Miley, South Carolina Weather Forecast Discussion

798
FXUS62 KCHS 271120
AFDCHS
Area Forecast Discussion
National Weather Service Charleston SC
720 AM EDT Sat Sep 27 2025
.SYNOPSIS...
A weak front will stall along the coastline through the
weekend. Potential Tropical Cyclone 9 is forecast to become a
tropical storm near the Bahamas this weekend then approach the
Southeast U.S. coast early next week as a tropical storm or
hurricane.
&&
.NEAR TERM /THROUGH TONIGHT/...
Satellite water vapor indicated a mid-level low over the Deep South,
with a notable vort max tracking across southern GA. In addition, a
60-80 kt H25 jet will remain across the Carolinas through this
afternoon, providing rounds of upper wind divergence across the
forecast area today. Scattered to numerous showers and thunderstorms
should develop ahead of weak front approaching from the west and a
afternoon sea breeze. Ongoing 6Z supplemental soundings indicates
that PW has increased to just above 2 inches. Forecast soundings
indicate that SBCAPE will range between 800-1000 J/kg, greatest
along the coast. The deep moisture and potential training cells may
yield swaths of 1 to 2 inches of rainfall. Temperatures will be
limited by cloud cover and rounds of rainfall, highs from the low
80s over the Lowcountry to the mid 80s across SE GA.
Tonight: The closed low should open to a trough at H5 by late today,
with the trough axis reaching the Midlands by late tonight. Deep dry
air should increase from the west through the night. Showers and
thunderstorms should continue across the adjacent Atlantic waters
through the night, coverage over land should remain minimal. Low
temperatures are forecast to range from the mid 60s inland to the
low 70s along the coast.
&&
.SHORT TERM /SUNDAY THROUGH TUESDAY/...
Sunday: Chances for precipitation will be much less compared to
Saturday as the weak cold front essentially washes out across the
region. Simultaneously, the upper-lvl jet streak that was previously
located offshore will bend back towards the west as Potential
Tropical Cyclone (PTC) Nine approaches the region from the south.
Initially, most of the region will be dry on Sunday morning with
shower and thunderstorm activity increasing in the afternoon.
Previously, WPC had a portion of the region under a Slight Risk
(Level 2 of 4) for excessive rainfall, however dynamics for flash
flooding look less favorable now and the Slight Risk has been
changed to a Marginal Risk (Level 1 of 4) for excessive rainfall. In
regards to accumulations, rainfall totals range 0.10 to 0.25 inches
along and west of I-95 and those near the Charleston Metro ranging
between 0.25 to 0.75 inches. Otherwise, highs will be in the low to
mid 80s across SE South Carolina and mid to upper 80s across SE
Georgia. Overnight lows will barely drop with temperatures falling
into the upper 60s to low 70s.
Monday and Tuesday: A great amount of uncertainty still remains as
PTC Nine approaches from the south. There has been a recent trend in
a slower northward speed with PTC Nine in the deterministic models
and ensembles, which allows for Hurricane Humberto to have a greater
steering influence on the system. It seems like Humberto`s quick
intensification and a more north-eastward track is also
creating it to have a greater influence on PTC Nine. This
solution shows the PTC Nine approaching the SC coastline and
then recurving northeastward with Humberto out to sea. However,
another alternative likely solution is that PTC Nine approaches
the coastline and then either (1) stalls offshore, or (2) makes
landfall along the SC/NC coastline as a strong tropical storm,
or a weak hurricane. If the system stalls offshore, or inland,
this could become a huge problem in terms of rainfall. This
forecast uncertainty comes from the system`s proximity to
Hurricane Humberto, the strength of a mid-lvl ridge, and the
upper-lvl trough axis. There is hope to gain more forecast
confidence once a well-defined center develops within PTC Nine.
Potential Impacts: There is a risk of storm surge with this system
and everyone should prepare to observe a high end tropical storm, or
low end hurricane wind speeds. This system has potential to produce
large tree damage, damage to some structures, and power outages.
Also, there is an increasing threat of heavy rainfall, which could
cause flash, urban, and river flooding. The time is prepare is now.
All residents should review their evacuation plans and have
emergency kits ready to go.
&&
.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
This forecast remains largely uncertain as most of it depends on the
movement and intensity of PTC Nine. However, outside of the
potentially landfalling tropical system, a strong upper-lvl ridge
will build across the southern portion Canada through the end of the
week and allow for breezy northeasterly winds to take shape across
the region. Also, it could feel a lot more like fall next week as
dry air advects into the Southeast and dewpoints drop into the low
to mid 60s.
&&
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
12Z TAFs: Guidance indicates that a weak front will slide over
SE GA/SC during the daylight hours today. In addition, the
passage of a mid-level disturbance and jet divergence should
trigger rounds of showers and thunderstorms through the day. A
short period of MVFR ceilings is expected from daybreak through
at least mid-morning at KSAV. It appears that KCHS and KJZI
will see the greatest potential for deep convection between
16-19Z, highlighted with TEMPOs. KSAV may see a round of
thunderstorms between 19-23Z, highlighted with a TEMPO.
Convection should slide generally over the Atlantic waters this
evening.
Extended Aviation Forecast: A tropical cyclone is forecast to
approach the region from the south. Multiple periods of visibility
and ceiling restrictions are possible with gusty winds and variable
wind directions.
&&
.MARINE...
Today and tonight: The pattern will generally support an east wind
between 5 to 10 kts. Wave heights should range between 2 to 3 ft
tonight, favoring values around 3 ft tonight.
Sunday through Thursday: As the weak front washes out early Sunday
morning, winds will turn to the northeast at 10 to 15 kts with gusts
up to 20 kts. Seas will be 2 to 4 ft on Sunday, and then build to 6
to 8 ft (possibly higher) by Monday afternoon as this PTC Nine
approaches from the south. Thereafter, a volatile sea state is
likely with waves reaching above 12 ft possible. Also, winds could
reach above storm force with tropical storm, or hurricane headlines
possible. Expect multiple rounds of showers and thunderstorms as
potential bands from the system traverse across the local
waters.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...NED
SHORT TERM...Dennis
LONG TERM...Dennis
AVIATION...Dennis/NED
MARINE...Dennis/NED

NWS CHS Office Area Forecast Discussion