756
FXUS62 KCHS 051143
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
743 AM EDT Fri Jul 5 2024

.SYNOPSIS...
High pressure will persist through Friday, then a weak cold
front will stall over the area this weekend and linger through
the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, subtle h5 vort energy will exit offshore and to
the south along the eastern edge of a ridge while an upper low
remains well offshore across the western Atlantic. At the sfc,
high pressure across the western Atlantic will extend across the
Southeast United States for much of the day, but should
gradually nudge east while some lee troughing takes place
inland. Despite large-scale subsidence associated with a the
mid-upper lvl ridge and light west/southwest winds aloft in
place, strong sfc heating co-located with PWATs around 2.0
inches and SBCAPE between 1500-2000 J/kg along with lee
troughing, should be sufficient to initiate convection just
inland to the local area, and eventually result in isolated to
scattered showers/thunderstorms drifting east across far inland
zones locally by mid-late afternoon. Shear remains weak
throughout this time frame, so activity will be driven by
daylight heating and be primarily pulse type in nature, but
clustering of thunderstorms and/or outflow boundary interactions
could allow convection to persist shortly after sunset. A
stronger thunderstorm can not be ruled out given strong sfc
heating.

Showers and thunderstorms far inland could very well provide some
relief to the heat mid-late afternoon for what appears to be the
warmest area of the day based on 1000-850 mb thicknesses and ample
sfc heating before convection occurs. However, sfc temps are still
expected to approach the mid-upper 90s away from coastal areas
today, and could even touch 100 degrees briefly across far interior
locations along a stretch from Allendale County to Jenkins County.
Low-lvl dry air depicted on soundings along with large-scale
subsidence aloft suggests that some mixing out of sfc dewpts takes
place heading into peak heating hours, and sufficiently so for heat
indices to remain just below Heat Advisory criteria, generally in
the 104-107 degree range. The exception could be well inland where
warmest temps are expected this afternoon before the arrival of
clouds/precip and/or along an inland advancing seabreeze, where
moisture pools temporarily and sfc dewpts remain in the mid 70s
during peak heating. However, the duration and coverage of these
events appears too short to justify a Heat Advisory locally at this
time.

Tonight: Any convection that has developed and/or drifted across far
inland zones should struggle to persist given a loss of diurnal
heating and weak shear in place. Those that do persist, could last
an hour or two post sunset, mainly due to outflow boundary
interactions. The rest of the night will remain rather quiet, but
mild ahead of a front approaching from the northwest this weekend.
In general, lows should range in the mid-upper 70s inland to lower
80s at the beaches.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
The upper ridge will be centered over northern Florida on
Saturday while a weak shortwave rotates around the northern
periphery during the afternoon. A weak cold front is forecast to
drop southeast into the area during the day, then stall nearby
through early next week. The greatest moisture and instability
will be across inland areas on Saturday which is where we show
the greatest coverage of showers and thunderstorms. High temps
in the mid 90s with mid/upper 70s dewpoints will produce heat
indices 105-110F for several hours during the afternoon in most
locations. Dewpoints could mix out just enough far inland to
keep heat indices below 105 in those areas. A Heat Advisory will
likely be needed for much of the area.

Additional shortwaves moving in from the west Sunday and Monday
will break down the upper ridge, reducing high temps by a couple
degrees. The deep moisture is expected to expand eastward, with
the entire area under at least 2.1" PWATs. Considerable
coverage of showers/tstms expected both days.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
A fairly wet pattern likely to persist for much of next week due
to deep tropical moisture in place, continual shortwaves, and a
weak convergence axis along the decaying cold front. The
greatest coverage should be during the afternoon and evening
hours. Wednesday looks like the hottest day during this period,
with the potential for Heat Advisories.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
VFR conditions are expected to prevail at CHS/JZI/SAV terminals
through 12Z Saturday.

Extended Aviation Outlook: Brief flight restrictions are possible in
showers and thunderstorms, mainly in the afternoon and evenings,
this weekend through the middle of next week.

&&

.MARINE...
Today and Tonight: After some nocturnal surging weakens early this
morning, high pressure extending across local waters from the
northeast along with lee troughing taking place well inland should
favor a modest pressure gradient across local waters. In general,
southwest winds will turn more south-southeast this afternoon,
peaking around 15 kt, highest near the coast where a seabreeze
develops and shifts inland. Overnight, a slightly weaker southerly
wind takes place (10-15 kt) with high pressure continuing across
local waters well in advance of the approaching front this weekend.
Seas will range between 2-3 ft through tonight.

Saturday through Wednesday, a typical summertime pattern will
persist, with prevailing southerly flow and winds/seas well
below advisory thresholds.

Rip Currents: A swell of 2 feet every 10 seconds and proximity to
the new moon will maintain a Moderate Risk for rip currents for
all beaches today, and likely through Saturday due to lingering
2-3 feet swell every 9 seconds and onshore winds.

&&

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

&&

$$

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