Area Forecast Discussion
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FXUS62 KILM 291736
Area Forecast Discussion
National Weather Service Wilmington NC
136 PM EDT MON AUG 29 2016
A warm and humid tropical airmass will remain in place through
much of the week across the Carolinas. A tropical depression over
the Atlantic will approach the Outer Banks through Tuesday.
Another tropical depression in the Gulf of Mexico should move up
through the coastal waters off the southeast coast on Friday while
a cold front drops down from the northwest. Cooler and drier high
pressure will build in behind the front over the weekend.
.NEAR TERM /THROUGH TONIGHT/...
As of 1000 AM Monday...Upper low just east of Savannah showing
just a slow westward drift. Counter-clockwise flow around this
feature has advected deep moisture into the Carolinas per 12Z
area RAOBs. There is little ascent however to turn much of this
moisture into precipitation so for the most part just expecting a
fairly cloudy day. Light showers have been showing up along the
coast. They appear to be generated by land-sea convergence and
have had little luck moving inland. May lower rain chances a bit
should this trend continue but for now have no changes in mind.
As of 600 AM Monday...Several small and light showers dotted the
landscape this morning with heavier convection offshore. Low stratus
Tropical Depression Eight was dealing with considerable shear
this morning and will continue to battle some drier air and this
will at least slow any significant development. It is still
possible the cyclone reaches tropical storm status later today or
tonight. For this reason, Tropical Storm Watches have been posted
for portions of the Outer Banks.
Further south, across southeast North Carolina and northeast South
Carolina, the environment will be tropical in nature today. An
upper low was located off the Georgia and southern South Carolina
which will help draw moisture north and west. The column will
exhibit precipitable water values around 2 inches. We expect
offshore showers and some thunderstorms to continue to roll inland
and these showers will make good inland progress as much deeper
moisture has replaced the drier air experienced inland on Sun. For
this reason, we have increased POPs, mainly 40 to 50 percent for
the eastern third of the Forecast Area and 30 to 40 elsewhere,
slightly lower west of Interstate 95.
Considerable cloud cover should keep highs in the mid and upper
80s. Lows will be in the lower 70s.
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 300 AM Monday...A tropical cyclone will be on a NW course as
it nears the Outer Banks of North Carolina Tue. As the cyclone nears
the immediate coast, it should begin to get picked up by the
developing east coast trough and get steered north.
A tropical environment will remain across southeast North Carolina
and northeast South Carolina Tue with some drier and more subsident
air perhaps working into the area on Wed on the backside of the
departing tropical cyclone which will be accelerating away from the
Outer Banks Wed and Wed night. We expect showers and some
thunderstorms will continue to roll ashore, making good inland
progress. Will carry highest POPs along the coast Tue, up to 50
percent for the Cape Fear area. POPs will trend lower as you move
westward, with a slight chance west of Interstate 95. Then by Wed,
will carry mainly chance at the coast with the bulk of the
remainder of the area in the slight chance category.
The rip current risk is expected to remain elevated through the
Temperatures will be within a few degrees of seasonal norms through
.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 300 AM Monday...NHC keeping TD #9 on a track from Gulf
waters south of the panhandle of Florida on Thurs moving NE
reaching off the coast of GA/SC through Friday. This system will
be lifted north as a mid to upper trough digs down from the Great
Lakes and picks it up. Although there are model differences in
terms of intensity and exact track, they seem in agreement that it
will be lifted north tracking to the E-NE off the southeast coast
following around the periphery of Atlantic ridge. At the same time
this trough will push a cold front south into and through the
forecast area. This should make for a unsettled day on Thurs into
early Fri with plenty of clouds and increased chc of shwrs/tstms.
The greatest QPF should remain over the waters associated with TD
#9.The GFS shows greatest plume of tropical moisture with pcp
water values above 2 inches running up through the off shore coastal
waters about 250 miles southeast of the Cape Fear coast Thurs
night. At the same time another enhanced area of moisture and lift
will be aligned with along and ahead of cold front with values up
close to 2 inches of pcp water.
