Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 201124
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
724 AM EDT Wed Sep 20 2017

.SYNOPSIS...
High pressure will extend south across the region into early
next week as Hurricane Maria moves northwest to near the
Bahamas this weekend and then likely north just off the
Southeast U.S. coast.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Weak short wave ridging early will give way to a lazy
mid-level trough which will sag southeast and extend from the
Mid Atlantic area to the lower Gulf Coast region. Very light
west flow in the boundary layer across the forecast area today.
We expect another warm day with temps warming to around 90
degrees along the U.S. 17 corridor to some lower 90s across
inland GA zones. Despite a slight uptick in deep layered
moisture today, we think diurnal convective rain chances remain
fairly low given the lack of any focus aloft across our region
and extremely weak progs for potential low level moisture
convergence. Isolated showers and tstms are possible, but we
maintained POPs below 20 percent all areas.

Tonight: Mainly dry weather will persist but again not ruling
out isolated showers as a mid level vort lobe approaches the
region. We could see some area upgraded to a slight chance POP
overnight but for now, we maintained silent POPs in the forecast.
Lows will range from the upper 60s inland to lower-mid 70s
right along the coast. There also may be some patchy fog inland
and northern zones late tonight.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
High pressure centered over eastern Canada/New England will continue
to ridge southward into the area. Meanwhile an extension of the
upper trough from the remnants of once Hurricane Jose off the
southern New England coast will linger over the region into
Saturday. Increased moisture/instability and the sea breeze will
bring a risk for some showers and a few thunderstorms, mainly
Thursday and Friday afternoons. Some showers could linger into
Saturday mostly near the GA coast but drier air will be filtering in
from the north during the day. Temperatures will stay above normal
through the period, generally upper 80s to around 90 during the day
and around 70 at night.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
Inland high pressure will persist into early next week but the main
forecast concern is what will happen to Hurricane Maria which will
be near the Bahamas this weekend. Much will likely depend on what
happens to Jose which is expected to still be lingering off the
southern New England/Mid-Atlantic coast. Just too much uncertainty
at this point so everyone is encouraged to pay close attention to
the forecast later this week into early next week. Best, albeit
small, rain chances look to be near the coast Friday night into
Saturday, assuming Maria tracks well offshore. Temperatures look to
stay above normal.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
Through 12Z Thursday, VFR conditions will prevail at the terminals.
There is patchy MVFR vsbys at KCHS around dawn this morning and
5-6SM BR is possible at either location again late tonight. Isolated
convective rains may be possible with a short wave moving thorugh
the region late today and tonight, but the potential appears quite
low at this time.

Extended Aviation Outlook: No significant concerns through Mon,
although expect some impacts from late night/early morning fog and
showers/storms (mainly Thu/Fri).

&&

.MARINE...
A light southwest synoptic flow will persist over the waters
through tonight with the flow over GA waters backing a bit more
to the southeast this afternoon. Speeds will be light for the
most part, less than 15 kt. There is still at least 2 ft of
long period swell lingering and wave model guidance shows very
little change through tonight. Seas 2-3 ft on average.

Thursday through Monday: No significant concerns before swells from
Hurricane Maria nearing the southeast Bahamas later this week begin
to impact the waters Thursday night or Friday. Advisories will be
likely for the offshore waters starting Friday and the nearshore
waters starting Friday night. Seas could build to 10 feet or more
near the Gulf Stream Saturday night and persist in Monday, although
much depends on the exact track/strength of Hurricane Maria.

Rip Currents: Increasing astronomical influences and a very
minor lingering swell component from Jose will support another
moderate rip current risk at area beaches today.

&&

.TIDES/COASTAL FLOODING...
Tides/Coastal Flooding... Much of the coast remains vulnerable in
the wake of Irma with many dune lines either completely washed away
or severely compromised. Even if the tide gages at Charleston Harbor
and Fort Pulaski fall short of shallow coastal flooding criteria,
some flooding problems are still likely with many of the natural
coastal protection systems compromised. Powerful swells from
Hurricanes Jose and Maria will also drive significant wave run-up,
which could cause further erosion. Thus, the potential for
shallow coastal flooding will persist into early next week
around the times of high tide, particularly along the SC coast.

&&

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

&&

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



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