Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 240126
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
926 PM EDT Sat Sep 23 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 into the first half of next week. A
cold front may approach the forecast area late next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 920 PM: Regional observations that most areas have
decoupled or have very light east winds. Sky conditions across
the forecast area remained clear to mostly clear this evening.
Based on MOS and NAM12 sfc condensation pressure deficits it
appears that fog will be less of an issue tonight compared to
last night. Overall, the forecast appears in good shape.

As of 745 PM: Convection has faded across the forecast area this
evening. I will update the forecast to reduce PoPs and sky.

Previous Discussion:
Until Sunset: Showers across portions of Southeast GA are
diminishing and dry weather should return within the next few
hours.

Tonight: Dry weather is forecasted as high pressure remains in
control. Some clouds may linger in GA, with mostly clear skies
further north. We cannot rule out some patchy fog again tonight,
but winds look to high enough that we`re keeping it out of the
forecast.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Models continue to show a relatively dry forecast through the
period with above normal temperatures. As Maria moves northward,
it is still expected to remain well offshore. It will likely
put much of at least the land area under large scale subsidence
on the far western periphery of the circulation associated with
Maria. Thus, have continued to keep out mention of any pops over
the land, with only isolated showers and thunderstorms over the
Atlantic waters.

Low level winds will be north-northeast 10-15 mph during the day
through Monday, then back to north-northwest Tuesday as the
circulation of Maria moves well north and east of the region. Any
afternoon seas breezes are expected to remain with 10-15 miles of
the coast. These winds, along with large scale subsidence, will keep
temperatures above normal, with highs in the mid to upper 80s and
lows in the mid 60s well inland, and lower 70s at the coast.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Despite the presence of Maria offshore, weak NVA under high pressure
should help mitigate precipitation chances locally, with the best
chances for showers/thunderstorms occurring late week into early
next weekend associated with an approaching cold front. The front
appears poised to cross the Appalachians Thursday into Friday, with
passage through the forecast area likely by early Saturday. Above
average temperatures are expected through the second half of the
week in advance of the front, with cooler temperatures and lower
dewpoints likely behind the front as cool high pressure builds back
into the area.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
VFR conditions expected across KCHS and KSAV through the 0Z TAF
period. Winds are forecast to shift from the NE around midnight
and continue through Sunday. Deepening mixing and momentum
transfer should support low end gusts during the daylight hours
across SC, KSAV should see less gust potential.

Extended Aviation Outlook: Expect mainly VFR conditions to
prevail at both KCHS and KSAV through early next week. There is
a small probability for some early morning flight restrictions
due to fog into early next week.

&&

.MARINE...
Tonight: Swell from Maria is moving through our waters. The
NOAA buoys are reporting swell ranging from 4-6 ft and periods
anywhere from 11-14 seconds. Swell will continue to gradually
build tonight and Small Craft Advisories are in effect for all
of the coastal waters.

Sunday through Thursday: Still expect a prolonged period of
Small Craft Advisories, mainly due to high seas as Hurricane
Maria tracks northward well off the southeast U.S. coast later
this weekend and early next week. Winds will be north-northeast
15 to 20 knots through Monday, then backing to northwest 10 to
15 knots Tuesday through Thursday.

Seas will build through Sunday, peaking at 10 to 14 feet beyond 20
nm offshore, and mainly 6 to 10 feet out to 20 nm. Seas remain high
Monday, then start to slowly fall Tuesday and beyond as the
circulation from Maria moves well north and east of the waters.

Rip Currents: Swell from Hurricane Maria will continue to
slowly build at the beaches as Maria moves northward. The High
Risk will continue into Sunday, with an elevated risk
persisting into Tuesday or maybe Wednesday.

&&

.TIDES/COASTAL FLOODING...
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. High Surf Advisories are in
effect Sunday and Monday. Also, the potential for shallow salt
water flooding will persist through early next week around the
times of high tide, particularly along the South Carolina coast.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Rip Current Risk through Sunday evening for GAZ117-119-
     139-141.
     High Surf Advisory from 8 AM Sunday to 8 PM EDT Monday for
     GAZ117-119-139-141.
SC...High Rip Current Risk through Sunday evening for SCZ048>051.
     High Surf Advisory from 8 AM Sunday to 8 PM EDT Monday for
     SCZ048>051.
MARINE...Small Craft Advisory until 8 PM EDT Tuesday for AMZ352.
     Small Craft Advisory until 4 PM EDT Wednesday for AMZ350-374.
     Small Craft Advisory until 11 PM EDT Monday for AMZ354.

&&

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



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