752
FXUS62 KCHS 042236
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
536 PM EST Thu Dec 4 2025

.SYNOPSIS...
High pressure will prevail across the region before a frontal
system impacts the area Friday into the weekend. High pressure
will then return next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Under a broad trough aloft, an inverted surface trough will be
building into the region throughout the rest of the afternoon
and into the evening hours. Moisture transport in combination
with isentropic lift will saturate the atmospheric column from
top-down, resulting in increasing coverage of rain showers
building in from the west. High temperatures remain seasonably
cooler as a result, with highs ranging from the lower 50s to
lower 60s, warmest along the coast. Will likely see two rounds
of more focused rainfall this afternoon into tonight, each
associated with a period of increased frontogenesis at varying
levels. The first is building in this afternoon at around the
700mb level, as evident by the band of rain showers on radar,
and will be focused further south near/along the I- 16 corridor.
However, given the dry air near the surface layer, not
expecting more than a tenth of an inch before this band
dissipates.

As a weak surface low begins to form and move up the inverted
trough into southern Georgia overnight, a second band of
frontogenesis is expected to form near the 850mb layer. This
band is expected to pivot more from the southwest to northeast,
and remain across interior southeast Georgia into the midlands
of South Carolina. As the surface low continues to approach the
region, the 850mb band will be sagging southwards increasing
rainfall chances to include coastal southeast South Carolina and
coastal southeast Georgia. Overall, the various ensembles would
suggest probabilities for a quarter of an inch are highest
(40-60%) across interior southeast Georgia and into interior
southeast South Carolina, dropping to 10% for those along the
coast. Overnight lows are a touch warmer than previous, in the
lower to upper 40s.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/...
Multiple rounds of rain are expected Friday through the
weekend. Synoptically, the forecast area will remain ahead of
mid level trough axis, with a series of shortwaves expected to
pass overhead. At the surface, Friday will begin with a ridge of
high pressure extending into the Carolinas and an area of low
pressure over the northern Gulf. A front will extend from the
low across southeast Georgia, and then off the Southeast coast.
Through the day, the low will lift northeast along the front. An
axis of deeper moisture will become oriented across the region,
with PWats expected to surge to over 1.5 inches at times, which
is well above normal for this time of year per SPC sounding
climatology. Increasing isentropic ascent and larger scale
forcing will lead to rain spreading across the area. The highest
coverage is expected to be in the daylight hours. Friday
rainfall totals are largely 0.75-1.25", except lesser south of
I-16, in the 0.25-0.75" range.

Additional waves of rainfall are expected Saturday and Sunday.
Saturday rainfall totals are forecast to fall in the 0.75-1.25"
inch range. Sunday rainfall coverage is a bit more uncertain
with larger model spread. Regardless, southeast Georgia should
see the higher rainfall totals on that day. NBM indicates the
probability for seeing greater than an inch in 24 hours ending
Monday morning is only around 10-20%.

All in all, the current forecast indicates a widespread 2-3
inches of rain through the event (tonight/Thursday night through
Sunday night). No thunder is expected at this time. Luckily,
rain rates will not be particularly high and given almost half
of the area is classified in severe drought, flooding is not
anticipated at this time.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
The storm system that impacted the area over the weekend will
exit, allowing high pressure and drier weather to return. The
main weather concern during this time period is the chance for
freezing temperatures both Tuesday and Wednesday mornings. The
probability for reaching 32F or colder is highest over inland
counties, with only a 20-50% chance closer to the coast, roughly
along and east of Highway 17 (away from the beaches).

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
05/00z TAF Discussion:
KCHS/KJZI/KSAV: Dry air has kept rain generally confined to
sprinkles so far this afternoon/evening. The atmosphere will
slowly saturate through the night with cigs expected to slowly
lower. As daybreak approaches, things should change quickly as
the column becomes nearly saturday in tandem with impulses
passing through aloft. This will support an extended period of
very low cigs across the region with rounds of light to locally
moderate rain falling at all terminals. VFR cigs will give way
to LIFR cigs by 13-14z Thursday as vsbys begin to lower with the
onset of more significant rainfall. Low cigs, likely below
alternate minimums, but above airfield minimums, will persist
through the remainder of the 00z TAF period. Rain may begin to
pull out after 21z, especailly at KCHS and KJZI, but stratus
build-down will likely keep some reductions in vsbys in place
with fog.

Extended Aviation Outlook: Flight restrictions, likely to IFR
or lower, are expected in low clouds and rain Friday into the
weekend.

&&

.MARINE...
Tonight: No concerns. The pressure pattern will support wind
speeds between 10 to 15 kts. Seas will remain between 2 to 3 ft.

Friday through Tuesday: Low pressure is expected to pass across
the region Friday, with another wave passing through later in
the weekend. Rounds of rainfall are expected, but otherwise no
marine concerns with winds averaging 15 knots or less and seas
2-4 feet. The storm system should finally pull away on Monday
with increasing winds and seas in its wake. Wind gusts and seas
could approach Small Craft Advisory criteria Monday into Monday
night. No additional concerns anticipated for Tuesday.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will continue to rise with the morning high
tide cycles through Friday and remain elevated through the
weekend. Coastal Flood Advisories will likely be needed for
morning high tide cycles, primarily at Charleston Harbor
(Charleston and Coastal Colleton counties) through Sunday
morning.

Friday, astronomical high tides peak (6.8 ft MLLW at Charleston
Harbor and 8.86 ft MLLW at Fort Pulaski) and this is when winds
are forecast to turn from the northeast. Overall, this type of
setup can over-perform given the building anomalies from the
northeast winds. There is potential for tides to reach moderate
flooding criteria (7.5 ft MLLW), but current forecast keeps
levels just shy.

Further south, from Beaufort County through the southeast
Georgia coast, the main tide of concern is Friday morning. There
is potential for tides to reach minor flooding criteria (9.5 ft
MLLW), but current forecast keeps levels just shy.

&&

.CLIMATE...
Record Precipitation:

December 7:
KCHS: 1.14/1976
KCXM: 0.82/1976
KSAV: 0.79/2017

&&

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

&&

$$