104
FXUS62 KCHS 290519
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
119 AM EDT Sat Jun 29 2024

.SYNOPSIS...
A weak front will dissipate across the area tonight. Atlantic
high pressure will return over the weekend, while a trough of
low pressure resides inland. A cold front will likely to impact
the area early late Sunday into early next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Tonight: Mainly quiet conditions will persist through late night
with weak mid-lvl ridging and dry air aloft across the Southeast
United States. However, ample low-lvl moisture resides across the
local area where a stationary front gradually dissipates, which
could spawn a few showers and/or thunderstorms overnight, mainly
along and east of the I-95 corridor across southeast South Carolina.
Thunderstorms are expected to remain pulse type in nature given weak
shear and SBCAPE 1500-2000 J/kg in place, but brief downpours are
possible as activity drifts onshore and inland late.

Patchy fog and stratus could impact some areas in the early morning
hours, especially places which received precipitation. Overnight
temps are forecast to dip into the lower 70s well inland to the mid
and upper 70s along the coastal counties.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY/...
Saturday and Saturday night: The area will be dominated by a deep
layer ridge, centered to the south and east. Very little in the way
of upper level features to help force afternoon convection. However,
with light southerly flow, ample deep layer moisture with PWs around
2 inches, and mean CAPE values of 1500-2000 J/Kg, expect scattered
afternoon showers and thunderstorms. The main trigger will be the
seabreeze, then the combo of the seabreeze and convective outflow
boundaries. Have continued likely PoPs west of I-95 and chance
elsewhere. With light steering flow, locally heavy rainfall will be
possible. Convection should be diurnally driven, decreasing into the
evening. Temperatures above normal, with highs in the lower to mid
90s and lows in the mid to upper 70s.

Sunday and Sunday night: The pattern becomes a little more active
during this period as a broad upper trough takes shape over the
northeast U.S. and OH River Valley area. The associated surface cold
front approaches from the northwest by late day/Sunday night, but
should remain well northwest of the area through the day. However,
the increased low level convergence upstream/northwest of the area
will likely help to spark a line of shower/thunderstorms, which
could propagate southeast into our northern area via outflow
boundaries. The presence of some cyclonic flow at upper levels,
better low level convergence, and CAPE values near 2000 J/Kg will
lead to the potential for isolated strong to severe storms,
especially over our SC region, which is where the SPC has a Marginal
Risk. Main impact from stronger storms will be strong/gusty winds.
Also, depending on cloud/convective coverage, temperatures could
spike into the lower to mid 90s due due to some compressional
warming ahead of the front. These temps combined with surface Tds in
the lower to mid 70s, would result in max heat indices of 105 to
109, which would be marginal Heat Advisory conditions. Will continue
to monitor this potential. Again, convection likely to decrease by
evening with loss of heating. However, given the presence of the
upper trough along with the cold front sagging into the area, would
not be surprised to see isolated to scattered convection last
through the night, especially north of the Savannah River.

Monday:  The cold front that was advancing into the area Sunday
night is shown by models to stall over the region. Deep layer
ridging builds north and west of the area, with low level easterly
flow. Given the lingering front and sufficient moisture /PWs around
2-2.25 inches/, expect scattered to numerous showers/thunderstorms.
Highs a tad lower than the previous day given the front and cloud
cover.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
A slightly quieter weather pattern is expected for much of this
period as a deep layer ridge continues west and north of the area
with light south-southeast winds. With little to no upper level
features to trigger convection, any convection during this period
will mainly be triggered by afternoon heating and the presence of a
seabreeze. Expect a weak front to linger over the area Tuesday, but
then dissipate Wednesday and beyond. Given the lingering front on
Tuesday, have continued likely PoPs, especially over the southern
half of the area where the best moisture will reside. Wednesday and
beyond, kept more climo level/chance PoPs. Given PWs remain 2+
inches much of this period, along with light steering flow, any
stronger showers/thunderstorms could produce locally heavy rainfall.
Temperatures generally near normal Tuesday, then possibly climbing
back to above normal Wednesday and Thursday.

&&

.AVIATION /05Z SATURDAY THROUGH WEDNESDAY/...
KCHS/KJZI/KSAV: VFR will prevail through most of the valid 00Z
TAF cycle.

There could be some light fog/stratus a few hours either side of
daybreak at any or all of the sites resulting in sub-VFR
weather.

There is then the potential for some SHRA/TSRA activity along
the sea breeze Saturday as it moves inland. No more than VCSH
during the late morning and early afternoon at KJZI as it passes
through, with VCTS at KCHS and KSAV during the afternoon hours.
Any direct impacts would result in brief flight restrictions.

Extended Aviation Outlook: Prevailing VFR. Brief flight
restrictions are possible in showers and thunderstorms, mainly
in the afternoon and evenings.

&&

.MARINE...
Tonight: A weak pressure gradient will reside across local waters,
resulting in conditions that remain rather quiet through the night.
In general, south to southwest winds around 10-15 kt or less will be
common across most coastal waters. Seas will be around 2 ft or
less.

Extended Marine: No highlights are expected through the period.
Generally southerly winds are expected to persist through
Monday as a surface ridge remains east and south of the waters.
Winds of 15 knots or less and seas 2 to 4 feet. Slightly
stronger winds possible Sunday and Sunday night as the pressure
gradient increases ahead of a cold front. Monday and Tuesday, a
cold front is expected to stall over the waters, creating
lighter winds, generally 10-15 knots from the south- southeast
and seas 2 to 3 feet.

Waterspouts: We`re well into the local "Waterspout Season", and
an in-house Waterspout Index provides us with a Moderate Risk
Saturday morning. Much will depend on whether or not a late
night sea breeze that transitions into the sea breeze develops.
For now it is just something to be aware of.

Rip Currents: Latest guidance indicating very marginal Moderate Risk
for rip currents on Saturday. Given surrounding offices going with
Moderate, and we are going into a weekend, have opted to maintain
Moderate Risk for Saturday. Low risk for Sunday.

&&

.FIRE WEATHER...
The South Carolina forestry commission reported low fuel moistures
across portions of the area on Thursday. However, rainfall on
Thursday and the potential for rainfall over the next few days
will help to alleviate some of the low fuel moisture values.

&&

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

&&

$$

NEAR TERM...DPB
SHORT TERM...CPM/RFM
LONG TERM...RFM
AVIATION...
MARINE...Adam