Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 240229
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1029 PM EDT Sat Mar 23 2024

.SYNOPSIS...
A cold front will move through the region tonight. High
pressure will prevail through early Tuesday. A storm system
will impact the area Wednesday into Thursday, followed by high
pressure into next weekend.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Main surface cold front and remaining showers are offshore with
perhaps a secondary boundary/dewpoint boundary advancing down
through the midlands. Last round of cloud cover is also
advancing through the region with a definitive back edge through
the midlands and eastern Georgia. Thus skies will remain on the
cloudy side for the next several hours before clearing out in
earnest heading into early Sunday morning.

Temps and dewpoints currently remain on the mild/moist side of
things. But stronger cold and dry air advection will be kicking
in after midnight and should eventually knock temperatures down
into the 40s by Sunday morning. We made some adjustments to the
hourly temps to address the expected trends.

Wind-wise: We are in a bit of a lull at the moment. But gustier
northerly winds will be kicking in after midnight as strong
high pressure and a tighter pressure gradient build across the
region. Not enough for land based Wind Advisories, but gusts in
excess of 25 knots look on track on Lake Moultrie and the Lake
Wind Advisory will remain as-is.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Aloft, a trough will shift further offshore across the western
Atlantic Sunday, making way for a ridge to expand across the
Southeast United States with an axis that becomes positioned
across the local area Monday into Tuesday. At the sfc, high
pressure will build south across the Mid-Atlantic and Southeast
states on Sunday behind a departing cold front well offshore,
then hold across the local area through Tuesday.

The pattern will favor dry and cooler conditions on Sunday with
a northeast flow limiting high temps in the low-mid 60s. Sunday
night lows should also be a bit cooler with light northeast
winds in place. In general, lows should range in the mid-upper
30s north and inland across southeast South Carolina to low-mid
40s elsewhere away from the immediate coast. An onshore wind
should keep temps in the upper 40s at the beaches.

By Monday, mid-lvl ridging across the Southeast United States
will be ongoing, then will strengthen Tuesday as the ridge axis
becomes placed across the local area. This feature will favor
some airmass modification early week, leading to high temps in
the mid-upper 60s across most areas, and temps potentially
around 70 degrees along the Altamaha River. Monday night lows
will also become noticeably warmer than the previous night,
ranging in the mid-upper 40s north and inland to low-mid 50s
near the beaches and across areas along and south of I-16 across
southeast Georgia. By Tuesday, the combination of mid-lvl
ridging and sfc winds turning more easterly should result in
noticeably warmer temps, with highs peaking in the low-mid 70s
across southeast South Carolina to upper 70s across much of
southeast Georgia.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A potent upper trough will move through the area Tuesday night
through Thursday, along with a surface low moving up the
Southeast coast. Deep tropical moisture streaming into the area
during this time, combined with ample synoptic scale forcing,
could bring widespread showers and a few tstms Wednesday into
Thursday. Most of the guidance is showing 1-2" of QPF across
much of the area during this time, with some models showing
upwards of 3" in spots.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Shower threat has largely ended at the terminal sites with VFR
conditions and gustier northerly winds. Forecast soundings
suggest there may be another band of MVFR cloud cover pressing
through the region later this evening into the overnight hours.
Our confidence in MVFR conditions is not great however, but we
do show some cloud cover (with a sct MVFR deck) lingering
through much of tonight. Cloud cover will clear out in earnest
toward sunrise Sunday.

Gusty northerly winds will be the rule tonight and through much
of Sunday with gusts into the 20 to 25 knot range. Winds
diminish later in the afternoon Sunday and heading into Sunday
night.

Extended Aviation Outlook: VFR conditions are expected at
CHS/JZI/SAV terminals Sunday afternoon through early Tuesday. A
storm system/cold front could bring showers and/or thunderstorms
to the area Wednesday and Thursday, resulting in flight
restrictions due to reduced vsbys/cigs at all terminals.

&&

.MARINE...
Tonight: Strong high pressure will build from the north and
northwest, leading to an increasing pressure gradient across the
region and a period of gusty northerly winds overnight. A
relatively brief window of gale force wind gusts still looks on
track for the Charleston nearshore waters and outer Georgia
waters, with solid Small Craft Advisories for the remaining
marine areas including Charleston Harbor. Expect seas to build
in response to the winds, peaking late, highest far offshore.

A large trough and associated cold front will shift further
offshore across the western Atlantic to start off the week,
supporting cold air advection across local waters and a tight
pressure gradient into Sunday morning, while low-lvl mixing taps
into 1000 mb geostrophic winds between 35-40 kt. A Gale Warning
will remain in effect across nearshore waters off the
Charleston County coast and offshore Georgia waters at this
time, but conditions should show signs of improving late morning
as cold air advection wanes during afternoon hours. Gale
Warnings should transition into Small Craft Advisories
thereafter, mainly while northeasterly winds associated with
high pressure allow for elevated seas to linger into
Tuesday/Wednesday. Elsewhere, Small Craft Advisories will be
ongoing Sunday morning with conditions following a
weakening/subsiding trend by late Sunday morning. Conditions
should fall below advisory criteria across the Charleston Harbor
by noon Sunday, but remain across nearshore waters due to
elevated seas associated with a northeast flow into Tuesday.

A storm system is anticipated to arrive across the region
Wednesday into Thursday, bringing showers and thunderstorms
across local waters. The pressure gradient will strengthen and
seas build with a cold front shifting offshore, which should
require additional Small Craft Advisories across local waters
late Wednesday into Thursday.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Lake Wind Advisory until noon EDT Sunday for SCZ045.
MARINE...Small Craft Advisory until noon EDT Sunday for AMZ330.
     Small Craft Advisory until midnight EDT tonight for AMZ350-374.
     Gale Warning until noon EDT Sunday for AMZ350-374.
     Small Craft Advisory until 6 PM EDT Tuesday for AMZ352-354.

&&

$$

NEAR TERM...Adam
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...Adam/DPB
MARINE...Adam/DPB


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