250
FXUS62 KCHS 210535
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
135 AM EDT Tue May 21 2024

.SYNOPSIS...
High pressure will persist for most of this week. A series of
upper level disturbances should impact our area this weekend.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Patchy diurnally driven cumulus/stratocumulus will continue to
diminish and eventually dissipate by around 9-10 pm, leaving us
with generally clear skies the rest of the night. As winds go
light or calm away from the coastal corridor, radiational
cooling will allow for late night lows to get down to the the
upper 50s and lower 60s inland from US-17, mid and upper 60s
closer to the coast, and in downtown Charleston and downtown
Savannah.

We already had mention of patchy fog well inland late, and with
simulated satellite images and some of the guidance indicating
it can happen (albeit not a very high probability), we
maintained mention in the forecast. Mainly light fog is expected,
but with the lowering subsidence inversion through the night,
there could be enough moisture concentrated into the boundary
layer for some patchy fog.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/...
High pressure will prevail both at the surface and aloft through the
middle portion of the week. With a weak subsidence inversion around
850 mb, PWat down near the 10-25 percentile, and the lack of any
forcing mechanisms, it`ll be a quiet weather pattern. We aren`t
going as warm as the low level thickness would on Tuesday and
Wednesday given an onshore flow. We have lower-middle 80-s
inland from the coast Tuesday, then add a few degrees for highs
Wednesday. The synoptic flow turns to the south-southwest on
Thursday, and that`ll be the warmest day of the short term
period. Highs will be more in line with the 1000-850 mb
thickness; pushing 90F most places inland from US-17.

Excellent radiational cooling both Tuesday and Wednesday night,
prompting us to go a bit below the consensus of guidance,
especially in the typically cooler rural locations. Conditions
could favor some fog Tuesday night and early Wednesday morning.
But given the time of year when it`s difficult to get fog, we
refrained from including it in the forecast at this time.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
A cold front drops into the Southeast by Friday, although it
never gets into the local region. Instead it lifts back north as
a warm front over the weekend. We then lie near the western
edge of Atlantic high pressure into early next week. Any forcing
will occur from a series of short waves that traverse the area
within a westerly flow aloft. Moisture is more plentiful during
this time, so we do expect some convection to occur, most
especially Saturday through Monday. We prefer not to show
anything more than scattered activity this far out, which is in
line with the NBM and GEFS guidance. Due to 850 mb temperatures
as warm as 17-19C, which is near or above the 90th percentile,
it appears that each day will be 90F or warmer away from the
coast. Night time lows will also be quite a bit warmer with a
noticeable increase in dew points.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
KCHS/KJZI/KSAV: Overall VFR conditions will prevail at the
terminals through 06Z Wednesday. Development of some low cloud
cover is possible along the coast toward sunrise, expanding into
a SCT Cumulus deck through the morning hours and into the
afternoon. A brief period of BKN cloud cover is possible at KSAV
during the morning.

Meanwhile, an uptick in easterly winds to around 10 knots will
take place during the morning and persist through afternoon.
Winds diminish during the evening.

Extended Aviation Outlook: Maybe a little ground fog late
Tuesday night into early Wednesday, otherwise VFR will prevail.

&&

.MARINE...
Ridging inland builds stronger over the waters this evening with
troughing persisting well offshore. The gradient will continue
to very slowly weaken, with breezy (15-25 kt) NE winds this
evening trending more moderate (10-15 kt) by the early morning
hours.

Seas remain elevated in mainly northerly windswell, but slowly
diminish overnight as well. 3 to 5 ft seas prevail, with some 6
ft seas beyond 30 nm offshore/near the western wall of Gulf
Stream this evening. Seas fall below 6 ft offshore late tonight,
with to SCA for the offshore Georgia waters expiring
accordingly. 2-4 ft seas prevail through the early morning
hours, with some 5 ft seas beyond 30 nm.

Extended Marine:
Tuesday and Tuesday night: High pressure centered to the north
and northeast will extend across the immediate waters,
resulting in NE and E winds as high as 10 or 15 kt during the
day, and 10 kt or less at night. Seas that are 3-5 feet Tuesday
drop about a foot or so Tuesday night.

Wednesday through Saturday night: High pressure remains the main
feature during mid and late week, although a cold front does get a
bit closer as it drops into the Southeast Friday. No significant
marine concerns, even with some afternoon/evening enhancement from
the sea breeze in Charleston Harbor and near the coast. However,
there does appear to be at least some potential for t-storms late in
the period.

Rip Currents: With the Full Moon is approaching, it won`t take more
than a small swell to lead to enhance of rip currents at the local
beaches. Since there is some uncertainty regarding the amount of
swell energy, we are showing a low risk of rip currents at areas
beaches Tuesday and Wednesday, and an adjust later if necessary.

&&

.TIDES/COASTAL FLOODING...
The combination of rising astronomical tides with the upcoming
Full Moon and onshore winds will cause tides to be elevated
through the middle of this week. Minor flooding is possible with
the evening high tides again Tuesday and Wednesday along
coastal Charleston and coastal Colleton. There are no concerns
at this time along the remainder of our coast.

&&

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

&&

$$