279
FXUS62 KCHS 121505
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1005 AM EST Wed Feb 12 2025

.SYNOPSIS...
A warm front will lift just north of the area on today ahead of
an approaching cold front that will impact the area Thursday.
This boundary is expected to stall just south of the region on
Friday, lifting back north as a warm front Friday night into
Saturday, with a stronger cold front impacting the area on
Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Update: Webcams and surface observations indicate the dense fog
has lifted in most locations, so we expired the advisory. While
pockets of fog could persist across inland GA for the next hour
or two, it`s not enough to keep the advisory going in that
location. We are closely monitoring the temperature trends. The
hourly observations so far indicate it being colder across our
north and warmer across our extreme southeast than initially
forecasted. The concern is this will persist, which could make
our SC highs too warm. But we`ll keep monitoring trends before
making any massive changes. The same with POPs across extreme
inland locations. Radar only points to slight chance at this
time, and that`s what we kept the forecast.

Today: Aloft, southwest flow will prevail as the area sits
between a ridge over the southwest Atlantic and a trough moving
into the Northern Plains. At the surface, a stationary boundary
will begin the day oriented west to east across south GA
extending into the nearby outer coastal waters. Overall,
precipitation is not a significant concern today as the forecast
area remains displaced from the deep moisture and strongest
forcing back to the west and northwest. An isolated shower or
two could briefly brush our inland- most counties this
afternoon, but otherwise dry. Instead, the main forecast concern
is the aforementioned stationary boundary and its attempt to
slowly lift north and push inland across the forecast area. The
boundary and its movement will have significant implications for
temperatures, leading to an exceedingly tricky forecast. The
morning begins with widespread low stratus across the entire
forecast area. This is not exactly an ideal setup for the
boundary to lift north as a warm front and scour out the well
established cold air damming. Model guidance is notoriously too
aggressive in lifting the boundary northward in these situations
and we suspect this time is no different. The boundary is
expected to lift into a position where it is roughly right
across the middle of the forecast area. The high temperature
gradient will be nearly impossible to depict, but could be 20
degrees or more. Forecast highs are in the low 80s along and
south of I-16, ranging to around 60 for areas around Allendale,
and even in the low to mid 50s north of Lake Moultrie.

Tonight: The warm front should finally lift completely through
the forecast area overnight as the upstream cold front finally
starts to push eastward and approach the area. Much like the
daytime, the forecast is pretty much dry as the best forcing and
moisture will reside to the west along the cold front. Fog
could again be an issue, especially if fog lingers along the
nearshore coastal waters into the evening and is advected inland
within the southerly flow. For inland areas where the warm
front arrives latest, temperatures will be at the lows in the
evening and then rise through the overnight. By sunrise Thursday
most locations should be in the low to mid 60s.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
An active day is on tap for Thursday as southwesterly flow
prevails aloft and a cold front approaches the region from the
west. With the forecast area solidly within the warm sector
temperatures on Thursday will reach into the mid to upper 70s,
with dew points in the mid to upper 60s. A line of showers and
thunderstorms is forecast to push through the region, entering
the far western zones around 14Z and clearing the coast by 22Z.
It is worth noting that CAMs show the line becoming jagged and
almost falling apart as it reaches the forecast area.
Additionally, thunder chances do not look as favorable as
previous forecasts. Instability will likely be a limiting
factor, with CAPE values only around 300-400 J/kg. While there
is plentiful shear, on the order of 40 knots, Lifted Index
values as well as Total Total values are not painting a picture
for convection. The forecast currently features a slight chance
of thunder associated with the line of showers/storms. Moisture
will still be plentiful, with PWATs approaching 1.7-1.8", which
would be near the daily maximum according to SPC Climatology.
Generally rainfall amounts across the area range from 0.5 inches
to 0.75 inches, with the highest amounts across southeastern
GA. Temperatures Thursday night post-FROPA will drop into the
40s across the region.

