046
FXUS62 KCHS 041114
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
614 AM 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 /THROUGH TONIGHT/...
The center of high pressure will remain centered over the CWA this
morning. Given the recent soaking rainfall, the combination of wet
soil and calm winds, there is potential for at least ground fog by
dawn this morning. The forecast will limit the mention of patchy to
areas of fog along and west of a line from Millen to Allendale. Any
fog should dissipate within the first hour or two of daylight.

Forecast soundings indicates that the atmosphere will moisten from
the top-down through the day. PW values are forecast to increase by
.5 inch or more before sunset this evening. Moisture will streaming
north from a developing low pressure system, deepening near the
Mississippi Delta today. Increasing jet divergence and approaching H5
vort should support isolated to scattered showers across SE GA this
afternoon. Rainfall is forecast to remain very light, with
measurable amounts limited to areas south of I-16. High
temperatures should favor values in the mid to upper 50s this
afternoon.

Tonight, the center of a 1030 mb high will remain centered over New
England. Low pressure will track northeast across the Deep South,
reaching the FL Panhandle by 12Z Friday. NAM indicates that
widespread isentropic lift will develop across the region after 3Z,
deepening through rest of night. The strengthening upglide over the
developing CAD will support likely to categorical PoPs tonight.
Rainfall amounts tonight are forecast to range from around 0.2"
inland to around 0.1" along the coast. Low temperatures are forecast
to range from the low 40s inland to the upper 40s along the
coast.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
Friday: The main takeaway for Friday, Saturday, and into Sunday is
the continued high confidence in multiple rounds of rain. The
synoptic setup will feature a mid-level ridge off of the west coast
of the United States with a long wave trough axis over the central
United States. The main item of interest will be an upper level low
over the Baja of California. Guidance is in very good agreement that
the low over the Baja will help to quasi-anchor the long wave trough
axis Friday to the southwest (or bring the group velocity to a
temporary halt). On the eastern flank of the long wave trough,
widespread warm air advection (WAA) will commence with PVA moving
overhead. Simultaneously, a weak mid-level wave will move off of the
coast of the Mid-Atlantic states with high pressure building over
NY. This will allow winds to turn from the northeast across SC and
GA with a weak CAD taking place. This coupled with the WAA, and the
associated isentropic upglide, will allow for widespread rain to
move across the Midlands and Lowcountry of SC. The precipitation
will likely be most enhanced across the Midlands were the affects of
the CAD are felt. By Friday afternoon into evening, another mid-
level wave embedded in the long wave trough will quickly move east
over VA causing surface cyclogenesis to occur off of the SC/ NC
coast. This newly formed surface low will help drive the CAD further
south, as well as the resultant precipitation. This means that the
highest chances of precipitation Friday will be in the afternoon
hours. Rainfall totals Friday will be highest along and northwest of
a I-95 to Highway 17 line with up to 1" possible. South of I-16 and
along coastal GA, totals will generally be 0.25" - 0.75".

Saturday: The area of low pressure over the Baja of California will
slowly start to become dislodged with the overall long wave trough
axis/ group velocity starting to increase. Near the Hudson Bay, a
potent closed area of low pressure will help drive an arctic cold
front south across the Midwestern United States. This strong thermal
gradient will result in an strengthening upper level jet streak on
the divergent side of the trough axis while nudging the primary
channel vorticity straight overhead. The remnant CAD boundary will
also remain just offshore helping to further focus rainfall towards
the coast (compared to Friday). It should be noted that PWATs for
this period are forecast to be between 1.25 - 1.6". These type of
values are right around the 90th percentile for this time of year.
Hourly rainfall rates will likely be around a few hundredths to a
tenth of an inch, not that impressive, but these rates over the
entire day will equate to rainfall totals in the 0.75" - 1.25"
range.

Sunday: A potent shortwave will dive southeast out of the Colorado
Rockies helping to finally shear apart the pesky Baja of California
low. This shortwave appears to be what will finally push the
rainfall off of the SC/ GA coast. The wave will be over the southern
plains of the United States Sunday with surface low pressure over
the northern Gulf. The surface low will then accelerate northeast
with the shortwave helping drive a cold front through the region
Sunday night/ Monday morning. Precipitation will likely linger
through Sunday morning into the afternoon before coming to an end
from west to east in the evening.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
A cold front will be moving off of the southeast coast of the United
States will CAA setting in behind. No precipitation is forecast
through the long term with temperatures below normal for the period.

The main concern will be the chance for freezing temperatures
Tuesday and Wednesday mornings.

* Tuesday morning: ~20 to 50% of reaching freezing in the coastal
  counties. Inland counties have ~75% of reaching freezing.


* Wednesday morning: ~30 to 50% of reaching freezing in the
  coastal counties. Inland counties have ~85% of reaching
  freezing. Chances are higher Wednesday due to high pressure
  moving directly overhead.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
12Z TAFs: Terminals should remain VFR with light to calm winds
through this morning. KCHS and KJZI TAFs will feature a mention
of MIFG until 13Z. Forecast soundings indicates that moisture
will increase from the top-down today, with some shower
activity over SE GA by this afternoon. The KSAV TAF will feature
a mention of VCSH starting at 20Z. Moisture should surge across
the region this evening, supporting MVFR at KSAV by 1Z. The
coverage of showers should gradually increase this evening,
highlighted in each TAF with a TEMPO. Increasing moisture and
forcing is expected to result in lowering cloud bases late
tonight, reaching IFR 8Z. Rainfall rates may restrict visibility
within the MVFR range. It is possible that LLWS conditions may
develop over KSAV around dawn Friday.

Extended Aviation Outlook:
Friday and Saturday: Multiple rounds of rain through the period with
prevailing MVFR likely (>80%) with IFR conditions also likely (
~70%). Thunder is currently not forecast as the terminals remain on
the cool side of the boundary.

Sunday: IFR conditions recovering to MVFR with rain slowly pushing
south of the terminals late.

Monday: A cold front will cross the terminals late Sunday/ early
Monday with cigs recovering to VFR.

&&

.MARINE...
Today and tonight: No concerns across the marine zones. The pressure
pattern will support wind speeds between 10 to 15 kts. Seas will
remain between 2 to 3 ft.

Friday and Saturday: Winds will veer from the northeast 10 to 15 kt.
Widespread showers and possibly a thunderstorm expected Friday and
Saturday as a coastal low moves northeast. Expect seas 2 to 4 ft.

Sunday: Showers and possibly a thunderstorm. Northeast winds 10 to
15kt. Seas 2 to 4 ft.

Monday: A cold front will cross the waters with winds from the north
around 20 kt. Gusts will approach Small Craft Advisory criteria with
seas 3 to 7 ft.

&&

.TIDES/COASTAL FLOODING...
Minor coastal flooding is forecast along and near tidal
waterways of Colleton and Charleston counties this morning. High
tide should peak around 6:47 AM. A Coastal Flood Advisory is in
effect until 8 AM.

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 Saturday
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.
The forecast remains largely unchanged, with moderate coastal
flooding at Charleston Harbor and just shy of minor coastal flooding
at Fort Pulaski.

&&

.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 until 8 AM EST this morning for SCZ049-
     050.
MARINE...None.

&&

$$

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