459
FXUS62 KCHS 080820
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
420 AM 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/...
IR satellite indicated that a deck of debris cirrus will across the
I-26 corridor this morning. Otherwise, sky conditions should remain
mostly to partly sunny today. The H5 ridge axis along the coast this
morning will shift east today, with broad ridging remaining across
the forecast area. The CWA will remain under a sfc ridge, with the
high center south of Bermuda. Winds should remain from the southwest
this morning, shifting from the south-southwest along the coast in
the wake of a mid to late afternoon sea breeze. Given strong
insolation, warm llvl thicknesses, SSW winds, and a late sea breeze,
high temperatures are forecast to reach the low to mid 90s this
afternoon. In fact, the temperatures could challenge record highs,
especially at KCHS, see Climate section below. Conditions are
forecast to remain dry under the broad H5 ridge and MLCIN remaining
between 10-25 J/kg through this afternoon.

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 /08Z WEDNESDAY THROUGH SUNDAY/...
KCHS/KJZI/KSAV: VFR will prevail through 06Z Thursday. KCHS and
KJZI may experience wind gusts around 20 kt this afternoon,
highlighted with TEMPOs from 18-21Z.

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