529
FXUS62 KCHS 202008
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
408 PM EDT Fri Sep 20 2024

.SYNOPSIS...
High pressure is expected to gradually strengthen across the
region through early next week. A weak cold front may approach
from the west around the middle of next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
GOES-E water vapor and latest SPC Mesoscale Analysis indicated a mid-
level vort max along the SC coast, tracking south between a trough
over the western Atlantic and a ridge over the Ohio River Valley. At
the sfc, visible satellite, sfc wind observations, and KCLX radar
indicated that a weak sea breeze was developing over the coastal
counties of SC/GA, drifting slowly inland. CAPE analysis indicated
the MLCAPE will likely remain between 1000-1500 J/kg along and west
of the sea breeze into early this evening, with little to no CIN.
Recent runs of the HRRR indicate that isolated showers may develop
on the sea breeze across the coastal counties of SE GA. The forecast
will feature SCHC for showers. Any convection that does develop
should dissipate by sunset.

Tonight, H5 heights should gradually rise as a ridge pivots south of
around the high centered over TX. At the sfc, high pressure should
gradually build across the forecast area, rising by 4 to 5 mbs
overnight. The building high should support northeast winds between
3-5 mph, especially near the coast. The wind should aid in limiting
the potential for fog formation late tonight. However, winds could
become very light to calm for a couple hours across the far inland
counties. The forecast will feature a mention of patchy fog across
the inland counties. Low temperatures are forecast to range from the
mid to upper 60s inland to around 70 along the coast.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
The mid-levels will consist of a trough just off the East Coast
Saturday morning and ridging over the central U.S., with embedded
High pressure over TX. By Monday, the trough will have shifted
further offshore, pushed by the ridge that`ll have moved over the
East Coast. Additionally, the embedded High should be over the FL
Panhandle. At the surface, High pressure will remain over the
Southeast U.S. Subsidence associated with the High is expected to
bring mainly dry weather during the short term. We`ll note that most
of the synoptic models are completely dry on Saturday. Though, the
long-range CAMs are split between it being completely dry and some
members showing light showers along the GA coast. PWATs are around
1.5", but many model soundings show decent dry air in place. So we
opted to go with 10% POPs in these locations Saturday afternoon. If
anything does manage to form, it`ll be isolated, brief, light, and
may just be sprinkles. Saturday evening through Monday are
completely dry. Temperatures will trend higher due to approaching
ridge. Highs will be in the mid to upper 80s Saturday, and the upper
80s to around 90 degrees on Sunday and Monday. Though, it`ll be
cooler at the beaches. Lows Saturday will be in the mid to upper 60s
for most locations. Sunday night they`ll be in the upper 60s inland
to the lower 70s along the immediate coast.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Surface High pressure will initially be over our region, then shift
offshore mid to late next week. A cold front should approach from
the northwest on Friday. This synoptic pattern will yield dry
conditions through Wednesday, with increased POPs Thursday and
Friday. High temperatures should be at or slightly above normal
Tuesday and Wednesday, trending lower Thursday and Friday.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Prior to the 18Z TAFs, satellite indicated densely packed cloud
streets over KCHS and KSAV, bases just above 3 kft. Cloud bases
should lift through the rest of the afternoon, reaching between
050-060 kft this afternoon. Winds are forecast to remain
generally from the ENE through the TAF period, between 5-10 kts
during the day and around 3 kts at night. KSAV could see some
ground fog or patchy fog during the pre-dawn hours Saturday
morning, highlighted with a TEMPO from 10-12Z.

Extended Aviation Outlook: VFR.

&&

.MARINE...
High pressure will increase across the marine zones tonight. Winds
across the nearshore and outer waters will remain from the ENE
around 10 kts this evening, increasing to 10-15 kts late tonight.
Seas should range between 2 to 4 ft.

Saturday: The interaction between High pressure inland and a weak
trough south of FL will yield sustained NE winds 10-15 kt during the
day. Winds will ease during the evening and overnight. Seas will
average 2-4 ft during the day with some 5 footers in the GA waters
from 20-60 nm. Seas should drop about 1 foot during the evening and
overnight.

Sunday through midweek: High pressure will prevail inland, then
begin to move offshore midweek. Expect sustained winds to be mainly
10 kt or less. Seas will average 2-3 ft within 20 nm and 3-4 ft for
the GA waters from 20-60 nm.

&&

.TIDES/COASTAL FLOODING...
The astronomical high tide at the Charleston Harbor high tide is
6.19 ft MLLW at 1044 PM. Winds along the coast are forecast to
remain from the ENE through the high tide cycle. The winds should
support tidal departures around 0.9 ft MLLW. A Coastal Flood
Advisory has been posted from 9 PM until midnight for minor
flooding, 7.1 ft MLLW.

Positive tidal anomalies and high astronomical tides from the recent
full moon will lead to elevated tides through the weekend. Although
the astronomical high tides are lowering, coastal flooding is
expected with each daytime high tide cycle along the Charleston and
Colleton county coasts. In fact, major coastal flooding is possible
with the Saturday late morning high tide. Further south and along
the Georgia coast, minor coastal flooding is likely with the daytime
high tide cycle.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Coastal Flood Advisory from 9 PM this evening to midnight EDT
     tonight for SCZ049-050.
MARINE...None.

&&

$$

NEAR TERM...NED
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...NED