362
FXUS62 KCHS 040424
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1224 AM EDT Wed Jun 4 2025

.SYNOPSIS...
A coastal low will result in unsettled weather across the
region late tonight through late in the week. A cold front
could approach the region over the weekend into early next
week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
KCLX/KJAX radars show convection is slowly picking up across
the coastal waters early this morning, which is on target to
spread/expand into parts of Southeast Georgia into far southern
South Carolina through daybreak. There is enough instability
present to support a mention of tstms through the night. Pops
were adjusted slightly per recent radar and short term model
trends, ranging from 60-70% across parts of coastal Georgia,
including the Savannah Metro area with 20-40% pops elsewhere,
except around 10% for areas adjacent to the CSRA and Southern
Midlands. Lows from the upper 60s well inland to the mid 70s at
the beaches and Downtown Charleston look good.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/...
Wednesday: With strong mid-lvl ridging situated over the Eastern
CONUS, a coastal low will shift off the Florida coastline in the
morning. This low will then slowly drift northward up the coastline
towards the region throughout the day. Tropical moisture that has
already caused heavy rains across South Florida, will be ushered up
with this low. The more concerning part of this is that PWAT values
exceed 2+ inches tomorrow, and enhanced rainfall will rates will
likely be realized within pockets of more concentrated convection.
In these pockets, Flood Advisories may be needed. At this
moment, rainfall values range from 1.50 to 2.50 inches across
the region. It`s hard to pick out a particular area that will
receive the most rainfall at this time as it will depend on
where exactly these thunderstorms train over. 12Z HREF suggests
showers and thunderstorms entering Southeastern Georgia ~11-12Z
tomorrow and slowly moving into the rest of the region
throughout the day. There seems to be a little break in showers
and thunderstorms the evening (23-00Z) and then ramps back up
again overnight (~04Z) through Thursday morning. All
deterministic models have kept the idea that numerous to
widespread showers will persist across the entire area for the
majority of the day, which seems to match up with what the HREF
is showing. With not a lot of instability and lapse rates
remaining unimpressive, the severe threat looks to be on the
lower end with excessive rainfall being more of the main threat
with these storms. However, with the instability being better
over the waters, it is possible to see few strong storms just
off the Atlantic coastline. Due to the amount of cloud cover
tomorrow, temperatures were lowered a bit with highs only
reaching into the upper 70s to low 80s. Lows will be mild with
temperatures only dipping down to the upper 60s to low 70s.

Thursday and Friday: Depending on the forward motion of this system,
this coastal low should move out of the region sometime on Thursday
afternoon. However, the ECMWF has a slower progression and doesn`t
have the low moving out of the region until Thursday night .. but
this seems to be the only outlier. Deep tropical moisture will
remain in the area with PWAT values 2+ inches. Showers and
thunderstorms will likely continue throughout most of the day on
Thursday, until the low shifts up north. Expect PoPs to decrease
overnight on Thursday into Friday morning. With the sea breeze
pushing inland on Friday afternoon, this could cause for another
chance of showers and thunderstorms to form. There are some hints
that instability could be more than the previous days and the severe
threat will be monitored in the upcoming days. Expect highs to reach
into the upper 80s to low 90s for both days.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
With west-north-westerly flow in place Friday night, this should
give a chance for the pattern to change to longwave troughing over
the weekend. A cold front could potentially approach the region from
the northwest over the weekend. This will create typical diurnal
summertime pattern of scattered showers and thunderstorms in the
afternoon. Expect temperatures to be above-normal throughout the
period.

&&

.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
04/06z Aviation Discussion:
KCHS/KJZI: Showers/tstms will spread into both terminals by
mid/late morning as low pressure tries or organize well to the
south. The period great impact looks to be 17-21z with
prevailing MVFR conditions in TSRA with conditions occasionally
dropping to IFR. IFR conditions where addressed with a TEMPO
group during this time. The main belt or showers/tstms could
move north of both terminals by late afternoon, although it will
be not be too far. Widespread IFR cigs (likely above alternate
minimums) should fill behind this area of convection. A
secondary area of showers/tstms could develop near the terminals
after sunset, but confidence on location and timing are a bit
uncertain this far out. VCSH was highlighted from 02-06z for
now.

KSAV: A band of showers/tstms could move inland off the Atlantic
and impact the terminal roughly 09-12z. This could bring a brief
sting to MVFR conditions in TSRA. A band of steadier
showers/tstms will develop near and just to the east of the
terminal by 15z which will translate north through the day. This
could bring occasional IFR conditions in TSRA, mainly through
about 18z. Prevailing MVFR conditions in TSRA with a TEMPO for
IFR conditions in TSRA was highlighted 15-18z. After 18z, the
main area of showers/tstms should be north of the terminal,
although some shower/tstm activity may linger through the rest
of the afternoon given the moist/unstable conditions in place.

Extended Aviation Outlook: As the aforementioned coastal low shifts
up the coastline, showers and thunderstorms could cause brief flight
restrictions through the period.

&&

.MARINE...
Tonight, as a sfc trough approaches from the south, east winds will
gradually strengthen. By dawn, east winds are forecast to reach 10
to 15 kts with gusts into the low 20. As a result, seas should build
from 2 to 4 ft this evening to 3 to 5 ft by late tonight. Given an
area of low pressure approaching from the south, non-supercell index
may develop values exceeding one unit. It is possible that the
environment may support a moderate risk for waterspouts early
Wednesday.

Wednesday through Saturday: With the coastal low slowly shifting
northward up the coastline on Wednesday, expect westerly winds to
become fairly gusty (up to 23-25 kt) beginning ~10-12Z and remain
quite gusty until Thursday afternoon. Winds will shift more
southerly Wednesday evening as the coastal low moves into the
region. East-southerly swell will mix into the Atlantic waters and
cause for some decent waves to take shape on Wednesday and Thursday.
The low will then shift northwards out of the region on Thursday
evening and winds will ease down a bit and become easterly for a
brief moment and then switch back to southerly Saturday morning.
Seas should range from 4 to 5 ft through Friday morning with 6
footers in the outer Georgia waters on Wednesday evening into early
Thursday morning. Then, expect seas to back down to 2 to 3 ft for
the rest of the period.

Rip Currents: Given a coastal low moving up the coastline, a
Moderate risk of rip currents is expected Wednesday (tomorrow)
and Thursday at all beaches.

&&

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

&&

$$