Hilton Head Island, South Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

817
FXUS62 KCHS 180648
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
148 AM EST Sat Jan 18 2025

.SYNOPSIS...
High pressure will prevail tonight. An area of low pressure and
associated cold front will impact the region this weekend.
Another low pressure system could impact the region early to
mid next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Tonight: Aloft, broad ridging along the Eastern Seaboard will shift
offshore with time as a trough advances across the Mississippi River
Valley and toward the central/southern Appalachian Mountains late.
At the sfc, weak high pressure will prevail with a subtle inverted
trough across the nearby Atlantic.

The main focus for the overnight period will be how cool temps reach
during the next hour or two, before cloud cover associated with
a strong upper lvl jet thickens across the local area and weak
warm advection takes place. At this time, temps have dipped into
the upper 30s across parts of the Tri-County Area along with
Colleton County, but temps remain more mild to the southwest,
generally in the low-mid 40s. Temps should gradually begin to
warm late tonight and through daybreak.

Another concern will be the arrival of light rain in advance of the
frontal system to the west and possibly with the inverted trough
across the nearby Atlantic late. At this time, model soundings
suggest a large amount of dry air in the low-mid levels, which will
take time to moisten up through overnight hours, and should result
in most areas precip-free through daybreak. However, light rain
could enter western most zones an hour or so prior to daybreak
as moisture deepens and stronger forcing arrives.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY/...
Saturday and Sunday: Saturday will be a wet day across
Southeast South Carolina and Southeast Georgia ahead of cold
front. Model vertical cross sections show strong forcing induced
by a series of embedded southern stream shortwaves passing
through juxtaposed with deep moisture with mean RH values >90%
throughout the column. This should result in a large area of
light to moderate rain moving steadily east across the Deep
South, which is on target to push west- east across the local
area during the day Saturday. HREF pops for QPF >0.01" remain
near 100% and the forecast will continue to reflect categorical
pops with the highest pops focused on the morning hours.
Elevated rain chances will persist into Saturday night into
Sunday as anther surge of shortwave energy passes through ahead
of the arctic cold front. A drier trend should occur Sunday
afternoon as the front pushes offshore and colder, drier air
begins to advect into the region. High will warm into the 58-65
degree range Saturday (warmest south of I-16) with lower-mid 60s
Sunday before FROPA. Lows Sunday morning will drop into the
upper 40s/lower 50s. It will begin to get a bit breezy mid-late
afternoon Sunday with the onset of post-frontal cold air
advection.

Sunday Night and Monday: Both periods look to remain dry as
arctic high pressure builds into the region. Highs will only
reach the lower 40s for many areas Monday afternoon with lows
Sunday night dropping into the mid 20s inland to upper 20s
closer to coast. Enhanced northwest winds will help push wind
chills into the 15-20 degree range, which is solidly in Cold
Weather Advisory criteria.

Lake Winds: Breezy conditions will develop on Lake Moultrie
late Sunday afternoon as a cold front pushes through. Strong
post-frontal cold air advection will push winds into the 15-20
kt range with gusts 25-30 kt Sunday night and a Lake Wind
Advisory could be needed during this time. Speeds should below
advisory criteria by mid-morning Monday.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
The forecast is starting to narrow in on a wetter and colder
solution for the upcoming mid-week winter event as arctic high
pressure settles in. All of the operational runs of the GFS, EC
and CMC are starting to align with support from many of their
accompanying ensemble members. This coupled with trends noted in
the NBM is finally allowing for some increased confidence in
how the event will unfold as low pressure passes by to the south
and offshore. There remains some uncertainty on how the p-types
will evolve as the event progresses, but it is becoming
increasingly favorable for a snow/freezing rain event which
could bring impacts, possibly significant, to Southeast South
Carolina and Southeast Georgia. Complicating matters is there
are signals that enhanced forcing induced by bands of mid-level
frontogenesis could yield corridors of enhanced precipitation
rates, which could result in pockets of moderate to locally
heavy precipitation. How much of this enhancement will occur is
yet to be determined and can not be readily identified this far
out. This is certainly something to watch as these bands could
augment both p-types, precipitation rates and accumulations. It
is still too far out to identity any specific snow/ice
accumulations and impacts this far out, but the probabilities
for both accumulating snow and ice are increasing and the
forecast will reflect this trend. Timing for the period of
greatest impacts looks to center on the Tuesday afternoon to
early Wednesday period when the coldest air will align with the
strongest forcing and heaviest precipitation. Some light
precipitation could reach parts of the Georgia coast before
daybreak Monday with precipitation ending Wednesday morning.

In addition to winter weather, bitterly cold temperatures will
occur. Temperatures are trending colder with highs mid-week
poised to stay in the 30s both Tuesday and Wednesday afternoons.
Lows Tuesday night will drop into the lower-mid 20s with upper
teens/lower 20s Wednesday night. Wind chills will drop 15-20
Monday night, 8-15 Tuesday night and just a tad warmer for
Wednesday night. A Cold Weather Advisory will likely be needed
during this time and there is even a chance for some areas to
reach Extreme Cold Warning criteria (10 or colder), especially
Tuesday and Wednesday nights.

Another area of low pressure could develop off the South
Carolina coast Thursday into Friday. With temperatures still
quite cold, a brief period of freezing rain could occur, mainly
Thursday morning and again early Friday morning with the best
chances across the interior.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions will prevail at CHS/JZI/SAV terminals tonight through
mid morning Saturday. Rain/showers are then expected to develop
across the region with the approach of a frontal system, likely
leading to periods of MVFR cigs by around 19Z at all terminals.
Precip coverage expands throughout Saturday afternoon with cigs
expected to lower to IFR conditions at all terminals by around
22Z. IFR cigs should then prevail through 06Z Sunday at all terminals.

Extended Aviation Outlook: Flight restrictions are likely
Saturday evening into Sunday morning as widespread rains move
through in association with a cold front. The risk for
restrictions in low vsbys and ceilings will return Tuesday
morning into Wednesday morning as a potential winter storm
impacts the region. There is an increasing chance for freezing
or frozen precipitation to impact all terminals during this time
period.

&&

.MARINE...
Tonight: A weak pressure gradient will be in place well ahead of a
frontal boundary to the west as high pressure remains north/offshore
while a subtle inverted trough nearby. The pattern will result in
light winds (at times variable) up to 5-10 kt, but generally turning
from east to south late. Seas will range between 1-2 ft.

Saturday through Wednesday: Gusty southwest winds will prevail
Saturday into Sunday ahead of a cold front. Gusts will be close
to Small Craft Advisory criteria a times. Advisory conditions
are more likely Sunday night as strong cold air advection
spreads over the waters behind a cold front. Stronger winds are
expected Tuesday into Wednesday as the pressure gradient
tightens between inland high pressure and low pressure passing
well offshore. Northerly winds could reach as high as 25-30 kt
at times with periods of gale force gusts. Small Craft
Advisories are likely with a possibility for a Gale
Watch/Warning. Seas look to peak early Wednesday morning, 5-8 ft
nearshore waters out 20 NM and 9-14 ft over the Georgia
offshore waters out 20-60 NM. Finally, mariners should be alert
that some winter precipitation could fall over the coastal
waters Monday night into Wednesday morning, reducing vsby to 1
NM or less at times.

&&

.CLIMATE...
Record Low Temperatures:

Thursday, January 23:
KCHS: 19/1985
KCXM: 24/2003
KSAV: 19/1960

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

$$

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