Hilton Head Island, South Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

774
FXUS62 KCHS 220555
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1255 AM EST Sun Dec 22 2024

.SYNOPSIS...
Arctic high pressure will build across the region through
Monday. A coastal trough will then develop nearby and persist
into the middle of next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Early this morning: No changes needed to the forecast through
sunrise. Cold dry high pressure will prevail with a northeast
pressure gradient tightening across the forecast area through
the night. Looks look to be on track for the upper 20s inland
and the low to mid 30s as you get closer to the coast. We will
maintain some northeast flow with the coldest temperatures,
producing wind chills in the low to mid 20s right around sunrise
for areas away from the immediate coast. We should remain just
above the Cold Weather Advisory threshold of 20 degrees.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY/...
Modified arctic air mass will continue to build in from the
north Sunday. A mid-level trough will exit the Eastern Seaboard,
leaving northwesterly flow aloft along . Despite full sunshine,
it will be the coolest day of the set with highs topping out in
the upper 40s to lower 50s across southeast South Carolina and
low/mid 50s across southeast Georgia. Lows Sunday night will
fall to the mid/upper 20s inland and 30s along the coast. There
will be some wind present which will lead to wind chills in the
20-25F range, with portions of the northeast tier in the upper
teens. A Cold Weather Advisory could be needed for a few inland
counties.

Surface high pressure will persist inland Monday and Tuesday,
while a coastal trough develops offshore. Models even trend in
the direction of a cut-off low developing during this period.
Aloft, ridging will briefly traverse overhead followed by a weak
shortwave. Isolated to scattered showers look to spread onshore
Monday night from south to north, focusing on the coastal
locations. A tight moisture gradient across the land/sea could
even begin to take shape heading into Tuesday afternoon, if the
trough is able to deepen. However, we still maintain a forecast
that reflects 20-30% POPs inland with near 40% along the
immediate coast. Flow aloft shifting southwest MOnday will
advect warmer and moist air causing highs in the low/mid 50s
Monday to jump several degrees for Tuesday, with most locations
reaching the upper 50s/low 60s. Lows Monday night will range
from the mid/upper 30s far inland to low/mid 40s closer to the
coast.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A restrengthening wedge of high pressure will prevail through
the end of next week, while a coastal trough lingers offshore.
Ridging largely prevails aloft, with a couple of weakening
shortwaves briefly moving through the region. Precip coverage is
a bit unclear throughout the week but with PWat progs near or
over an inch and some signs of lift present, maintained 20-30%
PoPs nearly each day. Temps will trend on the warmer side of
normal, with some upper 60s forecast near the end of next week.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
VFR conditions will prevail at KCHS, KJZI, and KSAV through 06z
Monday.

Extended Aviation Outlook: Flight restrictions are possible in
showers and low clouds associated with a coastal trough late
Monday night through the middle of next week.

&&

.MARINE...
Tonight: A 1035 mb high will build south out of Ontario,
Quebec, and the eastern Great Lakes through the night. This will
cause a tightening of the pressure gradient across the
immediate waters overnight. This along with isallobaric pressure
climbs of almost 3 mb between 1 AM and 7 AM, will result in
strengthening winds once again. We`ll be able to mix about
70-75% of the 35 kt of geostrophic winds at 1000 mb, which will
support hoisting Small Craft Advisories for all oceanic waters.
They`ll began at 1 AM for the Charleston County Atlantic waters,
and 4 AM elsewhere. Seas will average 3-5 feet throughout.
Charleston Harbor winds will reach up to 15 or 20 kt overnight,
but not enough for an advisory.

Sunday through Thursday: A high pressure wedge inland and a
developing coastal trough will result in northeast winds around
15-20 kt Sunday and Monday. Gusts up to 25 kt will prompt Small
Craft Advisories for all marine zones. Seas will gradually
build with 6 footers breaching the nearshore waters by Monday
night. Northeast flow will persist Tuesday through Thursday with
prevailing high pressure inland. SCAs are set to end later
Tuesday as conditions slowly improve. Winds speeds could remain
slightly elevated through the period with a pinched pressure
gradient, averaging 15 knots.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 10 PM EST Tuesday for AMZ350.
     Small Craft Advisory from 4 AM early this morning to 1 PM EST
     Tuesday for AMZ352-354.
     Small Craft Advisory from 4 AM early this morning to 10 PM EST
     Tuesday for AMZ374.

&&

$$

NEAR TERM...BSH
SHORT TERM...
LONG TERM...
AVIATION...BSH
MARINE...