Severe Thunderstorm Warning 91, NWS Charleston, SC

Area Forecast Discussion
National Weather Service Charleston SC
159 PM EDT Mon Jul 14 2025

.SYNOPSIS...
Atlantic high pressure will prevail into the upcoming weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
This Afternoon: Aloft, a weak upper-lvl ridge will remain across the
Southeast as a surface low offshore of the Florida coastline
continues to track westward. These features will yield east-
northeastward flow throughout the day, which is uncommon for this
time of the year. At the surface, this low developing off the
Florida coastline will dominate the flow across the region and might
cause for a more progressive seabreeze this afternoon. From KCHS 12Z
sounding, moderate instability and a K index value of ~35 suggests
isolated to numerous thunderstorms will develop in the
afternoon (mainly along and west of I-95 corridor). Recent hi-
res guidance has been indicating that drier air will be located
along the immediate coastline and just inland of the South
Carolina coastline with PWAT values from 1.4 to 1.8 inches with
the deeper moisture (PWAT values > 2.0 inches) west of I-95.
Thus, the current idea remains that showers and thunderstorms
will initiate along and west of the I-95 corridor. DCAPE values
will be ~800 J/kg, but nothing looks particularly noteworthy in
terms of the severe threat. However, there is still a
possibility of strong to marginally severe storms where boundary
interactions occur. Locally heavy rainfall will be possible
along and west of I-95 where the ample moisture and storm
coverage is expected. As far as rainfall amounts .. 1-2 inches
with higher amounts possible with these storms.

Heat index values as of 2PM are generally between 100-106 across the
forecast area, just shy of Heat Advisory criteria. As convection
begins this afternoon some relief in the heat is expected.

Tonight: Showers and thunderstorms should shift further inland and
off to the southwest throughout the evening. Temperatures will drop
into the mid to upper 70s (with warmer temperatures closer to the
beaches). As the developing low offshore of the Florida coastline
travels westward, showers and thunderstorms could develop over the
coastal waters overnight. Coverage should increase overnight and
could draw closer to the coast by daybreak.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Tuesday: A weakening TUTT will be approaching Florida with dry
air located on the northwest flank. PWATs drop to less than
1.5", with 2"+ PWATs on either side. Surface convergence from
Monday will have moved further inland over GA on Tuesday with a
sea breeze forecast to move inland during the afternoon. The
lower PWAT air will likely limit convection slightly, but the
overall extent of coverage should still be at least chance. High
temperatures will also be lower on Tuesday as 1000/ 850 mb
thicknesses fall to 1415 m (or about 10 m cooler than Monday)
due to the undercutting TUTT.

Wednesday - Thursday: Another TUTT will break off and approach the
region Wednesday allowing thunderstorms to continue both days. Storm
motions Wednesday are forecast to be around 10 kt, but increase to
near 20 kt by Thursday as the TUTT moves overhead and elongates the
wind field slightly. This means the greatest chance for locally
heavy rainfall will be on Wednesday, with slightly lower chances on
Thursday due to increased storm motion. High temperatures will be
near climo or in the lower 90s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
The TUTT that was near the area on Thursday will cross Florida
Saturday keeping afternoon thunderstorm chances in the forecast
through the weekend. High temperatures will also remain near
climo/ slightly above climo as low level thicknesses slowly
recover. Max heat index values each afternoon will be near or
just below advisory criteria (108 F).

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
00Z TAFs: Expect VFR conditions to persist at KCHS/KJZI/KSAV.
Showers and thunderstorms are expected to develop along and west of
I-95 this afternoon and maintained VCTS starting at 21Z. Most of the
thunderstorm activity should remain inland of KCHS and KJZI. There
is a chance of fog developing at KSAV before daybreak (~09Z),
however left the mention out of the TAFs at this moment as
confidence is low with this.

Extended Aviation Outlook (Tuesday through Saturday): 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: Expect generally northeast to east-
northeast flow at 5 to 10 kt to prevail through tonight. This flow
pattern will generally be driven by the circulation around the
developing low pressure off the Florida coastline. It could become a
bit gusty in the 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 and seas will be 1 to 2
ft. Showers and thunderstorms will develop over the coastal
waters tonight and increase in coverage closer to daybreak.
Otherwise, no marine concerns expected.

Tuesday through Saturday: A TUTT will be located just off of the SC
coast through the extended while at the surface Bermuda high
pressure will be in control. For the marine zones, this will
translate to each afternoon featuring wind gusts peaking 15 to 20 kt
due to an inland advancing sea breeze. Seas through the period will
be 2-4 ft.

&&

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

&&

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

Hazardous Weather Outlook
National Weather Service Charleston SC
146 PM EDT Mon Jul 14 2025

GAZ087-088-099>101-114>119-137>141-SCZ040-042>045-047>052-151800-
Jenkins-Screven-Candler-Bulloch-Effingham-Tattnall-Evans-
Inland Bryan-Coastal Bryan-Inland Chatham-Coastal Chatham-Long-
Inland Liberty-Coastal Liberty-Inland McIntosh-Coastal McIntosh-
Allendale-Hampton-Inland Colleton-Dorchester-Inland Berkeley-
Inland Jasper-Beaufort-Coastal Colleton-Charleston-Coastal Jasper-
Tidal Berkeley-
146 PM EDT Mon Jul 14 2025

This Hazardous Weather Outlook is for southeast Georgia and
southeast South Carolina.

.DAY ONE...This afternoon and tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

See the Graphical Hazardous Weather Outlook for more information
about the following possible hazardous weather:

- Extreme Heat

&&

The Graphical Hazardous Weather Outlook can be found at:
https://www.weather.gov/erh/ghwo/?wfo=chs

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