991
FXUS62 KCHS 201538
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1138 AM EDT Sat Jul 20 2024

.SYNOPSIS...
High pressure will remain over the western Atlantic while a
surface trough lingers inland.

&&

.NEAR TERM /THROUGH TONIGHT/...
Shortwave ridging extends across coastal southeast GA which is
suppressing mid-morning Cu development. Elsewhere, relatively
weak fair weather Cu has developed with the tallest towers
currently across eastern Charleston and Berkeley Counties.
Ongoing scattered convection currently exists in the Central
Savannah River Area (CSRA) associated with a potent shortwave
forecast to push ENE through central and northern portions of
the CWA this afternoon. Surface flow is SW to WSW across much of
the area, albeit relatively weak, but this will delay the sea
breeze`s inland push until a bit later in the afternoon.
Interestingly, the HRRR remains unimpressed with convective
potential until closer to 6pm, though the RAP is showing a bit
more development during the day. The HRRR seems too dry given
the environment. The Cu field is showing a few towers that may
soon become showers, after which an increase in mesoscale
boundaries will likely spur additional convection. Coverage
should slowly increase across the area through the afternoon,
with additional activity likely developing or moving into
western areas as the shortwave gets into the area. Temps have
been warming steadily, with most areas in the middle 80s. We
should top out in the lower 90s in most spots, though convection
will locally reduce temps.

Conditions support a few strong to perhaps marginally severe
t-storms during the mid and late afternoon due to MLCAPE of
1500-2500 J/kg and some stronger mid and upper level winds
moving through. Where boundary interactions occur there could be
the consolidation of a few multicellular clusters capable of
generating localized downbursts. The better chances are over
inland South Carolina, but could be anywhere in Georgia.

Tonight: Convection shifts east through the evening and off the
coast at some point, or simply weakens in place due to the loss
of daytime heating.

There could be some stratus and/or light fog forming if we get
enough clearing overnight. But not enough probability to show in
the forecast. Low temperatures will essentially be a persistence
forecast; lower and middle 70s.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
Deep/closed upper level low pressure will continue to cycle through
eastern Canada through the short-term period with troughiness
extending all through way down through the eastern CONUS and
southwest flow through the southeast states. Stalled boundary will
also be lingering along the lee of the Appalachians with deep
moisture (PWAT values largely > 2 inches) draped through the Deep
South and southeast states. Daily heating/destabilization cycle
coupled with weak short-wave energy rippling through the region and
some larger scale forcing along the tail end of an upper jet will
lead to scattered-numerous showers and thunderstorms each day,
particularly during the afternoon and evening hours when instability
is greatest and the sea breeze is active. However, modest
instability could persist through overnight hours, so isolated
convection will be possible just about any time of day. Highs will
be in the lower to mid 90s each day with dewpoints in the 70s. Heat
indices currently expected to remain below Heat Advisory criteria.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
The typical summertime pattern will persist through next week with
deep layered ridging to our east across the Atlantic and tropical
moisture continuing to stream across the area. Scattered to numerous
mainly afternoon/evening showers and thunderstorms anticipated each
day. Daytime highs will continue to run in the lower to middle 90s
through the period with nighttime lows in the 70s.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
Convection will develop during the afternoon and continue into
this evening, resulting from daytime heating, the interaction of
various boundaries, and an added boost from a short wave moving
in late. For the 12Z TAFs we have higher confidence of flight
restrictions at KSAV, but all sites could experience sub-VFR
weather, especially between 19Z Saturday and 04Z Sunday.

The risk for low stratus and/or light fog late tonight is not
sufficient enough to show anything in the TAFs at this time.

Extended Aviation Outlook: Convection could produce brief flight
restrictions, especially each afternoon/evening.

&&

.MARINE...
The coastal waters will be positioned under the west and
northwest side of the typical sub-tropical ridge, while a trough
remains inland. There will be some modest increases in the S
and SW winds this afternoon with the sea breeze, and maybe again
tonight with nocturnal low level jet enhancement. But in
general, no more than about 15 or maybe 20 kt. Seas will average
2-4 feet, highest further out.

Saturday through Wednesday: Bermuda high pressure will remain the
dominant feature through the period. This will yield the typical
summertime southerly/southwesterly winds across the coastal waters.
The strongest winds will be along the coast each afternoon as the
sea breeze develops. We could also see a slight wind enhancement
along the coast overnight due to a nocturnal jet. Seas will average
2-4 ft.

Rip Currents: Based on the in-house calculator and the Rip
Current MOS Average both showing a low risk for today, that`s
what we`re forecasting. However, a low-end moderate risk
forecast for Sunday due to the 2-3 ft swell period increasing
from 7 to 8 seconds, combined with greater than normal tidal
range and daytime onshore winds.

&&

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

&&

$$

NEAR TERM...JRL
SHORT TERM...Adam
LONG TERM...Adam
AVIATION...
MARINE...