-- Discussion containing changed information from previous version are highlighted. --
006
FXUS62 KCHS 150546
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
146 AM EDT Wed May 15 2024

.SYNOPSIS...
A cold front will move through late Wednesday, followed by high
pressure into Friday. A storm system will affect the area this
weekend, followed by high pressure from the north next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
A southwest flow will maintain a moist, but marginally unstable
environment across the local area overnight well in advance of a mid-
upper level trough positioned to the northwest of the region.
Within this environment, isolated to scattered showers and
thunderstorms are possible for the remainder of the night while
weak h5 shortwave energy traverses the Carolinas. Unidirectional
wind fields will remain rather enhanced through much of the
night as well, with at least 50-60 kt wind speeds expected at
the 500 mb level and an upper lvl jet core passing aloft. These
winds could promote some organization to a few thunderstorms
that develop over the course of the night within an environment
displaying SBCAPE around 1000-1500 J/kg. A few stronger
thunderstorms can not be ruled out given the setup with strong
wind gusts being the primary concern.

Late tonight there are indications that convection will form along a
baroclinic zone across Florida, and also in advance of a h5 shortwave
approaching form the northwest in the trough aloft. This could
require some fine-tuning to the forecast, but for now we still
have no more than scattered PoPs.

If we get enough clearing of the mid and high level clouds, there
will be the formation of low stratus overnight. But not enough to
cause any major reduction in visibilities given too much mixing in
the planetary boundary layer. Lows tonight will only be down in the
mid 60s to lower 70s given mostly cloudy skies, a southwest flow,
and elevated dewpoints.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/...
Low and mid level flow will become westerly on Wednesday as a
broad shortwave trough moves into the Carolinas. Downslope flow
and subsidence will result in a warm day with highs in the mid
to upper 80s. Fairly deep mixing should bring drier air aloft
down to the surface, with surface dewpoints mixing down into the
low 60s inland. For much of the day, there doesn`t look like
there will be enough forcing or moisture to support precip.
However, late in the afternoon into the evening, the main
shortwave will pass to the north, pushing a weak cold front
through the area from the northwest. Models show a slight uptick
in PWATs and SBCAPE across our northern zones ahead of the
front, so scattered showers and thunderstorms could develop as
the front drops through late Wednesday. Given the 35 kt bulk
shear values and decent instability, it`s not out of the realm
of possibility that we could see isolated severe thunderstorms
across southern SC, particularly north of Beaufort. Damaging
winds appear to be the main concern, though large hail would
also be possible.

Dry high pressure will build in for Thursday with highs
reaching the mid to upper 80s. Friday also looks warm, though
moisture should start to increase during the day as a southerly
flow develops. A shortwave moving in from the west late in the
day could spur scattered showers and thunderstorms.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Several potent upper shortwaves will move through Saturday
through Monday, likely bringing several rounds of showers and
thunderstorms. Drier high pressure may rebuild on Tuesday.
Temperatures will remain a couple degrees above normal.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
KCHS/KJZI/KSAV: VFR conditions are expected at CHS/JZI/SAV terminals
through 09-10Z Wednesday, but low stratus should develop across the
terminals for a few hours thereafter, resulting in MVFR cigs between
10-13Z at CHS/JZI and 09-13Z at SAV. A brief period of IFR cigs can
not be ruled out during this same time frame, but confidence remains
too low to include in the latest TAF issuance. VFR conditions are
expected to return at all terminals by late morning Wednesday, but
gusty west-southwest winds around 20 kt are anticipated during much
of the afternoon.

Extended Aviation Outlook: Occasional flight restrictions possible
Saturday through Sunday in scattered showers and tstms.
-- End Changed Discussion --

&&

.MARINE...
Tonight: A south to southwest flow will prevail between low
pressure centered across the Ohio River Valley and high
pressure centered near Bermuda. This will allow for winds to
reach as much as 15 to 20 kt. Seas will mainly be in the range
of 3 to 5 feet, although some 6 footers will continue over the
outermost parts of the Charleston County waters for much of the
night. Because of this we have a Small Craft Advisory in effect
through 6 AM.

SW winds on Wednesday should turn to the W Wednesday night
through Thursday after a cold front moves through. Southerly
flow briefly returns late in the week as high pressure builds
over the western Atlantic. Conditions expected to remain below
advisory thresholds, although Charleston Harbor might get close
to advisory levels Wednesday afternoon, depending upon how warm
it gets.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 6 AM EDT early this morning for
     AMZ350.

&&

$$

NEAR TERM...DPB
SHORT TERM...JRL
LONG TERM...JRL
AVIATION...DPB
MARINE...DPB