461
FXUS62 KCHS 190506
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
106 AM EDT Wed Jun 19 2024

.SYNOPSIS...
High pressure will extend across the region this week. A trough
of low pressure will impact the Southeast U.S coast Thursday
into Friday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Isolated to perhaps scattered showers will impact parts of the
area from off the ocean through the overnight hours. This is
mainly across the coastal coutnies, where we find Theta-E
ridging and deep moisture convergence. There might also be a
subtle inverted trough that could add to the potential as it
moves closer to shore.

A decent gradient remains in place associated with strong
surface high pressure, keeping east and northeast winds as high
as 15-20 mph and gusty along coast, with 5-10 mph winds
elsewhere. This difference in the winds will result in a fairly
large range of min temperatures. We have mid and upper 60s well
inland, to the lower and middle 70s closer to the Atlantic.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/...
Wednesday and Thursday: The southern flanks of the expansive upper
level anticyclone centered over the eastern United States will begin
to buckle just a bit as a well defined TUTT located north of the
Greater Antilles approaches the Southeast U.S. coast. The
operational GFS is has finally come in line with the rest of the
global guidance in keep any surface reflection of the TUTT as an
open tropical wave/inverted trough as it moves onshore late Thursday
night into the day Friday. Given a modest northeast low-level flow
is expected to continue ahead of the approaching tropical wave,
steering trajectories favor coastal Georgia for the best chances for
measurable rainfall. Still not seeing a strong QPF signal in the
various guidance for any concentrated areas of showers given the
development of deep convection seems unlikely with the degree of
subsidence noted aloft, but isolated to scattered low-topped showers
with a few tstms appear likely. Pops 20-40% were maintained for
mainly the coastal counties, highest along the Georgia coast. Highs
will warm into the upper 80s/lower 90s away from the coast both days
with lows Thursday morning dropping into mid-upper 60s well inland
to the mid-upper 70s at the beaches. Breezy to locally windy
conditions will also persist along the immediate coast and beaches.

Thursday Night and Friday: Rain chances will begin to ramp up late
Thursday Night and especially Friday as the approaching tropical
waves moves onshore. Shower coverage may lessen a bit Thursday
evening as subsidence ahead of the tropical wave spread in from the
east, but this will rapidly change as daybreak approaches Friday and
the primary wave axis pushes inland. The wave will be accompanied by
a ribbon of PWATS in excess of 2 inches. This coupled with some
forcing with the weakening TUTT aloft and the convergent/east side
of the westward propagating surface wave should be enough to support
scattered if not numerous showers with a few tstms. Pops were
trended up a bit to 40-60% (highest coast), but given the TUTT will
likely be rapidly dampening as it approaches the expansive upper-
level anticyclone, there is some hesitancy to go any higher with
pops at this time. Further adjustments will likely be needed. Lows
Thursday night will drop into the mid-upper 60s well inland to the
mid-upper 70s at the beaches. Highs Friday will range from the upper
80s/lower 90s away from the coast with cooler conditions at the
beaches.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The tropical wave and associated TUTT aloft will quickly dissipate
over the weekend with the region positioned along the eastern flanks
of the large subtropical anticyclone. Despite the dissipation of the
TUTT, a broad weakness looks to remain through early next week.
This coupled with sea breeze influences and lingering deep-layered
moisture featuring PWATS in excess of 2 inches will support
scattered showers/tstms each day. The heat will also begin to build
through the weekend and especially Monday with highs warming into
lower-mid 90s Saturday with the mid-upper 90s into early next week.
The warmest day looks to occur Monday where a few spots far inland
could make a run for 100 before the onset of showers/tstms.
Dewpoints do not look to really mix out during this period with heat
indices expected to peak 100-103 Saturday, 102-105 Sunday and 105-
110 Monday, highest across the inland portions of the coastal counties.
Heat Advisories could be needed at some point with Monday being
the best day for reaching the Heat Advisory criteria of 108.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
KCHS/KJZI/KSAV: While there will be VFR ceilings and the risk
for some light showers at times moving in from the Atlantic, VFR
is forecast at all sites through 06Z Thursday.

Similar to the past two days, gusty easterly winds will occur
from late this morning through about sunset in response to a
tight gradient and deep mixing. Winds will frequently gust to
20 or 25 kt, occasionally even stronger.

Extended Aviation Outlook: Brief flight restrictions are possible in
afternoon showers/thunderstorms Thursday, especially at KSAV.
Chances of flight restrictions increase at KCHS/KJZI/KSAV
terminals Friday and Saturday with lesser chances Sunday.

&&

.MARINE...
Overnight: A large and strong ridge of high pressure will
encompass the coastal waters, with a subtle inverted trough to
form nearby. The pattern will favor an enhanced pressure
gradient across local waters through the night, with easterly
winds gusting upwards to 20-25 kt. Favorable long duration
onshore fetch will also allow seas to build across local waters,
eventually peaking between 4-6 ft across nearshore waters and
5-7 ft across offshore Georgia waters. Small Craft Advisories
will therefore be in effect for all local waters outside the CHS
Harbor tonight, but a brief lull in winds is possible this
evening before 6 ft seas arrive across nearshore waters around
midnight.

Wednesday through Saturday: Gusty northeast winds will persist into
Friday as a tropical waves approaches from the east and a modest
gradient persists over the coastal waters. Northeast winds will
average 15-20 kt with gusts to 25 kt during this time. Seas will
remain above 6 ft through Thursday night within 20 NM and into
Friday evening for the waters 20-60 NM offshore. Small Craft
Advisories are in effect for these waters. Seas look to peak 5-6
nearshore waters and 6-8 ft in the offshore waters, mainly on
Thursday. Winds in the Charleston Harbor will be near advisory
thresholds, but are expected to hold just sky. The need for an
advisory there will be reevaluated Wednesday morning. Both winds and
seas will begin to diminish Friday night into Monday.

Rip Currents/High Surf: Expect the risk for strong and
dangerous rip currents to spread into all beaches Wednesday
which will persist into Thursday. A high risk for rip currents
is being highlighted for all beaches for both days. NWPS
breaking wave guidance shows breakers reaching 3-5 ft along the
beaches on Wednesday and Thursday, highest in the Folly Beach
area. Given only spotty instances of 5 ft breakers are being
depicted, the situation for Wednesday looks to marginal for a
High Surf Advisory at this time.

&&

.TIDES/COASTAL FLOODING...
Surface high pressure will remain off the coast of New England with
a tight pressure gradient and elevated winds across the South
Carolina and Georgia coast. A full moon on 6/22 will also cause the
astronomical tides to slowly build. There is a chance that minor
coastal flood stage could be reach on the Wednesday and Thursday
evening high tides for Charleston Harbor.

Tides at Fort Pulaski are forecast to remain below minor flood
stage.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents through this evening for GAZ117-119-139-
     141.
SC...High Risk for Rip Currents from 8 AM EDT this morning through this
     evening for SCZ048>051.
MARINE...Small Craft Advisory until 6 AM EDT Friday for AMZ350-352-354.
     Small Craft Advisory until 11 PM EDT Friday for AMZ374.

&&

$$

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