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012
FXUS62 KCHS 120608
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
208 AM EDT Sat Jul 12 2025

.SYNOPSIS...
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Weak high pressure will extend across the area into early next
week. A surface front may sag into the area during the middle of
next week.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Today: Aloft, the ridge and anticyclone currently centered near
south FL should start to take greater hold on the pattern
across southeast GA and up the Southeast coast. At the surface,
the setup will be typical of summertime with the subtropical
high over the Atlantic to the east and a subtle inland trough.
The ridge aloft starting to build a bit further north would seem
to favor seeing a little less coverage than the past few days,
especially for the southeast GA area. There isn`t much
consistency in hi-res model guidance, though if you squint you
could perhaps see a bit more coverage developing first inland
closer to the Midlands in the mid to late afternoon and then
pushing to the east or southeast towards the coast through the
evening. However, much like the past few days, once convection
gets going and throws out a few outflow boundaries we could see
development just about anywhere. The severe threat does not look
particularly noteworthy, with MLCAPE values of 2,000-2,500
J/kg, meager lapse rates, and DCAPE values only in the 500-700
J/kg range. As such, the forecast area is not included in an SPC
Day 1 severe risk area. But, as with most summer days there
will be the potential for an isolated severe storm, especially
where the more significant boundary interactions occur. Locally
heavy rainfall will again be a potential issue with the area
remaining within a pocket of 2-2.25" precipitable water and
relatively slow storm motion (~10 knots). So while most areas
will see rainfall amounts of 0.50" or less, there could be
isolated amounts of 1-2" where the heaviest storms track. Highs
are forecast for the low 90s, with max heat index values mostly
in the 102-106 degree range.

Tonight: Clusters of showers and thunderstorms could linger
into the mid to late evening hours, but should generally be on a
diminishing trend. Then for the overnight hours, attention
should again shift offshore for shower and thunderstorm
development. Pretty typical summer night with lows in the mid
70s for most areas.
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.SHORT TERM /SUNDAY THROUGH TUESDAY/...
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Sunday into Monday, an upper ridge will briefly build to our
west, with increasing heights across the Southeast. High temps
will be in the mid to upper 90s except near the coast where
upper 80s to lower 90s will be the rule. Bermuda high pressure
will prevail at the surface, maintaining a moist southerly flow
into the area. Dewpoints are expected to surge into the mid to
upper 70s, particularly over the eastern half of the area both
days. Our latest forecast shows a few hours of heat indices of
106-110F over a significant chunk of the forecast area, so we
may eventually need Heat Advisories for part of the area. A
slight increase in mid-level subsidence from the upper ridging
may limit diurnal convective coverage to be more scattered vs
widespread.

Tuesday could see greater convective coverage as a weak
shortwave rotates around the northeast side of the ridge and
interacts with a moderately unstable airmass. Temps should be a
few degrees cooler than on Monday.
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&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
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A weak surface trough or front could stall over the area on
Wednesday and Thursday, providing an additional focus for
convection. Upper ridging then expected late week, though an
active sea breeze and ample moisture should still allow for at
least scattered showers and thunderstorms.
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&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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The 06z TAF period begins with VFR conditions at KCHS, KJZI,
and KSAV. All 3 TAF sites picked up some rainfall today, so we
can`t completely rule out some fog and low stratus right around
sunrise but confidence is too low to include at this time.
Attention then turns to the potential for afternoon and evening
thunderstorms. We have maintained the TEMPO group for TSRA at
all 3 sites, but shifted the time a little later to favor the
late afternoon and into the evening. Also, there are some
indications in model data that there could possibly be less
coverage across southeast GA today which could lower the
thunderstorm risk at KSAV. Will continue to evaluate the need
for changes with the 12z TAF issuance.

Extended Aviation Outlook: The main concern will continue to be
brief flight restrictions from showers and thunderstorms. The
greatest threat window will be in the afternoon and early
evening hours.
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&&

.MARINE...
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Today and tonight: Pretty typical summertime pattern expected
across the local waters through tonight. Southwest winds will
turn more southerly in the afternoon with a modest surge in wind
speeds peaking in the afternoon and evening hours. Speeds
should mostly top out in the 10-15 knot range but there could be
some gusts up to 20 kt at times along the land/sea interface.
Then overnight, winds will turn more southwesterly and even
westerly late with speeds diminishing into the 5 to 10 knot
range. Seas should mostly average 2-3 feet. Thunderstorms will
again be a potential hazard as land- based storms develop this
afternoon and try to move to the coast and the coastal waters
through the evening. Frequent lightning and gusty winds will be
the primary concerns.

Sunday through Wednesday, southerly flow will continue as
Atlantic high pressure remains off the coast. A decent sea
breeze will develop each afternoon, with winds in Charleston
Harbor potentially gusting close to 20 kt at times. No headlines
expected.
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&&

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

&&

$$

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