Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 191737
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
137 PM EDT Fri Oct 19 2018

.SYNOPSIS...
High pressure centered north of the region will shift offshore
through tonight. A cold front will move through the area
Saturday night, before high pressure prevails into the middle
of next week. Low pressure could approach the Southeast next
weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
A weak high pressure wedge pattern will exist today as high
pressure to the north spreads south in the lee of the
Appalachians. Meanwhile a weak coastal trough developing off the
GA coast will lift northeast during the day. Weak moist
isentropic ascent will result in fairly dense clouds over
southern areas and the waters, eventually spreading north. Quite
a bit of dry air in low levels will fight any precip that tries
to develop. The best chance for a few light showers will be over
the marine area and immediate coastal sections. Highs will range
from mid to upper 70s.

Tonight: A few showers may linger in the evening along coastal SC,
however overnight we should trend toward a mainly dry night. Clouds
will prevail SC zones but drier air moving over southern GA may
allow for favorable radiational fog conditions late. We introduced
patchy fog toward daybreak Saturday to the south of I-16 to the
west of Savannah. We will see higher surface dew points tonight
and low temps will be milder northern zones, generally low to
mid 60s across the entire area.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
Saturday: Deep-layered high pressure marked by the presence of a
large ridge of high pressure in the mid-lvls will give way to a
large mid-lvl trough of low pressure sweeping through the Great
Lakes region to the Northeast United States by the night. A
northeast to southwest oriented sfc cold front associated with this
trough will quickly push through the Southeast United States late
evening through the night, bringing isolated to scattered showers
(greatest coverage over northern areas) before shifting well
offshore with much cooler and drier high pressure building over the
region from the north behind it late. Ahead of the front, temps will
likely warm into the low/mid 80s (warmest across Southeast Georgia)
before the onset of cold air advection and diurnal heat loss
Saturday evening. Overnight lows will be considerably cooler under
clearing clouds and a northwest/north flow late. In general, temps
will dip into the low/mid 50s inland to upper 50s along the
immediate coast.

Sunday and Monday: A mid/upper lvl trough of low pressure will
quickly exit off the Northeast coast while a somewhat flattened
ridge of high pressure remains over the Gulf of Mexico and Southern
Florida. At the sfc, dry and cool high pressure will prevail through
early week within a north/northeast flow, helping temps remain much
cooler than previous days. In general, highs should only peak in the
mid/upper 60s on Sunday under a full sun. Sunday night lows will be
some of the coldest recently with temps that dip into the low/mid
40s away from the coast. Temps will be slow to rebound on Monday,
but should gradually warm as high pressure modifies over the
Southeast United States. In general, temps should approach the upper
60s to lower 70s Monday afternoon while a few locations peak in the
middle 70s near the Altamaha River.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Conditions will remain mostly dry through the middle of next week as
dry/cool high pressure prevails over the Southeast United States.
However, a few showers associated with a weak coastal trough could
drift onshore (mainly over Southeast Georgia) within a northeast
flow Tuesday and Wednesday, before shower chances increase with a
more direct onshore flow by Thursday. Latest guidance in split in
regards to the track and strength of a low pressure system impacting
the area next weekend. Regardless of the track, the system should
bring at least chances of showers over Southeast South Carolina and
Southeast Georgia next weekend. In regards to temps, highs should
range in the mid 70s Tuesday and Wednesday before clouds and
increasing shower chances keep max temps in the lower 70s Thursday
and Friday. Overnight lows should generally range in the mid/upper
50s inland to lower 60s along the immediate coast.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Mainly VFR at both sites. Slight chance for MVFR ceilings at
KCHS this afternoon as stratocumulus expands due to a coastal
trough. However, ceilings have developed around 3500 ft early
this afternoon and will likely remain close to this height
through the rest of the afternoon.

Diminishing winds and partial clearing over southeast GA may
allow for a period of IFR stratus/fog at KSAV late tonight but
probabilities are currently pretty low.

Extended Aviation Outlook: Brief flight restrictions are
possible with showers along a passing cold front Saturday
evening into early Saturday night, mainly at the CHS terminal.
Otherwise VFR conditions are expected at both CHS and SAV
terminals through early next week.

&&

.MARINE...
A wedge pattern maintaining modest northeast flow in the 15-20 kt
range outside of the pilot buoys early this morning. The flow near
the coast was just a bit weaker, closer to 15 kt. A coastal trough
will sharpen today with a weak wave of low pressure expected to
ride north along it`s axis late day and this evening. The flow
should gradually veer around to offshore with the passing of weak
low late tonight. Speeds will continue to weaken, probably becoming
light and variable at some point this evening. Seas will slowly
subside through tonight.

Saturday through Wednesday: High pressure will give way to a quickly
advancing cold front that shifts over the coastal waters Saturday
evening and night. A quick punch of cold air advection associated
with high pressure building from the north/northwest along with an
enhanced pressure gradient will likely support Small Craft Advisory
level conditions for much of coastal waters Saturday night into
Sunday. In general, northwest winds could gust upwards to 25-30 kts
over all waters while seas build up to 5-7 ft, highest in northern
South Carolina and offshore Georgia waters. Gale force wind gusts
remain possible briefly over northern South Carolina waters late
Saturday night into early Sunday. The pressure gradient is then
expected to weaken later Sunday, supporting winds that top out near
20 kt and seas that subside to 3-5 ft Sunday night. Expect
conditions to gradually improve into the middle of next week as
winds become more northeast/east and a weak coastal trough
potentially develops off the Southeast Georgia coast.

&&

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

&&

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


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