611
FXUS62 KCHS 221355
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
955 AM EDT Sun Sep 22 2024

.SYNOPSIS...
High pressure will linger across the region through the early
week. A weak cold front could approach from the west around mid
to late week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, a ridge centered across southern TX will extend east
across the Deep South and Southeast United States while a low and
associated trough axis shift off the Northeast Coast. At the sfc,
weak high pressure will prevail across the region, while weak low
pressure develops across the Midlands and Upstate. Mid-upper ridging
aloft is expected to gradually increase from the west with time
while a weak downslope flow is also present. The setup suggests
slightly warmer sfc temps than the previous day. In general, high
temps should range in the upper 80s to lower 90s. Closer to the
coast, high temps will be a bit cooler (low-mid 80s), likely due to
onshore flow and sea breeze shifting inland during the afternoon. By
mid-late afternoon, some guidance suggests weak sfc low pressure
nudging into western most zones while weak mid-lvl vort energy
arrives from the northwest late. Warm temps along with these subtle
forcing features could be sufficient to produce a few late afternoon
showers or even an isolated thunderstorm well inland given SBCAPE
around 1000 J/kg along and west of the I-95 corridor. However,
overall precip coverage should remain limited given the downslope
flow in place aloft.

Tonight: A few showers could linger across inland areas into early
evening, but expect activity to diminish fairly quick with the loss
of daytime heating. Weak sfc high pressure should then prevail for
much of the night while additional ridging continues aloft. Light
southerly winds under a few clouds should result in low temps that
are noticeably warmer than the previous night. In general, lows
should range in the upper 60s to lower 70s. Locations could stay in
the mid 70s along the beaches.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
A deep upper ridge centered over the northwestern Gulf will traverse
eastward across the Florida Peninsula Tuesday and shift over the
Atlantic by Wednesday. Surface high pressure anchored over northern
Maine extending southward along the Eastern Seaboard will persist
through the period. A subsidence inversion around the 600-550mb
layer noted via model soundings will limit convection, resulting in
mostly quiet weather. Deep dry air aloft with some moisture trapped
in the lower levels will result in a few low clouds, however mostly
sunny skies are expected each day. There are some indications within
the models that show spotty light showers far inland Monday/Tuesday,
due to weak shortwave impulses aloft. However, low cloud tops
indicate any showers that may develop should be brief with little
measurable rainfall. We will continue with no mentionable rain
chances (POPs less than 15%) in the forecast.

Temperatures will be relatively mild through the period due to the
ridge aloft. Expect highs in the upper 80s/low 90s each day. Both
Monday and Tuesday night will feature lows around 70 degrees inland
and low/mid 70s along the coast.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
An upper low over the Ohio Valley and elongated trough digging into
the Deep South will propagate eastward pushing a cold front toward
the area late Wednesday. With the trough progged to quickly lift out
of the Southeast U.S. Thursday, the front will slow and weaken as it
moves over the forecast area. Isolated to scattered showers are
possible Wednesday night, and could potentially persist through
Thursday depending on the progression of the front.

From here on out, details for the long-term forecast will largely
depend on the intensity, placement, and timing of a potential
tropical system sourced from the Gulf of Mexico. See latest NHC
Tropical Weather Outlook for the latest information. Based on the
collaborated low position per WPC, the system is expected to remain
west of the Carolinas. Given the FROPA, thick cloud cover, and
anticipated rainfall, high temperatures are forecast to dip into the
upper 70s/low 80s through the weekend.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
VFR conditions are expected at CHS/JZI/SAV terminals through 12Z
Monday.

Extended Aviation Outlook: VFR conditions expected to prevail
through Wednesday.

&&

.MARINE...
Today and Tonight: Weak high pressure will lead to quiet marine
conditions across local waters. In general, light northerly winds
this morning will become southerly between 5-10 kt this afternoon
while a sea breeze circulation develops, then shifts inland. Seas
will range between 2-3 ft across nearshore waters and 3-4 ft across
offshore Georgia waters today, then slowly subside about a foot
during the night.

Monday through Thursday: Weak, broad high pressure offshore will
result in southeast winds around 10 kt or less. Seas will average 1-
3 ft for the nearshore waters out 20 nm and 3-4 ft for the outer GA
waters from 20-60 nm. Near the end of the period, there could be an
increase in winds and due to a potentially developing tropical
system in the Gulf of Mexico.

&&

.TIDES/COASTAL FLOODING...
Today: A Coastal Flood Advisory has been issued for our entire
coast. Moderate coastal flooding is expected along the Charleston
and Colleton County coasts. Further south and into Georgia,
minor coastal flooding is expected to briefly occur.

Positive tidal anomalies and high astronomical tides from the
recent full moon will lead to elevated tides through early week.
Although the astronomical high tides are lowering, coastal
flooding is expected with each daytime high tide cycle along the
Charleston and Colleton County coasts.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Coastal Flood Advisory until 1 PM EDT this afternoon for
     GAZ117-119-139-141.
SC...Coastal Flood Advisory until 1 PM EDT this afternoon for
     SCZ048-051.
     Coastal Flood Advisory until 2 PM EDT this afternoon for
     SCZ049-050.
MARINE...None.

&&

$$

NEAR TERM...
SHORT TERM...BRM
LONG TERM...BRM
AVIATION...BRM/DPB
MARINE...BRM/DPB