504
FXUS62 KCHS 150216
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1016 PM EDT Tue May 14 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 WEDNESDAY MORNING/...
Local radars showing isolated shower and t-storm activity
within a very moist southwest flow in advance of strong mid and
upper level trough moving through the Tennessee Valley. In
addition, there is at least 50-60 kt of winds at 500 mb and 90
kt or greater at 250 mb that occur in tandem with each other.
These conditions along with MLCAPE near 1000 J/kg will still
support slight chance/chance PoPs the first part of the night.

Later tonight there are indications that convection will form
along a baroclinic zone across Florida, and also in advance of
a short wave 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.

The low temperature at KCHS Tuesday has been 71F so far, which
for the time being has tied the record high minimum temperature
for the date. 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 WEDNESDAY 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 /02Z WEDNESDAY THROUGH SUNDAY/...
KCHS/KJZI/KSAV: We maintain VFR conditions at all sites through
00Z Thursday, although there are concerns that flight
restrictions can occur in low stratus late tonight into
Wednesday morning. Guidance shows two entirely different
solutions; one with IFR ceilings and the other with VFR
ceilings. So we split the difference at went MVFR at the sites
between 08Z and 13Z.

Isolated to scattered SHRA/TSRA will be in the area later
tonight and Wednesday. But with such a low probability of a
direct impact on any site, we opted not to carry any mention at
this time.

All terminals will experience SW wind gusts as high as near 20
kt at times Wednesday afternoon with a somewhat tight gradient
in advance of a weak cold front, supplemented by deep mixing.

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

&&

.MARINE...
Tonight: A S to SW flow will prevail between low pressure in
southern Indiana and northern Kentucky, and high pressure
centered near Bermuda. This will allow for winds to reach as
much as 15 or 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. Because of this we have a
Small Craft Advisory in effect through 1 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 1 AM EDT Wednesday for AMZ350.

&&

$$

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