221
FXUS62 KCHS 061127
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
727 AM EDT Thu Jun 6 2024

.SYNOPSIS...
A cold front will approach from the northwest tonight and move
through Friday morning. High pressure returns for the weekend,
then another cold front will move through Monday. High pressure
will build back in behind the front.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, the early morning shortwave will shift offshore
with another shortwave poised upstream across the Deep South and
along the central Gulf Coast. The flow will flatten out into
the afternoon and the main portion of the shortwave looks as
though it will track to the southeast and pass south of the
forecast area. At the surface, the subtropical high will
continue to extend westward into the area which will place the
forecast area in between the high to the east and an approaching
front to the west. The main forecast challenge concerns how
much convective coverage there will be in the afternoon and into
the evening. Hi-res model solutions are quiet consistent from
run to run in producing little, if any, convection this
afternoon. Perhaps this is a result of a little subsidence in
the wake of the departing shortwave energy, as well as warm
profiles noted in model soundings. Overall, these hi-res models
have done reasonably well the last few days showing considerably
less coverage compared to global models and current thinking is
that this will continue today. Therefore, we have lowered the
forecast to include just isolated thunderstorms this afternoon.
The near storm environment today is similar to the last few days
where DCAPE values are progged to be up around 1,000 J/kg. Also
of note in model soundings today, flow in the 700-850 mb layer
will be on the order of 25-30 knots. So, if a storm can initiate
and get going, it certainly has the potential to produce
damaging wind gusts. However, the expected lack of coverage will
help keep the overall threat low.

Surface winds will take on more of a westerly component today
which is usually a recipe for warmer temperatures. Thicknesses
will also increase, setting the table for a very warm day. The
forecast calls for low to mid 90s, but heat index values should
only top out in the upper 90s thanks to dew points mixing out a
bit in the afternoon.

Tonight: With convection likely holding off until it develops
upstream across the South Carolina Midlands and moves in during
the evening hours, the first part of the tonight period will
likely be the most active. We have the highest chances during
the mid to late evening hours, favoring southeast South
Carolina. It is possible there will be a low end severe threat
with damaging wind gusts being the main risk. Any ongoing
convection should shift offshore by the early morning hours, and
the rest of the overnight should be dry for land areas. It will
be a mild night, with lows only falling into the low 70s in
most locations.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
A cold front will move through Friday morning with drier air
gradually building in. Subsidence will overspread southern SC
during the afternoon, likely preventing convection from
developing. There is a slight chance that an isolated shower or
tstm will develop along the GA coast in the afternoon where a
weak sea breeze coincides with the cold front and slightly
greater moisture. Downslope flow will push highs into the lower
90s.

Broad upper ridging will occur Saturday into Sunday while dry
high pressure overspreads the area at the surface. Surface
dewpoints will drop into the 50s inland, with lower 60s near the
coast, resulting in a noticeable change in airmass despite high
temps in the low to mid 90s under downslope flow.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
Another cold front will drop through the area Sunday night,
then stall near or just south of the area. Moisture will
gradually increase across the Southeast early next week, and
diurnal convection will return.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
VFR conditions will mostly prevail at KCHS, KJZI, and KSAV
through 12z Friday. Most of the day is expected to be dry and
the best chance for thunderstorms will come this evening, mainly
at KCHS and KJZI. We have added in VCTS from 01-04z at these
sites, but left any mention out of KSAV.

Extended Aviation Outlook: VFR.

&&

.MARINE...
Today and tonight: South to southwest flow will prevail across
the local waters today, mostly in the 10-15 knot range.
Enhancements along the land/sea interface are expected with the
afternoon sea breeze, producing gusts up to around 20 knots.
Overnight, southwest flow will increase as the gradient tightens
when the local waters get pinched between the high to the east
and a front approaching from the west. Winds around 15 knots
will be more common, with 15-20 knots possible for a period of
time in the outer Georgia waters and the Charleston County
waters. Seas should average 2-3 feet today, increasing to be 3-4
feet overnight.

Southerly flow on Friday will turn to the W Friday night, then
N on Saturday behind a cold front. The pattern quickly reverts
to a typical southerly flow by Saturday night and Sunday as
Atlantic high pressure rebuilds.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will remain elevated today. Although the
wind direction along the coast isn`t ideal for driving large
positive tidal departures, conditions should still be sufficient
to produce departures in the 0.4 to 0.6 ft. Therefore, the high
tide Thursday evening could peak right around 7.0 ft MLLW in
Charleston. Coastal Flood Advisories could be needed for
Charleston and coastal Colleton counties.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

$$

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