Walterboro, South Carolina Weather Forecast Discussion

756
FXUS62 KCHS 281811
AFDCHS
Area Forecast Discussion
National Weather Service Charleston SC
211 PM EDT Sun Sep 28 2025
.SYNOPSIS...
Tropical Storm Imelda will move through the northern Bahamas
Monday, then northeast away from the Southeast coast Tuesday and
Wednesday. Cooler high pressure will then build in from the
northwest.
&&
.NEAR TERM /THROUGH TONIGHT/...
The mid-levels consist of a broad trough over the Southeast
U.S. At the surface, a stationary front is located just off our
coast. While it may get near our beaches this evening, it`s
expected to move back offshore overnight. This is ushering deep
moisture into our region, with PWATs ~2". The CAMs and the
deterministic models have showers along our coastal waters early this
evening, moving onshore later this evening, and shifting further
inland overnight. This is what the NBM and our general forecast
has. Locally heavy rainfall is possible, mainly near the coast,
which is why the WPC has our area under a Marginal Risk of
Excessive Rainfall. Even with this in mind, the risk of
widespread flash flooding is low. Low temperatures will be around
70 degrees.
&&
.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
Tropical Storm Imelda is forecast to move slowly north and out
of the Bahamas on Monday while gradually strengthening.
Fortunately the guidance and official forecast continue to show
the system turning abruptly to the ENE on Tuesday, keeping the
system well away from SC/GA. However, we still expect some
impacts, primarily from rainfall, marine winds, coastal
flooding, and high surf and rip currents.
A fairly large area of 2+ PWATs is forecast to overspread
southern SC and coastal GA Monday and remain in place through
Tuesday before drier high pressure sinks into the area from the
northwest Tuesday night and Wednesday. Most guidance continues
to show a large area of synoptic forcing across the eastern half
of the area between an in-situ upper trough and Imelda
offshore, particularly Monday into Tuesday. There should be
ample moisture and forcing for ascent for scattered to numerous
showers and a few tstms. Models have been trending downward with
overall QPF, though we still show the potential for 1-3" across
the eastern half of the Charleston Tri-County Area Monday-
Tuesday.
Tuesday night and Wednesday now look dry as strong high
pressure builds in from the north and west as Imelda pushes
farther away from the Southeast coast.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
Cool and dry weather expected for most of the area Wednesday
night through Friday, though a weak coastal trough along the GA
coast could bring isolated showers to far southern areas. The
weekend is trending wetter with the potential for Gulf low
pressure to move north toward the area.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
18Z TAFs: Satellite imagery indicates SCT-BKN stratus across our
area, with surface observations showing ceilings bouncing
between VFR and MVFR. Instead of trying to account for this with
TEMPO groups, we opted to just have prevailing MVFR. This
evening, ceilings drop while showers start to overspread the TAF
sites. We initially have VCSH and MVFR to account for this.
Then, we transition to SHRA BR with IFR ceilings later tonight
through the end of the TAF time period. MOS and the ensembles
are consistent and in good agreement with the IFR ceilings.
Finally, winds should become gusty towards the end of the TAF
time period.
Extended Aviation Forecast: An extended period of MVFR ceilings
is expected through Tuesday night or Wednesday, along with
occasional vsby reductions due to showers and thunderstorms.
Gusty NE winds also expected through Wednesday.
&&
.MARINE...
Through Tonight: A stationary front will meander over or just
east of our coastal waters. The will yield NE winds 15-20 kt
with higher gusts. Seas will build to to 4-5 ft tonight.
A prolonged period of strong NNE winds expected Monday through
Saturday due to a tight gradient between inland high pressure
and TS Imelda offshore. We have Small Craft Advisories for all
waters except Charleston Harbor starting Monday morning,
continuing through Friday night, for a combination of
winds/seas. We`ll likely eventually need a Small Craft Advisory
for Charleston Harbor starting later Monday or Monday night.
Rip Currents: A High Risk of Rip Currents will continue through
at least Tuesday due to large, long-period swells and strong
winds.
&&
.TIDES/COASTAL FLOODING...
Strengthening NNE winds this week will result in an increase in
tidal anomalies. There is quite a bit of uncertainty about
exactly how large the positive anomaly will be given that the
wind directions could be more NNE rather than NE. There is a
fine line between what wind directions cause the greatest Ekman
forcing along the SC/GA coast. A wind direction closer to 040
degrees is much more favorable than 010-020 degrees. The latest
forecast for Imelda points toward a more northerly fetch, in
which case the anomaly may not get much higher than +1.6 ft. We
trended the tide forecast upward a bit with the morning
forecast, but at this point the only flooding we are showing is
minor coastal flooding at Charleston Wednesday afternoon.
A High Surf Advisory may be needed for part or all of the
coastline as early as Monday afternoon, though the greatest
threat for 5+ ft breaking waves would be Tuesday and Tuesday
night.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents from Monday morning through Monday
     evening for GAZ117-119-139-141.
SC...High Risk for Rip Currents from Monday morning through Monday
     evening for SCZ048>051.
MARINE...Small Craft Advisory from 10 AM Monday to 8 AM EDT Saturday
     for AMZ350-352-354.
     Small Craft Advisory from 6 AM Monday to 8 AM EDT Saturday for
     AMZ374.
&&
$$
NEAR TERM...
SHORT TERM...JRL
LONG TERM...JRL
AVIATION...JRL
MARINE...JRL

NWS CHS Office Area Forecast Discussion