Area Forecast Discussion
Issued by NWS Charleston, SC

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860
FXUS62 KCHS 190739
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
339 AM EDT Thu Oct 19 2017

.SYNOPSIS...
Strong high pressure will build over the area through Saturday,
then shift off the coast. A cold front will move through the
area on Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 340 AM: A weak H5 trough will ripple over the CWA late
this afternoon and this evening. During the overnight hours, the
center of 590 DM ridge will drift east over the Deep South, the
ridge axis north over the southern Appalachians. At the sfc,
high pressure is expected to remain centered over the western
Carolinas, building slightly east. The air mass will remain
dry, PW around .70 today decreasing to less than .5 tonight. I
will forecast clear to mostly clear through today and tonight.
In fact, any cloud cover and mentionable PoPs will remain over
the marine areas. Using a blend of temperature guidance, high
temperatures are forecast to range around 80 degrees this
afternoon and cooling into the 50s tonight.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
A deep layered ridge will remain over the southeast United
States Friday into Saturday before shifting off the coast on
Sunday. As the surface high shifts off the coast late Saturday
through Sunday, onshore flow will develop and low-level
dewpoints will rise into the 60s. A weak coastal trough
developing over the Georgia waters may produce isolated showers,
potentially shifting into coastal Georgia Saturday night. A weak
shortwave approaching the area from the west, combined with
deepening moisture, may produce scattered showers or an isolated
thunderstorm on Sunday. High temps are expected to reach the low
to mid 80s each day, highest far southwest.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
A potent upper low will affect the area Monday into Tuesday,
pushing a cold front through the area late Tuesday. Good chance
for showers and tstms along and ahead of the cold front,
followed by drying and eventually cooler temps as high pressure
builds from the west and north.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
VFR.

Extended Aviation Outlook: VFR conditions are expected at both
CHS and SAV terminals through this weekend.

&&

.MARINE...
Today and Tonight: Winds and seas will remain elevated into this
afternoon given a continued pressure gradient across the local
waters, 2-3 mb spread from near the Santee River and the Altamaha
River. In addition, forecast sounding over buoy 41004 indicates very
shallow mixing today. The pressure gradient will begin to relax over
the coastal waters during the mid and late afternoon while high
pressure builds east. As a result, northeast winds between 20-25 kts
will gradually weaken to 15-20 kt late today into tonight. Seas of 4-
7 ft in nearshore waters and 6-8 ft in offshore Georgia waters will
also slowly subside. Winds/seas should drop below Small Craft
Advisory levels this afternoon in nearshore waters, lingering across
the offshore Georgia waters.

Moderate NE winds will persist through the weekend before
shifting to E and eventually SE early next week as the surface
high pressure system pushes off the Mid-Atlantic coast. Seas
should drop below 6 ft over the offshore GA waters late Fri
afternoon, but will likely build back above 6 ft Sunday through
early to mid next week due to increasing fetch.

Rip Currents...Steady northeast winds, long period swell from the
northeast/east, and new moon influences will support an elevated risk
of rip currents through late this week. A moderate risk of rip
currents will continue for all beaches today.

&&

.TIDES/COASTAL FLOODING...
New moon occurs today and base tides are expected to increase by 0.1
to 0.2 feet from yesterday. Given expected steady NE winds, peaking
astronomical forces, and existence of long period swells it appears
that the SC coast may see shallow coastal flooding during this
morning`s high tide. Fort Pulaski will be close, with guidance
supporting a crest above flood stage. However, given recent trends
of high tide levels at FPKG1 and changes in base tide it appears
this morning`s high tide will crest around 9.1 ft, it will be
watched. Coast Flood Advisory will be issued for the SC coast until
10 AM this morning.

The risk for minor high tide coastal flooding may remain
through Saturday. Coastal Flood Advisories will likely be
needed.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Coastal Flood Advisory from 7 AM to 10 AM EDT this morning for
     SCZ048>050.
MARINE...Small Craft Advisory until 2 PM EDT this afternoon for AMZ352-
     354.
     Small Craft Advisory until 5 PM EDT this afternoon for AMZ350.
     Small Craft Advisory until 6 PM EDT Friday for AMZ374.

&&

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



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