656
FXUS62 KCHS 181426
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1026 AM 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/...
The forecast area will remain under thick cloud cover today.
KCLX has detected a band of rain with embedded thunderstorms
across the inland counties of SC/GA. The rainfall should push
east toward the coast through the rest of the morning. The area
under the swath of rainfall should see instability limited to
1000-1500 J/kg heading into this afternoon. However, extreme
southeast GA has remained rainfall-free so far this morning.
This area of SE GA should warm into the low to mid 80s early
this afternoon. CAPE values between Long to McIntosh north to
Chatham County may develop values in excess of 2000 J/kg this
afternoon. In addition, effective bulk shear is forecast to
increase to 40-45 kts. This environment could certainly support
a organized band of thunderstorms, yielding strong to severe
wind gusts. SPC has recently highlighted this area with a MCD,
indicating a 40 percent chance for a Watch later today.

Otherwise, the potential for heavy to excessive rainfall will
remain through this afternoon. The 12Z KCHS sounding indicate PW
values around 2 inches with K-index approaching 40. Deep
moisture should support thunderstorms with efficient rainfall
rates. The heavy rainfall appears most likely across extreme SE
GA.

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 /14Z SATURDAY THROUGH WEDNESDAY/...
KCHS/KJZI/SAV: SCT-BKN MVFR cloud cover has materialized at the
KSAV terminal in the last few hours. Otherwise, VFR conditions
is looking to hold early this morning.

Meanwhile, terminal locations will see increasing chances for
showers and some thunderstorms later this morning and into the
afternoon hours, with the greater impact likely to occur at the
KSAV terminal. We have a period of flight restrictions at all
three terminals between roughly 14Z and 20Z with further timing
refinements highly likely. Bulk of showers/thunder will exit the
region Saturday evening.

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...Adam
MARINE...Adam