Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 212142
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
542 PM EDT Thu Sep 21 2017

.SYNOPSIS...
High pressure will prevail through this weekend. The high will
weaken and shift inland as Hurricane Maria tracks northward off
the Southeast U.S. coast through the first half of next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Updated the forecast to increase pops across interior areas next
few hours as scattered showers/tstms have developed. A few of
the storms have become strong to locally severe late this
afternoon and this risk will continue through sunset, mainly
along outflow boundary collisions.

A few showers or thunderstorms could linger into early tonight,
but a diminishing trend is anticipated due to a loss of daytime
heating. Weak high pressure and diminishing cloud cover should
support decoupling winds and another fair radiational cooling
night. Guidance suggests temps will dip into the upper 60s
inland to lower 70s near the coast. These temps along with
dewpts remaining in the upper 60s inland to around 70 closer to
the coast suggests the potential of fog developing over some
locations after midnight, especially inland where winds go calm
and showers and/or thunderstorms are experienced this evening.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
A weak upper trough pattern and lingering low-level moisture on
Friday will support isolated showers/tstms mainly in the
afternoon associated with the sea breeze. As dry high pressure
steadily builds down the east coast, the best rain chances on
Saturday will be across southeast GA where better moisture
resides. By Sunday all areas should be too dry to support
precipitation. Above normal temps expected with highs in the mid
to upper 80s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Inland high pressure will persist through early next week while
confidence is increasing that Hurricane Maria will remain offshore
of the Southeast U.S. coast as it tracks north through the middle of
next week. Some showers could skirt coastal areas early next week as
Maria passes by but otherwise mainly dry conditions are anticipated.
Temperatures look to stay above normal.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
Primary concern:
* Fog

Scattered showers/tstms should remain west of the terminals
before dissipating. Shallow ground fog likely again early Friday
as skies clear, winds go calm and low-level moisture pools.
Given the shallow nature of the fog, vsbys could be high
variable. Will carry MIFG at both sites roughly 08-09z through
daybreak, but keep conditions above MVFR thresholds for now.
This will be reevaluated for the 06z TAF cycle.

Extended Aviation Outlook: Low probability for brief flight
restrictions in early morning fog and/or low clouds Saturday morning
and in mainly afternoon showers/thunderstorms Friday at KCHS/KSAV
and at KSAV Saturday.

&&

.MARINE...
This Evening and Tonight: Fairly tranquil conditions are expected
within weak sfc high pressure over the coastal waters. In general
south/southeast near 10 kt will become east 5 kt later tonight. Seas
will range between 1-2 ft nearshore and 2-3 ft in offshore Georgia
waters early, but will slowly build up to 3-4 ft mainly in a long
period swell after midnight.

Friday through Monday: The main issue will be building swells
associated with offshore Hurricane Maria. Some 6 ft seas are expected
to push into outer GA waters by late Fri afternoon and the nearshore
waters by Sat morning. A prolonged period of Small Craft Advisories
are expected.

Rip Currents: Swell from offshore Hurricane Maria will slowly build
at the beaches. This results in a Moderate Risk of rip currents
through Friday and will likely maintain an elevated risk through
early to mid next week.

&&

.TIDES/COASTAL FLOODING...
A light onshore wind along with long-period swell and astronomical
influences could lead to minor coastal flooding along parts of the
Southeast South Carolina coast during/near high tide early tonight.
A Coastal Flood Advisory could be needed.

Powerful surf created by offshore Hurricane Maria will drive
significant wave run-up, which could cause further beach erosion
this weekend into early next week. Also, the potential for
shallow salt water flooding will persist through early next week
around the times of high tide, particularly along the SC coast.

&&

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

&&

$$


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