Area Forecast Discussion
Issued by NWS Charleston, SC

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446
FXUS62 KCHS 190849
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
349 AM EST Sun Nov 19 2017

.SYNOPSIS...
A cold front will push offshore this morning, followed by high
pressure through Tuesday. A coastal low may move up the coast
Tuesday and Tuesday night, followed by a second low pressure
system late in the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Early this morning: The narrow band of showers just ahead of
the approaching cold front continues to display a weakening
trend as it enters the forecast area. At its current pace, this
band of showers will be along the coast or just offshore around
or just after sunrise. Rainfall amounts will be light, only a
few hundredths in most locations.

Today: The axis of the vigorous upper trough will swing into
the region today as an associated cold front pushes offshore.
Any lingering showers will mainly impact the coast for a couple
of hours this morning and the rest of the day will be dry as
high pressure begins to build in from the west. Skies will clear
out quickly this morning, such that by late morning land areas
should be clear. Winds will be breezy this morning beginning
just after sunrise in the post- frontal airmass as cold
advection takes place and the pressure gradient remains tight.
By the afternoon though the gradient will relax a bit and winds
will begin to diminish. Temperatures will be nearly steady this
morning with little diurnal rise into the afternoon. Daytime
highs are expected to top out in the low to mid 60s.

Tonight: The surface high to the west will begin to bridge
across the southern Appalachians and into the lee which will
help to maintain the gradient along the coast and the adjacent
coastal waters. Inland areas will likely maintain at least some
light flow for much of the night before decoupling late. With
clear skies and the expected configuration of the surface high,
the best radiational cooling conditions will favor locations
inland of I-95. Forecast lows in these areas are in the low to
mid 30s and patchy to scattered frost is anticipated. Will
continue to highlight the possible need for a Frost Advisory in
the Hazardous Weather Outlook.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
Dry, cool high pressure will prevail on Monday with below
normal temperatures in the low to mid 60s. Temperatures will
rebound on Tuesday as the surface high shifts offshore and a
warm air advection pattern commences. As an upper trough
develops over the eastern United States, a weak surface low will
move up the Southeast coast late Tuesday and Tuesday night. The
best chance for showers will be along the immediate coast and
the coastal waters, though isolated showers will be possible
farther inland due to weak isentropic ascent. Dry high pressure
will rebuild on Wednesday.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
A strengthening upper shortwave over the northern Gulf of
Mexico on Thursday will lift northeast through Friday night,
pushing another surface low up the coast. A fairly sharp
precipitation gradient is possible with inland areas seeing
little to no precip while much greater coverage occurs over the
coastal areas. Dry weather currently anticipated next weekend.
Below- normal temperatures will prevail.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
The main concern for this TAF period is the line of showers
that will move through KCHS and KSAV roughly in the 09-11z time
frame. The showers will not be particularly strong, and
visibility values are expected to remain VFR. However, there
could be a brief period of MVFR ceilings as the showers and the
front pass through. Skies will clear out later this morning and
remain clear through the remainder of the period. Southwest
winds will be gusty ahead of the front, before turning west and
then northwest through the remainder of the morning.

Extended Aviation Outlook: MVFR ceilings may develop late
Monday night and persist through Thursday. Brief vsby
restrictions in scattered showers late Tuesday through Thursday.

&&

.MARINE...
Today: A sharp cold front will push across the local waters
this morning. Strong southwest winds continue early this morning
ahead of the approaching front, and Small Craft Advisories are
in effect for all zones including the Charleston Harbor. Just
after sunrise, winds will veer around to west-northwest and then
northwest with the passage of the front. There will likely be a
temporary lull in wind speeds before they pick up again with
the onset of cold advection. By late morning wind speeds are
expected to drop off enough that the advisories will begin to
come down, though winds will remain elevated in the 15-20 knot
range through the afternoon. Seas will peak in the Charleston
County waters and the outer Georgia waters in the 4-7 ft range
this morning. Elsewhere, seas will mainly be in the 3-5 ft range
before dropping off to 2-4 ft by the late afternoon.

Tonight: A surface high pressure center will slide in to the
northwest and north of the local waters. As it does, winds will
steadily veer to northerly and eventually northeasterly. The
pressure gradient will be tightest along the coast and over the
local waters, keeping speeds in the 15-20 knot range. Seas will
remain in the 2-4 ft range.

A series of high pressure systems will affect the waters next
week. An area of low pressure may shift up the coast Tuesday
into Wednesday, followed by another system Thursday into Friday.
A prolonged northeast gradient will result, with increasing
winds/seas mid to late week, potentially necessitating Small
Craft Advisories.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 10 AM EST this morning for AMZ330.
     Small Craft Advisory until noon EST today for AMZ350-352-354.
     Small Craft Advisory until 4 PM EST this afternoon for AMZ374.

&&

$$

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



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