Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
344 PM EDT Wednesday Oct 7 2015
high pressure will build into the region overnight through Friday.
A weak cold front will approach from the northwest this weekend.
Near term /until 6 am Thursday morning/...
this evening and tonight...high pressure will settle into the
region...producing dry weather conditions through the overnight
period. Clear skies and light/calming winds will result in fair
radiational cooling. Given the setup...some patchy but shallow
ground fog is possible after midnight...especially where the
ground remains saturated from previous rainfall. The greatest
chance of fog should occur within a few hours of daybreak. In
general...low temperatures are expected to dip into the middle 50s inland to
low/middle 60s along the immediate coastline.
Short term /6 am Thursday morning through Saturday/...
Thursday...another mostly sunny day is expected as a ridge of high
pressure at the surface settles over South Carolina. I do expect some
radiational ground fog in the morning due to the light winds...but
that should burn off by middle morning. There could be some high clouds
moving in late as an upper level jet and associated weak disturbance
approach from the west...but that should not prevent temperatures
from getting into the lower to middle 80s...except along the coast as
onshore winds kick up in the afternoon. Overnight lows should drop
back to the 60-65 range.
Friday...heights should build aloft ahead of a shortwave moving into
the Ohio Valley during the day and into the evening. Moisture will
be increasing a little...so I cant rule out the slight chance of an
afternoon or evening shower as a cold front approaches from the
northwest. However...no significant rainfall amounts are expected.
Temperatures will again be in the 80s.
Saturday...the front will slide into the area...providing a better
chance of showers and thunderstorms. Clouds will keep temperatures down
into the upper 70s to lower 80s. Right now...models indicate one
inch or less rain...which would not cause new flooding but could
slow down the recession of flood waters a bit. Will keep a close
eye...though...as the models are getting a bit stronger with the middle
level disturbance accompanying the front.
Long term /Saturday night through Wednesday/...
Saturday night the front will move out to sea and high pressure
will begin building back in from the west. Dry conditions will
gradually return from west to east across the County Warning Area. Sunday an upper
level low develops off the Carolina coast. This low may bring some
showers along the immediate coast and plenty of clouds.
Temperatures will also be a few degrees below normal...the low to
middle 70s. The low will quickly move to the northeast...away from
our area...on Monday and high pressure will build back into our
area where it will remain in place through Tuesday. Temperatures
will moderate each day...reaching normal (upper 70s to near 80) on
Aviation /20z Wednesday through Monday/...
VFR conditions will prevail at both terminals through 18z
Thursday. There is a low chance of shallow fog at both terminals
within a few hours of daybreak Thursday morning.
Extended aviation outlook...mainly VFR through Friday night. There
could be a brief period of MVFR/IFR on Saturday and Saturday night
in the vicinity of showers and thunderstorms.
this evening and tonight...a Small Craft Advisory will remain in
effect for offshore Georgia waters early tonight...mainly for
lingering 6 feet seas. Otherwise...high pressure will settle over the
coastal waters through the overnight period...producing a brief
surge in winds that remain at or below 10-15 kts. Seas will
gradually subside during the overnight period...ranging between
2-3 feet in nearshore waters and 3-5 feet in offshore Georgia waters
Thursday though Monday...winds and seas will drop on Thursday as
surface high pressure settles in...collapsing the gradient. Winds
and seas should remain well below Small Craft Advisory criteria through Saturday as
the pressure gradient will remain weak despite the approaching cold
front. Winds could pick up again on Sunday behind the front...but
should still remain 15 knots or less with seas 3 feet or
less...except possibly 4 feet beyond 40 nm in the outer Georgia
areal flooding...flood waters left by historic rainfall will slowly
recede over the next few days. Although some areas will see slow
improvement...spots near the edisto and Santee rivers could see
worsening conditions as river levels rise.
River flooding...major flooding is expected to continue on the
edisto river near Givhans Ferry through the weekend.
Additionally...flooding is expected to rise from the current
moderate level to major over the weekend on the Santee river at
a coastal Flood Advisory is valid until 700 PM this evening for
Charleston/coastal Colleton counties. The 452 PM high tide will
likely peak between 7.2 to 7.5 feet mean lower low water in the
High tides are expected to approach...or slightly eclipse...7 feet
MLLW for Charleston Harbor during the next several days. Any
expected levels above 7 feet would require coastal flood advisories.
SC...coastal Flood Advisory until 7 PM EDT this evening for scz049-
Marine...Small Craft Advisory until midnight EDT tonight for amz374.