432
FXUS62 KCHS 211125
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
725 AM EDT Tue Jul 21 2026

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

&&

.KEY MESSAGES...
- 1) Smoke from the Horse Island Wildfire will impact northeast
  Berkeley County tonight into Tuesday.

- 2) Hot and humid conditions across coastal South Carolina and
  Georgia through mid-week. Heat Advisories could be needed.

- 3) A slow-moving cold front may bring greater rainfall chances
  late this week through this weekend.

&&

.DISCUSSION...
KEY MESSAGE 1: Smoke from the Horse Island Wildfire will impact
northeast Berkeley County tonight into Tuesday.

A Dense Smoke Advisory has been requested by the U.S. Forest Service
for northeast portions of Berkeley County in response to the Horse
Island Wildfire. Smoke in the vicinity of the fire is significant
and conditions will deteriorate overnight as the nocturnal inversion
develops. The latest Hysplit output shows the worst of the smoke
will remain across northeast Berkeley County and extend across
the Santee River into a small area of southwest Georgetown
County. Visibilities may drop below 1 mile at times overnight,
especially along parts of Highway 45. Road closures are
possible. Smoke will likely remain an issue into Tuesday
although visibilities should improve some by mid-morning as
dispersion increases and mixing heights rise. Another Dense
Smoke Advisory may be needed Tuesday night as smoke settles
during the overnight hours.


KEY MESSAGE 2: Hot and humid conditions across coastal South
Carolina and Georgia through mid-week.

Hot and humid coniditons are expected to continue the next 48
to 72 hours as the forecast area remains on the western
periphery of the upper ridge. Overall heat indices have come
down a bit compared to the last few forecasts. This is likely a
result of the moisture from now Tropical Storm Bertha remaining
increasing further south and west and the ridge being a little
stronger. With decreased moisture compared to previous
forecasts, dewpoints are now expected to mix into the low 70s
across inland areas keeping heat indices in the 100 to 105 range
for most of the area today and Wednesday. While these values
will still make things rather uncomfortable they are not quite
advisory criteria. Closer to the coast, things will be
determined by the movement of the afternoon seabreeze. As it
moves slowly inland each afternoon, dewpoints will surge into
the upper 70s behind the boundary leading to heat indices in the
105 to 108 range. However, this will likely only be for a
couple hours during the late afternoons leading to lower
confidence in reaching advisory criteria. On top of the shorter
duration, isolated showers and thunderstorms during the early
afternoon may limit how hot temperatures get during the
afternoon leading to increased uncertainty. As a result we have
continued to hold off on an heat advisories for coastal areas.

Despite not having any advisories, conditions will still remain
rather uncomfortable and with dewpoints in the upper 70s
overnight very little relief will occur each night. Given we
have set record high minimum temperatures the last few nights,
continued heat stress through Wednesday can be dangerous to
vulnerable communities including elderly and those who do not
have access to adequate cooling. The heat is expected to come
to an end by the end of the week as increasing rain chances
arrive with a slow moving front.


KEY MESSAGE 3: A slow-moving cold front may bring greater rainfall
chances late this week through this weekend.

As a mid-lvl trough situates itself over the eastern CONUS on
Wednesday, an associated front will slowly progress towards the
forecast area. The front will likely reach the region on Thursday
and then remain nearly stationary through the end of the week. This
will yield increased chances of showers and thunderstorms on
Thursday through Sunday. Forecast soundings continue to indicate
very moist conditions across the region, with PWAT values ranging
from 2.2 to 2.4 inches throughout most of the week. Given the deep
moisture, synoptic scale forcing, and periods of moderate
instability, the forecast will feature at least likely PoPs. The
Weather Prediction Center (WPC) continues to highlight the region in
a Marginal Risk of Excessive Rainfall on Thursday and Friday.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
21/12z Aviation Discussion:

KCHS/KJZI/KSAV:Mostly VFR conditions will continue throughout
the period with a narrow band of MVFR ceilings located near JZI
as the land breeze/seabreeze begins to setup this morning.
Southerly winds around 10 knots will become gusty during the
afternoon as the seabreeze slowly moves inland. Wind gusts up to
20 to 25 knots will be possible during the afternoon. An
isolated shower or two could be possible around CHS/JZI around
14Z to 16Z as the seabreeze moves inland but minimal impact to
aviation is expected. Isolated showers and storms will also be
possible late in the forecast over eastern Georgia near SAV from
about 23Z to 1Z.

Extended Aviation Outlook: Prevailing VFR through mid-week.
Chances of flight restrictions increase later this week with a
greater coverage of showers/thunderstorms.

&&

.MARINE...
Tuesday through Saturday: As a mid-lvl trough slowly situates itself
across the region through the period, an associated cold front will
approach the local waters and then stall out in the vicinity. This
will yield breezy south-southeasterly flow on Tuesday through
Wednesday. Also, southerly swell will briefly surge overnight on
Tuesday yielding seas from 4 to 6 ft across the South Carolina
waters. Otherwise, seas will mostly range from 2 to 4 ft throughout
the period. Small Craft Advisories are in effect from Tuesday
afternoon through Wednesday night. As the cold front inches closer
on Thursday, the pressure gradient will slack back and allow for
more tranquil marine conditions on Thursday through Saturday.
Otherwise, seas will

Rip Currents: A Moderate Risk of rip currents is in effect for the
SC and GA beaches today and tomorrow (Wednesday), given enhanced
winds along the coastline and wave periods up to 6 seconds. Breakers
may exceed 4 ft on Wednesday, with wave periods between 6 to 7
seconds. It is possible that a portion of the SC coast may need a
high risk if swell waves and/or wind speeds increase from the
current forecast.

&&

.CLIMATE...
Record High Minimum Temperatures:

July 20:
KCHS: 79/2025
KCXM: 83/2000
KSAV: 79/1942

July 21:
KCHS: 80/1986
KCXM: 83/1998

July 22:
KCHS: 81/2011
KCXM: 83/2011

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Dense Smoke Advisory until 10 AM EDT this morning for SCZ045.
MARINE...Small Craft Advisory from noon today to 5 AM EDT Thursday for
     AMZ360-362.
     Small Craft Advisory from 2 PM this afternoon to midnight EDT
     Wednesday night for AMZ364-384.

&&

$$

Black/Dennis