National Weather Service United States Department of Commerce

 


647
FXUS62 KILM 300816
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
416 AM EDT TUE AUG 30 2016

.SYNOPSIS...
A warm and humid tropical airmass will remain in place through
much of the week across the Carolinas. Tropical Depression 8 is
forecast to become a tropical storm as it approaches Cape
Hatteras through Tuesday. A cold front will drop down from the
northwest on Friday as Tropical Depression 9 tracks north from
the Gulf of Mexico parallel to the Carolina coast on Friday into
Saturday. Cooler and drier high pressure will build in behind the
front over the weekend into early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Tuesday...Significant swell from Gaston will peak today
and a High Risk of Rip Currents remains in effect for all beaches
into this eve.

Tropical Depression Eight still looks weak and disorganized from a
satellite perspective very early this morning. The depression was
creeping to the NW but is expected to gradually turn to the N today
as it follows a weakness in the subtropical ridge, making its
closest approach to land near the Outer Banks tonight. Thereafter,
it will get picked up by the developing east coast trough and
accelerate to the NE on Wed.

Showers were occurring mainly offshore very early this morning
although a few light showers did occur across portions of the
Pee Dee earlier.

A mid-level area of low pressure was still evident in the
vicinity of SAV. This feature is not expected to move much during
the period. Still looks like even deeper moisture lurking offshore
will get drawn inland around this feature and ahead of TD Eight with
a general troughiness aligned along the coast. It is a little
perplexing that the high resolution HRRR is not showing much of any
shower activity across the FA today. Given the deep onshore flow and
high moisture content of the air, do not see why POP gradient and
magnitude should be that much different from Mon. Through tonight,
will carry mainly good chance along the coast, trailing back to
slight chance west of Interstate 95.

We under-forecast the high temps on Mon and so tried to correct for
that this go around with highs near 90 or in the lower 90s with
upper 80s at the beaches. Lows tonight will be in the lower to mid
70s.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 300 AM Tuesday...It does not appear any significant subsidence
will occur in the wake of Tropical Depression Eight. A general
troughiness will remain with perhaps some shortwave energy
pivoting around the weakening upper low along the GA/SC coast. A
cold front will approach from the NW Thu night and should move into
if not through the area before stalling late Thu night and Fri
morning. At the same time, a tropical cyclone is expecting to be on
a NE heading as it moves off the east coast of FL. Still too early
to know how strong this tropical system will be and how close it
will pass as it accelerates to the NE ahead of the front. At this
time, its main impacts should be across the waters, but we will
continue to closely monitor.

At any rate, the risk for at least scattered showers and
thunderstorms will remain on Wed throughout and then again Thu and
Thu night ahead of the approaching front.

Temps will be slightly above normal. Despite the showers and
associated cloud cover, highs will be within a deg or two of 90 both
days and lows will be in the lower to mid 70s. The beaches will be
mainly in the mid and upper 80s.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 300 AM Tuesday...A cold front will continue to drop south
while a tropical system moves northeast parallel to the Carolina
coast Friday. NHC is currently forecasting TD #9 to lift out of
the Gulf and ride by within a couple of hundred miles off the
southeast coast as a tropical storm. The forecast winds will be
determined by the exact strength and track of this system but at
this time expect strongest winds should brush our outer coastal
waters on Friday. Should see increased shwr/tstm activity as front
moves through, but looks like drier and cooler air will be making
its way south into area behind front and associated with
subsidence on the back end of the tropical storm. GFS continues to
show pcp water values up near 2 inches Fri morning, but dropping
off to 1.25 inches by Fri eve and down below an inch most places
by Sat morning. Deep mid to upper trough will move slowly
southeast through the weekend and although there should be
subsidence and dry air on the back end of tropical system,
dynamics aloft may keep some clouds and possible pcp mainly over
coastal waters over the weekend. Otherwise should see high
pressure build in at the surface with cooler and drier northerly
flow bringing temps down below normal into early next week.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
As of 06Z...Showers and thunderstorms should remain off shore
overnight and therefore have not included in coastal TAFs. Kept
stratus scattered overnight and have included some fog mainly in
inland TAF sites through early morning hours. Cloud bases should
lift above 1000 feet around or shortly after 13z with some
potential for VCTS or TSRA Tues aftn.

EXTENDED OUTLOOK...Chance of IFR/LIFR cigs during the early morning
hours Wednesday and Friday. Generally VFR Thu. Moisture increases
again Friday and Friday night with areas of MVFR possible in
showers.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Tuesday...Tropical Depression Eight was still hanging
on and on a NW to N course will make its closest approach to land
near the Outer Banks tonight, perhaps as a weak tropical storm.

For this reason, Tropical Storm Warnings have been posted for
portions of the Outer Banks. We have issued a Small Craft Should
Exercise Caution headline through today for the waters from Cape
Fear to Surf City for 4 to 5 ft seas. Otherwise seas will be 3 to 4
ft. These higher seas are due to swell energy moving across our
waters from distant hurricane Gaston. The easterly swell will have
periods of 12 to 14 seconds. NE winds will range from 10 to
15 kt, but up to 15 to 20 kt for the northernmost waters today.
NE to ENE winds near 10 kt are expected tonight. Seas tonight
will be mainly 3 to 4 ft.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 300 AM Tuesday...The swell from Gaston will be weakening
across the area. However, we will be closely monitoring a
tropical cyclone which will be accelerating to the NE from FL
ahead of a cold front. The cold front will reach our waters
Fri morning. It is still too early to forecast the impacts across
the Carolina waters from this tropical system. Mariners should
prepare for building seas and increasing NE winds, from S to N, as
early as the early morning hours of Fri.

LONG TERM /FRIDAY THROUGH SATURDAY/...
As of 300 AM Tuesday...Tropical Depression 9 should lift north
and track up within a couple of hundred miles of the Carolina
coast on Friday as a cold front drops south. This tropical system
may reach tropical storm force in outer waters on Friday
especially out toward Frying Pan Shoals. Will need to keep a close
watch on track and intensity of this tropical system. Overall
expect northerly winds to increase on back end of system through
Friday with tropical storm conditions possible through Friday
possibly into early Saturday.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...High Rip Current Risk through this evening for SCZ054-056.
NC...High Rip Current Risk through this evening for NCZ106-108-110.
MARINE...None.

&&

$$

NEAR TERM...RJD
SHORT TERM...RJD
LONG TERM...RGZ
AVIATION...RGZ