978
FXUS62 KCHS 081039
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
639 AM EDT Mon Jul 8 2024

.SYNOPSIS...
A surface trough will remain over inland areas this week while
high pressure persists over the western Atlantic.

&&

.NEAR TERM /THROUGH TONIGHT/...
This morning: A strong upper level ridge remains anchored
across the western United States with a mid-level trough axis
centered across the central United States. Towards SC and GA, an
upper level low just east of the region has been slowly
retrograding the last couple of days and has almost become
quasi-stationary. In between this upper level low and the mid-
level trough axis is a weak mid-level ridge. This ridge has
remained stubbornly in place across central FL over the last
several days and is forecast to slightly strengthen today. The
08.00z 500 mb heights have actually risen at FFC to 593 dam.
Latest guidance indicates a slight rise of mid-level heights
across central FL to 594 dam. At the surface, convection from
the Midlands of SC has continued to progress south slowly all
night. Most of the convection has weakened, with the exception
being across Screven and Jenkins counties. Rainfall totals of 1
- 2" are currently being estimated on radar. This convection
will continue to slowly sink south and weaken. However, the
likely item to drive todays weather is another MCV that has
developed near the SC/ NC border. The latest run of the RAP
700/500 mb vorticity shows this MCV progressing northeast
through the morning hours.

Behind the aforementioned MCV a convectively reinforced cold
pool is slowly oozing south and east this morning. Behind this
dense viscous cold pool and wind shift, skies are overcast with
a rather expansive stratus/ strato-cu deck. High res guidance
has this boundary arriving at the coast by late this morning.
Mostly cloudy skies are expected this morning with most of the
area dry.

Afternoon: The MCV will be approaching the coast of NC with
1000/ 850 mb thicknesses slightly recovering to 1425 m (about 5
m above Sunday afternoon). This will translate to high
temperatures a degree or two warmer today, or mostly in the
lower to mid 90s (mid 80s at the beaches). By mid- afternoon a
sea breeze will begin to move inland with showers and
thunderstorms forming. The MCV will likely be far enough away at
this point to only have a modest subsidence influence (esp
towards the Tri- County). The greatest chance of showers and
thunderstorms will be along the GA coast today (given the
increased distance from the exiting MCV) with ML cape values
around 1500 - 2000 J/kg. One item that was noticed was the bulk
shear values around 20 kt forecast (thanks to the proximity of
the retrograding mid-level low pressure). The overall chance for
severe weather looks low today, but the 20 kt of shear does
increase the chance slightly from what it has been the last
several days. The primary threat would be damaging wind gusts.

Evening: Showers and thunderstorms will be on-going across the
coastal counties with the highest coverage likely being across
southeast Georgia. A slow decrease in coverage is expected as
evening progresses. Expect low temperatures mostly in the mid
70s to near 80 degrees at area beaches.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
An upper ridge over the central and northern Atlantic will
expand west into the local area Tuesday through Thursday.
Meanwhile, a weak surface trough will linger across inland
areas Tuesday and Wednesday, then shift east on Thursday. Deep
tropical moisture will persist Tuesday and Wednesday with PWATs
above 2.2". On Thursday some drier air is expected to move into
eastern GA, leaving the deepest moisture over southern SC. A
progressive sea breeze is expected to develop each day, pushing
well inland by mid/late afternoon. The greatest convection
coverage is expected to again be across far inland areas
Tuesday and Wednesday, closer to the lee trough and where upper
heights are lower. On Thursday the best coverage could flip to
the other side of the forecast area due to the drier air moving
into southeast GA and better moisture convergence over southern
SC. Throughout the Day 2-4 period we have continued to undercut
model PoPs due to the notable wet bias we have been noticing.

High temperatures all three days are expected to be in the lower
90s. We`re currently showing the highest dewpoints across the
eastern portion of the area Tuesday and Wednesday where we have
a corridor of 105-110F heat indices. We may need Heat Advisories
for part of the area one or both days.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
The upper ridge will gradually expand over the area late week
into the weekend with Atlantic surface high pressure also
building in. Although subtle upper shortwaves could pass
through at any time, the sea breeze will be the primary forcing
for convection. We capped PoPs at 40-50% each afternoon.
Afternoon heat indices will top out around 105F most days.

&&

.AVIATION /10Z MONDAY THROUGH FRIDAY/...
This morning: Convection from Sunday evening has finally
dissipated near KSAV this morning with some weak showers and
thunderstorms along the GA coast south of KSAV. MVFR clouds have
also mostly dissipated this morning with only a few strato-cu
out there this morning.

Afternoon: A very difficult forecast with low confidence for
this afternoon. The MCV over the Midlands of SC will be exiting
the region this afternoon with another round of weak subsidence
on the backside of the forcing. The latest runs of the high res
guidance continues to show redevelopment along a weak wind
shift (from the exiting MCV) that is pinned along coastal SC/
GA. The sea breeze then collides with this boundary causing
convective initiation. However, the HRRR is again playing catch-
up this morning with the exiting MCV and appears to slow. The
wind shift on the high res guidance also appears to strong. The
cold pool will likely not be reinforced as much as at least the
latest HRRR indicates. This would favor less coverage and a more
dispersive/ less focused solution. For now, have maintained
VCTS at all terminals.

Evening: Showers and thunderstorms will be coming to an end
this evening as daytime heating is lost. Mostly VFR conditions
are forecast.

Extended Aviation Outlook: Scattered afternoon showers and
thunderstorms may produce brief flight restrictions.

&&

.MARINE...
Seas will remain 2 to 3 ft with winds mainly out of the south 5
to 10 kt. A slight uptick in the wind speed near the land/ sea
interface is expected due to the sea breeze circulation this
afternoon. Expect gusts of 15 to 20 kt possible. Winds will
then slowly decrease this evening as the sea breeze circulation
relaxes.

Tuesday through Saturday will feature typical summertime
conditions with 10-15 kt southerly winds and seas 2-4 ft.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

$$

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