sc discuss
Office: CHS
FXUS62 KCHS 050035
AFDCHS
Area Forecast Discussion
National Weather Service Charleston SC
835 PM EDT Fri Jul 4 2025
.SYNOPSIS...
A tropical system is expected to move slowly north-northwest
off the Southeast coast tonight, then move north toward eastern
South Carolina Saturday into Sunday. High pressure will rebuild
next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
As we head into the overnight, convection across SE GA/SC has
mostly cleared out for the evening. Earlier this afternoon, the
aforementioned low pressure off the Southeast U.S. coast formed
into a tropical depression. NHC has labeled the name of the
system as Tropical Depression Three. Charleston County is
currently under a Tropical Storm Watch until Sunday. As the
system approaches the coast, it could become better organized
and could strengthen over the Gulf Stream. Thus, this might
yield Tropical Storm Warnings if this does happen. Regardless
of the strength, rain bands should push onshore along the coast
of the South Carolina Lowcountry late tonight into early
Saturday morning. The forecast will feature a tight gradient of
PoPs from likely across the adjacent Atlantic waters to SCHC
PoPs along the I-95 corridor. In addition, northeast winds along
the coast will gradually strengthen, with gusts around 25 mph
possible along the beaches late tonight. Low temperatures are
forecast to range from near 70 inland to the mid to upper 70s
along the coast.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
The main concern over the weekend is a low pressure system well
off the GA/SC coast that is forecast by most models to gradually
strengthen as it moves NNW or N. An NHC aircraft is
investigating the system this afternoon so more information
should be available later this afternoon or early this evening.
The 12Z guidance is in reasonably good agreement that the system
would slowly strengthen as it moves NNW, then moves inland over
eastern SC somewhere between Charleston and the SC/NC border on
Sunday. There are currently no indications that it would
strengthen substantially. The reasonable worst case scenario
would be for it to strengthen into a low-end tropical or
subtropical storm before it makes landfall in SC during the day
Sunday. The latest NBM probabilistic guidance shows only a 10%
chance for peak wind gusts along the SC coast to exceed 45 mph
during the strongest winds Saturday afternoon/night.
A very moist airmass will overspread the area Saturday. PWATs
will exceed 2.2" over the eastern half of the area by Saturday
afternoon, then this moisture will spread across the remainder
of the area Saturday night into Sunday. An increase in cloud
cover will depress temperatures somewhat, which in turn will
limit instability. However, approximately 1000 J/kg CAPE
expected during the daytime hours both days. Isolated to
scattered showers and tstms could develop Saturday morning in
response to an early sea breeze, then greater coverage will
overspread the area from the east as rain bands from the low
move in.
Numerous showers and tstms will likely continue Saturday night
into Sunday morning until the low pressure system moves inland
over eastern SC and dissipates. Locally heavy rainfall will be
possible Saturday through Sunday given the very moist airmass
and potential for training cells.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
A deep layered ridge will build over the eastern U.S. next week,
with increasing temperatures and dewpoints. Heat indices
expected to rise above 108F for many areas Tuesday through
Thursday so Heat Advisories are possible.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
00Z TAFs: Showers and thunderstorms have cleared out for the
most part across the Lowcountry as we head into the overnight.
A tropical depression will approach tonight into Saturday. Rain
bands and deep moisture associated with low are timed to push
onshore along the SC coast during the pre-dawn hours, edging
inland through the rest of the 00Z TAF period. KCHS and KJZI
will feature a TEMPO at all terminals for -SHRA by daybreak. As
the system nears the coast, it is expected to interact with an
area of high pressure centered over the Mid Atlantic states,
resulting in gusty northeast winds north of the center of low
pressure. The terminals may see gusts around 25 kts after
sunrise Saturday. As rainbands from this system continue to
break off throughout the day and move onshore, a TEMPO groups
was added at all terminals for -TSRA beginning at 18Z. Outside
of the TEMPO group, all terminals will feature a mention of VCSH
throughout the day.
Extended Aviation Outlook: Occasional ceiling restrictions
possible Saturday through Sunday as low pressure moves up the
coast. Brief ceiling/vsby restrictions possible Saturday through
Wednesday due to scattered showers and thunderstorms.
&&
.MARINE...
Tonight: A tropical depression off the Southeast U.S. coast
will slowly track towards the Carolina coast tonight. As the
system approaches, it could become better organized and could
strengthen over the Gulf Stream. See latest NHC information. As
the system nears the coast, it is expected to interact with an
area of high pressure centered over the Mid Atlantic states,
resulting in gusty northeast winds north of the center of low
pressure. By late tonight, northeast winds are forecast to
strengthen to 20 kt with gusts around 25 kts. In addition, seas
should build through tonight, generally ranging between 4 to 5
ft by sunrise Saturday.
