579
FXUS62 KCHS 140405
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1205 AM EDT Sun Jul 14 2024

.SYNOPSIS...
A weak front will meander across the area into tonight.
Atlantic high pressure will then rebuild across the area while
a surface trough exists inland Sunday through the middle of
next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
No major changes were made for the midnight update. There is a
weak signal in some of the near term guidance that isolated
showers/tstms could pop along parts of the Charleston County
coast just before daybreak as a weak land breeze develops.
Slight chance pops were introduced in this area to account for
this given the warm/moist airmass that is in place. The rest of
the forecast is on track.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
The region will remain on the west side of a deep layer ridge,
centered well to the east-southeast over the Atlantic. This will
keep southerly low level flow, which will become onshore each
afternoon near the coast. Given the lack of any significant upper
level features, expect any afternoon/evening convection to be
initiated by the seabreeze, differential heating and/or convective
outflow boundaries. Model guidance has been trending a bit too high
with PoPs, especially in this pattern. So, have kept chance/high end
chance PoPs for afternoon into early evening. Light steering flow
and PWs around 2 inches will once again lead to the potential for
locally heavy rainfall, especially where multiple boundaries
collide.

Guidance temperatures also seem a bit high, but very difficult to go
too low given the deep ridge centered just to the southeast. Have
kept low to mid 90s. Amount of convective coverage will dictate high
temperature values. Lows will also continue to be very warm, in the
mid 70s to around 80, warmest near the coast. Max heat indices
through this period showing 105 to 109, which if they verify, would
be marginal Heat Advisory levels, especially along and east of I-95.
For the past several days, afternoon convection has made it
difficult to predict whether max Heat Indices will reach criterion
levels. Thus, stay tuned for the potential for Heat Advisories to be
issued during this period.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Models indicate that a broad upper level trough will develop over
the Great Lakes and TN River Valley, and sag southward through this
period. Further east, the deep layer Atlantic ridge should retreat
east-southeastward. With decreasing upper heights gradually working
into the region from the northwest, helping to pool deep layer
moisture/PWs of 2-2.5 inches, expect an increase in PoPs through the
period. However, still concerned that guidance/blended PoPs continue
to be a bit high, especially for this far out in the forecast
period. Have generally gone high end chance to very low end likely
PoPs, which is above climo for this time of year. Low level flow
should veer to south-southwest, which will likely help to keep the
afternoon seabreeze from moving as far inland as earlier in the
week. High temperatures slightly above normal, and could fall back
toward normal or even slightly below by late in the week, deepening
on amount of clouds/convection that develop. Given the very humid
low levels, still not much relief with the low temperatures, which
are expected to remain in the mid to upper 70s most areas.

&&

.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
14/06Z TAF Discussion:
KCHS/KJZI/KSAV: VFR. There are some weak signals that an
isolated shower/tstm could pop near the coast just before
daybreak as a weak land breeze develops. This could run in the
vicinity of KCHS and KJZI. Confidence is not high enough to
include a mention at this time. Otherwise, the risk for
isolated, afternoon showers/tstms is too low to include a
mention at any of the terminals this afternoon.

Extended Aviation Outlook:
Sunday night through Tuesday: More typical scattered afternoon
and early evening showers and thunderstorms could produce brief
flight restrictions, especially given storms will likely be slow
moving with the potential for locally heavy rainfall.

Wednesday and Thursday: Increasing chances precipitation, with
scattered to numerous afternoon showers/thunderstorms as an upper
trough of low pressure starts to advance toward the region from the
northwest.

&&

.MARINE...
Tonight: Light to moderate SW flow prevails with Bermuda High
ridging in from the west. Seas remain mostly 3-4 ft as medium
period SE swell very slowly fades.

Sunday through Tuesday Night: A deep layer Atlantic ridge will
remain centered well east-southeast of the waters. This will
maintain southerly flow at 15 knots or less and seas generally 2 to
4 feet. Winds could be locally stronger in the afternoon near the
coast with the seabreeze. Mostly late night through morning
scattered showers and thunderstorms.

Wednesday and Thursday: An upper level trough of low pressure starts
to advance toward the area from the northwest. As the Atlantic ridge
slowly retreats eastward, the pressure gradient could increase
during this period, with southwest winds 10-20 knots and seas 3 to 5
feet, highest beyond 20 nm. However, still not expecting conditions
to reach SCA levels. Mostly late night through early afternoon
scattered to numerous showers and thunderstorms.

&&

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

&&

$$