435
FXUS62 KCHS 121803
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
203 PM EDT Sat Jul 12 2025

.SYNOPSIS...
Weak high pressure will continue to build across the region
into early next week. By mid-week, a surface front might sag
into the region increasing storm activity.

&&

.NEAR TERM /THROUGH TONIGHT/...
This Afternoon: A typical summertime pattern is expected this
afternoon as ridging aloft centered near southern Florida
extends northward into the region. Similar to the last several
days there is not much consistency between the CAMs. Convection
has begun just west of the forecast area and will likely be
pushing into the region within the next hour or so. Coverage is
forecast to increase this afternoon as outflow boundaries
interact and the sea breeze pushes inland. The severe threat
this afternoon remains low as ML CAPE is around 2000-2500 J/kg
but DCAPE values are only around 500 J/kg. However, a strong
thunderstorm cannot be ruled out, with damaging wind gusts the
main hazard. Additionally, a significant amount of lightning
will be likely with storms this afternoon, as seen over the last
several afternoons. The atmosphere is very moist, the 12Z KCHS
RAOB Sounding showed a PWAT value of 2.25 inches. Heavy rainfall
will be possible this afternoon, with the 12Z HREF highlighting
the coastal counties in a 10% probability of >3 inches. Minor
flooding of low lying and poor drainage areas is possible,
especially over areas that have seen lots of recent rainfall.

Tonight: Showers and thunderstorms are forecast to diminish with
nightfall, when the best chances for precipitation shifts
offshore. Overnight temperatures will be near normal in the 70s.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
A weak upper-lvl ridge will briefly build across the Gulf Coast this
weekend. Simultaneously, a broad ridge will remain off the East
Coast as rich moisture continues to advect into the region with PWAT
values ~2.0 inches through early next week. This will be more than
enough moisture to spark up some showers and thunderstorms each
afternoon as the sea breeze pushes inland. Expect temperatures to be
in the mid to upper 90s on Sunday and Monday, with upper 80s to low
90s on Tuesday. Heat index values look to be in the 100 to the 107
degree range, specifically on Sunday and Monday in the afternoon
hours. As of right now, these values remain under Heat Advisory
Criteria (108F), however we will continue to be monitor these values
over the next couple days. With these temperatures in place and
dewpoints in the the low to mid 70s, moderate instability should
develop and it`s possible to see strong to severe thunderstorms each
afternoon. Overnight lows will remain mild and only dip into the low
to mid 70s (with warmer temperatures closer to the beaches).

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
This current pattern will be slow to change as this weak upper-lvl
ridge eventually begins to break down in the middle part of next
week. A weak front could settle nearby with storm activity gradually
increasing by the end of the week. In addition to the front, there
is some indication of a weak surface low developing over the Florida
Panhandle sometime next week and allow for an enhanced region of
moisture to advect across the Southeast. With this setup, heavy
rainfall could be an issue, however models remain all over the place
with the rainfall amounts that it`s difficult to pinpoint exact
locations this far out in the forecast. Temperatures will remain
near normal for this time of the year.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
The 18Z TAF period will initialize with VFR conditions at
KCHS/KJZI/KSAV. There are some MVFR cigs lingering around KSAV,
however these are expected to quickly erode to VFR. Showers and
thunderstorms are possible again this afternoon, with VCTS
included at all three TAF sites starting around 21/22Z.
Confidence in direct impacts to KSAV remain low, so the 18Z TAF
only features VCTS. A TEMPO group for TSRA has been maintained
at KCHS/KJZI from 22Z to 01Z. Thereafter prevailing VFR is
expected through the remainder of the 18Z TAF period.

Extended Aviation Outlook: VFR will mainly prevail throughout the
period, however brief flight restrictions are possible within
showers and thunderstorms that develop in the afternoon and/or
evening hours.

&&

.MARINE...
This Afternoon and Tonight: Surface high pressure will hold
strong over the local marine waters through tonight with SW
winds generally less than 15 knots. There could be some gusts to
around 20 knots this afternoon along the immediate coastline
associated with the sea breeze. Thunderstorms are possible again
this afternoon as land-based storms push offshore. Additional
thunderstorms are possible over the marine zones through the
overnight period. Frequent lightning and gusty winds will be the
main hazards. Seas through the period should average 2 to 3 ft.

Sunday through Wednesday: Expect generally southerly winds at 5 to
10 kt to prevail throughout the period. It could become a bit gusty
each afternoon with gusts up to 15 to 20 kt as the seabreeze pushes
inland (gusts strongest across the immediate coastline and the
Charleston Harbor). Southeasterly swell will continue to mix into
the local waters over through early next week. Seas will be 2 to 3
ft, then increase to 3 to 4 ft on Wednesday. Otherwise, no marine
concerns expected.

&&

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

&&

$$

NEAR TERM...CPM
SHORT TERM...Dennis
LONG TERM...Dennis
AVIATION...CPM/Dennis
MARINE...CPM/Dennis