639
FXUS62 KCHS 072041
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
441 PM EDT Sun Jul 7 2024

.SYNOPSIS...
High pressure will continue over the western Atlantic while a
weak surface trough of lower pressure remains inland of the
area through the upcoming week.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
An unscheduled update was issue to make the following changes:
1. Updated near term pops to reflect lower pops east of I-95 and
to increase them to 70% for parts of Candler, Evans, Long and
Tattnall Counties. Pops were also adjusted through mid-evening
to try and capture the evolution of the band of convection
moving form the south a bit better in the hourly pop grids.

2. Increased heat indices to near 108 through 6 PM across parts
of McIntosh, Long and Liberty Counties based on observations
and near term model trends. A Special Weather Statement has been
issued to address this through 6 PM in lieu of a Heat Advisory.

The region today will remain positioned along the downstream
side of a mid-level trough extending across the Midwestern
States. At the surface a strung out stationary front was
analyzed by WPC across the SC upstate into NC. With the weak
front displaced to the north and little to no forcing aloft,
afternoon showers and thunderstorms will be diurnally driven,
aided by the afternoon sea breeze.

Showers and thunderstorms have begun to form across southeast
GA. SPC mesoanalysis depicts a region of PWATs of 2.5 inches
across this area, with ~2 inches analyzed elsewhere. Coverage of
showers and thunderstorms is forecast to increase into the
afternoon, with the highest PoPs across SE GA.

Temperatures today have been a little tricky, as some low
clouds have lingered longer than anticipated. Overall, highs
today should reach into the upper 80s to low 90s. Dew points are
not as high as previous days, only in the low to mid 70s,
yielding heat indices in the upper 90s to around 100.

Tonight: Showers and thunderstorms will dissipate in the early
evening with low temperatures in the mid 70s (near 80 degrees
along the beaches).

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
Monday through Tuesday Night: At upper levels, a large upper level
low well east of the region over the Atlantic, is shown my all
models to push west-southwestward and dissipate through the period.
Very high values of deep layer moisture will reside over the entire
southeast U.S., with PWs 2-2.5 inches. At the surface, a trough of
lower pressure will generally reside well inland. This trough, along
with any seabreeze and/or differential heating boundaries, will
likely be the main triggers for afternoon and evening convection.
With ample deep layer moisture and relatively slow storm motions,
locally heavy rainfall will be the main threat from any stronger
showers/thunderstorms. Models have been focusing the highest PoPs
along and west of I-95 through much of this period. Concerned that
guidance PoPs are too high for this time of year, and have tried to
taper PoPs down a tad for the afternoon/early evening periods. High
temperatures near to slightly above normal, but low temperatures
likely to continue 3 to 5 degrees above normal. Current grids keep
max Heat Indices in the 100-105 range. Thus, not concerned about
Heat Advisory conditions at this time, at least across widespread
areas.

Wednesday: The upper low center that was over the Atlantic is shown
by models to dissipate southeast of the region as a developing upper
trough moves into the central MS River Valley. This is the same
upper trough that appears to pick up the remnants of Beryl. Our
region will remain under the presence of ample deep layer moisture,
with PWs 2-2.5 inches. Given slightly better upper level troughing
and some vorticity reaching at least well inland locations, would
not be surprised if convective coverage was a bit higher than
current forecast shows. For now, have continued high chance/low end
Likely PoPs, mainly due to uncertainty. High temperatures slightly
above normal. Max Heat Indices may be a tad higher than previous
days, with marginal Heat Advisory conditions possible in some areas.
However, the amount of convective development will impact max Heat
Indices, which leads to a good amount of uncertainty. Will continue
to monitor the situation.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
In general, a deep layer Atlantic ridge of high pressure looks to
stay in place during this period. At the surface, an inland trough
of lower pressure will also persist, which along with the sea
breeze, will be the main initiator of afternoon/evening convection.
Again, concerned that model/guidance PoPs are a bit too high for
this time period and time of year. Climo PoPs are generally 30-40%,
but guidance has been going likely to categorical. Have again tried
to trim PoPs down a tad, while also keeping collaboration thresholds
in check with surround offices. Again, with ample moisture and weak
steering flow, will continue to watch the threat for locally heavy
rainfall with any stronger showers/thunderstorms. Temperatures,
especially low temperatures, are expected to remain above normal.
Afternoon Heat Indices of 100-105 each day, which is below Heat
Advisory criteria.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
KCHS/KJZI: Isolated to scattered showers and thunderstorms are
possible this afternoon, however confidence in direct impacts to
either of the terminals remains low. Therefore, there is no
mention of precipitation or flight restrictions in the 18Z TAF.
If a terminal were to be impacted, KCHS has a better chance than
KJZI.

KSAV: Showers have begun to develop in the vicinity of KSAV by
18Z. These showers will likely persist until around 00Z. The 18Z
TAF will begin with VCSH, with a TEMPO group from 18 to 22Z to
cover possible direct impacts to the terminal. After nightfall
additional flight restrictions are unlikely, with prevailing
VFR.

Extended Aviation Outlook: Scattered to numerous afternoon
showers and thunderstorms each afternoon may produce brief
flight restrictions, especially for KSAV.

&&

.MARINE...
Tonight: Seas 2 to 3 ft. Winds will then slowly decrease this
evening as the sea breeze circulation relaxes, generally around
5 to 10 knots.

No highlights expected through the period. An Atlantic ridge of high
pressure will generally remain centered well east of the waters,
which is typical for this time of year. The low level flow will be
mostly southerly at 15 knots or less and seas 2 to 3 feet. This
pattern also tends to favor nighttime over daytime convection.

&&

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

&&

$$