449
FXUS62 KCHS 050542
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1242 AM EST Fri Dec 5 2025

.SYNOPSIS...
A frontal system will maintain unsettled weather through early
next week, then cold high pressure will build in.

&&

.NEAR TERM /UNTIL 6 AM THIS 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 THIS 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 /06Z FRIDAY THROUGH TUESDAY/...
6Z TAFs: The leading edge of cold air damming will spread across
the terminals around daybreak. North winds should generally
remain, speeds between 5 to 10 kts through the TAF period.
Deep forcing and moisture should yield widespread moderate
rainfall across the region through much of the day. Forecast
soundings indicate that cloud basses will gradually lowers
through the day, reaching IFR to LIFR by late this morning.
Lingering CAD tonight may yield some stratus build down,
however, ongoing rainfall may keep the BL mixed enough to limit
and fog formation. Each TAF will highlight the potential for
ceilings falling below 500 ft.

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...Coastal Flood Advisory from 6 AM to 9 AM EST this morning for
     SCZ049-050.
MARINE...None.

&&

$$

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