168
FXUS62 KCHS 241316
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
916 AM EDT Mon Jun 24 2024

.SYNOPSIS...
High pressure will remain over the western Atlantic this week
while occasional surface troughing prevails over the Southeast.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: The forecast is mostly on track. Another hot day is
expected with highs expected to peak in the mid-upper 90s away
from the coast. Dewpoints are expected to mix out across the
interior, but will pool back into the mid-upper 70s near/behind
the sea breeze as it moves inland later this afternoon. Expect a
ribbon of heat indices around 108 to occur across parts of
Beaufort County and points south along the Georgia coast where a
Heat Advisory is currently valid Noon until 6 PM. Scattered
convection is expected to form by early afternoon across the
interior which will spread east to the coast through the
afternoon hours. It is very possible that storms could cool off
some spots across the Heat Advisory area before reaching the 108
criteria, so some portions of the advisory may be cancelled
early. This was one reason why the advisory was not expanded
into Charleston County since convection is timed to reach that
area prior to the time of max heating. This will be closely
monitored throughout the day.

Scattered showers and tstms are expected to impact much of the
area this afternoon as a surface trough to the northwest
approaches. A few of these storms could be strong to marginally
severe with damaging winds and frequent cloud-to-ground
lightning being the primary hazards.

Tonight: Initial showers/thunderstorms will move off the coast
by early evening. But of note, recent high-res guidance runs
show another cluster of showers/storms developing across the
Midlands late this afternoon along the stalling surface trough,
then advancing down through portions of southeast South Carolina
this evening and off the coast overnight. Will see how that
plays out, but forecast will hold on to showers/thunderstorm
chances through the evening into early overnight, particularly
for southeast SC. Lows largely in the middle 70s anticipated,
warmer at the beaches.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Tuesday: Mid-level troughing initially offshore will shift away as
time progresses. Meanwhile, broad High pressure centered over the
Southern Plains tries to make its way towards our region. But it`s
not expected to make much progress. A weak cold front should be
located across our far inland counties or just north of them at
daybreak. It`s forecasted to slowly shift southward during the day,
moving across our area. After briefly transitioning to a stationary
front over our area, it should reverse direction and head back to
the north during the evening and overnight while weakening. The
front will keep the highest PWATs south and offshore of our area.
But they could still exceed 1.75" closer to the coast, which is a
bit above normal for this time of year. The heat will be the main
concern due to 850 mb temperatures, low-level thickness values, and
compression near the front. Highs are expected to reach the mid to
upper 90s across most of our area, except cooler at the beaches. Dew
points well into the 70s near the coast will cause heat indices to
rise to ~106 degrees, which is just short of Heat Advisory criteria.
Afternoon convection is expected with the front and afternoon sea
breeze as forcing mechanisms. The models differ on the convective
coverage. The synoptic models point towards isolated coverage while
the long-range CAMs point towards scattered or greater coverage.
Given the setup and time of year, we leaned heavily with the long-
range CAMs. MLCAPEs should approach 2,000-2,500 J/kg across portions
of our area with some shear. With DCAPEs exceeding 1,000 J/kg, a few
marginally severe storms with damaging winds are possible just about
anywhere. Additionally, there will be the potential for locally
heavy rainfall underneath the thunderstorms due to weak steering
flow and the potential for training. Convection should quickly
decrease during the evening, with the overnight being mainly dry.
Lows will be in the 70s.

