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404
FXUS62 KCHS 202154
AFDCHS

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

.SYNOPSIS...
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High pressure will strengthen across the region through early
next week. A weak cold front may approach from the west around
the middle of next week.
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&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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No major changes were made for the early evening update.
Isolated showers along parts of the Georgia coastal counties
will quickly wane after sunset.

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.
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&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
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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 will 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 will 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 will 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 will 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.
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&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
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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.
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&&

.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
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21/00z TAF Discussion:
KCHS/KJZI/KSAV: VFR through 22/00z.

Extended Aviation Outlook: There are no concerns.
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&&

.MARINE...
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Tonight: 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.
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&&

.TIDES/COASTAL FLOODING...
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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.
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&&

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

&&

$$