0-3 km helicity
around 300 m2/s2. This environment should support a few organized
storm clusters, producing swaths of strong to severe wind gusts. In
addition, it is possible, that a few supercells may develop ahead of
the MCS. SPC has highlighted most of the interior counties with a
Slight risk for severe thunderstorms.

The region will remain under the H5 trough axis on Monday. Isolated
to scattered showers and thunderstorms may develop across the
coastal counties during the afternoon. High temperatures are
forecast to range in the low to mid 90s.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Aloft, an upper-level trough extending from extreme eastern Canada
down to Florida Keys will stall nearby into mid-week before finally
being pushed offshore over the weekend. By Monday night, this
pattern should feature a building high pressure to the north as the
cold front from the associated trough becomes stationary offshore.
This set-up should allow for cold air damming, or CAD, to take
place over the region allowing for cooler temperatures and drier
conditions Monday through Thursday. However heading into
Friday, due to some isentropic lifting, chances for some
isolated to scattered showers become likely.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are expected to prevail at the KCHS/KJZI/KSAV
terminals through 00Z Sunday.

Extended Aviation Outlook: A cold front is forecast to impact the
region late this weekend/early next week, bringing the risk of brief
flight restrictions within showers and thunderstorms.

&&

.MARINE...
Tonight: Hurricane Ernesto will pass by Bermuda, while high pressure
prevails across local waters. The setup will favor winds around 10
kt or less that veer from southeast to south overnight. Latest buoy
obs indicate guidance remains overdone by about a foot, likely
resulting in seas that remain below 6 ft across South Carolina
nearshore waters. Thus, the Small Craft Advisories have been
canceled for nearshore South Carolina waters for the night. For
Georgia waters, seas will remain 5 ft or less across nearshore
waters, but further offshore, seas are expected to build to around 6
ft. A Small Craft Advisory will therefore remain in effect across
offshore Georgia waters through the night.

Saturday through Wednesday: Seas should decrease to 3-5 ft with
light and variable winds early Saturday with high pressure in place.
Saturday night into Sunday winds and seas will gradually increase
ahead of an approaching cold front that is expected to push across
the local waters Monday. Winds could surge from the SW to around 20
kts with gusts 20-25 kt Sunday night. In addition, seas could build
up to 6ft across portions of the outer GA waters Sunday. Conditions
will improve throughout the day Monday with seas dropping to 2-3 ft,
and winds shifting northeast 10-15 kt for Tuesday and Wednesday.

Rip Currents: Long period swell (13 to 15 seconds) from Hurricane
Ernesto will continue to impact the beaches through the weekend,
leading to a High Risk for rip currents at all beaches through
Saturday, and potentially through Sunday.

&&

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

&&

$$

NEAR TERM...DPB
SHORT TERM...NED
LONG TERM...Dennis
AVIATION...DPB
MARINE...Dennis/DPB