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000
FXUS62 KCHS 281947
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
347 PM EDT Wed Jul 28 2021

.SYNOPSIS...
High pressure will build over the area through Saturday,
bringing dry and hot conditions. A cold front will then stall
over the area Sunday through the middle of next week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
A return to quieter weather is expected tonight as a mid level
trough axis shifts off the coast and drier advects in from the
northwest. For reference, precipitable water values are expected
to drop from near 2.25 inches this afternoon (well above
climatology) to less than 1.5 inches by daybreak. Any lingering
convection will subside with loss of heating with no rain
chances overnight. The main forecast concern then turns to
potential for fog. Given clearing skies, light winds and low
condensation pressure deficits, we have maintained mention of
fog in the forecast. There could be higher coverage and/or
intensity across areas that received substantial rainfall
earlier in the day, mainly over the far interior and over
southeast South Carolina. Low temperatures are expected to
average in the low 70s, except mid 70s near the immediate coast.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
An upper ridge will expand to the east during the period,
bringing hot temperatures and mainly dry conditions. The warmest
temps are expected Friday through Saturday once a 15-20 kt
westerly flow develops at 850 mb. A somewhat drier airmass will
move in, with PWs at or below 1.75" most of the time. This,
combined with strong mid-level subsidence, will prevent
convection from developing Thursday and Friday. A slight
increase in moisture late Saturday, combined with a weak
shortwave, could spur a few showers and tstms to develop or move
in from the northwest.

The hot temps and heat indices are the main concern during the
period. Although far inland dewpoints should mix down to the low
70s each day, a fairly good sea breeze will surge dewpoints into
the mid/upper 70s across the eastern half of the area during the
afternoons. Temps forecast to reach the low to mid 90s Thursday
and mid/upper 90s Friday/Saturday. We`re currently showing heat
indices of 105-109F on Thursday with a significant area of
110-114F Friday and Saturday. A few areas closer to the coast
where hot temps intersect with particularly high dewpoints could
touch 115F at times Friday and Saturday. We will likely require
Heat Advisories for much of the area Friday and Saturday.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
An upper ridge will set up to our west late this weekend into
the middle of next week while a front stalls over the area. A
wet period is anticipated with numerous showers and tstms each
day, including during the overnight hours.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
The threat for impacts from showers/thunderstorms will shift
more to KSAV this afternoon, although there is still uncertainty
as to if a direct impact will occur. Will opt to amend if
necessary. Overnight, the main concern will be the potential for
fog and/or low clouds. Given recent rains, the chance appears
highest at KJZI and KCHS. Included MVFR for now, although there
is potential for lower reductions. Any restrictions will
improve after in the morning.

Extended Aviation Outlook: Flight restrictions are possible in
afternoon/evening showers and thunderstorms Saturday and Sunday.

&&

.MARINE...
Tonight: Quiet marine conditions will prevail. Wind directions
will be variable, with speeds less than 10 kt. Seas will average
2-3 feet.

Fairly persistent SW flow anticipated Thursday through early
next week. Winds could get close to Small Craft criteria Friday
afternoon due to a tightening gradient ahead of a cold front.
Winds along the coast each afternoon will back slightly and
strengthen with the sea breeze.

&&

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

&&

$$

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