Wednesday: The mid-levels will consist of troughing developing over
the East Coast. At the surface, a weak stationary front should be
located to our west and north at daybreak. It`s forecasted to
dissipate into the afternoon. Though, surface troughing should
remain in place across our region. A cold front should approach from
the northwest overnight. Though, it`s not expected to reach our area
during that time frame. Higher PWATs should gradually creep into our
area as time progresses, especially along the coast. Similar to
Tuesday, high temperatures are expected to reach well into the 90s
for most areas. Dew points well into the 70s near the coast will
cause heat indices to rise to ~106 degrees, which is just short of
Heat Advisory criteria. Afternoon convection is expected with the
sea breeze. Though, the synoptic models point towards isolated
coverage, which may be underdone. Scattered coverage seems more
reasonable given the setup and time of year. Instability, DCAPEs,
and sheer should be similar to Tuesday, so a few marginally severe
storms with damaging winds can`t be ruled out. Additionally, there
will be the potential for locally heavy rainfall underneath the
thunderstorms due to fairly weak steering flow and the potential for
training. Convection should quickly decrease during the evening,
with the overnight being mainly dry. Lows will be in the 70s.

Thursday: Mid-level troughing initially over the East Coast will
shift offshore. A cold front located to our northwest at daybreak
should slowly move across our area later in the day. There will be a
plume of deep moisture ahead of the front. Forcing from the front
and afternoon sea breeze are expected to generate convection.
Though, the coverage will depend on how much instability is in place
and the amount of shear. So this aspect of the forecast will need to
be adjusted. Similar to the previous two days, high temperatures are
expected to reach well into the 90s for most areas. Dew points well
into the 70s near the coast will cause heat indices to rise as high
as 108-110 degrees along the coast, which could prompt Heat
Advisories. But they may be brief as the convection would quickly
cool temperatures.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Mid-level troughing initially over the East Coast will eventually
transition to ridging over the Southeast U.S. by the weekend.
Surface troughing or weak fronts will be impacting the Southeast
U.S. while High pressure is near Bermuda. This summertime pattern
will yield diurnal convection. The highest POPs are each afternoon
and evening, then trending lower overnight. High temperatures will
be well into the 90s each day. Additionally, heat indices could
approach 108 degrees along the coast each day.

&&

.AVIATION /13Z MONDAY THROUGH FRIDAY/...
VFR conditions will prevail at CHS/JZI/SAV terminals through
12Z Tuesday. However, tempo MVFR cigs/vsbys can not be ruled
out this afternoon through this evening as a trough pushes
through the region with showers and/or thunderstorms that
potentially impact the terminals. Confidence in timing/duration
of the event remains low at this juncture and latest forecast
will feature VCSH in the forecasts after 18Z.

Initial round of showers/storms move off the coast early this
evening. However, another round of showers and/or thunderstorms
may roll through the southeast South Carolina counties during
the evening hours. Again, confidence in timing/duration remains
low and will not be included with the 12Z forecasts.

Extended Aviation Outlook: Mostly VFR. However, convection will
bring brief flight restrictions, mainly each afternoon and
evening.

&&

.MARINE...
Through tonight: An enhanced pressure gradient across southeast
coast is producing rather stout southwest flow across the
coastal waters early this morning, with winds running 15 to 20
knots and gusts 20 to 30 knots, including Charleston Harbor.
Thus, Small Craft Advisories have been expanded into all SC
nearshore zones including Charleston Harbor until 11 AM. Winds
appear to be a little weaker in the Georgia coastal waters with
a Small Craft Advisory for the outer waters still valid through
8 AM.

Winds and seas should diminish late morning and through the
afternoon, but later shifts will need to assess whether or not
headlines need to be extended.

Tuesday through Friday: A typical summertime pattern is
expected with High pressure in the western Atlantic and
occasional surface troughing over the Southeast. Each day,
expect gradually backing winds. They`ll be strongest along the
land/sea interface and the Charleston Harbor with the formation
of the afternoon sea breeze. Each night, winds will gradually
veer, possibly surging closer to the coast. Seas will average
2-4 ft.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory from noon today to 6 PM EDT this evening for
     GAZ117-119-139-141.
SC...Heat Advisory from noon today to 6 PM EDT this evening for
     SCZ048-051.
MARINE...Small Craft Advisory until 11 AM EDT this morning for AMZ330-
     350-352-374.

&&

$$