387
FXUS62 KCHS 061321
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
921 AM EDT Sun Apr 6 2025

.SYNOPSIS...
Strong high pressure centered over the Atlantic will prevail
today, before a cold front impacts the area on Monday. High
pressure will then return for the middle of next week. Another
cold front could move through late in the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: It will be another warm one across the South Carolina
Lowcountry and Southeast Georgia. Conditions are starting out
rather muggy with temperatures in the 70s and dewpoints within a
degree or two of 70. After a warm night, temperatures are poised
to warm into the upper 80s/lower 90s away from the coast again
today with onshore winds keeping the coast and barrier islands
quite a bit cooler. Pronounced subsidence associated with deep-
layered high pressure centered offshore will keep conditions
rain-free again today with capping inversions noted on both
area model soundings and the modified 06/12z KCHS raob (although
the cap is not nearly as strong as the past few days). Breezy
conditions will once again occur across the coastal counties,
especially the lower South Carolina coastal counties, where
gusts as high as 30 mph could occur.

Tonight: A cold front will slow over the western Carolinas and
northern GA, remaining between a positively tilted trough. High
resolution guidance indicates that a band of showers and embedded
thunderstorms will also slow, remaining west of the CWA through late
tonight. Guidance does agree that the leading edge of showers may
reach the far inland counties during the pre-dawn hours. Given gusty
southwest winds and thickening cloud cover should keep temperatures
mild tonight, generally ranging in the upper 60s.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
A mid level trough will shift towards the east coast on Monday, with
an associated cold front expected to approach and eventually pass
through the area later in the day. Airmass will be juicy with PWats
near or exceeding 1.75", which is 2-3 standard deviations above
climo per NAEFS ESAT. Large scale forcing for ascent will also be
present from the incoming trough and upper divergence in the
favorable right entrance region of the jet. These features will lead
to a large band of showers with embedded thunderstorms moving across
the area, largely late morning into the afternoon and evening. Wind
fields will be supportive of storm organization, with deep layer
shear increasing to 50+ knots. Mid level lapse rates are still
rather unimpressive and CAPE looks to average 500-750 J/kg, but some
higher pockets around 1000 J/kg will be possible. There is a risk
for a few strong to severe thunderstorms, and the SPC Day 2 Outlook
places roughly the southern half of the forecast area in a Slight
risk for severe weather (level 2 of 5) with a Marginal risk (level 1
of 5) elsewhere. Damaging wind gusts will be the primary hazard
though an isolated tornado cannot be ruled out with 0-1 km SRH of
100-150 m2/s2. Even outside of storms, winds will become gusty
reaching 25 mph in many locations. This system will bring much
needed rainfall, with the latest forecast indicating 0.75-1.25" on
average, locally higher amounts possible. There should be decent
warming before convection moves in, so highs are expected to peak
back in the 80-85 range over most locations. The exception being
over the far interior where precip will move in the earliest and at
the beaches. Precip will exit off the coast Monday night, with dry
conditions expected by daybreak.

High pressure will build for Tuesday and Wednesday. Dry and cool
conditions will return. High temperatures will be in the upper 60s
to around 70 both days, while lows span the 40s, coolest inland.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
High pressure will extend into the area for Thursday, but the next
frontal system will be approaching. Dry conditions should hold, with
temperatures moderating back to normal. The cold front will move
into the area on Friday as a mid level trough drops into the eastern
U.S. Evolution of these features are still uncertain, but this
system will bring rain chances back in the forecast. High pressure
and dry weather should return for Saturday.

&&

.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
Prior to the 12Z TAFs, IR satellite and observations indicated a
large area of MVFR ceilings across the SC Lowcountry early this
morning. Ongoing 12Z KCHS sounding shows a thin layer of llvl
moisture associated with the restrictive ceilings. The low
ceilings should mix out between 13 to 15z. The terminals will
remain between a cold front pushing across the Deep South and
high pressure centered over the western Atlantic through the TAF
period. This pattern will result in a 3 mb pressure gradient
across SE GA/SC today into to tonight. As mixing deepens to 3
kft, southwest winds should develop gusts around 25 kts during
the heat of the afternoon. Otherwise, the pressure gradient
should support gusts 20 kts or greater beginning this morning
and remaining through late tonight. Conditions will remain VFR
this afternoon and tonight.

