681
FXUS62 KCHS 061638
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1238 PM 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/...
Mid-day Update: No major changes made with the noon-time update.
Forecast is on track.

Today: Morning convection induced by the shortwave aloft has
pushed well offshore, and has moved east of the marine zones.
Will see a lull in convective activity into mid-afternoon, when
isolated showers/tstms may begin to develop inland well ahead
of a surface front. A lagging shortwave is 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 /18Z THURSDAY THROUGH TUESDAY/...
VFR conditions will mostly prevail at KCHS, KJZI, and KSAV
through 18z 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.

&&

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

&&

$$

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