008
FXUS62 KCHS 181808
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
208 PM EDT Tue Jun 18 2024

.SYNOPSIS...
High pressure will extend across the region early this week. A
trough of low pressure could approach the Southeast U.S coast
by late week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, a large ridge will remain centered across the Mid-
Atlantic and Southeast United States. At the sfc, high pressure
centered across the western Atlantic off the Mid-Atlantic and
Northeast Coast will extend southwest across the local area. The
pattern will favor large scale subsidence across the region and with
drier air depicted on water vapor imagery just offshore, should
suppress/limit afternoon convection. However, an easterly wind along
the southern edge of the sfc high centered north of the region will
help drive low-lvl moisture onshore and when combined with peak
diurnal heating should support few to perhaps scattered showers
along coastal areas, mainly across southeast Georgia. In this area,
moisture convergence and instability (SBCAPE around 1000 J/kg) are
greatest along the I-95 corridor, and could even result in a
thunderstorm or two by late afternoon, but wane by early evening.

1000-850 mb thicknesses along with ample sunshine support afternoon
highs in the upper 80s/lower 90s inland and mid 80s closer to the
coast. A tight gradient along the southern edge of the sfc high,
deep mixing and a boost from the sea breeze, will favor easterly
winds gusting between 15-20 mph, and up to as high as 25-30 mph near
the coast.

Tonight: Little to no change in the pattern both at the surface and
aloft, with even some increase in the strength of both ridges. A
continued deep easterly flow and sufficient moisture will result in
at least isolated showers coming in off the ocean, especially
impacting coastal Georgia. Although winds diminish inland, they do
continue rather gusty near and at the coast. This will result in a
fairly large range of temperatures; lows 64-68F degrees well inland
(where the lowest dew points are found, and middle 70s on the
barrier islands, and over the Charleston and Savannah metro
regions.


Tonight: Little to no change in the pattern both at the surface
and aloft, with even some increase in the strength of both
ridges. A continued deep easterly flow and sufficient moisture
will result in at least isolated showers coming in off the
ocean, especially impacting coastal Georgia. Although winds
diminish inland, they do continue rather gusty near and at the
coast. This will result in a fairly large range of
temperatures; lows 64-68F degrees well inland (where the lowest
dew points are found, and middle 70s on the barrier islands, and
over the Charleston and Savannah metro regions.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
The local forecast area will remain within the southern periphery
of upper level high pressure centered over New England on
Wednesday. A similar pattern will be present at the surface. The
high pressure at the surface will shift further eastward
towards Bermuda on Thursday and Friday. The high pressure aloft
is forecast to remain over the East Coast through the period.
Unseasonably quiet weather is forecast Wednesday and Thursday as
subsidence persists aloft, with only slight chance to chance
PoPs featured in the forecast. Additionally, thunder chances are
rather low as instability is negligible across the forecast
area. Thunder chances have been capped at slight chance for
Wednesday and Thursday.

Friday the pattern turns more active as the subsidence begins to
break down as well as an influx of moisture arrives, originating
from a low pressure disturbance off the east coast of Florida. The
development of the low pressure into anything other than a broad
area of low pressure/open trough is still very low confidence. Most
ensemble guidance continues to suggest little formation. Showers and
thunderstorms are forecast to come ashore Friday afternoon,
increasing in coverage in the afternoon hours. The greatest chances
remain across southeast GA where the greatest moisture profile is.

Temperatures through the period are forecast to be right around
normal, with highs in the upper 80s to around 90 and overnight lows
in the upper 60s to low 70s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
A broad upper level trough will begin to trek across the southeast
U.S. on Sunday as high pressure aloft shifts further south. At the
surface a cold front will approach the region late this weekend.
Between forcing from the approaching cold front and the local
afternoon sea breeze, precipitation chances are forecast to increase
through the weekend heading into next week. Temperatures will warm
through the period, with low to mid 90s on Saturday warming to upper
90s on Monday.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Prevailing VFR conditions are expected at CHS/JZI/SAV terminals
through 18Z Wednesday. However, brief showers and therefore brief
MVFR conditions could impact the SAV terminal this afternoon, then
again late morning into early afternoon Wednesday. Otherwise, expect
gusty east winds at all terminals this afternoon (20-23 kt), then
again at a similar speed late morning into the afternoon Wednesday.

Extended Aviation Outlook: Prevailing VFR. Brief flight restrictions
are possible in afternoon showers/thunderstorms Wednesday,
especially at KSAV. Chances of flight restrictions increase at
CHS/JZI/SAV terminals later in the week with showers and
thunderstorms moving onshore.

&&

.MARINE...
This Afternoon and Tonight: A large and strong ridge of high
pressure will encompass the coastal waters, with maybe a subtle
inverted trough to form nearby. There will be as much as a 2-3
millibar pressure gradient in place locally, resulting in rather
elevated easterly winds of at least 15-20 kt. The favorable
long duration onshore fetch will allow for seas to reach 4-5
feet within 20 nm today, and 5-6 feet across the outer Georgia
waters. It is there where a Small Craft Advisory begins early
this evening. Seas will build another foot or so tonight all
waters, and we might need to expand the coverage of the Small
Craft Advisories.

Wednesday through Saturday: Generally, high pressure will prevail
across the local marine waters. Northeasterly winds 15 to 20 knots
will persist across the local waters Wednesday into Friday morning.
Gusts may approach 25 knots at times. Winds Friday will remain out
of the NE, however easing slightly to 10 to 15 knots. Conditions
will continue to improve into Saturday, with winds shifting to the
SE around 10 knots by Saturday night. Seas are forecast to build
across the local marine zones, peaking Thursday with 5 to 6 ft
across the nearshore waters and 7 to 8 ft across the 20-60 nm
offshore GA waters. Small Craft Advisories will be needed for all
waters outside the Charleston Harbor through Thursday night. Seas
will decrease Friday, with 3 to 4 ft forecast Saturday morning.

Rip Currents: Although there still isn`t much swell that will
impact the beaches today, given the modest onshore winds and
numerous rip currents at Tybee yesterday, and enhanced risk of
rip currents will occur. In combination with the Rip Current MOS
and a locally developed Rip Current Calculator, we are showing
a Moderate Risk of Rip Currents for the South Carolina beaches,
and High Risk for the Georgia beaches today.

A High Risk for rip currents has been hoisted for Wednesday
across all area beaches. An enhanced risk of rip currents will
likely persist through the end of the week as long period swell
impacts the region.

High Surf: Breaking wave heights could reach 5 ft or greater
Wednesday night into Thursday, especially along the Charleston
County coast. A High Surf Advisory may be required.

&&

.TIDES/COASTAL FLOODING...
With the approaching full moon (6/22) tides in the Charleston Harbor
could reach minor flood stage with the evening high tides both
Wednesday and Thursday. Coastal Flood Advisories could be required
for Charleston and Coastal Colleton Counties.

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

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents until 8 PM EDT this evening for GAZ117-
     119-139-141.
SC...None.
MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EDT
     Saturday for AMZ374.

&&

$$

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