863
FXUS62 KCHS 201925
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
325 PM EDT Thu Jun 20 2024

.SYNOPSIS...
A tropical wave will approach the Southeast coast tonight and
shift inland along the northeast Florida and southeast Georgia
coastline on Friday. High pressure will then become the primary
weather feature into the middle of next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
High pressure will persist inland through tonight, while a tropical
wave tracks west-northwest well north of the Bahamas and towards the
Southeast U.S. coast. NHC currently has an aircraft out to
investigate this system, but formation chance is still at 40%. A few
light returns were noted on radar imagery this afternoon, but most
are producing no more than sprinkles and are very brief. Much
of the night should then be dry over land, before some shower
activity possibly starts drifting onshore a few hours prior to
sunrise as deeper moisture arrives with the approaching
disturbance. No significant rainfall amounts are expected
through 12z. Low temperatures will be seasonable, generally
ranging from the mid 60s across the far interior to mid 70s at
the immediate coast and in Downtown Charleston.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
Friday and Friday night: The forecast for Friday will really hinge
on the tropical disturbance (AL92) and its progression inland during
the first part of the day. While the disturbance could still
strengthen and possibly develop into a Tropical Depression, the
impacts really don`t change much either way. The main impact will
come in the form of increased shower and thunderstorm activity as
the envelope of deep tropical moisture spreads inland. We expect to
see scattered to numerous showers and thunderstorms load up across
the coastal waters and then rotate onshore through the mid to late
morning hours. The best rain chances will be along the immediate
coast, especially the southeast Georgia coast which will be closer
to the center of circulation. As the day progresses, the best
coverage should shift inland and also shrink to the southwest,
favoring the southeast Georgia coast and all of interior southeast
Georgia. Rainfall amounts from this increased coverage will be
highly dependent on where individual shower/storm elements pass as
this will not be a large shield of precipitation. No significant
change to expected amounts, with 0.25-0.50 along the coastal
corridor with some potential for locally higher amounts along the
immediate coast (especially the GA coast). There are no severe
weather concerns. Winds will again be breezy thanks to the onshore
flow on the northside of the circulation, but gusts will be less
than previous days. High temperatures should mostly top out in the
upper 80s, with low 90s possible for interior southeast Georgia.
Overnight, rain chances should diminish, though we could still see
isolated to scattered development across southeast Georgia, closer
to the remnant circulation.

Saturday and Sunday: We will begin to transition back to a more
typical summertime pattern with the subtropical high extending into
the area from the east. However, there will still be the remnant
circulation from the disturbance across south Georgia as well
as the nearby deeper moisture profiles. The Saturday time period
is now within the hi-res model window and the overall consensus
is for the best convective coverage to be across southeast
Georgia closer to the remnant circulation and associated deeper
moisture. Therefore, the forecast has 60-70 percent chances in
the afternoon hours for southeast Georgia. For Sunday, we should
transition to a more typical diurnal thunderstorm pattern with
40-50 percent chances everywhere. Neither day looks to be
particularly supportive of severe thunderstorms, though you can
never count out boundary interactions producing a stronger
storm. Temperatures will begin a warming trend over the weekend,
with highs getting back into the low to even mid 90s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The early to middle part of next week looks hot with a return to
more typical diurnal coverage of showers and thunderstorms. The
forecast generally has rain chances peaking in the afternoon and
evening, then gradually transitioning to favor the Atlantic coastal
waters through the overnight hours. High temperatures are forecast
to rise into the mid to upper 90s, which will push heat index values
considerably higher than they have been. In fact, we expect to see
widespread 100-105 degree heat index values each afternoon Monday
through Wednesday. As the highest dew points reside within the
coastal corridor, we could see heat index values rise to around 108-
110, and we might have to consider Heat Advisories.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
VFR will prevail through at least the first half of the night.
A tropical wave is expected to approach the Southeast coast
tonight and move onshore near the Georgia/Florida border on
Friday. This will bring a potential for a period of MVFR
ceilings and showers in the morning. Otherwise, gusty east winds
this afternoon will subside after sunset.

Extended Aviation Outlook: Conditions should mostly be VFR. There
could be brief rounds of flight restrictions each afternoon and
evening with showers and thunderstorms.

&&

.MARINE...
Tonight: Pressure gradient will remain tight tonight between inland
high pressure and a tropical wave approaching the Southeast coast.
Northeast winds will generally average in the 15-20 knot range with
higher gusts to 25 knots. Seas will build to 5-7 feet out 20
nm and 7-8 ft beyond. These conditions will support a continuation
of Small Craft Advisories through the night across all marine
zones outside of the Charleston Harbor. For the Harbor, wind
gusts should subside some later this evening with the Advisory
scheduled to come down at 8 PM.

Friday through Tuesday: A tropical disturbance is expected to shift
onshore on Friday somewhere along the northeast Florida and
southeast Georgia coast. The circulation around this feature will
drive elevated northeasterly to easterly flow across the waters into
Friday evening. Seas should peak early Friday, then gradually
diminish through Friday night. Ongoing Small Craft Advisories remain
in effect, with ending times spanning the afternoon through the
evening as seas relax. Thereafter, conditions across the local
waters will transition to a more typical summertime pattern.
Southerly to southwesterly flow will tend to be strongest along the
land/sea interface with the diurnal sea breeze and sea will
typically be in the 2-4 ft range.

Rip Currents: Persistent onshore flow and lingering elevated seas
will again produce a High Risk of rip currents at all beaches on
Friday. Lifeguards continued to indicate hazardous swimming
conditions at area beaches, and these conditions are expected to
continue through Friday. As we get into Saturday, winds and seas
will relax and overall conditions should improve. However, we will
advertise a Moderate Risk of rip currents for Saturday. High
Surf: While there can be some occasional 5 foot breakers in the
surf zone today, most breakers will be 3 or 4 feet, so no High
Surf Advisory is required. Even so, some coastal areas will
experience erosion.

&&

.TIDES/COASTAL FLOODING...
Tide levels will continue to be elevated through Friday thanks
to persistent onshore flow and elevated seas. However,
astronomical tide values aren`t particularly high which will
reduce the overall coastal flooding risk. Based on current tidal
departure trends, the upcoming high tide (~8 pm) will likely
fall short of 7 ft MLLW at Charleston Harbor. Likewise, the
Friday evening high tide (~8:30 pm) will be elevated but should
fall short of the threshold for minor coastal flooding.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents through Friday evening for GAZ117-119-
     139-141.
SC...High Risk for Rip Currents through Friday evening for SCZ048>051.
MARINE...Small Craft Advisory until 8 PM EDT this evening for AMZ330.
     Small Craft Advisory until 4 PM EDT Friday for AMZ350-352.
     Small Craft Advisory until 7 PM EDT Friday for AMZ354.
     Small Craft Advisory until 11 PM EDT Friday for AMZ374.

&&

$$

NEAR TERM...ETM
SHORT TERM...BSH
LONG TERM...BSH
AVIATION...BSH/ETM
MARINE...BSH/ETM