447
FXUS62 KCHS 120814
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
414 AM EDT Mon May 12 2025

.SYNOPSIS...
A front will remain stalled near the area, before lifting north
of the region by midweek. High pressure is expected to return
late week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Early this morning, GOES water vapor showed a nicely organized mid-
level low pressure circulation centered over the lower
Mississippi River Valley. East of the closed low, a dry slot was
wrapping around the circulation from the Gulf north across GA
to over eastern TN. A band of H5 vorticity should swing east
over SE GA/SC this morning. High resolution guidance shows that
widespread moderate rain with embedded thunderstorms will
develop ahead of the disturbance, lifting to the north through
this afternoon. Instability across the Atlantic waters will see
CAPE values of 1000-1500 J/kg, decreasing inland. Given the wide
field of instability over the Atlantic and NW storm motions,
thunderstorms sourced over the ocean will stream inland this
morning, favoring the greatest rainfall rates over the coastal
counties and cities. Rainfall amounts this morning may generally
range between 1 to 2 inches, with pockets of higher amounts.
Given the recent wet conditions, the rainfall rates this morning
may necessitate a Flood Advisory or two.

This afternoon, convection should become more cellular and storm
motions around 25 mph. Moderate to heavy downpours are possible with
these storms, given deep warm cloud depth and PW values around 1.9
inches. Categorical PoPs this morning will transition to likely PoPs
this afternoon. The CWA will remain in the warm sector between a
lifting warm front and approaching cold front this afternoon. High
temperatures are forecast to range in the mid to upper 70s.

This evening, the cold front is timed to push over SE GA this
evening, then over the SC Lowcountry late tonight. This boundary
should focus the development of thunderstorms, possibly developing
into a band of storms. These storms will push NE across the CWA this
evening and tonight. The storms may remain strong to severe across
SE GA this evening given lingering instability and shear, with
damaging wind gusts the primary hazard. SPC has highlighted the
region with a marginal risk for severe weather. Low temperature
are forecast to range in the mid to upper 60s.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
The closed low in the mid-levels will begin to open up and progress
northeastward towards the Mid-Atlantic states on Tuesday and into
Wednesday. By Thursday the mid-level trough will eject off the Mid-
Atlantic coast with ridging beginning to build into the southeastern
states. At the surface a cold front will push off the southeastern
coast on Tuesday, with high pressure building in on Wednesday and
into Thursday. The wet pattern across the region will shift drier as
the front exits the region and high pressure begins to dominate the
synoptic pattern. Scattered to widespread showers and thunderstorms
will be possible Tuesday and Wednesday afternoon, mainly diurnally
driven with some lingering forcing from the departing front.

Temperatures Tuesday and Wednesday will generally be in the low to
mid 80s, with overnight lows in the 60s to around 70 at the beaches.
As high pressure builds into the region both aloft and at the
surface temperatures on Thursday will rise into the upper 80s to
around 90 in some locations.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
The main forecast highlight for the long term period is the hot
temperatures. With ridging building in aloft and high pressure at
the surface temperatures will soar above normal, with highs forecast
in the low to even mid 90s across the region. These temperatures
combined with dew points forecast in the upper 60s to low 70s could
yield heat index values of 100-103F at the end of the week. While
below advisory criteria, this could be the real first blast of heat
across the region.

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Prior to the 6Z TAFs, KCLX detected clusters of showers and
thunderstorms passing near the KSAV terminal. Further to the
south, an arching band of thunderstorms was developing ahead of
mid-level disturbance over southern GA, these storms are timed
to track across KSAV between 9-12Z, highlighted with a TEMPO.
High resolution guidance indicates that an area of moderate to
heavy rain showers with embedded thunderstorms will reach
KCHS/KJZI around daybreak, then remain through until mid-day.
South winds this afternoon should develop gusts into the low 20
kts with deeper mixing. Another band of thunderstorms may
develop ahead of an approaching cold front, reaching KSAV
between 0-4Z. Generally ceilings across the terminals should
favor MVFR values, however, periods of IFR are possible during
thunderstorms and after sunset this evening.

Extended Aviation Outlook: MVFR or lower cigs and/or vsbys possible
Tuesday and Wednesday afternoons due to showers/tstms.

&&

.MARINE...
Thunderstorms will remain common across the marine zones today and
tonight, the greatest coverage this morning with another band of
storms this evening. Some of these storms could produce wind gusts
of 34 kts or greater, a waterspout cannot be ruled out this morning.
The pattern will support southeast winds between 10 to 15 kts with
gusts around 25 kts across the Atlantic waters. Seas will build to 4
to 7 ft by this afternoon, then slowly decreasing after midnight
tonight. Small Craft Advisories have been posted to highlight the
wind and wave conditions for today into tonight.

Tuesday through Saturday: A front will push offshore into the
adjacent Atlantic waters on Tuesday with high pressure building in
thereafter and into the weekend. Some 6 ft seas will likely be
lingering in the Charleston County nearshore waters and the 20 to 60
nm offshore GA waters through around noontime on Tuesday. A Small
Craft Advisory will remain in effect for those waters. Through the
remainder of the week generally quiet marine conditions are
forecast, with winds around 15 knots. Higher gusts are possible
along the coastline and in the Charleston Harbor each afternoon with
the sea breeze. Seas will decrease to 2 to 3 ft into the weekend.

Rip Currents, the combination of onshore flow and 2 to 3 breakers
may produce rip currents along the SC/GA coast today. Breakers
could exceed 3 ft along the Charleston County coast this
afternoon.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 2 PM EDT Tuesday for AMZ350.
     Small Craft Advisory from 2 PM this afternoon to 8 AM EDT
     Tuesday for AMZ352.
     Small Craft Advisory from 2 PM this afternoon to 2 AM EDT
     Tuesday for AMZ354.
     Small Craft Advisory until 2 PM EDT Tuesday for AMZ374.

&&

$$

NEAR TERM...NED
SHORT TERM...CPM
LONG TERM...CPM
AVIATION...CPM/NED
MARINE...CPM/NED