Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 232003
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
403 PM EDT Fri Jun 23 2017

.SYNOPSIS...
A cold front will gradually move through the area this weekend,
moving off the coast Monday. Drier high pressure will build in
from the northwest for much of next week before moving offshore
late week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Atlantic high pressure will continue to stretch westward
across much of the area while troughing approaches from the
northwest as the remnants of Cindy move northeast toward the Mid-
Atlantic region. Much of the lingering showers/thunderstorms will
end this evening with the loss of daytime heating and sea breeze
forcing. Some convection may develop near the SC coast late as
moisture convergence increases. Otherwise expect generally partly
cloudy skies and mild temperatures in the mid to upper 70s for most
locales. The record high minimum temperatures of 79 degrees may be
challenged at KCHS/KSAV, although probably more likely at KCHS.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
A broad upper trough will persist across the central United
States while a cold front gradually sinks southeast into the
area. Most of the upper shortwave energy will remain to the
northwest of the area Saturday into Sunday. However, deep
tropical moisture will spread across the area with Precipitable
Water values 2.0-2.2" during the period.

Given the deep WSW flow in the lowest 500 mb of the atmosphere
on Saturday, the morning will be mostly dry. The best chance for
precipitation will come later in the afternoon as the cold front
begins to approach. We held the PoPs until the latter half of
the afternoon with the highest values farther inland. The
ensuing morning subsidence should allow for considerable
sunshine and the development of moderate surface-based
instability. 0-6 km bulk shear vectors increase to around 25 kt
late in the afternoon farther inland with CAPEs 2500-3000 J/kg.
Some organized thunderstorms may move into our area late in the
afternoon or during the evening with at least some damaging wind
potential.

The cold front will stall out along our coast on Sunday while
deep moisture persists. Greater cloud cover in the morning
should somewhat limit instability, and with the greatest upper
forcing remaining to the northwest, convergence will primarily
be driven by the nearby cold front. Fairly good coverage of
showers and tstms expected, especially closer to the coast.

Low to mid 60s dewpoints are progged to move into inland areas
on Monday as drier high pressure gradually builds southeast. The
front will slowly drift southeast, though sticking around long
enough to maintain at least isolated showers and tstms over
coastal areas and the adjacent Atlantic waters.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Monday night the cold front will be offshore of our area, dissipating
as it moves further away. Meanwhile, high pressure from the
central U.S. will gradually be building towards our area. The
high is expected to pass north of our area Wednesday, then move
offshore Thursday. Dry conditions are expected for most of the
land area. The only shower threat appears to be over the coastal
waters each night and maybe along portions of the immediate
coast. Temperatures will be slightly below normal through
Wednesday, then creeping up on Thursday.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
VFR. Some showers/tstms are expected to develop inland this
afternoon but chances of significant impacts at the terms are
too low to mention.

Extended Aviation Outlook: Periods of flight restrictions are
expected late Saturday into Monday due to a cold front slowly moving
through the area.

&&

.MARINE...
Tonight: Atlantic high pressure will hang on to the east while
the remnants of tropical cyclone Cindy move northeast toward the
Mid-Atlantic region. This will set up a pressure pattern
favorable for increasing south/southwest winds, generally
highest across the Charleston County waters where the best
gradient/jetting is likely. Think winds will gust near 25 kt
across this area along with seas building to 6 ft toward 20 nm
offshore and thus an Advisory will remain in effect for this
area. Conditions will be close to Advisory thresholds
elsewhere as well but confidence in coverage/duration of
criteria is low.

Saturday, a tightening gradient ahead of a cold front will
maintain 25 kt gusts and 6 ft seas over portions of the
Charleston nearshore. Thus a Small Craft Advisory persists
through Saturday evening. Our forecast wind gusts in Charleston
Harbor for Saturday afternoon are currently just shy of Small
Craft Advisory given gusts of 22-23 kt when the sea breeze
enhances the existing flow.

Winds and seas will diminish considerably later Saturday night
through the middle of next week as the cold front drops south
and high pressure gradually expands southeast.

Rip Currents: The combination of breezy conditions in the surf
zone and influences from the new moon, lunar perigee and ongoing
elevated tides will support a moderate risk for rip currents
through Saturday. An elevated risk for rip currents will be
possible again Sunday.

&&

.TIDES/COASTAL FLOODING...
A Coastal Flood Advisory may be needed for portions of the lower
South Carolina coast during the evening high tide cycle.

Tides will continue to run a little high through Monday due to
various astronomical influences. Fortunately the wind directions
are not very conducive to much surge so we still might only
barely touch 7 ft MLLW at Charleston Harbor during some of the
evening tides.

&&

.CLIMATE...
Record high minimums for 24 June:
KCHS 79/2016.
KCXM 85/1998.
KSAV 79/1932.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory from 8 PM this evening to 2 AM EDT Sunday
     for AMZ350.

&&

$$
NEAR TERM...RJB
SHORT TERM...JRL
LONG TERM...
AVIATION...JRL/RJB
MARINE...JRL/RJB
TIDES/COASTAL FLOODING...
CLIMATE...



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