305
FXUS62 KCHS 010858
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
458 AM EDT Mon Jul 1 2024

.SYNOPSIS...
A cold front will impact the area today into Tuesday before
dissipating offshore. High pressure will return for the latter
half of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, a large ridge will extend across the Central United
States while a trough shifts off the Northeast and Mid-Atlantic
coast by late morning. At the sfc, a cold front will be forced south
across the local area as the mid-upper trough advances further
offshore, encountering a very moist environment and spawning
numerous to widespread showers/thunderstorms locally heading into
peak diurnal heating hours. PWATs around 2.50 inches and slow storm
motions along/ahead of the slow moving front could produce rounds of
heavy rainfall this afternoon into early evening hours, particularly
across coastal areas where moisture convergence and forcing are
enhanced for a few to potentially several hours. Given a concern for
prolonged rainfall in a favorably moist environment along with
guidance (HREF in particular) trending slightly higher in regards to
rainfall totals, a Flood Watch will remain in effect from noon
to 9 PM for much of the area, with a focus for greatest concern
being urban areas closer to the coast. Rainfall amounts of 2-4
inches should be common along with the potential for localized
amounts up to 5-6 inches, especially near the coast. However,
high rainfall rates will bring some concern for flooding across
locations away from the coast as well, primarily along and east
of the I-95 corridor. In fact, recent guidance continues to
suggest the cold front to slowly push south across the local
area this afternoon, then begin to stall across southern areas
late. Should this occur, there will be an increasing concern for
flooding across the Allendale County, SC to Tattnall County, GA
stretch where roughly 2-4 inches of rainfall fell the previous
evening/night. Should this scenario unfold, the Flood Watch
could need to be extended across all counties.

Outside of heavy rainfall, there remains a Marginal Risk for severe
weather across the local area. Although widespread convection could
limit the potential for stronger and/or severe thunderstorms today,
there is a limited concern for stronger convection to occur across
southern areas (southeast Georgia) later today where a longer
duration of strong sfc heating takes place south of the arriving
front and before anticipated showers/thunderstorms. DCAPE is not
particularly impressive late day, but clusters of thunderstorms
should eventually progress south and encounter an environment marked
by SBCAPE around 2500 J/kg and weak 0-6 km bulk shear. In this area,
a few thunderstorms could produce damaging wind gusts.

The combination of high temps in the lower 90s and sfc dewpts in the
mid-upper 70s will also lead to heat indices approaching 103-107
this afternoon, but given the likelihood of widespread showers and
thunderstorms, conditions should remain shy of Heat Advisory
criteria.

Tonight: By mid evening, convection will trend weaker and wane
overnight, although some showers and thunderstorms could persist
across far southern areas should the front stall and/or linger
nearby prior to daybreak. A northeast wind post fropa and previous
shower/thunderstorm activity will lead to noticeably cooler low
temps. In general, lows will range in the upper 60s/lower 70s well
inland to mid-upper 70s near the beaches.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
A stalled front will linger just off the coast and to the south near
the Altamaha on Tuesday. The front is expected to become more
diffuse through the day on Wednesday. Aloft, a mid level ridge
centered over the Gulf coast states will expand over the local area
with time as troughing offshore shifts further away. Scattered to
numerous showers and thunderstorms will be possible each day, with
highest coverage over southeast Georgia where deeper moisture of
PWats >2 inches is expected to still reside. Locally heavy rainfall
is possible. Areas further inland and to the north should not see as
much activity. There will be notable relief from the heat,
especially on Tuesday when highs only peak in the mid 80s. Lows both
nights will mainly be in the low to mid 70s.

Atlantic high pressure will prevail on Thursday, while a trough of
low pressure develops inland. Upper ridge settling overhead will
help limit convection with just isolated to scattered showers and
thunderstorms possible with the sea breeze. Temperatures will rise
back up to the low to mid 90s, but heat indices should remain in
check below headline criteria (peaking 100-105F).

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Strong upper level ridge initially overhead will transition offshore
through the weekend. The surface will feature troughing inland and
high pressure offshore. Main concern this period will be the heat.
The pattern will favor increasing temperatures and humidity. Some
interior locations could even see max temperatures hit triple
digits. Excessive heat headlines are certainly possible. Otherwise,
isolated to scattered diurnally-driven showers and thunderstorms are
expected.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
KCHS/KJZI/KSAV: Lingering showers across southeast Georgia and newly
developed showers near the CHS/JZI has led to TEMPO MVFR cigs/vsbys
being included between 06Z-08Z tonight. VFR conditions should then
return late tonight and persist into late morning hours. However,
the next chance for convection and prolonged flight restrictions
will occur Monday afternoon as a cold front slowly moves over and/or
stalls across the area. Showers and thunderstorms, some possibly
moderate to heavy rain producers, are expected to impact all
terminals by 19Z Monday, then persist for at least a few hours into
early evening. TSRA remains at all terminals during this time frame,
followed by SHRA Monday evening. Tempo IFR cigs/vsbys are possible
during thunderstorms and will likely be added in future TAF
issuances as timing of direct impacts becomes more clear. Precip
should come to an end by 03-04Z Tuesday, but flight restrictions
will remain at all terminals for at least MVFR cigs through 06Z
Tuesday.

Extended Aviation Outlook: Flight restrictions in low clouds could
linger into Tuesday. Otherwise, brief flight restrictions are
possible in showers and thunderstorms, mainly in the afternoon and
evenings through the period.

&&

.MARINE...
Today and Tonight: A cold front will shift south across the area
this afternoon with east-northeast winds prevailing in its wake
tonight. Widespread showers and thunderstorms could also reduce
vsbys across local waters to 1 NM of less at times and produce gusty
winds, some of which could necessitate Special Marine Warnings.
There will be a bit of a post-frontal surge tonight with speeds
increasing to 15-20 kt over the South Santee to Edisto Beach
nearshore leg with 10-15 kt elsewhere. Seas should also build
upwards to 3-5 ft tonight (highest across Charleston County
waters).

Tuesday through Saturday: Gusty northeast winds are expected on
Tuesday in between high pressure inland and a stalled front
offshore, especially across the Charleston county waters. Conditions
look to hold below small craft advisory criteria. Gradient weakens
for mid to late week with winds 15 knots or less and seas averaging
2-3 ft.

&&

.CLIMATE...
Daily Rainfall Records for July 1:
KCHS: 2.66 set in 1948
KCXM: 1.64 set in 1966
KSAV: 2.76 set in 1871

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Flood Watch from noon EDT today through this evening for
     GAZ101-116>119-137>141.
SC...Flood Watch from noon EDT today through this evening for
     SCZ042>045-047>052.
MARINE...None.

&&

$$

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