268
FXUS62 KCHS 172344
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
744 PM EDT Mon Jun 17 2024

.SYNOPSIS...
High pressure will extend across the region through early next
week. A tough of low pressure could approach the Southeast U.S
coast by late this week.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Early evening update: Inland convection has fizzled/moved
inland. There are spotty showers in the coastal waters with some
additional development anticipated tonight into Tuesday
morning, particularly from Beaufort south. Just cosmetic tweaks
made to the going forecast through tonight.

Previous discussion...
Tonight: Aloft a large ridge will remain centered across the
Southeast and Mid-Atlantic states, favoring large scale
subsidence across the local area. At the sfc, high pressure
centered across the western Atlantic off the Mid- Atlantic and
Northeast Coast extends south across the local area, providing
an onshore flow throughout the evening and overnight period.
Despite onshore flow, dry air depicted on water vapor imagery
favors rain-free conditions across coastal areas and much of
southeast South Carolina. However, a few showers (and perhaps a
thunderstorm) could occur during the next few hours well inland,
mainly across southeast Georgia where adequate moisture and
SBCAPE between 1500-2000 J/kg reside. Subsidence aloft will
limit the strength of convection across the noted area, but a
few showers (or perhaps a thunderstorm) could produce gusty
winds given low-lvl lapse rates around 7.5 to 8 C/km and DCAPE
around 1000 J/kg. The window of opportunity should come to an
end within an hour or two before sunset, as activity drifts
further west. Conditions will remain quiet overnight while high
pressure dominates the pattern near the sfc and aloft. Sfc
dewpts will also generally range in the 60s tonight, and with
winds weakening and partly cloudy to mostly clear skies in
place, should yield slightly cooler min temps, generally in the
mid-upper 60s inland to low-mid 70s near the coast.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
A strong subtropical anticyclone will dominate the upper flow aloft
over the eastern U.S. with local heights averaging 5920-5940 dam. At
the surface, Atlantic high pressure centered offshore of the Mid-
Atlantic states will prevail. A weak coastal trough is forecast to
sharpen a bit just offshore by Tuesday and linger near the Northeast
Florida, Georgia and far southern South Carolina coasts through late
week. Although model soundings do show broad subsidence dominating
aloft, a modest onshore flow and weak convergence in the vicinity of
both the sea breeze and coastal trough will likely support isolated
to scattered showers for mainly the coastal areas through the
period. The greatest coverage looks to focus along the Georgia coast
where some weak 850 hPa moisture transport and theta-e advection
will occur, but even these fields are not overly strong. Pops were
capped 20-40% as model QPF signals are not all that impressive
suggesting deep convection will likely struggle given the degree of
subsidence noted. Any mention of thunder was limited to slight
chance. Highs each day will warm into the upper 80s to lower 90s
away from the beaches with overnight lows ranging from the upper 60s
well inland to the mid-upper 70s at the beaches. Breezy to locally
windy conditions will occur at the immediate coast and beaches
through the period.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
A well-defined TUTT located north of the Greater Antilles is
forecast to meander closer to the Southeast U.S. coast later this
week as Atlantic high pressure holds off the Mid-Atlantic coast. The
operational GFS continues to be the most robust in developing a well-
defined surface cyclone within the TUTT as it propagates to the
west, but most of the guidance keeps any surface reflection as more
of an open wave/inverted trough as it nears the coast. Overall
confidence on how this scenario will unfold remains rather low, so
further adjustments will likely be needed as trends become more
apparent. For now, pops were limited to the chance category along
the coastal counties with the highest probabilities centered along
the Georgia coast. A broad upper trough will begin to dig across the
Southeast U.S. Sunday as a cold front approaches from the northwest.
As any surface reflection moves north in latitude, the heat will
begin to build. Highs Friday will warm into the lower-mid 90s then
increase to the mid-upper 90s Saturday and Sunday.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Prevailing VFR conditions are expected at CHS/JZI/SAV terminals
through 00Z Wednesday. However, brief MVFR cigs are possible
late tonight/early Tuesday with onshore flow off the Atlantic,
particularly at the SAV terminal. Confidence remains too low to
include in the latest forecasts.

Otherwise, winds will further weaken tonight. But another round
of gusty east winds (13-18 kt) is anticipated at the terminals
Tuesday starting mid to late morning and persisting through the
afternoon.

Extended Aviation Outlook: Brief flight restrictions are possible in
afternoon showers/thunderstorms with the best chances occurring at
KSAV and KJZI.

&&

.MARINE...
Tonight: High pressure will remain the dominant weather feature,
extending across the region from the north and enhancing the
pressure gradient across local waters. The gradient along with some
nocturnal low-lvl jetting will favor easterly winds between 10-15 kt
with gusts to around 20 kt at times overnight. Seas will also slowly
build during the period due to a prolonged onshore fetch. In
general, seas should build to 3-4 ft across nearshore waters and 4-5
ft across offshore Georgia waters overnight.

Tuesday through Friday: Solid northeast winds 15-20 kt will persist
through much of the period. The gradient may tighten a bit as a
trough of low pressure approaches late in the week. Seas will build
due to a combination of increasing swell and continued breezy
northeast winds. Seas will reach 6 ft in the Georgia offshore waters
by early Tuesday evening, so a Small Craft Advisory has been issued
for those waters through Friday. Seas 6 ft or greater will reach all
nearshore legs by Wednesday and the advisory will likely need to be
expanded into those waters overnight. Seas look to peak 5-7 ft
across all waters Wednesday night into Friday morning.

Rip Currents/High Surf: A Moderate Risk for rip currents will
continue along all beaches into this evening. Many strong rip
currents have been reported at Tybee Island today and with both
winds and waves expected to increase a bit more on Tuesday and
Wednesday, a High Risk has been advertised for both days for the
Georgia beaches consistent with the latest rip current MOS. For
the South Carolina beaches, local rip current calculators
support a high-end moderate risk both days, but this may need
to be upgraded to a high risk later, especially Wednesday.
Breaking waves could reach 5 ft or greater Wednesday night into
Thursday, especially along the Charleston County coast into
Edisto Beach. A High Surf Advisory may be needed.

&&

.TIDES/COASTAL FLOODING...
Tides in the Charleston Harbor could reach minor flood levels with
the evening high tides both Wednesday and Thursday. Coastal Flood
Advisories could be needed for Charleston and Colleton Counties.
Tides at Fort Pulaski look to hold below minor flood levels for
now.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents from Tuesday morning through Tuesday
     evening for GAZ117-119-139-141.
SC...None.
MARINE...Small Craft Advisory from 6 PM Tuesday to 6 AM EDT Saturday
     for AMZ374.

&&

$$

NEAR TERM...Adam/DPB
SHORT TERM...ST
LONG TERM...ST
AVIATION...Adam/ST
MARINE...DPB/ST