786
FXUS62 KCHS 240837
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
437 AM EDT Tue Jun 24 2025

.SYNOPSIS...
High pressure will remain across the Southeast U.S. over the
next couple days, then slowly shift offshore by the end of the
week. Hot and humid conditions are expected to continue with
rain chances increasing mid to late week as surface troughing
begins to form over the region.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, a large/strong ridge centered across the Mid-Atlantic
states will remain the dominating weather feature extending across
the Southeast United States, leading to another warm and mostly dry
day along the western edge of sfc high pressure extending across the
local area from the nearby Atlantic. Large-scale subsidence will
once again play a toll in regards to limiting convection/precip
across the area today, as well as a substantial amount of dry air
depicted on water vapor imagery and local model soundings. However,
a few showers and/or isolated thunderstorm can not be ruled out
heading into peak diurnal heating hours ahead of an inland moving
sea breeze, mainly across the Tri-County Area and perhaps inland
Colleton County.

The main issue for the day will be the heat as deep-layer ridging is
perhaps the strongest across the local area for the week. Strong sfc
heating under mostly sunny skies along with 1000-850 mb thicknesses
support afternoon highs in the mid-upper 90s away from coastal
areas, although a few spots could touch 100 degrees briefly well
inland. These temps along with sfc dewpts in the low-mid 70s should
support peak heat index values generally in the 105-109 degree range
this afternoon, but these values could be limited to a few hours in
duration given ample low-lvl mixing and some lowering of sfc dewpts
mid afternoon. Highest heat index values should occur across the Tri-
County Area, especially if some pooling of moisture occurs along the
inland moving sea breeze, but conditions remain precip-free. Further
south (into Southeast Georgia), the mixing out of sfc dewpts could
play a larger role in limiting the overall max heat index potential
and duration, but given environmental conditions support slightly
warmer temps and sfc dewpts a degree or two higher than previous
days, it will still feel quite warm and humid, with impacts similar
to those that fall within a Heat Advisory. Given the overall setup,
a Heat Advisory will remain in effect from 1 PM to 8 PM EDT today,
with max heat index values likely occurring within a few hour subset
of this time frame this afternoon.

Tonight: No significant changes are expected to the overall pattern
in regards to high pressure dominating the weather pattern across
the Southeast. Sfc winds will likely decouple early evening, with
most areas experiencing light/calm winds away from the coast after
midnight. Temps will remain mild, with lows generally ranging in the
mid-70s inland to upper 70s/around 80 closer to the coast and across
Downtown Charleston.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
This strong upper-lvl ridge that has been sitting across the
Southeastern CONUS the last couple of days will finally begin to
break down Wednesday afternoon. According to latest model guidance,
500MB heights on Wednesday morning will be ~594 dam, and then weaken
to ~590 by Wednesday evening. While these are still high heights for
the region, the highest heights will continue to remain just to the
north. Temperatures will climb to the mid to upper 90s on Wednesday,
with heat indices creeping ~104-106 in the afternoon. Over the last
couple days, the NBM has been overplaying temperatures and dewpoints
and thus, have adjusted the temperatures and dewpoints down a little
in this period due to these recent trends. As of right now, heat
indices remain below Heat Advisory criteria (108F), but this will
continue to be monitored. Models have been fairly consistent with a
weak surface trough forming over the Bahamas sometime on Wednesday
and then meandering across the northeastern portion of the Gulf
through the weekend. This feature will allow for some moisture to
finally return back into the region. Additionally, SPC has placed the
majority of region in a marginal risk and the far interior South
Carolina counties in a slight risk for severe thunderstorms on
Wednesday. According recent runs of the NAM and GFS, PWAT
values will be ~1.75 to 2.0 inches for Wednesday afternoon. This
will yield the chance for showers and thunderstorms to develop
in the afternoon along the seabreeze. With strong instability
~1500-2500 J/kg, mid-lvl lapse rates ~7.5-8.0 C/km, and DCAPE
values in excess of 1250 J/kg in the afternoon, thunderstorms on
Wednesday could become severe with the main threat being
damaging wind gusts.

As this weak surface trough floats nearby, the aforementioned
upper-lvl ridge will continue to weaken and eventually move
offshore by the end of the week. Therefore, a more typical
summertime pattern will set up for Thursday and Friday, with
showers and thunderstorms developing in the afternoon along the
seabreeze. Overnight lows will remain mild and only dip into the
low to mid 70s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
This weak surface trough will meander across northeastern portion of
the Gulf before eventually dissipating sometime on Sunday. A more
zonal pattern will set up over the Southeastern CONUS thereafter.
With moisture making a full return into the region, ensembles
continue to indicate daily chances of rain through early next week.
Temperatures will remain above normal for this time of the year.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
VFR conditions will prevail at CHS/JZI/SAV terminals through 06Z
Wednesday. However, shallow ground fog will be possible near
KSAV in the 10-13z time period and this is reflected in the
latest TAF issuance.

Extended Aviation Outlook: VFR will mainly prevail throughout the
period, however there could be brief flight restrictions in the
afternoon hours through the end of the week as rain chances make a
return.

&&

.MARINE...
Today and Tonight: Atlantic high pressure will dominate the pattern
across local waters, favoring conditions that remain well below
Small Craft Advisory levels through tonight. In general, a westerly
offshore wind associated with a land breeze will take place early,
but sfc winds will gradually turn southeast mid-late morning, then
south this afternoon as a sea breeze develops and pushes inland.
Wind speeds should top out around 10 kt for a bulk of the day. Winds
should then turn more southwest by mid evening, remaining around 10
kt through the night. Seas will generally range between 1-2 ft.

Wednesday through Saturday: As a weak ESE swell continues to mix in,
seas will remain around 1 to 3 ft. Expect 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).

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will peak around 6.5 ft MLLW at Charleston with
the evening high tide cycle this evening and Wednesday night.
Afternoon winds will only be marginally supportive of increasing
tidal departures each day. The evening high tide will likely
peak around 6.8-6.9 ft MLLW each evening, falling just short of
Coastal Flood Advisory criteria.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory from 1 PM this afternoon to 8 PM EDT this
     evening for GAZ087-088-099>101-114>119-138.
SC...Heat Advisory from 1 PM this afternoon to 8 PM EDT this
     evening for SCZ040-042>045-047>052.
MARINE...None.

&&

$$

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