619
FXUS62 KCHS 242106
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
506 PM EDT Fri May 24 2024

.SYNOPSIS...
A series of weak disturbances will move through the area
through Saturday. Hot conditions expected for Sunday and
Memorial Day. A cold front could bring impacts to the region
Monday night into Tuesday.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Convection continues to develop along an east-west oriented
boundary developing along a PWat and MLCAPE axis. The steering
flow is toward the east, and now that the sea breeze has made
some headway inland (roughly near or inland from US-17, there
will be a further increase in both the coverage and the
strength of t-storms. An MCV will continue to approach from the
west-northwest, which will further aid in the forcing for
ascent.

The overall thermodynamics are quite favorable for strong to
severe weather, and many of the convective parameters are
conducive as well. This includes a K-Index of 38; Total Totals
Index of 52; Lifted Index of -7. The DCAPE is around 900-1100
J/kg, suggesting that damaging winds are likely in the
strongest storms. The hail potential is lower due to a Wet Bulb
Zero that is only around 11-12K feet. However, local radars
have shown small hail in the taller storms, while SPC
mesoanalysis of SARS Hail Size does have some 1 inch values in
and near the local counties. We maintain mention of isolated
severe through 9 PM, with the highest chances still looking to
be north of I-16 in Georgia and through the counties of South
Carolina. This is also where the greatest coverage will exist,
with PoPs having been increased to 70% due to the interaction of
the activity from inland interacting with the sea breeze.

There is some risk for heavy rains and at least a minor to
perhaps moderate flooding concern in a few areas. The 12Z HREF
shows high enough probabilities of 1" or greater in the 3 hour
period from 21-24Z that Flood Advisories are possible. This
includes the areas in and near Charleston, Beaufort, and
Savannah. Despite the steering flow to the east, convection will
get hung up on the sea breeze, and this too can enhance the
flooding rain potential. The latest QPF for this event has as
much as 0-75 to 1.50 inches, greatest along parts of the
coastal counties. It is also certainly plausible that if the
heavier rains are slower in ending this evening, that there is
an additional concern about the 930 PM high tide in Charleston,
as we are currently showing 6.8 ft MLLW around that time.

Convection fades during the mid and late evening with the loss
of heating and the passage of the MCV. However, within the
west-northwest flow aloft some of the guidance has been
implying that at least isolated to scattered activity will
persist through the overnight. This seems plausible since there
will be lingering outflow boundaries, sufficient moisture, and
modest CAPE. This activity though does not look to be severe.

There is an outside chance of some stratus and/or fog late at
night due to the wet grounds. But this is dependent upon how
much clearing takes place. Since most guidance does not have any
reductions in visibilities, we do not have any mention in the
forecast.

The hourly temperatures have been altered to show an atypical
curve to account for convection early on. But actually lows will
be down only into the upper 60s and lower 70s due to similar
dew points.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Saturday: The broad mid-level trough will ripple over the Atlantic
during the morning, with heights beginning to rise during the
afternoon. Short term guidance indicates that a small disturbance
could track SE across the region Saturday afternoon. Surface
conditions should feature high temperatures in the low 90s with
dewpoints in the low 70s. Model guidance indicates that a field of
CAPE of 1500-2000 J/kg with shallow CIN should develop by the heat
of the afternoon. Isolated to scattered thunderstorms should develop
across the forecast area, especially along a sea breeze. Once again,
some areas could see pockets of heavy rainfall given weak shear and
PW values in excess of 1.6 inches.

Sunday: GFS indicates that a broad H5 ridge will build across the
region. Conditions should become hot and humid during the
afternoon. High temperatures are expected to range in the mid 90s
with dewpoints in the low 70s along the coast. Heat index values may
exceed 100 degrees across the coastal counties, especially across SE
GA. Given poor mid-level lapse rates, convection will be limited to
a SCHC.

Memorial Day: The mid-level ridge axis is expected to shift east,
but is expected to remain near the region. A cold front is expected
to sweep across the Southern Appalachians Monday afternoon. Winds
will remain from the southwest through the day. Temperatures should
warm similar to values reached on Sunday, generally in the low to
mid 90s. A few pockets across the coastal counties may see heat
index values rise to around 100 degrees.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Monday night: During the evening, short term guidance indicates that
an MCS may develop over the Midlands of SC ahead of the front. This
system may track towards the coast with the cold front Monday night.
Given a wide field of instability and weak shear, it is possible
that these storms could arrive with damaging wind gusts. This
activity may remain into Tuesday morning.

Wednesday through Friday: Conditions for the rest of the week should
remain dry. High temperatures are forecast to range in the upper 80s
each day.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Showers and thunderstorms will impact the terminals late this
afternoon and early evening, and produce flight restrictions.
This is mainly between 20Z and 01Z. Convection diminishes
thereafter, although some additional convection might advance
back into the region late overnight. However, confidence is too
low to add any mention to the current terminal forecast. Also,
there might be a low end risk for stratus and/or fog closer to
daybreak Saturday, dependent on how much clearing can occur.

Extended Aviation Outlook: Brief flight restrictions are possible
due to showers/thunderstorms each afternoon/evening.

&&

.MARINE...
This evening and tonight: The synoptic pattern will become
muddled due to convection, as a few strong or severe t-storms
will occur through late evening as they move offshore. Wind
gusts could be enough to produce Special Marine Warnings for
winds of 35 kt or greater. Outside of convection winds will be S
or SW at 15 kt or less, with seas around 2 feet.

Saturday through Wednesday: The forecast area will remain between
high pressure across the western Atlantic and Gulf of Mexico and a
series of low pressure tracking over the Mid West. This pattern
should result in a sea breeze to develop each afternoon. A cold
front should sweep across the coastal waters Monday night into
Tuesday. Wind and sea conditions should remain below Small Craft
Advisory conditions.

&&

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

&&

$$

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