905
FXUS62 KCHS 131802
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
202 PM EDT Mon May 13 2024

.SYNOPSIS...
A storm system will bring active weather through Wednesday.
High pressure will build in late week before another storm
system moves through this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Extensive high cirrus along with some mid-level cloudiness
continues to overspread the forecast area this morning out ahead
of a developing upper trough across the central U.S. Weak moist
isentropic ascent will lift north through the area, bringing
scattered light to moderate rain to the area. Later this
afternoon, somewhat greater coverage and intensity of showers
and thunderstorms should move through southeast GA in
association with a convective complex driven by Gulf Coast
shortwave. The cloud cover will limit instability so we are not
concerned about severe weather today.

Tonight: The overall convective trend of upstream thunderstorms
could play a large role in precip chances across southeast South
Carolina and Southeast Georgia, at least during evening hours. Given
latest model trends, precip chances have been lowered to 40-50%
during evening hours. However, there should be an uptick in precip
coverage and thunderstorm potential during the second half of the
night as isentropic ascent increases along/ahead of a warm front
lifting north into the region approaching daybreak while h5
shortwave energy continues to traverse the Southeast along the
eastern edge of the mid-lvl trough to the northwest. Numerous to
widespread showers and scattered thunderstorms could impact the
local area by a few hours prior to daybreak, and a few stronger
thunderstorms can not be ruled out with increasing instability
locally as the warm front shifts north into the area.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
To start on Tuesday a mid-level trough will be positioned over the
central Mississippi Valley. This trough will then trek eastward
towards the Mid-Atlantic states into Wednesday, pushing off the East
Coast on Thursday. At the surface a warm front will be to the north
of the forecast area on Tuesday, with a cold front pushing through
later on Wednesday. High pressure will briefly build into the region
on Thursday.

The most active part of the forecast is Tuesday, with numerous
showers likely ongoing to start the morning. There is significant
uncertainty in how the precipitation coverage is going to evolve
through the day, but most guidance points to the heaviest rainfall
remaining offshore. However, it is possible that some of the heavy
rainfall could impact the immediate coastline, especially the SC
coastline. Generally around 1 to 1.5 inches is expected over the
forecast area, with some locations around 2 inches in Charleston and
Berkeley Counties. An additional point of uncertainty is the
convective evolution throughout the day on Tuesday. Models are not
in agreement regarding the amount of instability. The forecast
includes mention of a chance of thunder, as shear values are
impressive and only a little bit of instability would likely trigger
a thunderstorm. While the overall severe threat remains low, a
strong storm cannot be ruled out. Thick cloud cover on Tuesday will
yield high temperatures only in the upper 70s to low 80s.

Precipitation will shift offshore Tuesday night, leaving only some
lingering showers Wednesday and Wednesday night. Temperatures on
Wednesday will likely reach into the mid to upper 80s. All
precipitation should clear the forecast area by Thursday morning
with clearing skies and highs in the mid to upper 80s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Zonal flow will develop aloft on Friday, with a shortwave poised to
ripple through into Saturday. Broad ridging will then build in for
the remainder of the weekend. An active weather pattern is expected
Friday and Saturday, as showers and thunderstorms associated with
the passing shortwave aloft and surface cold front impact the
region. Temperatures through the period are expected to be above
normal.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
A warm front will lift north late tonight and Tuesday morning.
This afternoon and tonight, moisture and forcing north of the
front will spread occasional light rain showers over the
terminals. Most guidance shows the brunt of the afternoon
precipitation shifting off the coast by mid-evening, then mainly
dry for much of the overnight hours. The statistical guidance
seems particularly aggressive with lowering ceilings this
evening. We are leaning more toward the SREF which is more
optimistic in keeping the MVFR/IFR ceilings across the SC
Midlands through much of the night.

At least MVFR ceilings seem fairly likely shortly after
daybreak Tuesday as the warm front lifts north through the area.
There should also be a better chance for robust convection
during the day Tuesday, with occasional vsby restrictions as
well.

Extended Aviation Outlook: Showers and thunderstorms could bring
flight restrictions to the terminals from Tuesday into Wednesday
morning.

&&

.MARINE...
Today and Tonight: High pressure will linger across local waters for
much of the day, before shifting further offshore in advance of a
trough well inland. Expect marine conditions to remain quiet through
the afternoon with south-southeast winds slowly increasing mid-late
afternoon to around 10-15 kt. Seas will also slowly build during the
day, ranging between 1-2 ft across nearshore waters and 2-3 ft
across offshore Georgia waters. An uptick in winds and seas is
expected during the overnight period as a warm front slowly lifts
north late. South-southeast winds should approach 15-20 kt across
most waters after midnight, and could gust to 25 kt across Georgia
waters late. Seas will also build overnight, reaching 3-5 ft across
nearshore waters and 4-6 ft across offshore Georgia waters. A Small
Craft Advisory could eventually be needed across Georgia waters
starting late tonight.

Tuesday through Saturday: A warm front will be positioned to the
north of the marine waters on Tuesday, with SW winds 15 knots with
gusts to 20 knots. Seas should average 4 to 6 ft across the
Charleston County nearshore waters and the 20 to 60 nm offshore GA
waters. A Small Craft Advisory may be required Tuesday afternoon
into Wednesday. Seas 3 to 5 ft elsewhere. A cold front is forecast
to push through the region overnight Wednesday into Thursday, with
winds shifting from the SW to the NW, remaining around 15 knots.
Seas will continue to diminish, with 2 to 3 ft forecast on Thursday.
Friday and into the weekend SW winds around 10 knots and seas 2 to 3
ft will prevail.

&&

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

&&

$$

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