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084
FXUS62 KCHS 241706
AFDCHS

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

.SYNOPSIS...
A series of weak disturbances will move through the area late
week into the holiday weekend. A cold front could bring impacts
to the region Monday night into Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
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The sea breeze is not far inland from the Intra-Coastal Waterway
(ICW), but it is having a difficult time moving too quickly
inland given a deep offshore flow. Cumulus clouds are steadily
showing some vertical growth as of early afternoon, and now that
we`ve reached our convective temperature, we look for
convection to start developing. One weak MCV over southern
georgia falling apart; a stronger short wave in the Tennessee
valley is riding east; and now a third perturbation near
the Georgia-South Carolina border over the upper Savannah River
is dropping east-southeast. That feature will move in later this
afternoon, and will help in triggering convection. No major
changes to the ongoing forecast. We did raise some places about
1-2F based on latest trends. Most communities will reach 90-92F,
except holding in the 80s near and along the coast.

Today: Morning analysis indicates the Atlantic ridge across the
Florida peninsula, while a lee side trough is also indicated to
our northwest. There is also a weak warm front to our west that
edges closer this afternoon. Upper air analysis reveals a weak
MCV moving east through southern Georgia, with a stronger short
wave heading east from western Tennessee and northern
Mississippi. The first feature aloft will dampen further as it
moves through our southern zones early afternoon. This will
likely not have have any impacts on our convective potential.
The further upstream wave will approach might take until very
late or this evening until it gets close enough to aid in
development of showers ands t-storms.

Even so, our convective temperatures will be reached by early
to mid afternoon, and with less of a cap than recent days, the
sea breeze could become more active, as well as other micro and
meso scale boundaries. Given PWat near 1.75 inches, plus
sufficient SBCAPE around 2000-2500 J/kg, and only minimal CINH,
we do foresee decent coverage of showers and t-storms during the
mid and late afternoon.

Some of the convective parameters are indicate of some strong or
severe storms. This includes a K-Index of 38; Total Totals
Index of 52; Lifted Index of -7. The DCAPE is around 1000-1200
J/kg, suggesting that damaging winds are possible in the
strongest storms. While the hail potential is lower since Wet
Bulb Zero is around 11-12K feet. But since the SPC outlook has a
5% chance, it is certainly a possibility.

Guidance provides mixed solutions on where the greatest
coverage and severe potential exists. But there are indications
that the nearby warm front would help in getting activity going
across central Georgia as it spreads east with the steering
flow. Then it combines with the other small scale boundaries to
produce as much as numerous showers and t-storms. We have
numerous convective coverage over most of our South Carolina
zones and Chatham County in Georgia. But adjustments will likely
be required as more recent model data and trends become
available.

There is some risk for heavy rains and at least a minor to
perhaps moderate flooding concern. the 00Z HREF shows high
enough probabilities of 1" or greater in 3 hour periods from
18-21Z and again from 21-24Z that Flood Advisories are possible.
This includes the areas in and near Charleston, Beaufort, and
Savannah. It is 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.

Low level thickness supports temperatures in the lower and
middle 90s. But given the convective rains, we didn`t go that
hot. We kept the previous forecast which had highs a few degrees
either side of 90F away from the beaches.

Tonight: Convection will wind down during the course of the
evening with loss of heating and exit of the MCV. But, another
MCV/ripple in the flow may be right behind potentially
bringing additional showers and thunderstorms into the area
late. Again, each successive high resolution guidance run offers
a differing scenario leading to low confidence. For now, we
have precip chances starting to increase again toward Saturday
morning.
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&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
Northwest flow develops aloft on Saturday as a shortwave trough
shifts offshore. There could be some convective activity moving
through in the morning, with additional development expected in the
afternoon during peak heating. Shear remains around 20 knots, so an
organized severe threat is not expected, but a few stronger storms
with gusty winds are possible with drier air in the mid levels and
DCAPE progs approaching 1000 J/kg. Temperatures will peak around
90/lower 90s. Showers/thunderstorms should fade/shift offshore
Saturday evening. Lows mainly in the upper 60s to lower 70s.

Mid level heights continue to build overhead on Sunday. Convection
will be limited with mainly just isolated diurnal showers and
thunderstorms possible. The hot temperatures will continue with
highs forecast to reach the low to mid 90s (this is 5 to even 10
degrees above climo). Low temperatures stay mild, only falling to
the lower 70s.

The ridge axis will get pushed offshore on Monday/Memorial Day as a
mid level trough shifts into the eastern CONUS. Concurrently, a cold
front will approach the region. Convection could stay pretty
isolated through much of the daylight hours, before activity
possibly moves in from the west later in the day and overnight.
Forecast features just 20% rain chances through 00z. It will be
another hot day with highs again in the lower to mid 90s.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
A cold front moves into the region Monday night into Tuesday. There
should be an uptick in shower/thunderstorm coverage during this
timeframe with larger scale forcing for ascent. Quieter weather
looks to return mid week and beyond with deepest moisture exiting
off the coast. Unseasonably warm temperatures will moderate back to
normal through the period.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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Showers and/or thunderstorms will eventually impact the
terminals mid-late 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.
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&&

.MARINE...
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Surface high pressure will remain off the southeast coast
through tonight with south to southwest winds prevalent. Wind
speeds of 10 to 15 knots and gusty will be common and seas 3
feet or less. A few strong or severe t-storms can occur during
the late afternoon through late evening as they move offshore.
Wind gusts could be enough to produce Special Marine Warnings
for winds of 35 kt or greater.

Saturday through Wednesday: Southerly flow prevails through early
next week, until a cold front cross the waters late in the period.
Conditions stay below Small Craft Advisory criteria, with winds
generally 15 knots or less and seas 2-3 feet on average.
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&&

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

&&

$$

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