721
FXUS62 KCHS 301149
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
749 AM EDT Sun Jun 30 2024

.SYNOPSIS...
Atlantic high pressure will prevail today, while a trough of
low pressure resides inland. A cold front will impact the area
Monday into Tuesday before dissipating offshore. High pressure
will return for the latter half of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, a ridge will extend across the Deep South and
Southeast United States, but gradually weaken mid-late afternoon
with the arrival or a pronounced h5 shortwave from the west-
northwest. At the sfc, high pressure extending across the western
Atlantic and to Florida will gradually shift south-southeast,
allowing a trough across the Midlands to nudge closer the local area
late afternoon into early evening. Ahead of the h5 shortwave and sfc
trough warm and humid conditions will be in place. Latest 1000-850
mb thicknesses support high temps in the low-mid 90s away from the
beaches, and with a light downslope wind aloft in place, should
suppress shower and thunderstorm development initially through late
morning hours. However, ample sfc heating and low-lvl moisture
driven onshore favor afternoon showers/thunderstorms away from the
immediate beaches, with a focus along/near a sea breeze circulation
initially, followed by far inland areas with the arrival of the h5
shortwave from the west-northwest late day. A few thunderstorms
could become strong and/or marginally severe as the h5 shortwave
encounters an environment displaying SBCAPE around 2500 J/kg, PWATs
around 2.25 inches, but weak 0-6 km bulk shear. Damaging wind gusts
and brief heavy downpours remain the primary concern for locations
across far inland southeast South Carolina late day into early
evening.

Even before convection occurs today, temps in the low-mid 90s along
with sfc dewpts in the mid-upper 70s will support heat indices in
the 105-109 range for at least a few hours across much of the area.
As a result, a Heat Advisory will be in effect from noon to 7 PM
today for all southeast South Carolina counties and a few counties
across southeast Georgia along the I-95 corridor. The exception
remains across areas well inland in southeast Georgia, where
strongest low-lvl mixing occurs and lowers dewpts during peak
heating hours. Shower and thunderstorm activity will also play a
significant role in relief from the heat mid-late afternoon into
early evening, but latest guidance suggests the bulk of convection
to occur after peak heating is achieved early-mid afternoon.

Tonight: The h5 shortwave will continue to advance across the local
area overnight, likely promoting few to scattered showers and
thunderstorms through about midnight, potentially longer across
southeast South Carolina. However, activity will likely show signs
of weakening by mid evening due to the loss of diurnal heating and
mostly weak shear in place. Conditions will remain mild and humid
once again. In general, low temps should range between the mid 70s
inland to upper 70s/around 80 closer to the coast.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
Monday will be the most active day of the set. A cold front will
sink into the area and eventually stall in the vicinity later in the
day and Monday night. The airmass will be quite juicy ahead of the
front with anomalously high precipitable water values exceeding 2.25
inches in many spots. Numerous to widespread showers and
thunderstorms are expected to impact the area late morning into the
evening, generally over the northern zones first and then moving
further south with time. Current forecast rainfall totals Monday
through Monday night average 1-2 inches across the eastern half of
the forecast area, with some pockets of 2-3 inches. It is worth
noting that latest HREF guidance does show probabilities for 3
inches or greater in spots. This could produce localized flooding
especially in urban and poor drainage areas. Elsewhere, further
inland, totals are less than an inch. Organized severe weather is
not anticipated, however isolated instances of damaging wind gusts
will be possible in strongest storms. SPC maintains the area within
a Marginal risk of severe weather. With anticipated cloud cover and
convection, temperatures will not be as hot as previous days. Highs
will range from the upper 80s to lower 90s, warmest near the
Altamaha. Convection could still percolate Monday night, but highest
rain chances eventually become more focused over the coastal waters.

High pressure will ridge south into the area on Tuesday, while a
stalled front lingers near the coast and across far southern
Georgia. Scattered to numerous showers and thunderstorms will be
possible, with best coverage across southeast Georgia where deepest
moisture of PWats >2 inches still resides. It will be notably cooler
with highs largely in the mid 80s. Lows Tuesday night will range
from the upper 60s inland to mid/upper 70s closer to the coast.

The front will largely wash out on Wednesday, with high pressure
returning as the primary feature. Shower/thunderstorm chances remain
in the forecast with again the highest coverage appearing to be over
southeast Georgia. Highs will mainly be in the upper 80s to low 90s.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
Strong mid level ridge will build over the Southeast for late week
into the weekend. At the surface, high pressure will reside offshore
with a trough of low pressure inland. Isolated to scattered showers
and thunderstorms will be possible each day, mainly in the afternoon
and evenings, driven primarily by mesoscale boundaries such as the
sea breeze. Perhaps the bigger story will be the heat. The synoptic
pattern favors increasing temperatures and humidity. Current
forecast indicates a potential need for excessive heat headlines for
Friday and Saturday.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
VFR conditions will prevail at CHS/JZI/SAV terminals through 12Z
Monday. However, showers/thunderstorms should develop across the
region mid-late Monday afternoon, and could produce MVFR conditions
temporarily at CHS and SAV terminals between 1930Z Sunday to 00Z
Monday, with a late day/early evening arrival becoming more likely.
VCTS remains at both terminals to account for late afternoon and
early evening convection, but will likely need to be refined in
future TAF issuances. VCSH has also been introduced at CHS after 00Z
Monday as trends indicate additional showers (and potentially
thunderstorms) arriving late evening. Gusty winds will also be
possible should activity directly impact the terminals.

Extended Aviation Outlook: Widespread shower/tstm impacts are
possible Monday afternoon/evening at all terminals. Otherwise, brief
flight restrictions are possible in showers and thunderstorms,
mainly in the afternoon and evenings through the period.

&&

.MARINE...
Today and Tonight: Local waters will remain nestled between high
pressure across the Atlantic and an inland trough. The pressure
gradient between these two features should favor a slight uptick in
south-southwest winds through the period, around 15 kt at times,
highest near the coast when a sea breeze takes shape during the
afternoon and perhaps into late evening hours with some nocturnal
surging. Seas will be no higher than 2-3 ft.

Monday through Friday: Southerly flow initially will turn northeast
and easterly as a cold front sinks into the area later Monday into
Tuesday. Speeds increase a bit, but conditions still stay below
Small Craft Advisory criteria. Winds will eventually turn southerly
again late week as Atlantic high pressure returns. Seas through the
period average 2-3 feet, except they could build as high as 4-5 ft
Tuesday behind the front. Widespread showers/tstms will impact the
waters Monday, possibly reducing vsbys to 1 NM or less at times.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory from noon today to 7 PM EDT this evening for
     GAZ101-116>119-137>141.
SC...Heat Advisory from noon today to 7 PM EDT this evening for
     SCZ040-042>045-047>052.
MARINE...None.

&&

$$

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