687
FXUS62 KCHS 181140
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
740 AM EDT Tue Aug 18 2026

.WHAT HAS CHANGED...
The Aviation Section has been updated for the 12Z TAF issuance.

&&

.KEY MESSAGES...
- 1) Heat will remain a concern today into late week.

- 2) A few strong to severe thunderstorms are possible each afternoon
  through Thursday. Scattered to widespread thunderstorms are
  expected Friday into the weekend.

&&

.DISCUSSION...
KEY MESSAGE 1: Heat will remain a concern today into late week.

Today: A warm pattern will remain in place with large-scale ridging
across the Deep South and Southeast United States. Much like the
previous day, strong heating is expected during morning and
afternoon hours with little to no relief from the heat in regards to
shower/thunderstorm activity. Record warmth is possible as the
intensity of the heat wave peaks with another day of favorable
downslope flow across the local area. Many areas will see temps peak
in the upper 90s to around 100 degrees, warmest along and east of
the I-95 corridor, but away from the beaches. Despite some mixing
out of low-lvl moisture across the local area late morning and
afternoon, sfc dewpts in the mid-upper 70s support heat index values
up to the 106-112 range inland to 113-119 range across the coastal
corridor. An Extreme Heat Warning remains in effect from 11 AM
to 8 PM today for SC/GA coastal counties and also includes Dorchester
County, SC and Effingham County, GA. A Heat Advisory remains in
effect from 11 AM to 8 PM today for all remaining inland areas as
well.

Wednesday into Friday: There are signs of the expansive ridge
starting to weaken while isolated to scattered convection returns
during peak heating hours mid to late week. We could see Heat
Advisory conditions prior to showers/thunderstorms developing
Wednesday and Thursday afternoons, especially along the coastal
corridor where maximum heating and sfc dewpts remain in the mid-
upper 70s. Despite hot temperatures that peak in the upper 90s to
perhaps 100 degrees in some spots Wednesday and Thursday, inland
areas (west of I-95) should experience more substantial mixing out
of sfc dewpts into the 60s. Friday remains warm (mid-upper 90s for
most areas), but guidance supports greater convective coverage and
some relief from the heat during peak heating hours, as shortwave
energy associated with a large-scale trough approaches the Mid-
Atlantic and Southeast states this weekend. Nevertheless, there
remains a risk for heat headlines into Friday should convective
coverage remain less or become more delayed.


KEY MESSAGE 2: A few strong to severe thunderstorms are possible
each afternoon through Thursday. Scattered to widespread thunderstorms
are expected Friday into the weekend.

The above normal temperatures and stifling humidity that have been
persisting across our area for more than a week will continue to
generate instability each afternoon this week. The various models
continue to have differences regarding how much instability will be
in place and where the highest values will be. Though, the ongoing
trend has been a general consensus of SBCAPE values in the 2,000-
3,000 J/kg range with locally higher peaks each day. Likewise, DCAPE
values should easily exceed 1,000 J/kg. There are larger differences
with the latest CAMS and the deterministic models. The deterministic
models generally have it dry this afternoon, along with Wednesday
and Thursday afternoons. Meanwhile, the CAMs lean towards some
convection this afternoon and Wednesday afternoon. Given the amount
of instability in place, it`s hard to say it`ll be completely dry.
It won`t take much for at least isolated convection to form along
the sea breeze this afternoon and then shift inland, and for the
same thing to happen again Wednesday and Thursday afternoons. Any
convection that manages to form should generate outflow, and that
along with boundary interactions should play a major role in
additional storm formation and persistence. Strong to severe
thunderstorms are possible each afternoon with the main threat being
damaging winds. Heavy rainfall is also a concern due to the very
weak steering winds and elevated PWATs. Any convection should
dissipate each evening with the setting sun.

The pattern turns more active towards the end of the week,
especially as a slow moving front approaches our area from the west
and northwest. This should generate scattered to widespread
thunderstorms starting Friday afternoon, continuing each afternoon
through the weekend. But the fine details and largest threats will
need to be better refined with future forecasts.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
VFR conditions are expected at CHS/JZI/SAV terminals through 12Z
Wednesday. However, an isolated shower or thunderstorm can not
be ruled out at the SAV terminal late day. A PROB30 group remains
at SAV between 21-24Z today for thunderstorms and associated
MVFR conditions.

Extended Aviation Outlook: Mainly VFR through Thursday. Afternoon
showers and thunderstorms could bring brief flight restrictions
starting Friday.

&&

.MARINE...
Today and Tonight: Conditions are expected to remain quiet across
local waters between high pressure across the western Atlantic/Gulf
and weak troughing inland. West winds around 10 kt or less this
morning should turn south with gusts up to 15-20 kt this afternoon,
strongest near the coast where a sea breeze develops. Winds should
then return to southwest and weaken to below 10-15 kt during the
overnight period. Seas should be no larger than 2-3 ft.

Extended Marine: There will be areas of high pressure in the western
Atlantic and the northern Gulf, while surface troughing persists
over the Southeast United States. The interaction between these
synoptic features will support a typical summertime wind pattern
with winds/seas that remain below Small Craft Advisory levels. In
general, southwest winds should back to a more south direction each
day, peaking in speed along the coast due to a sea breeze, then
return to southwest during the overnight period. Seas will mainly be
in the 2-3 ft range.

&&

.CLIMATE...
Record High Temperatures:

August 18:
KCHS: 101/1995
KCXM: 97/1995
KSAV: 100/1995

August 19:
KCHS: 98/1983
KCXM: 98/1895
KSAV: 99/1900

August 20:
KCHS: 97/2005
KSAV: 102/1900

August 21:
KCHS: 100/1983
KSAV: 101/1902


Record High Minimum Temperatures:

August 18:
KCHS: 80/2017
KCXM: 82/2017
KSAV: 78/2010

August 19:
KCHS: 79/2010
KCXM: 83/2021
KSAV: 79/1878

August 20:
KCHS: 78/2017
KCXM: 82/2017

August 21:
KCHS: 79/2010
KCXM: 82/2023
KSAV: 80/1902

August 22:
KCHS: 79/2023
KCXM: 82/2014
KSAV: 79/1902

August 23:
KCXM: 81/2019
KSAV: 78/2016

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for GAZ087-088-099-100-114-115-137.
     Extreme Heat Warning from 11 AM this morning to 8 PM EDT this
     evening for GAZ101-216>219-238>241.
SC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for SCZ040-042-043.
     Extreme Heat Warning from 11 AM this morning to 8 PM EDT this
     evening for SCZ044-045-147>152.
MARINE...None.

&&

$$