903
FXUS62 KCHS 151749
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
149 PM EDT Sat Jun 15 2024

.SYNOPSIS...
A weak cold front will linger over the area this weekend before
the front slowly lifts back northward early next week. High
pressure will then ridge in from offshore mid to late next
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Rest of Today: The mid-levels will continue to be dominated by
ridging over the southeastern states, building in from the SW.
At the surface, a weak cold front located just to our north will
slowly move southward, possibly reaching our northern SC
counties by late this afternoon. However, it is not expected to
bring many impacts to our area. The CAMs, HRRR, and synoptic
models all indicate isolated convection, mainly across our SC
counties lat this afternoon into this evening. Though, model
soundings indicate a significant amount of dry air in the upper
levels, a result of subsidence aloft. Showers and thunderstorms
may struggle to overcome the dry air and minimal instability
indicated by the SPC Mesoscale Analysis. Otherwise, the main
concern remains the heat. 850 hPa temperatures are forecast to
be around 18/19C, which given decent daytime mixing today yields
surface temperatures in the upper 90s, except cooler at the
beaches. Dew points are mixing out, which will limit heat index
values to around 100 degrees, which is well below Heat Advisory
criteria. The temperature at KCHS may challenge the record high
temperature, see the Climate section for more details.

Tonight: The cold front will likely be over our northern SC
counties early this evening. It`s expected to slowly move south,
and stall near the SC/GA border. A quiet night is forecast,
with any showers/ thunderstorms likely dissipating by nightfall.
Overnight lows will generally be in the low 70s away from the
coastline, where temperatures should remain in the mid 70s.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
Sunday: Strong upper ridging persists aloft. At the surface, strong
high pressure over New England will build down the eastern seaboard,
forcing a weak cold front southward across the area. Rainfall
coverage Sunday will ultimately be dependent on the progression of
the front, which will most likely be bisecting the area by midday,
and potentially be pushing down into Georgia by the evening. While
very dry air aloft will inhibit convective growth, there should be
enough moisture pooling on the southern side of the front (PWATs
1.5+ in) and instability (1500+ J/kg) to get a few isolated to
widely scattered showers and storms following a mainly diurnal
pattern, with any storm activity diminishing in the evening and dry
conditions prevailing overnight.

Despite the very strong upper ridging, E to NE/onshore flow will
moderate low level thickness values, and temps Sunday will be only a
few degrees above normal, upper 80s to lower 90s near the coast, and
mid 90s inland.

Monday and Tuesday: Upper pattern remains similar Monday and Tuesday
with ridging directly overhead leading to strong subsidence/very dry
air aloft. The aforementioned front will deteriorate near/over the
area Monday as it begins to lift back north, with surface ridging
building in from offshore by Tuesday. Rainfall chances confined
roughly along and south of I-16 both days, where there could be just
enough moisture to develop some short-live showers/storms around
peak heating/maximum instability each afternoon. Onshore component
of BL flow keeps temps near to a few degrees above normal both days
despite the strong upper ridging.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
Upper ridging shifts north mid-to-late week, with height falls aloft
leading to diminishing upper subsidence. At the surface, high
pressure migrates off the Northeast coast and toward a more
seasonable Bermuda High location. Expect the forecast to trend back
toward a more summer-like precip pattern, with scattered afternoon
thunderstorms along and inland of the sea breeze and lesser storm
activity overnight. Temps remain within a few degrees of normal.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
18Z TAFs: Mainly VFR. Isolated convection associated with an
approaching cold front could approach KCHS and KJZI this
afternoon and evening. However, the probabilities of direct
impacts to either TAF site remains too low to include a mention
of VCTS for now. Will amend if radar trends show otherwise. Any
convection is expected to dissipate later this evening, with
the overnight being dry.

Extended Aviation Outlook: Mainly VFR. There will be low
probabilities of brief flight restrictions due to convection each
afternoon/evening.

&&

.MARINE...
Rest of Today: Generally tranquil marine conditions are
expected with sustained winds mainly from the S or SE. Expect
higher gusts along the land/sea interface with the afternoon sea
breeze. Gusts could reach 20 kt as it moves across the
Charleston Harbor.

Tonight: A weak cold front is expected to move south through
the waters late, possibly stalling near the SC/GA line.
Sustained winds from the S or SE in the evening will veer
overnight, becoming E by daybreak Sunday. Seas should average
2-3 ft.

Sunday through Wednesday: The gradient will remain fairly weak
through Monday as a front moves over the area and slowly
deteriorates. High pressure builds in from the north early next
week, then shifts offshore mid-to-late week, with mainly moderate
winds prevailing, but breezy/gusty conditions near the coast with
the sea breeze formation each afternoon. Modest medium period
southeast swell will keep 2-4 ft seas in place through Monday, with
seas increasing to 3-5 ft Tuesday through mid-week as increasing
fetch over the Sargasso sea causes the the southeast swell builds
further. 6 ft seas/SCA conditions could emerge by late week.

&&

.CLIMATE...
Record High Temperatures:

June 15
KCHS: 98/2015

&&

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

&&

$$

NEAR TERM...
SHORT TERM...CEB
LONG TERM...CEB
AVIATION...CEB
MARINE...CEB