Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 220124

Area Forecast Discussion
National Weather Service Charleston SC
924 PM EDT Fri Oct 21 2016

Cool high pressure will prevail this weekend. A dry cold front will
move through late Monday, followed by strong high pressure into the
middle of next week.


Skies were clear this evening in the wake of a cold front which
passed during the afternoon hours. Latest analysis indicated
building high pres with 1 MB per hour pressure rises across the
forecast area at 00Z. Northwest surface winds will remain gusty
at times while the nose of low level cold air advection passes
through. Temps will continue to fall at a steady pace overnight
and much colder low temps forecast still appear on track with
little adjustments for the evening updates.

Lake Winds: Recently Pinopolis was gusting in the 20-25 KT range
and our advisory will continue overnight.


Big changes this period featuring much cooler conditions, although
our noticeable lack of rainfall will continue.

High pressure extending from the upper Midwest to the northwest Gulf
on Saturday pushes east to a position directly overhead Sunday, then
gives way to a cold front from the north that approaches Monday. The
mean long wave trough aloft will remain over the eastern portion of
the nation into early next week, with a deep NW flow to prevail
across the local area.

The atmospheric column is void of any moisture this weekend, with no
more than a little jet induced cirrus clouds Monday. Suffice to say
abundant sunshine will be the rule, and that along with downslope
flow off the mountains will negate some of effects of the noticeably
cooler air mass. We`ll stay close to thickness forecast Saturday and
Sunday, which supports only upper 60s and lower 70s Saturday, with
moderating conditions Sunday allowing for max temps mainly in the
lower and middle 70s. Monday will be the warmest of the short term,
with compressional heating in advance of the cold front to boost
temps back above normal in the upper 70s and lower 80s.

Meanwhile, Saturday Night promises to be the coldest we have seen
since last March. Not anywhere near record lows, but with dew points
in the 30s and 40s, clear skies and little to no wind, temps will
easily fall to 40-45F inland from US-17, upper 40s or lower 50s
along the coast and in downtown Charleston. A few pockets of upper
30s are possible in Allendale, northern Berkeley County, and maybe
west of US-301 in Georgia, but frost seems unlikely. Sunday Night
will again be cool, but a modifying air mass and warmer conditions
during the daylight hours won`t allow for it to get quite as cool.


A dry cold front will cross through the region by Tuesday, leading
to cooler temperatures behind the front due to a northerly component
in the winds. High pressure is forecasted to build over the area
from the north Wednesday, allowing dry conditions and seasonal
temperatures. As the high shifts offshore Thursday temperatures will
start to moderate across the Southeast, rising to near normal for
this time of year. Additionally, a few showers are possible
offshore, near the Gulf Stream.


VFR. Gusty west to northwest winds ebbed a bit at dusk, but expected
to ramp up again later this evening as low level cold air advection
increases. Winds will slacken off overnight at both terminals.

Extended Aviation Outlook: VFR.


Overnight: Strong cold air advection will spread over the marine
area in the wake of a cold front. Expect solid Small Craft
Advisory conditions for all waters with some gale force gusts near
35 kt possible, mainly off the Charleston County coast and beyond
20 nm off the Georgia coast. Seas will build to 2 ft within CHS
harbor, 6 ft within 20 nm and 8 ft in the GA offshore waters,
generally highest to the east given the offshore flow.

Saturday through Sunday: Lingering cold advection and steady
isallobaric pressure rises will keep the ongoing Small Craft
Advisories in effect through late morning or early afternoon. As
high pressure builds from the lower Mississippi Valley later
Saturday and into the southeast states Sunday, more relaxed marine
conditions will take hold over the coastal waters.

Monday through Wednesday: High pressure along the Gulf coast
gradually becomes absorbed by a much larger and stronger area of
high pressure building out of southern Canada and the western Great
Lakes. An east-west aligned cold front will move in from the north
late in the day or early at night, followed by the aforementioned
high building into it`s wake. Modest pressure rises and a tightening
of the gradient behind the front might allow for another round of
Small Craft Advisories into the middle of next week.


SC...Lake Wind Advisory until 8 AM EDT Saturday for SCZ045.
MARINE...Small Craft Advisory until noon EDT Saturday for AMZ350-352-
     Small Craft Advisory until 2 PM EDT Saturday for AMZ374.
     Small Craft Advisory until 8 AM EDT Saturday for AMZ330.


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