949
FXUS62 KCHS 211902
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
302 PM EDT Fri Jun 21 2024

.SYNOPSIS...
Tropical low pressure will move onshore along the Northeast
Florida and Southeast Georgia coast tonight. High pressure will
then become the primary feature this weekend and into next
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Satellite and radar observations at 21/18z showed the center of
tropical low pressure off the Southeast Georgia coast located
about 75 NM southeast of Sapelo Island, GA. The low is on track
to move inland across the extreme northeast Florida coast or far
southern Georgia coast overnight. The system is fighting a lot
of dry air despite being embedded within an envelope featuring
PWATs above 2" per GOES-E Total Precipitable Water product.
Convection that formed near its center earlier today has waned
and visible satellite data show the circulation is completely
exposed. The window for intensifying into a tropical cyclone is
quickly diminishing despite it traversing the Gulf Stream. Refer
to the latest NHC products for additional information. Regardless
of its classification as landfall, impacts will be the same
with feeder bands wrapping cyclonically around its center
occasionally moving onshore along the Georgia and southern South
Carolina coasts and breezy to locally windy conditions linger
along the beaches throughout the night. There are signals that a
more concentrated area of convection could develop along the
circulaton`s eastern flanks as it approaches the Georgia coast
late. This could impact much of the Georgia coastal counties,
especially Liberty, McIntosh and Long Counties. Pops tonight
range from 20-30% inland to the 40-60% at the coast, highest
along the Georgia coast. Lows will range from the lower 70s
inland to the upper 70s at the beaches.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
Saturday and Saturday night: Aloft, the forecast area will sit
on the eastern extent of the upper ridge. At the surface, the
main feature of interest will be the remnant circulation of the
tropical disturbance that pushed inland along the northeast
Florida and southeast Georgia coast. This circulation and the
envelope of deep moisture associated with it will linger near
the Georgia coast and will be the focus for thunderstorm
activity likely ongoing at the start of the day. The highest
rain chances and greatest coverage of thunderstorms is expected
to be across the Georgia coastal waters, southeast Georgia, and
up along the Savannah River into southeast South Carolina. Rain
chances peak in the 60 percent range, but could certainly need
to be higher depending on how things evolve overnight. This will
yield the possibility of some locally heavy rainfall, given the
presence of the circulation, deep moisture, and potential for
training storms. For this highlighted area, rainfall amounts of
0.50-1.00" will be common, with potential for locally higher
amounts. Overnight, while the focus for nocturnal convection
should shift offshore, we could still see some showers and
storms periodically attempt to push onshore. Though the highest
chances are positioned over the waters, we do maintain 30-40
percent chances along the entire coast overnight. The presence
of clouds and the expected convection should keep temperatures
down a bit along the coast, with upper 80s common there.
However, further inland we could see some low 90s. Overnight,
lows will be typical of summertime with low to mid 70s.

Sunday through Monday: On Sunday, the remnant circulation should
completely dissipate or at least shift off to the northeast.
This should begin the transition to a more typical summertime
pattern as the subtropical high takes hold with a lee trough
inland across central Georgia and the Carolinas. Convection
should become more diurnal each day, favoring the afternoon and
evening time period. Temperatures will begin to increase as
well, with Sunday highs in the mid to upper 90s inland and low
90s elsewhere. Then by Monday, look for mid to upper 90s across
the entire forecast area. The result for Monday will be heat
index values rising to around 105 for much of the forecast area.


&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
Aloft, the pattern will transition to weak and broad troughing
for much of the upcoming week. At the surface, the pattern
should be typical of summertime with subtropical high pressure
in control. Rain chances will be diurnal, with the highest
chances in the afternoon and evening and then transitioning
offshore to the coastal waters during the overnight periods. The
most notable part of the forecast will be highs in the mid to
upper 90s Tuesday and Wednesday, with a few inland locations
possibly hitting triple digits. For Thursday, mid 90s should be
more common then coming down to the low to mid 90s by Friday.
Depending on how dew point values work out, there could be some
heat index values into the 105-110 degree range Tuesday-
Thursday, primarily along the coastal corridor. If this comes to
fruition, Heat Advisories could be needed.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
21/18z TAF Discussion:
KCHS/KJZI/KSAV: Scattered showers could impact all three
terminals this afternoon. Durations look to remain fairly brief
so VCSH will be highlighted for all terminals. The risk for
showers will linger at KCHS into early evening, KJZI through
late evening and KSAV through the overnight as low pressure
approaches the northeast Florida and far southern Georgia coast.
A more concentrated area of rain could approach KSAV as
daybreak approaches, but this will be highly dependent on the
track/intensity of the low as it treks onshore. VCSH was held
for now. There could be brief stints of MVFR cigs just about
anywhere this afternoon as showers push through. VFR should
prevail for much of the period, however.

Extended Aviation Outlook: Mostly VFR. However, convection will
bring brief flight restrictions, mainly each afternoon and
evening.

&&

.MARINE...
Tonight: Winds are certainly over performing a bit across the
coastal waters this afternoon with tropical low pressure
located just to the southeast of the Georgia offshore waters.
Enhanced winds will linger into this evening then diminish a bit
overnight as the low moves inland along the far northeast
Florida or southern Georgia coast. Winds/seas will diminish
first over the South Carolina waters, including Charleston
Harbor, and the Georgia waters late. However, there is uncertainty
on how quickly winds/seas will diminish, especially over the
South Carolina waters. The Small Craft Advisory has been
extended until 6 PM for the Charleston Harbor, 8 PM for the
South Santee- Edisto Beach nearshore waters and into the
overnight for the two Georgia marine legs. The highest seas will
occur early this evneing, 4-6 ft nearshore and 6-8 ft over the
Georgia offshore waters.

Saturday through Wednesday: South to southwest flow mainly in the
10-15 knot range should prevail across the local waters through
the weekend and into the middle of next week. The exception
will be Sunday night into Monday when winds are expected to
increase a bit as the gradient tightens, with 15-20 knots more
common. Seas should average 2-4 feet through the period, though
perhaps up to 5 feet at times in the outer waters as winds surge
a bit.

Rip Currents: Onshore winds and lingering swell energy will help
to keep the rip risk elevated Saturday and again Sunday. For
Saturday, depending on the peak winds and the amount of swell
that arrives at the beaches, the local rip current calculator
results in a borderline high risk. Current approach is to
maintain the moderate risk for Saturday and allow the overnight
shift to re-evaluate.

&&

.TIDES/COASTAL FLOODING...
Tidal departures are still running about 1 ft above predicted.
Levels in the Charleston Harbor should peak around 6.9 ft MLLW.
Depending on how quickly winds diminish this evening, it is
possible that a low end Coastal Flood Advisory could be needed
for Colleton and Charleston Counties. No issues are expected
elsewhere along the Georgia and far southern South Carolina
coasts.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents until 8 PM EDT this evening for GAZ117-
     119-139-141.
SC...High Risk for Rip Currents until 8 PM EDT this evening for
     SCZ048>051.
MARINE...Small Craft Advisory until 6 PM EDT this evening for AMZ330.
     Small Craft Advisory until 8 PM EDT this evening for AMZ350.
     Small Craft Advisory until midnight EDT tonight for AMZ352-354.
     Small Craft Advisory until 4 AM EDT Saturday for AMZ374.

&&

$$