North Charleston, South Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

676
FXUS62 KCHS 100650
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
250 AM EDT Sat Oct 10 2026

.WHAT HAS CHANGED...
All sections have been updated.

&&

.KEY MESSAGES...
- 1) Heavy rainfall and flash flooding is expected to impact
  southeast Georgia and southeast South Carolina through this
  evening.

- 2) An isolated tornado or two will be possible across
  southeast Georgia and southeast South Carolina today.

- 3) Several hazards are expected to impact the southeast
  Georgia and southeast South Carolina coast. Moderate to
  potentially major flooding is possible for Charleston and
  coastal Colleton Counties this morning.

- 4) A Lake Wind Advisory has been issued for Lake Moultrie
  through this evening.

&&

.DISCUSSION...
KEY MESSAGE 1: Heavy rainfall and flash flooding is expected to
impact southeast Georgia and southeast South Carolina through
this evening.

The forecast area will sit within the feed of deep tropical
moisture on the east side of the circulation of Isaias today.
All the necessary ingredients will be present including
precipitable water values into the 2.2-2.4" range bands of deep
convection likely tracking repeatedly over the same areas.
Unfortunately, there remains uncertainty regarding exactly where
the stripes of the highest rainfall totals will setup. The
initial round of rainfall will likely be the most widespread and
driven by convergence within the advancing warm front that
should clear the area by mid to late morning. Then into the
afternoon, we should transition into a regime driven by bands of
showers and thunderstorms streaming northward. It is within
these bands where the highest event totals will likely occur.
Though confidence isn`t high in exactly where the highest
bands/stripes of rainfall will be, guidance such as the 10/00z
HREF is instructive regarding the rainfall potential. The
probability- matched mean suggests widespread amounts of 1-3"
across all of southeast GA and southeast SC. There continues to
be signals in the localized probability-matched mean for pockets
of considerably higher amounts into the 4-6" range and
potentially even 6-8" depending on training bands eventually
setup and evolve.

The potential for drier air to wrap around the remnant
circulation of Isaias is the main driver for uncertainty
regarding where the heaviest rainfall occurs and what the
highest amounts end up being. But, the potential for flash
flooding continues to be high enough to warrant carrying the
ongoing Flash Flood Watch. The greatest threat for excessive
rainfall and flash flooding will run from the early morning pre-
dawn hours into the evening. Of greatest concern is the morning
along the coast around the time of the ~8:30 am high tide.
Coastal flooding along will produce flooding and inundation
along the coast and if pockets of heavy rain are also occurring,
the flash flood threshold will be even lower.

KEY MESSAGE 2: An isolated tornado or two will be possible
across southeast Georgia and southeast South Carolina today.

Surface analysis shows a well entrenched, albeit shallow, wedge
of high pressure across the Carolinas and into GA related to
the parent high sprawling across eastern Canada and into the Mid
Atlantic. A well defined warm front-like feature extends west
to east from the center of Isaias off the northeast FL coast
along a notable ThetaE gradient. SPC Mesoanalysis shows that
south of this boundary is where the reservoir of surface-based
instability is and this feature is forecast to steadily advance
northward through the overnight and should clear the forecast
area by mid morning.

There remains two primary areas and time periods of concern for
thunderstorms capable of producing severe weather and perhaps
an isolated tornado or two. The first area and time period will
come through the overnight and into mid morning along and near
the boundary itself, primarily along the coast. It is in this
corridor where we will likely see the duo of the best period of
low-level veering and SRH, with values peaking in the 200-300
m2/s2 coincident with MLCAPE peaking around 500 J/kg with
pockets of 500-1,000 J/kg. Such an environment will support low-
topped mini-supercells that will develop across the adjacent
coastal waters and attempt to push onshore. We are already
seeing this type of convection on the KJAX radar displaying well
defined supercell elements and clearly producing tornadic
waterspouts. This first threat will likely run from the early
morning pre-dawn hours through mid-morning, primarily following
the passage of the warm front.

The second area and time period of concern comes in the
afternoon and into the evening with diurnal heating and more
spatially broad destabilization. During this round we will
likely see a combination of less impressive low-level veering
and SRH coincident with a potentially more unstable environment.
Being south of the boundary, profiles will be a bit more uni-
directional and should yield SRH values more into the 100-200
m2/s2 range. However, instability should be higher than during
the first round as we start to see some cloud breaks and
temperatures warming into the low to mid 80s paired with
dewpoints into the upper 70s. MLCAPE values of 1,000-1,500 J/kg
appear likely, with pockets of higher values possible. Model
guidance depicts the primary zone of highest instability focused
across southeast GA especially up to around the I-16 corridor
though it should be stressed that the threat will exist across
the entire forecast area. During this time period, we should see
bands of more discrete convection with supercell structure,
mostly low-topped as well. To a lesser degree, this threat will
extend through Saturday night and into Sunday morning until the
cold front sweeps through from the west. As we move forward in
time the amount of instability available should wane through the
overnight and profiles will become even more uni-directional.

KEY MESSAGE 3: Several hazards are expected to impact the
southeast Georgia and southeast South Carolina coast. Moderate
to potentially major flooding is possible for Charleston and
coastal Colleton Counties this morning.

