North Charleston, South Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

698
FXUS62 KCHS 201001
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
601 AM EDT Tue Oct 20 2026

.WHAT HAS CHANGED...
The Aviation section was updated for the 20/12z TAFs.

&&

.KEY MESSAGES...
- 1) Below normal temperatures this week as high pressure
  prevails and a powerful nor`easter meanders off the Mid-
  Atlantic coast.

- 2) High risk for rip currents along the Georgia beaches
  through this evening.

&&

.DISCUSSION...
KEY MESSAGE 1: Below normal temperatures this week as high
pressure prevails and a powerful nor`easter meanders off the
Mid-Atlantic coast.

Through Daybreak: Early morning surface observations show the
boundary layer as mostly decoupled inland with calm winds being
reported. Strong radiational cooling will continue through
daybreak with calm winds, a dry airmass and clear skies all in
place. Temperatures are expected to bottom out in the lower-mid
40s inland with mid 50s at the beaches. A few upper 30s will
possible in some of the normally colder spots such as a Francis
Marion National Forest.

Today and Tonight: Sprawling high pressure (1035 hPa) centered
over southern Ontario will maintain its influence across the
Southeast U.S. and Deep South through tonight as the nor`easter
well offshore of the Outer Banks meanders farther to the north.
The airmass will remain very dry with PWATs holding <0.35" with
zero rain chances. Full insolation low-level thickness schemes
support highs in the 74-77 degree range this afternoon away from
the beaches which is consistent the forecast soundings and all
of the 20/00z statistical guidance. 20/01z NBM point
interquartile ranges (IQR) are also quite small, only averaging
about 1-2 degrees across the quartiles with no outliers. This
yields a high confidence forecast for the afternoon period.

Quiet conditions will persist into tonight. The boundary layer
should decouple inland again inland after sunset resulting in
fairly steady temperatures falls with light/calm wind, clear
skies the very dry airmass remaining in place. The strong
radiative process away from the coast may be interrupted
somewhat by early Wednesday morning with models showing a slight
tightening of the pressure gradient between the high and the
deepening nor`easter well east of the Virginia Tidewater. This
may allow the boundary layer to recouple to some degree with a
few knots of wind possible several hours prior to sunrise.
20/01z NBM lows Wednesday morning look too warm away from the
beaches (a well documented bias in radiational cooling dominated
regimes) and manual downward adjustments were made consistent
with output from the both the H3R and RAP hourly temperature
progs in the 09-12z time frame. These lows are about a degree or
two below the NBM`s lower quartile in the IQR (25% percentile).

Wednesday through Thursday: A nor`easter will be located well
off the coast of the Mid-Atlantic States Wednesday morning.
Meanwhile, strong High pressure will be located north of New
England, with it`s periphery stretching well down into the
Southeast U.S. The nor`easter will very slowly shift away from
our region through Thursday, then accelerate away Thursday
night. Though, the periphery of the distant High will persist
across the Southeast U.S. This will bring our area dry
conditions with sunny skies. High temperatures are forecasted to
be in the middle 70s Wednesday, and the middle to maybe upper
70s on Thursday. However, the dry conditions, clear skies, and
light to calm winds at night will cause decent radiational
cooling. This will lead to low temperatures that are several
degrees below Wednesday and Thursday nights.

Friday through Monday: High pressure will strengthen over the
Mid- Atlantic States while a coastal trough develops along the
Southeast U.S. coast. This will cause NE winds to increase and
become gusty, especially closer to the coast and over the
weekend. While it should remain dry, temperatures may be several
degrees below normal.


KEY MESSAGE 2: High risk for rip currents along the Georgia
beaches through this evening.

Today: Powerful, long period back-swell (periods 12-13 sec)
being generated by persistent northeast winds and the nor`easter
offshore of the North Carolina Outer Banks will keep a high
risk for rip currents in place along the Georgia beaches with a
moderate risk for the South Carolina beaches through this
evening.

Wednesday: Our internal rip current calculator along with RCMOS
indicates a borderline Low/Moderate risk for our SC beaches,
and a borderline Moderate/High risk for our GA beaches. We
anticipate waves to be subsiding, so we maintained the Low and
Moderate Risks respectively for each state.

Thursday through Sunday: An elevated risk of rip currents
should persist for our GA beaches Thursday, followed by an
increasing risk for all of our beaches Friday into the weekend.

&&

.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
20/12z TAFs:
KCHS/KJZI/KSAV: VFR through 21/12z.

Extended Aviation Outlook: Gusty winds are expected on
Saturday.

&&

.MARINE...
Through Tonight: Elevated seas and slightly enhanced north to
northeast winds will persist across the local marine area
through tonight. Winds will generally average 15-20 kt with
gusts to 25 kt with seas 3-5 ft nearshore waters and 6-8 ft
offshore waters. Small Craft Advisories remain in effect for all
Atlantic waters, not including the Charleston Harbor where
winds will remain below advisory thresholds.

Wednesday and Thursday: A nor`easter will be located well off
the coast of the Mid-Atlantic States Wednesday morning.
Meanwhile, strong High pressure will be located north of New
England, with it`s periphery stretching well down into the
Southeast U.S. The nor`easter will very slowly shift away from
our region through Thursday, then accelerate away Thursday
night. The interaction between these two synoptic features will
be generating strong and gusty NNE winds Wednesday morning.
Though, winds are expected to ease into Wednesday afternoon,
then maintain intensity Wednesday evening into Thursday morning,
followed by easing again Thursday afternoon. The Small Craft
Advisories are in effect for the waters within 20 nm through
Wednesday evening. Though, they may end sooner if the sea state
is lower than expected. But 6+ ft seas will prevail in the GA
20-60 nm waters through Thursday.

Friday and Saturday: High pressure will strengthen over the
Mid-Atlantic States while a coastal trough develops along the
Southeast U.S. coast. The interaction between these two features
will cause marine conditions to rapidly deteriorate. Winds and
seas will increase, with Small Craft Advisories likely, and Gale
Watches/Warnings possible for all of our coastal waters.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents through this evening for GAZ217-219-239-
     241.
SC...None.
MARINE...Small Craft Advisory until 9 PM EDT Wednesday for AMZ360-362-
     364.
     Small Craft Advisory until 8 AM EDT Sunday for AMZ384.

&&

$$