433
FXUS62 KCHS 081722
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
122 PM EDT Wed May 8 2024

.SYNOPSIS...
Atlantic high pressure will remain across the region today. A
cold front will approach the area Thursday night and push
offshore Friday bringing cooler conditions for the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Early this afternoon: No change to the forecast. Previous
discussion below.

Late this morning: Broad ridging will prevail aloft with
surface high pressure over the Atlantic extending back across
the forecast area. There does not appear to be a very good
chance of diurnal convection today thanks to warm profiles and
the ridging aloft, so we have maintained a dry forecast through
sunset. The main forecast challenge will be the heat. Low-level
thickness off the 12z KCHS RAOB is higher than it was 24 hours
ago and will support highs in the low to mid 90s across the
area. We will very likely come close to daily record highs at
Charleston and Savannah, see Climate section below.

Tonight: A slight H5 ridge should remain across the forecast
through tonight. However, the 0Z HREF indicates that MCSs will
continue to track across NC and portions of SC just south of the
NC/SC state line. This convection may be close enough to
observe lightning flashes to the north tonight, but should
remain outside the forecast area. Low temperatures are forecast
to range from around 70 inland to the low to mid 70s along the
coast.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
Thursday and Friday: A cold front extending from low pressure
over the Ohio Valley will approach the area during the day.
While the morning and early afternoon appears to be dry, ongoing
convection spanning across the Tennessee Valley and into the
Deep South should push toward the east. With a potential MCV
upstream, it is still quite uncertain when/if convection will
move into the forecast area. The NAM still depicts a drier
forecast with storms falling apart across the Midlands and only
isolated convection headed toward the forecast area. Meanwhile
the hi-res models point to a squall line/ cluster of storms
pushing southeast across the CWA. As far as timing goes, models
are beginning to trend toward a late afternoon/early evening
arrival time with most initial activity offshore by midnight.
Nonetheless, the environment will be supportive of strong to
severe storms Thursday with destabilization occurring early,
resulting in MLCAPE values in excess of 1500 J/kg. Steep lapse
and nearly unidirectional 0-6 km shear on the order of 40-50
knots could set the stage for a large hail and damaging wind
threat. Although any storms should be rather progressive in
movement, PWATS near 2" could result in locally heavy downpours
with intense rain rates in the core of the cells. The cold front
is not expected to clear the area until later on Friday, thus
we could see another round of convection moving in some time
between early Friday morning and Friday afternoon. Again, this
is highly uncertain with signals of yet another MCV propagating
across southern MS/AL/GA, which could greatly alter the
downstream environment. Given the earlier timing for
shower/thunderstorms, it is also unclear how the severe threat
(if any at all) will pan out Friday.

Temperatures Thursday will reach the low/mid 90s. Heat indices
could approach the triple digits especially across southeast
Georgia, but are expected to remain below our Heat Advisory
threshold. Overnight will be mild, only dipping into the upper
60s/low 70s. Friday will be slightly cooler due to potentially
ongoing convection and/or cloud cover, with highs in the mid to
upper 80s. The FROPA will cause temperatures to significantly
drop Friday night, with lows in the mid to upper 50s inland and
lower 60s along the coast.

Saturday: A cooler and dry air mass will move into the area in
the wake of the front bringing rain-free conditions. Mostly
sunny skies are expected with highs peaking in the upper 70s to
low 80s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
A modest warm up for Sunday will bring temperatures back into
the low to mid 80s with another day of mostly sunny skies. The
forecast becomes more uncertain early next week as model
guidance suggests that southern stream energy could move across
the Deep South along a residual boundary. Conditions could end
up becoming quite unsettled, or the bulk of the rainfall and
convection could slide south of the area. For now we have rain
chances capped at slight chance through mid next week.

&&

.AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions are expected to prevail at KCHS, KJZI, and KSAV
through 18z Thursday. Any Thursday thunderstorm activity is
expected to arrive after 18z at the TAF sites.

Extended Aviation Outlook: Chances of showers and thunderstorms
will increase Thursday afternoon through Friday with flight
restrictions and gusty winds possible within convection. VFR
conditions will return for the weekend.

&&

.MARINE...
The marine zones will remain under a ridge of sfc high pressure
today and tonight. Winds should remain from the southwest
between 10 to 15 kts, gusts around 20 kts will be possible
tonight. Seas should gradually build through today into tonight,
ranging between 2-3 ft this morning and reaching 3-5 ft
tonight.

Thursday through Friday: A strong cold front will approach
Thursday causing SW winds to increase. Marginal Small Craft
Advisory conditions are likely Thursday evening as gusts
approach 25 kt, and again Friday night behind the FROPA. At this
time, the Charleston County nearshore waters out to 20nm look
the most promising for any advisories that could be needed.
Another forecast issue for the local waters will be the
potential for strong thunderstorms Thursday evening through
Friday afternoon. The timing of thunderstorms remains unclear,
but any storms that do develop and move across the waters will
be capable of producing strong wind gusts.

Saturday through Monday: Marine conditions will rapidly improve
this weekend as weak high pressure builds in from the west. By
Saturday, winds will drop to 10-15 kt and seas to 3 ft or less
through Monday.

Rip Currents: Tybee Island observed around a dozen rip currents
on Tuesday. Today, wave heights may peak around a foot higher
than yesterday, continuing with swell periods of 10-11 seconds.
In addition, today is the new Moon, increasing astronomical
tides. Based on the recent observed rip currents and increase
breakers heights, a moderate risk for rip currents has been
posted for the GA beaches today.

&&

.TIDES/COASTAL FLOODING...
The New Moon today and recent Perigee (May 5) will lead to
elevated astronomical tides over the next few days.

Minor coastal flooding is possible along Charleston and coastal
Colleton Counties, including downtown Charleston, during the
evening high tides today and Thursday.

&&

.CLIMATE...
Record High Temperatures:
May 8:
KCHS: 93/1986
KSAV: 96/1986

May 9:
KCHS: 95/1963
KSAV: 95/1962

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

$$

NEAR TERM...BSH/NED
SHORT TERM...BRM
LONG TERM...BRM
AVIATION...BSH/BRM
MARINE...NED/BRM