037
FXUS62 KCHS 251728
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
128 PM EDT Wed Jun 25 2025

.SYNOPSIS...
Hot and humid conditions are expected to continue with rain
chances increasing today into late week as surface troughing
begins to form near the region and a few upper disturbances
pass through. A few thunderstorms may become strong to severe
on Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Early this afternoon: The Heat Advisory seems to be working out
well with quite a few areas already reporting heat indices in
the 106-110 degree range. We are seeing an earlier sea breeze
development than we did yesterday, with radar imagery already
showing the boundary start to slowly push inland. Overall, no
changes through sunset.

Late this morning: Overall, a very similar setup to yesterday.
The upper ridge and anticyclone will remain centered across
KY/TN, placing the forecast area within a region of northeast
flow. At the surface, the subtropical high remains the primary
feature but the gradient is quite weak along the coast. The
first order of business concerns hot and humid conditions and
elevated heat index values. Currently, temperatures and
dewpoints are running a bit ahead of where they were 24 hours
ago. Also, low-level thickness off the 12z KCHS RAOB is just a
touch higher than yesterday. So, we expect to at least equal our
temperatures from yesterday with slightly higher dewpoints. This
should yield heat index values of 105-110 degrees for most of
the forecast area, highest across the Charleston Tri-County
region down through Colleton, Beaufort, Jasper, Chatham, and
Bryan counties. The counties inland of this tier might not reach
the explicit Heat Advisory criteria of 108 degrees, but it will
be equally as hot and humid as yesterday. So we have issued a
Heat Advisory for most of southeast GA and southeast SC,
excluding McIntosh, Long, and Liberty counties.

Second order of business concerns thunderstorm potential this
afternoon. Model guidance continues to favor most of the day
remaining convection-free, with some hints of isolated
initiation occurring late this afternoon. However, severe
weather concerns continue to be concentrated in the evening
hours and there are no changes to that thinking as of yet.

This Evening: A broad mid-upper lvl low centered off the
Southeast Coast will slowly nudge eastward with time, forcing
the large-scale ridge to retreat further inland. Vort energy
wrapping around the north/northwest periphery of the low could
play a key role in the development of showers/thunderstorms
developing across a broad region of sfc troughing over the
Carolinas (starting across North Carolina), with a bulk of
global and hires models suggesting activity to congeal/broadly
organize into a cluster within a modestly sheared environment,
then tracking south-southwest, primarily just inland to the
local area near the arriving sea breeze. However, cold pooling
could easily allow activity to reach inland counties of
Southeast South Carolina and Southeast Georgia in a severe
state, and to a lessor degree coastal counties, mainly across
Southeast Georgia. Locally, environmental conditions are rather
impressive across inland areas ahead of this activity, with
SBCAPE around 3500 J/kg, low-lvl lapse rates around 8.5 C/km,
DCAPE near the 1200-1400 J/kg range and inverted-v soundings
suggestive of thunderstorms with damaging wind potential should
they occur locally. There is even some risk for small hail, but
this will be secondary concern. The primary time-frame for
severe weather remains between 6PM to 12AM this evening.

After Midnight: Weak shear and loss of diurnal heating will
eventually take a toll in regards to cold pooling and
thunderstorm intensity. However, showers and general
thunderstorms remain in the forecast across southern areas into
late night. Temps will remain very mild prior to
shower/thunderstorm activity, but should eventually dip into the
lower 70s inland to mid 70s near the beaches.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
The upper-lvl ridge situated over the Mid-Atlantic that has
been sitting across the Southeastern CONUS the last couple of
days will continue to break down throughout Thursday and Friday
as it moves offshore over the weekend. With this transition,
expect a more typical summertime pattern to finally setup for
the next couple of days. Remnant vorticity from an MCS on
Wednesday combined with a weak upper-lvl low meandering across
Florida might yield the chance for showers and thunderstorms to
form in the afternoons on Thursday through Saturday. At the
surface, an extensive field of moisture will remain over the
Southeast with PWAT values ranging from 1.50 to 1.75 inches
throughout the period. This will be more than enough moisture to
spark up some showers and thunderstorms each afternoon as the
sea breeze pushes inland. In addition, SPC has most of the
region highlighted by a level 1 out of 5 risk for severe weather
on Thursday with the primary concern being locally damaging
wind gusts. Overnight lows will remain mild and only dip into
the low to mid 70s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
This weak upper-lvl low will continue to meander across Florida
before eventually dissipating on Sunday. A more zonal pattern
will setup over the Southeast and ensembles continue to indicate
daily chances of rain through early next week. Temperatures
will remain slightly above normal for this time of the year.

&&

.AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
The 18z TAF period begins with VFR conditions in place at KCHS,
KJZI, and KSAV. The primary forecast challenge for this period
concerns thunderstorm potential later this evening. There
remains considerable uncertainty regarding the coverage and
track of thunderstorms this evening through the early morning
hours, with the potential that storms could remain completely
inland of the terminals. However, the risk is high enough that
we need to include some degree of TS in the TAF`s, so we have
introduced VCTS beginning at 01z at KCHS, 02z at KJZI, and 03z
at KSAV. Storms should move quickly through, if they occur at
all, and shouldn`t linger too long into the late evening and
early morning hours. If storm occur, there is potential for
strong wind gusts and this (along with TSRA TEMPO groups) will
need to be considered either with amendments or with the 00z TAF
package.

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.

&&

.MARINE...
Today and Tonight: Atlantic high pressure will prevail for a
bulk of the day and into tonight, favoring conditions that
remain well below Small Craft Advisory levels through tonight.
In general, a southwest wind will gradually turn south mid-late
morning, then peak in the 10- 15 kt range as a sea breeze
develops and pushes inland. A few showers and thunderstorms
could arrive to coastal areas late evening and after midnight
tonight, producing higher wind gusts, seas and some risk for
severe weather across Georgia waters, but outside this activity,
winds are expected to return to southwest and remain around 10
kt or less. Seas will generally range around 2 ft.

Thursday through Sunday: As a weak ESE swell continues to mix
in, seas will remain around 1 to 3 ft. 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). Otherwise,
no marine concerns expected.

Rip Currents: A 1.5 ft, 7-8 second swell will impact the
beaches along with a 10-15 kt onshore wind today. Given these
conditions are similar to yesterday with several rip currents
reported along Tybee Island, GA, a Moderate Risk for rip
currents is in place along Georgia beaches through this evening.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will peak around 6.5 ft MLLW at Charleston
with this evening`s high tide cycle. Late afternoon winds will
only be marginally supportive of increasing tidal departures.
This evening`s high tide will likely peak around 6.8-6.9 ft
MLLW, falling just short of Coastal Flood Advisory criteria.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory until 8 PM EDT this evening for GAZ087-088-
     099>101-114>119.
SC...Heat Advisory until 8 PM EDT this evening for SCZ040-042>045-
     047>052.
MARINE...None.

&&

$$

NEAR TERM...BSH/DPB
SHORT TERM...Dennis
LONG TERM...Dennis
AVIATION...BSH/Dennis
MARINE...Dennis/DPB