This tropical depression has the potential to develop into
tropical storm Saturday or Saturday night. Recent guidance
suggests this system would move north toward the eastern SC
coast, potentially moving onshore Sunday morning.
Regardless of the exact type and strength of the system, we
anticipate a tightening northeast gradient along the coast on
Saturday between the low pressure offshore and inland high
pressure. 6 ft seas and 25-30 kt wind gusts could spread into
the SC nearshore waters during the day Saturday, continuing into
Saturday night. These gusty winds would also impact Charleston
Harbor.
Conditions will drastically improve on Sunday as the
flow briefly becomes offshore, then settles into a SW flow as
high pressure rebuilds.
Rip Currents: Gusty winds and increasing swell energy will yield
a High Risk for rip currents along the SC coast and Moderate
risk for GA coast on Saturday. A Moderate Risk exists for all
beaches on Sunday, mainly due to residual swell.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Tropical Storm Watch for SCZ050.
High Risk for Rip Currents from Saturday morning through Saturday
evening for SCZ048>051.
MARINE...Tropical Storm Watch for AMZ330-350.
Small Craft Advisory until noon EDT Sunday for AMZ352.
Small Craft Advisory until 6 AM EDT Sunday for AMZ354-374.
&&
$$
NEAR TERM...Dennis
SHORT TERM...JRL
LONG TERM...JRL
AVIATION...Dennis/JRL
MARINE...JRL/NED
Office: CAE
FXUS62 KCAE 050043
AFDCAE
Area Forecast Discussion
National Weather Service Columbia SC
843 PM EDT Fri Jul 4 2025
.SYNOPSIS...
Isolated showers and storms possible again today as a weak surface
boundary sits over the area. Late this weekend and early next
week moisture returns to the region as low pressure develops
off of the Southeast coast. As the low moves away from the
region we return to near normal rain chances through the
remainder of the long term.
&&
.NEAR TERM /UNTIL 7 AM SATURDAY MORNING/...
Key Message(s):
- Lingering showers this evening should diminish after midnight.
Scattered convection continues to persist this evening on
outflow boundaries across the Midlands. Storms have been
overperforming with seemingly routine storms producing strong
wind gusts in excess of 35-40 mph within an environment
characterized by DCAPE values over 1200 J/kg and PWATs around
1.6-1.7 inches.
Expect these storms to dissipate later into the evening with
the loss of heating. Outside of gusty winds associated with
thunderstorm outflow boundaries winds should diminish to around
5 mph or less after 9-10pm through the remainder of the night.
Fog is not expected to be a concern Saturday morning.
&&
.SHORT TERM /7 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Key Message(s):
- Surface low pressure situated offshore
- Isolated to scattered showers and storms
A diffuse surface boundary will remain over the region with
relatively dry air over the western FA. A developing surface
low off of the GA/SC coast will wrap moisture into the
Lowcountry and eastern Midlands with PWAT values up to 1.75
inches in the eastern Midlands. With more moisture in place than
the previous day we would expect isolated to widely scattered
showers and thunderstorms for areas south and east of I-20. The
HRRR and NAM seem to be at odds with the depth of mixing
occurring on Saturday afternoon while the GFS is somewhere
between showing some weak potential instability over the area to
support convection. It will be breezy as the low approaches and
the pressure gradient tightens but gusts should remain limited
to around 25 mph, below Lake Wind Advisory criteria. Saturday
night the low could meander a little further towards the coast
leading to a chance of rain through the overnight hours.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Key Message(s):
- Tropical Depression Three has formed off the coast
- Moisture returns to the region in the long term
The first portion of the long term, from Sunday through Monday,
will largely depend on the positioning of TD3 currently sitting
offshore. Models tend to be in a little more agreement today on
shifting the low west and bringing stronger moisture advection
into the forecast area. This would likely bring rainfall into
SC/NC but otherwise winds should remain below any product
criteria in central SC and eastern GA. The deeper moisture
should shift away from the region by mid-week as ridging builds
over the area. This week lead to warming temps with
climatological rain/storm chances. Highs mid-week may climb into
the upper 90s.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions generally expected through the TAF period.
Lingering convection this evening with possible restrictions
early but otherwise expect VFR conditions through the remainder
of the period. Winds may stay up a bit through 03z given many
outflow boundaries around but winds should diminish to less than
5 knots overnight. Fog/stratus not favored during the predawn
hours, though its possible in areas that received rain which
could expand towards terminals but confidence not high enough to
include at this time. Winds should pick up quickly in the
morning with an increased pressure gradient as winds should
increase to over 10 knots by 13z-15z with gusts over 20 knots
possible through the afternoon. Subsidence around newly formed
TD3 should limit convection across the area.
