758
FXUS62 KCHS 181814
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
214 PM EDT Sat May 18 2024

.SYNOPSIS...
A storm system will bring impacts to our area this weekend.
High pressure returns to our region next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Since daybreak, a band of rain with rounds of thunderstorms has
streamed across the forecast area. The rain and thick cloud
cover has kept temperatures in the 70s, with a pocket of upper
60s across inland GA. The forecast area has been throughly
worked over, SPC mesoanalysis indicated a large pool of CIN of
200-400 J/kg across the CWA. A band of stratiform rain with
occasional lightning will persist into the late afternoon. The
risk for severe thunderstorms has passed, mention removed from
the HWO. Temperatures could rebound a few degrees, but likely
peaking in the 70s.

Tonight: Upper level trough settles into the region. The bulk
of showers/storms is looking to diminish and move off the
Atlantic Coast later in the afternoon into this evening, but
there may be some additional sub-severe convection that
percolates through the region through the course of the night as
the upper trough settles in.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
Sunday: A positively tilted mid-level trough will be over the
Southeast U.S. in the morning. It`ll slowly shift offshore into the
evening and overnight. Meanwhile, a ridge will build in from the
west. A cold front will be located just offshore in the morning, and
moving away as time progresses. Surface troughing is expected to
move over our region in the afternoon, then shift offshore into the
overnight. Deep moisture will remain in place across the region with
PWATs in the 1.5-2.0" range. These values are above the 90% mark per
SPC sounding climatology for CHS. They`re also about 2 standard
deviations above normal per NAEFS. With all of the moisture and lift
in place, models are in good agreement indicating scattered showers
in the morning increasing to numerous or widespread showers by the
afternoon. Temperatures should peak in the upper 70s or lower 80s,
limited by the aforementioned showers. This will also limit
instability. MLCAPE should peak around 1,500 J/kg, mainly across our
GA counties. Lapse rates won`t be that steep and 0-6 km bulk shear
may only peak in the 15-25 kt range, which is not that strong. So
while there should be some thunderstorms, the overall severe risk is
low. Locally heavy rainfall will be a bigger concern given the high
PWATs and slower storm motions. A relatively quick 0.5-1.0" is
possible, so we can`t rule out flooding in some areas. This could be
exasperated if soils are saturated from Saturday`s rainfall. Showers
will decrease in coverage and intensity from west to east during the
evening and overnight hours. Most locations should be dry by
daybreak Sunday, except maybe the immediate coast. Lows should range
from the upper 50s to the mid 60s.

Monday: The mid-levels will consist of a positively tilted trough
just off the Southeast U.S. coast in the morning, and a ridge just
to our west. The ridge will slowly build into our area as time
progresses. At the surface, High pressure centered well to our north
will build down the coast, with it`s southern periphery making its
way into our area. The High will bring drier conditions with skies
becoming mostly sunny/clear. Low-level thickness values support
temperatures in the middle 80s. But we went a little below this due
to the northeasterly surface winds and the expectation that surface
evaporation should limit temperatures. Highs should peak in the
lower 80s. Lows should range from the upper 50s far inland to the
mid 60s closer to the coast.

Tuesday: A positively tilted mid-level trough will be just off the
Southeast U.S. coast in the morning, while a ridge will prevail over
the Southeast U.S. High pressure centered just to our north in the
morning will shift off the Mid-Atlantic Coast as the day progresses.
Though, it`s southern periphery will continue to dominate our
weather. Subsidence will yield dry conditions with mostly sunny
skies. Temperatures should rise to near normal.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
Mid-level ridging will be over our region through Wednesday,
followed by southwest flow on Thursday. A weak trough may pass to
our north on Friday. Broad surface High pressure will stretch from
just to our north into the Atlantic Tuesday night into Wednesday.
It`s expected to shift offshore later Thursday. A cold front could
approach from the northwest later Friday, possibly bringing showers
and thunderstorms. Temperatures will be trending higher, reaching
into the 90s by Thursday.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
KCHS/KJZI/SAV: KCLX detected stratiform across the terminals,
occasional lightning strikes observed near KSAV. It is possible
that MVFR visibility during -TSRA may remain over KSAV into the
mid-afternoon. Otherwise, KCHS and KJZI should see showers
remain over the terminal into the mid to late afternoon. The
challenge overnight will be the potential development of fog
and/or MVFR ceilings. At this time, only the KSAV will indicated
MVFR fog developing at 8Z and remaining through the rest of the
night. MOS and forecast soundings indicate that MVFR stratus
will develop at daybreak at each terminal, remaining through
Sunday morning.

Extended Aviation Outlook: A departing storm system could bring
periodic flight restrictions on Sunday. VFR returns on Monday.

&&

.MARINE...
A weak surface pressure pattern will maintain overall lighter
winds (10 to 15 kt) and seas 2 to 4 ft across the coastal
waters through tonight. That said, a period of showers and
thunderstorms is anticipated later this morning and through the
afternoon hours. Some strong storms will be possible
which may produce locally strong winds and higher seas.

Extended Marine: Westerly flow early Sunday will turn to the NE
and increase Sunday night. Wind gusts could briefly approach 25
kt late Sunday night into Monday morning, mainly over the
Charleston County nearshore waters. But no Small Craft
Advisories are anticipated. Winds should gradually ease later
Monday. High pressure will continue to bring NE or E winds
through Tuesday. Winds should then shift to the SE on Wednesday.
Seas will remain in the 2-4 ft range.

&&

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

&&

$$

NEAR TERM...NED
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...Adam