The aforementioned cold front will linger just to the south of
the forecast area on Friday as high pressure briefly builds into
the region. Highs on Friday will be slightly below normal,
generally in the upper 50s to low 60s. The forecast is rain-free
with partly sunny skies. Temperatures on Friday night will
again dip into the 40s. Friday night and into Saturday morning
the boundary will begin to lift northward as a warm front. Warm
conditions will again take over the region as temperatures warm
into the mid to upper 70s with dew points increasing into the
low 60s by Saturday afternoon. Isolated to scattered showers
will be possible on Saturday as well.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
A mid-level trough will swing eastward Saturday night and into
Sunday, clearing the East Coast on Monday. Zonal flow will
prevail thereafter through mid-week. At the surface a strong
cold front will push through the region on Sunday, with high
pressure building in from the west post-FROPA and through mid-
week. Another cold front could approach the region mid-week.
Temperatures on Sunday will be above normal, generally in the
low to mid 70s. Showers and possible thunderstorms will impact
the region on Sunday associated with the cold front. The overall
severe threat remains low. Sunday could be a breezy day,
including over Lake Moultrie. A Lake Wind Advisory may be
required. Post-FROPA overnight temperatures on Sunday will
plummet to around freezing inland and upper 30s to near 40 along
the coastal counties. Temperatures Monday will be well below
normal, gradually warming into the week as high pressure builds
in. Rain chances will remain minimal early in the week, with the
next chance of rain mid week as another cold front approaches
the region.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
The 12z TAF period begins with widespread IFR ceilings and
visibilities, including KCHS, KJZI, and KSAV. Visibilities
should improve by mid morning though low ceilings will persist.
The stratus is expected to mix out and lift at KSAV this
afternoon allowing an improvement to VFR which will likely
continue into the early morning hours. At KCHS and KJZI, IFR
ceilings will persist longer. A warm front will eventually lift
through from the south which should allow ceilings to lift to
MVFR or even VFR for a period of time. Another round of fog and
stratus issues will be possible late in the TAF period.
Northeast winds will persist this morning and then turn
southerly behind the lifting front.

Extended Aviation Outlook: Flight restrictions are possible on
Thursday associated with a line of showers and thunderstorms.

&&

.MARINE...
Today through tonight: A warm front will eventually lift
northward through the waters today and the flow regime will turn
southerly behind it through the overnight. In fact 15-20 knots
of southerly flow is expected for much of the waters. Seas
should average 2-4 feet today, then increase through the
overnight with the strengthening southerly flow. In fact, 6 ft
seas are expected to get into the Charleston County waters
starting in the early morning hours and a Small Craft Advisory
has been issued there.

Marine fog: Webcams and the CHS Pilot Office indicate the dense
fog in Charleston Harbor has lifted, so we cancelled the Dense
Fog Advisory for that zone. Satellite imagery and coastal web
cams suggest that widespread dense fog is still ongoing across
all of the ocean waters. A Dense Fog Advisory remains in effect
through noon Wednesday. It is certainly possible that the dense
fog could linger beyond noon and the advisory could need to be
extended. Fog is then possible yet again during the overnight
period but confidence is low in the possible coverage and
density.

Thursday through Monday: A cold front will push through the
waters on Thursday, stalling just to the south of the region on
Friday. This boundary will then lift northward as a warm front
Friday night into Saturday, with a stronger cold front pushing
through on Sunday and high pressure building in thereafter.
Across the marine waters a Small Craft Advisory will be ongoing
to start Thursday across the Charleston County nearshore waters
for both 25 kt gusts and some 6 ft seas. Thursday night should
be SCA free, however beginning Friday morning a prolonged period
of Small Craft Advisories will likely be observed across all
marine waters outside of the Charleston Harbor. Gusts on Friday
will reach around 25 knots while seas increase to 4 to 6 ft.
While winds wane on Saturday, the 6 ft seas will likely linger.
On Sunday as the stronger cold front approaches winds will again
begin to ramp back up, with gusts to 30 knots possible
everywhere, including the Charleston Harbor. Additionally some
gale force gusts will be possible in the Charleston County
nearshore and the 20 to 60 nm offshore GA waters. A Gale Watch
may eventually be needed. Seas on Sunday will also build to 5 to
7 ft. Conditions will rapidly improve into Monday.

&&

.CLIMATE...
Record High Temperatures:

February 12:
KCHS: 79/2017
KCXM: 76/1898
KSAV: 84/2020

February 13:
KCHS: 78/1976
KCXM: 77/1927
KSAV: 86/2020

Record High Minimum Temperatures:

February 13:
KCHS: 61/2020
KCXM: 62/2020
KSAV: 64/1880

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Dense Fog Advisory until noon EST today for AMZ350-352-354-374.
     Small Craft Advisory from 1 AM to 4 PM EST Thursday for AMZ350.

&&

$$

NEAR TERM...
SHORT TERM...CPM
LONG TERM...CPM
AVIATION...CPM
MARINE...CPM