650
FXUS62 KCHS 201111
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
711 AM EDT Sun Jul 20 2025

.SYNOPSIS...
High pressure will prevail in the Atlantic through early next
week, with surface troughing inland. A front may stall over or
near our area during the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A H5 ridge will remain centered over the Gulf, extending north
across the forecast area through today and tonight. At the sfc, a
trough over the central Carolinas will drift east this afternoon as
broad high pressure remains over the Gulf coast. Recent runs of the
HRRR indicates that the sea breeze will likely develop late this
afternoon, drifting inland through the early this evening. The late
onset of the sea breeze, strong insolation, and very warm llvl
thicknesses should result in high temperatures in the upper 90s, 2-3
degrees warmer than values reached Saturday. The hot afternoon
temperatures combined with dewpoints in the mid to upper 70s will
yield heat index values between 108 to 110 across portions of the
Coastal Plain of GA/SC this afternoon. The peak heat index
values will likely be observed right along and just behind the
sea breeze late this afternoon. A Heat Advisory for the eastern
2/3 of the forecast area until 8 PM this evening. Latest HREF
indicates that shower and thunderstorm activity will remain
generally along and east of the I- 95 corridor this afternoon,
isolated showers and thunderstorms. The afternoon convection
should provide little to no relief from the afternoon heat.

Tonight, any convection that develops this afternoon should
dissipate or push offshore this evening. The rest of the night
should remain dry and very mild. Low temperatures are forecast
to range in the upper 70s, with values around 80 degrees near
the beaches.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
The mid-levels will consist of a 594 dam ridge centered over the
lower MS Valley Monday morning. The ridge should remain in place
through Wednesday, perhaps expanding and strengthening slightly to
about 595 dam. Our area will remain on the eastern periphery of it
throughout the short term. At the surface, on Monday our area will
be sandwiched between High pressure in the Atlantic and surface
troughing inland. A weak cold front will drop down into our region
Monday night, then transition into a stationary front on Tuesday. It
could hover over or near our area through Wednesday, then dissipate.
The location of the front will keep ushering plenty of deep moisture
into our area, with PWATs exceeding 2".

The main forecast highlight will continue to be the heat.
Temperatures on Monday will be in the mid to upper 90s, with a few
spots possibly reaching the century mark. Though, it`ll be slightly
cooler at the beaches due to the afternoon sea breeze. Dew points
well into the mid 70s will cause heat indices to rise into the 105-
110 degree range, with some spots being even higher due to pooling
of the dew points. A Heat Advisory will be needed for portions of
the forecast area, generally along and east of I-95 on Monday.
Tuesday, high temperatures will range from around 90 degrees to the
middle 90s. Heat indices will also be a few degrees lower. If we
need any Heat Advisories on Tuesday, they`ll most likely be for our
coastal GA counties. Wednesday temperatures look to be at or below
normal, generally around 90 degrees. Overnight temperatures will
bring little relief from the hot conditions, with lows only in the
mid to upper 70s to lower 80s along the beaches. Record high minimum
temperatures will be possible some days. See the Climate Section for
more details.

As for the convective potential each day, the NBM gives us 30-50%
POPs on Monday. POPs then rise to 70-80% on Tuesday, then 60-80%
POPs on Wednesday due to the proximity of the front. Monday`s
afternoon thunderstorms have the potential to be strong to severe,
with damaging wind gusts being the main hazard. Forecast soundings
indicate there will be plenty of instability to work with, with
MLCAPEs peaking around 2,000 J/kg and DCAPE values exceeding 1,000
J/kg. Therefore, the SPC has our area under a Marginal Risk for
severe thunderstorms that day. Heavy rainfall is also a concern
given the PWATs, slow storm motions, and potential for training
and/or back-building. While we cannot rule out a strong to
marginally severe storm Tuesday or Wednesday, the high PWATs may
make them more likely to have heavy rainfall. Hence, the WPC
has our area under a Marginal Risk for Excessive rainfall,
especially on Tuesday. Any convection should dissipate during
the evening hours, with the overnights being drier.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
Models remain in good agreement through the long term period, with a
weak upper level ridge remaining in place. The aforementioned weak
stationary front is forecasted to dissipate Thursday. But it`s
proximity to us will yield a slightly wetter pattern. Convection is
forecasted each afternoon, with POPs generally around 40-60% through
Friday, then lower on Saturday. High temperatures will trend closer
to normal Thursday and Friday, then possibly rise back above normal
on Saturday.

&&

.AVIATION /11Z SUNDAY THROUGH THURSDAY/...
12Z TAFs: VFR. The pressure gradient will tighten this
afternoon as a trough approaches from the west. Each TAF will
feature WSW winds this afternoon between 10-15 kts with gusts
around 20 kts. Isolated showers and thunderstorms may develop
east of I-95 this afternoon. Coverage of convection appears too
limited to mention in the TAFs at this time. Southwest winds
should settle to 10 kts or less by early this evening.

Extended Aviation Outlook: Mainly VFR. Though, there could be brief
flight restrictions due to afternoon/evening showers and
thunderstorms.

&&

.MARINE...
The pressure gradient will tighten this afternoon and evening across
the marine zones. Southwest winds should gradually strengthen
through the day, with speeds reaching 10 to 15 kts with gusts to 20
kts developing in the wake of the sea breeze. HREF indicates that
gusts will approach Small Craft Advisory criteria across the SC
nearshore waters this evening. Seas should favor values between
2 to 3 ft, peaking between 2-4 ft this evening.

Extended Marine: On Monday our coastal waters will be sandwiched
between High pressure in the Atlantic and surface troughing inland.
A weak cold front will drop down into our region Monday night, then
transition into a stationary front. It could hover over or near our
area through Wednesday, then dissipate. The front will cause surface
winds to shift to the NE around 10-15 kts, possibly higher at times.
Thursday, High pressure returns in the Atlantic, while troughing
will be inland. This will lead to a more typical summertime wind
pattern. During the day, expect backing winds with the formation of
the afternoon sea breeze. The highest gusts will be along the
land/sea interface and across Charleston Harbor (with its passage).
Thursday night, expect veering of the winds as a nocturnal jet tries
to set up close to shore. Seas should average 2-3 ft throughout the
extended marine time period.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will rise with the upcoming new moon (on
Thursday). Additionally, surface winds will turn to the northeast
Monday night and persist through midweek. This will cause tidal
anamolies to increase. Minor coastal flooding is possible with the
Tuesday evening high tide at the Charleston tide gauge. Elevated
tides could persist through Thursday.

&&

.CLIMATE...
Record Low Maximum Temperatures:

July 23:
KCHS: 83/2002


Record High Minimum Temperatures:

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

July 21:
KCHS: 80/1986
KCXM: 83/1998
KSAV: 81/1942

July 22:
KCHS: 81/2011

July 26:
KCHS: 78/2012
KCXM: 82/2023

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for GAZ101-116>119-137>141.
SC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
     for SCZ042>045-047>052.
MARINE...None.

&&

$$

NEAR TERM...NED
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...NED