Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 191136
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
736 AM EDT Tue Sep 19 2017

.SYNOPSIS...
High pressure will extend south across the region into early
next week as tropical cyclone Jose moves north toward the
southern New England coast later this week and then stalls.
Meanwhile Hurricane Maria will near the Bahamas this weekend
before likely turning north just off the Southeast U.S. coast.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 725 AM: I will issue a quick update to populate with
latest temperature observations. Otherwise, the current forecast
appears in good shape.

As of 640 AM: Most areas across the forecast area will start the
day with clear sky and calm winds. A few stations were reporting
light fog, but was trending less from a several hours ago. I
will update the forecast to end fog by 12z.

As of 340 AM: Shallow ground fog to patchy fog should become more
common through the pre-dawn hours. The fog will rapidly dissipate
with sunrise this morning. Mid level heights are forecast to
gradually increase from high pressure centered over the Rio Grande
Valley. Near term guidance suggests that light winds will begin the
day from the NW, shifting from the SSW during the afternoon as
surface high pressure expands across southern GA. GFS forecast
soundings continue to show a significant inversion around 680 mbs,
with slightly greater amounts of moisture above H85. It appears that
the field of fair weather Cu will peak a little greater than
yesterday. However, the potential for deep convection will remain
near zero. High temperatures are forecast to range from near 90
across inland GA to the mid to upper 80s across SC and the beaches.
Tonight, H5 ridging should flatten out, yielding west to east flow
during the overnight hours. Thin cirrus should push across Deep
South and Southeast U.S. overnight. Given the weak sw flow and
passing high clouds, low temperatures are forecast to favor values
around 70.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
High pressure centered over the eastern Great Lakes/New England will
continue to ridge southward into the area while tropical cyclone
Jose stalls near the southern New England coast. Mainly dry
conditions are expected through Wednesday but increased moisture and
upper troughing will bring a slightly better chance for showers and
maybe a few thunderstorms especially by Thursday and Friday
afternoons. Temperatures will stay above normal through the
period.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
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 TUESDAY THROUGH SATURDAY/...
TAFs will see unrestricted visibility and sky through the 12Z
period. The surface pattern will shift this afternoon as Jose
drifts northward and high pressure builds across the Southeast
U.S. The pattern shift is expected to support light SW winds by
the afternoon.

Extended Aviation Outlook: No significant concerns through Sun.

&&

.MARINE...
Today and tonight: TC Jose will continue to track north off the Mid
Atlantic coast through tonight. Swells across the SC and GA waters
will gradually subside, aided by sfc winds shifting from NW this
morning to SW this afternoon-tonight. Small Craft Advisory for
AMZ374 is scheduled to expire at 6 PM this evening. Overnight, wave
heights are expected to range between 1-2 feet within 20NM, to 2-3
feet across the outer GA waters.

Wednesday through Sunday: 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 into Sunday but seas and winds
will be worse if Maria tracks closer to the area than currently
expected.

Rip Currents: Although swells from Jose are diminishing,
astronomical influences will remain today. Conditions will support a
low-end moderate risk for all beaches today.

&&

.TIDES/COASTAL FLOODING...
The combination of an upcoming new moon, 9/20, and continued
swell activity from distant Tropical Cyclone Jose will likely
elevate water levels above projected high tide this evening
along the SC and GA coast. The running residual level at the
CHS Harbor and Fort Pulaski gauges were around 1 foot this
morning.

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, mainly the late day high tides,
and particularly along the SC coast.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory for hazardous seas until 6 PM EDT this
     evening for AMZ374.

&&

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



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