Extended Aviation Outlook: Gusty winds are expected on Monday.
Flight restrictions are likely Monday into Monday night as
showers/tstms impact the area with a cold front. VFR conditions will
then prevail by mid morning Tuesday.

&&

.MARINE...
Today: The marine zones will remain between a cold front
pushing across the Deep South and high pressure centered over
the western Atlantic through today and tonight. The pressure
gradient will support SSW winds with gusts around 25 kts across
the outer GA and nearshore SC waters, including the CHS Harbor.
The nearshore GA waters should see SSW between 15 to 20 kts.
These winds are forecast to persist through tonight as the cold
front slowly approaches from the west. As a result, wave heights
should gradually build through today and tonight, heights
ranging between 4 to 6 ft across the SC waters and outer GA
waters. The nearshore GA waters are forecast to range between 3
to 5 ft. The combination of gusty winds and building seas will
be highlighted with Small Craft Advisories for each marine zones
outside the nearshore GA waters through the near term period.

Monday through Friday: Gusty south winds will persist through Monday
ahead of a cold front. Small Craft Advisories have been expanded and
now include the South Carolina waters and the Charleston Harbor, in
addition to the outer Georgia waters. The nearshore Georgia waters
look more marginal and perhaps stay just shy, so no Advisory in
place for now. Mariners should also be aware of the potential for
stronger gusts in a band of showers with embedded thunderstorms that
are expected to impact the waters later in the afternoon into the
evening. Winds and seas should subside below advisory levels for
Tuesday, but another brief wind surge is expected on Wednesday. In
addition, 6 ft seas over the outer Georgia waters could return and
then persist into Thursday. Another front will move through on
Friday, with conditions currently below advisory levels.

Rip Currents: Strengthening winds should result in building wave
heights today, especially within the surf zone of Charleston
County beaches were breakers could range between 3 to 4 ft.
Swell periods are forecast to remain between 8 to 9 seconds.
Given the breaker heights around 4 ft, 8 to 9 sec period, and
rip current MOS with a high daily risk, a high risk was assigned
to the Charleston County coast today. Elsewhere, a moderate risk
for rip currents today. Gusty south winds ahead of a cold front
on Monday in combination with 7-8 second swells will support a
Moderate Risk for rip currents on Monday.

&&

.CLIMATE...
The low temperatures so far today for KCHS (Charleston Intl
Airport) is 71 degrees. If this low temperature holds through 1
AM EDT Monday, it will break the previous record high minimum
of 68 set in 2023.

The low temperatures so far today for KCXM (Waterfront
Park/Downtown Charleston) is 71 degrees. If this low
temperature holds through 1 AM EDT Monday, it will break the
previous record high minimum of 70 set in 2023.

The low temperatures so far today for KSAV (Savannah Intl Airport)
is 69 degrees. If this low temperature holds through 1 AM EDT
Monday, it will break the previous record high minimum of 68
set in 2023.


Record High Temperatures:

April 6:
KSAV: 90/1967


Record High Minimum Temperatures:

April 6:
KCHS: 68/2023
KCXM: 70/2023
KSAV: 68/2023

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...High Risk for Rip Currents until 8 PM EDT this evening for SCZ050.
MARINE...Small Craft Advisory until 5 PM EDT Monday for AMZ330.
     Small Craft Advisory until 2 AM EDT Tuesday for AMZ350.
     Small Craft Advisory until 11 PM EDT Monday for AMZ352.
     Small Craft Advisory until 2 AM EDT Tuesday for AMZ374.

&&

$$