Today: Breezy onshore flow combined with widespread rainfall
will yield tidal levels well-above the astronomical tide this
morning, with tidal departures increasing between 1.3 to 1.5 ft
within the Charleston Harbor. A forecast of 8.0 ft MLLW has been
predicted for this morning`s high tide (~8AM), therefore a
Coastal Flood Warning is in effect for this morning for
Charleston and coastal Colleton Counties from 7AM to 11AM.
Ongoing heavy rainfall combined with strong onshore flow should
keep departures elevated through Saturday evening, and a Coastal
Flood Advisory will likely need to be issued for Charleston
Harbor with this evening`s high tide (~9PM). These conditions
will also yield tidal levels into the minor flood stage at Fort
Pulaski for this morning`s high tide (~8AM) as a 9.8 ft MLLW has
been noted in the forecast. A Coastal Flood Advisory has been
issued for 7AM to 11AM for Coastal Bryan, Coastal Chatham,
Coastal Liberty, and Coastal McIntosh Counties. Thereafter, Fort
Pulaski will remain below minor flood stage for the evening`s
high tide (~9PM).

Sunday: Minor coastal flooding remains possible for the
Charleston Harbor on Sunday morning as a 7.2 ft MLLW has been
forecasted for the morning high tide (~9AM) and a Coastal Flood
Advisory might be warranted. As the cold front passes through on
Sunday, flow should turn more offshore and the coastal flood
threat should end.

Rip Currents/High Surf/Beach Erosion: Strong east-northeasterly
flow combined with east-southeasterly swell will yield a High
Risk of rip currents for southeast Georgia and southeast South
Carolina beaches through this evening (esp. during the the high
tide cycles). It`s possible to see large breakers as high as 6
ft along the coastline and this may lead to areas of significant
beach/dune erosion.

Sunday: Lingering east-southeasterly swell and strong
southwesterly flow will yield a High Risk of rip currents for
the Charleston County beaches with a Moderate risk for the
Beaufort County beaches and southeast Georgia beaches.

KEY MESSAGE 4: A Lake Wind Advisory has been issued for Lake
Moultrie through this evening.

As strong onshore flow persists through the evening, wind
speeds will reach into 15 to 20 kts with gusts up to 25-26 kts
possible across Lake Moultrie. Therefore, a Lake Wind Advisory
has been issued from 5AM to 8PM this evening. Afterwards, expect
the wind flow to switch to more offshore and wind speeds to
steadily decrease overnight.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
The 06z TAF period begins with showers increasing in coverage
across the region as well as MVFR or lower conditions. Starting
first at KSAV, steady rain and showers will arrive within the
first hour of the TAF period followed by the potential for
thunderstorms at least through the 09-13z time period. MVFR
conditions should prevail, with periods of IFR expected from
both lowering ceiling heights and reduced visibility within the
heaviest pockets of rainfall. Winds will start to turn from
northeasterly to easterly and eventually southeasterly as a warm
front lifts through this morning. The first round of rainfall
will likely stick around through about mid morning, followed by
a potential lull into the afternoon. Then another round of
showers and thunderstorms will be possible.

For KCHS and KJZI, the overall thinking is similar to KSAV
through the timeline is shifted a bit later. Showers and MVFR
conditions will pass through periodically over the next several
hours. The arrival of steadier rainfall and potentially thunder
will come after sunrise and continue through the morning. IFR
conditions will be possible for periods of time due to lower
ceiling heights and reduced visibility that could accompany the
heaviest pockets of rainfall. This round should come to an
around midday, followed by a lull in shower coverage. Then by
the late afternoon another round of showers and storms will be
possible that could run into the early evening.

Extended Aviation Outlook: Prevailing VFR conditions will
return Sunday and continue into early next week.

&&

.MARINE...
Today: See NHC forecast for the latest on Isaias. As the
pressure gradient continues to strengthen, expect onshore flow
to remain 20 to 25 kts with frequent gale-force gusts of 34 kts
possible. A Gale Warning has been issued for the nearshore and
offshore southeast South Carolina waters, while a Small Craft
Advisory has been issued for the Charleston Harbor and the
nearshore and offshore southeast Georgia waters. As the warm
front lifts northward out of the coastal waters, moderate south-
southeasterly flow at 10 to 15 kts with gusts up to 25 kts will
develop through the overnight. As east-southeasterly swell
surges onward, seas will range from 5 to 7 ft through the early
morning, before dropping down into the 4 to 6 ft range this
evening.

Sunday into Tuesday: Remnants of Isaias combined with a surface
high pressure offshore should keep winds breezy on Sunday and
Small Craft Advisory will likely persist for portions of the
coastal waters into Sunday night, with the potential for
continuing into Monday. Thereafter, expect these marine
conditions to become almost tranquil as we head into early next
week.

&&

.CLIMATE...
Record Precipitation:

October 10:
KCHS: 1.82/1990
KCXM: 2.13/1990

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Flood Watch through late tonight for GAZ087-088-099>101-114-
     115-137-216>219-238>241.
     High Risk for Rip Currents through this evening for GAZ217-219-239-
     241.
     Coastal Flood Advisory from 7 AM to 11 AM EDT this morning for
     GAZ217-219-239-241.
SC...Flood Watch through late tonight for SCZ040-042>045-147>152.
     High Risk for Rip Currents through this evening for SCZ148>151.
     Coastal Flood Advisory from 7 AM to 11 AM EDT this morning for
     SCZ148-151-152.
     Lake Wind Advisory until 8 PM EDT this evening for SCZ045.
     Coastal Flood Warning from 7 AM to 11 AM EDT this morning for
     SCZ149-150.
MARINE...Small Craft Advisory until 8 PM EDT this evening for AMZ340-
     364.
     Gale Warning until 5 PM EDT this afternoon for AMZ360-362-380-
     382.
     Small Craft Advisory until 8 PM EDT Sunday for AMZ384.

&&

$$