275
FXUS62 KCHS 121149
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
749 AM EDT Mon Aug 12 2024

.SYNOPSIS...
A stationary front will remain just to the west through Tuesday
before dissipating. Weak high pressure will build in from the
north during the middle of the week and prevail into the latter
part of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Stalled boundary remains draped through the eastern and central
Carolinas into central Georgia with high PWAT/dewpoint air
lingering along the southeast coast. Surface boundary may make
some push toward the southeast coast through tonight, spurred
on by expanding surface high pressure from the Upper Midwest
across the Ohio and Tennessee Valleys. But very warm and humid
conditions will continue through today before slightly cooler
and less humid air tries to press into the region through
midweek.

Today: Once again, daytime heating will quickly drive
temperatures into the lower 90s by noon, topping out in the
lower to middle 90s for highs this afternoon along with MLCAPE
values building to 1500-2500 J/Kg, perhaps a little lower
across southeast Georgia as some lower dewpoint air tries to
wrap into southeast Georgia. Similar to the last few days,
light southwesterly low level flow will promote an active sea
breeze developing and pressing inland through the afternoon.
Should be enough to kick off shower/thunderstorm development
early this afternoon with the greatest coverage of convection
anticipated across the SC Lowcountry where low level convergence
will be maximized and higher dewpoint air/instability will
reside. Morning forecast will continue to advertise isolated to
scattered showers/storms through the afternoon, with the highest
precip chances across the southeast SC quad-county area.

Organized severe weather threat remains low. But given the high
instability and DCAPE values around 1000 J/Kg, a few strong
storms will again be possible. Of course the bigger concern
rests with our ongoing hydro issues as any storms will be
capable of producing localized heavy rainfall on top of already
wet grounds and elevated river levels. Much of the forecast
area remains in a marginal risk for excess rainfall exceeding
flash flood guidance. Meanwhile, Areal Flood Warnings and Flood
Advisory remain in effect through early to mid-morning due to
lingering flooding issues/elevated rivers and will be
reevaluated later this morning.

Meanwhile, high surface dewpoints and temps warming into the
lower to middle 90s (90-95F) will again push Heat Index values
toward or exceeding Heat Advisory criteria along the coastal
corridor. Given the anticipated greater coverage of convection
across the quad-county area and the impact on temps, not as
confident that heat index values will attain advisory criteria,
or at least not for an extended period of time. More confident
further south from Beaufort County to the Altamaha, with lower
coverage of convection anticipated and a Heat Advisory has been
issued for those locations valid from noon until 6 pm.

Tonight: Convection will diminish through the evening hours
with quiet conditions overnight. Lows will dip back into the
upper 70s to around 80.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Tuesday: A weak surface front and area of low pressure across the
Midlands will meander across the area through the day. A trough
across the Northeast and Mid-Atlantic states will dig into the
Southeast late which will push those surface features southward.
Low-level convergence near the front, in addition to the sea breeze,
will be enough to support at least scattered showers and
thunderstorms during the afternoon and evening. Guidance favors
southeast South Carolina for the greatest coverage with conflicting
coverage across southeast Georgia. The forecast reflects at least
slight chance POPs across our southern zones considering PWATs in
that area will be around 1.7 inches. With plenty of instability, we
can`t rule out a stronger storm or two, especially where boundary
interactions occur. However, the overall severe threat will be low.
Also, some storms could produce locally heavy rainfall. Given that
ground conditions are wet and some areas are still experiencing
flooding, there is little to no tolerance for additional rainfall.
Therefore, any thunderstorm that develops will have the potential to
quickly produce flooding issues. High temperatures are forecast to
reach the low to mid 90s and overnight lows will be in the low to
mid 70s away from the coast.

Wednesday: A trough across the Northeast and Mid-Atlantic states
will continue to dig into the Southeast, helping to nudge the
aforementioned weak front offshore. Models suggest a very narrow
swath of deep moisture passing over the area associated with the
front, in addition to upper forcing, which will again bring at least
scattered convection during the afternoon/evening hours. Wednesday
will be touch cooler with highs in the upper 80s across our
southeast South Carolina counties and low 90s for our southeast
Georgia counties. Min temps will largely bottom out in the low to
mid 70s with some inland spots in the upper 60s.

Thursday: Weak high pressure will begin to build in from the north,
along with relatively drier and cooler conditions. This will keep
rain chances to a minimum. The current forecast features slight
chance to chance POPs, which may even be overdone. Highs are

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Weak high pressure will linger for a day or two before a cold front
quickly approaches. This will result in lesser chances of diurnal
convection during the weekend. The front could pass over the
forecast area early next week, which could lead to higher rain
chances. Temperatures should rise a degree or so each day with highs
back into the low 90s this weekend, around near-normal for this time
of year.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Isolated to scattered showers and thunderstorms are possible
again this afternoon along the sea breeze with high-res
guidance suggesting the higher precip chances will be at CHS.
12Z terminal forecasts will include VCSH for the CHS terminal
after 19Z. No mention for JZI and SAV for now.

Any showers/storms will diminish through the evening hours with
VFR conditions persisting overnight.

Extended Aviation Outlook: Brief flight restrictions are possible in
afternoon and evening showers/thunderstorms through the period.

&&

.MARINE...
Today: Southwest winds continue across the coastal waters today
with winds trending a bit more southerly this afternoon with the
sea breeze. Sustained winds of 10 to 15 kts with some higher
gusts. Seas should generally range between 2 to 3 ft in a mix
of southeasterly medium period swell and southerly wind chop.

Tuesday through Saturday: A deep offshore ridge will result in
southwest flow around 10 kt or less Tuesday. Wednesday afternoon,
high pressure will begin gradually build in from the north after a
weak front departs southward which will cause winds to shift out of
the northeast. Seas will average 2-3 feet; however, by the end of
the week seas will start to rise as increasing swell arrives from
what could be a strengthening tropical system over the open
Atlantic. Small Craft Advisories could be needed for a portion of
the marine zones for 6 ft seas.

&&

.HYDROLOGY...
Most of southeast Georgia and southeast South Carolina remains
quite vulnerable to additional rainfall following the 10-20
inches of rain that fell last week. Many areas are still
experiencing ongoing flooding, and any additional rainfall from
thunderstorms will certainly not help conditions improve.
Scattered to numerous thunderstorms are forecast each afternoon
and evening through midweek, and any locally heavy rainfall
could produce new areas of flooding.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory from noon today to 6 PM EDT this evening for
     GAZ116>119-137>141.
SC...Heat Advisory from noon today to 6 PM EDT this evening for
     SCZ047>049-051.
MARINE...None.

&&

$$