EXTENDED AVIATION OUTLOOK...There is the possibility of
diurnally driven showers and thunderstorms this weekend into
early next week with the potential for periodic restrictions.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...None.
GA...None.
&&
$$
Office: GSP
FXUS62 KGSP 050027
AFDGSP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
827 PM EDT Fri Jul 4 2025
.SYNOPSIS...
Dry high pressure will linger atop the region into Saturday with an
influx of Atlantic tropical moisture expected on Sunday. Hot and
more humid conditions will return on Monday and linger through
midweek featuring daily afternoon and evening shower and
thunderstorm chances.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of noon Independence Day: Upper ridge will shift eastward
over the eastern third of the CONUS through Saturday. Sfc high
now over the Appalachians and OH Valley in turn will center
offshore. Low level flow should remain generally northeasterly
thru the period. Weak instability will develop diurnally this
afternoon but subsidence inversion appears to limit the depth of
convection and thus keep precip chances very low. A few isolated
cells may develop over the SW NC mountains where the inversion
is weakest and warrants a 15-20% PoP. Can't completely rule out
a shower/storm in the Upstate, but any such activity should be so
isolated PoP is being kept below 10% there.
Invest AL92 looks not to have any direct sensible impacts on our
CWA thru the period. Some hi-res models depict low stratus making a
run at the eastern zones in the early morning, but that likely would
dissolve relatively quickly after daybreak. Subsidence is likely to
be enhanced on the periphery of the system, so PoPs Saturday end up
even lower than today, below slight-chance in all zones. Max temps
should end up slightly cooler, just on the warm side of normal.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 120 PM Friday: The cwfa is progged to be within the far
western periphery of tropical/sub-t system circulation on Sunday. As
it stands now, based on the 12z model suite, would expect
encroachment of higher level cloud shield Saturday night and
expanding wwd on Sunday. Given the reduced insolation and increased
chances for developing shower bands into the Carolina piedmont, have
lower MaxT for Sunday, with perhaps just mid 80s along the eastern
fringes of the cwfa. Very well may be suppressed along and west of
the Blue Ridge to preclude any showers in the mountains, we'll see.
The SE CONUS upper ridging with strengthen some on Monday, with very
warm air surging back NE acrs the region, bumping maximum
temperatures to above the early July climo along with a return to
more typical diurnal deep convective chances.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 145 PM Friday: Upper ridging will linger atop the region to
start off the period before beginning to breakdown in response to
Ohio or Mississippi valley energy translating eastward. Expect
Tuesday and Wednesday to be the hottest days of the week, featuring
apparent temperatures as high as around 100 for parts of the
Piedmont. With the trend toward a less suppressed atmosphere, chancy
type pop for Tuesday will increase to likely probabilities for
showers and storms on Wednesday. The eastern CONUS will continue to
transition to a more robust and dynamic looking pattern through the
latter half of the workweek resulting in the potential for numerous
showers and thunderstorms each day.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: E to NE flow will continue around the
southwestern side of the surface high that was anchored over the
Northeast and Mid-Atlantic. Winds have gradually diminished
over the past hour or two and the 15-18 kt gusts that was
observed during the afternoon has already subsided with the loss
of daytime heating. Speeds should generally decrease to 5 kt or
less after sunset. AVL and HKY the most likely for winds to go
light and variable (or calm) for much of tonight. VFR is still
forecast for all TAF sites tonight, but there is an outside
chance (20 percent) for MVFR CIGs at CLT late tonight into the
first half of the morning when a stratus deck advances inland.
However, most guidance keeps the western edge of this marine
layer about 50-75 miles from CLT. Limited potential for
valley/river fog late tonight. Similar conditions expected on
Saturday with few to sct cumulus deck around 5-7 kft as well as
high-level cirrus. The E-NE flow will be as strong, if not 1-2
kt stronger, resulting in sustained speeds between 8-13 kt.
Gusts of 15-20 kt are most likely between 15z-23z when daytime
mixing is strongest. There is a risk for a due E wind to develop
at CLT Saturday afternoon like it did this afternoon. Not
expected anything more than a rouge storm in the mountains on
Saturday.
Outlook: Chances for showers and storms will increase across
our area on Sunday and early next week. Depending on the track
of Tropical Depression Three, the western periphery of the outer
rain bands could approach eastern terminals, including CLT late
Saturday night and Sunday. While the heaviest rain with this
system is still expected to stay east of us, MVFR restrictions
would be possible in heavier showers. Fog and/or low stratus
will also be possible each morning, mainly in the mountain
valleys, as well as near lakes and rivers.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...CSH
NEAR TERM...Wimberley
SHORT TERM...CSH
LONG TERM...CSH
AVIATION...JRK