Plenty of drier and cooler air will make its way in behind the
cold front as Tropical system, now known as TD #9, makes its way
off to the NE. With this current forecast pcp water values drop
close to an inch by Sat morning as high pressure builds down from
the north. The mid to upper trough should clear the coast by late
Saturday with deeper drier and cooler air moving in northerly
flow on back end. Temps up closer to the mid to upper 80s through
Fri will only reach the lower to mid 80s through the weekend. The
big change will in low temps as dewpoint temps up into the 70s
will drop down below 65 in most places with overnight lows a good
5 to 10 degrees cooler. If the models stay of track with this
forecast, it could make for a beautiful Labor Day weekend.
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
As of 18Z...The low-levels of the atmosphere are charged with
moisture, while aloft conditions are much drier. This is
supporting areas of showers along the coast of the Carolinas, but
with only limited potential for the development of thunderstorms.
For the next several hours these showers should continue moving SW
around 10 knots with the best concentration remaining near the
coast where moisture and instability are richest. Dewpoint values
are high enough that cumulus cloud bases won`t rise much above
3000 feet at the coast this afternoon, and will likely remain
below 3000 feet (MVFR) in and near showers.
Showers should dissipate with cooling temperatures this evening
with VFR conditions. Late tonight look for another round of low
stratus clouds (IFR) to form in the 08z-10z timeframe. Best
potential is inland. Cloud bases should lift above 1000 feet
around or shortly after 13z.
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
NEAR TERM /THROUGH TONIGHT/...
As of 10 AM Monday...Impressive spectral plot at 41013 with peak
power at 14 seconds, this swell energy from distant hurricane
Gaston. The secondary peak is showing up at 9 seconds, and the
minimal wind wave showing up a distant third in power at 6
seconds. There are no changes to the previous forecast so the
previous discussion follows:
As of 600 AM Monday...Tropical Depression Eight was dealing with
considerable shear this morning and was still battling some drier
air which was keeping the system weak and disorganized. It is
still possible the cyclone reaches tropical storm status later
today or tonight. For this reason, Tropical Storm Watches have
been posted for portions of the Outer Banks. We have issued a
Small Craft Should Exercise Caution headline this afternoon and
tonight from Cape Fear to Surf City for 4 to 5 ft seas. Otherwise
seas will be mainly 3 to 4 ft. These higher seas are due to
increasing swell energy moving across our waters from distant
hurricane Gaston. The easterly swell will have periods of near 15
seconds. NE winds will range from 10 to 15 kt, but up to 15 to 20
kt for the northernmost waters very late tonight.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 300 AM Monday...The tropical cyclone is expected to be on a NW
course Tue as it approaches the Outer Banks of NC. A developing
trough across the east coast is expected to turn the cyclone to the
N and then NE. Even if the depression becomes a storm it should
remain rather weak and far enough removed such that its influences
will be modest at best. Distant Hurricane Gaston will still be
producing an easterly swell with periods of 12 to 14 seconds Tue
through Wed night. NE winds Tue morning will be up to 15 to 20 kt
far northern waters, otherwise up to 10 to 15 kt during the forecast
period throughout. The wind direction will be more easterly on Wed,
but should back to the N on the back side of the departing tropical
cyclone. Seas will be up to 4 to 5 ft, subsiding to 3 to 4 ft Wed
LONG TERM /THURSDAY THROUGH FRIDAY/...
As of 300 AM Monday...If TD #9 remains on its current forecast,
the tropical low should make its way up through the off shore
coastal waters off the southeast coast Thurs into Fri. At the same
time a cold front will drop down from the N-NW. This should
maintain a lighter more northerly flow on the back end of system
but winds should come around to the south ahead of cold front
Thurs aftn or become variable depending on the track and intensity
of this system. Once the low tracks off to the E-NE on Friday and
cold front drops south, a deep N-NW flow should pick up to 15 kts
or so. Seas 2 to 4 feet through early Fri will rise up possibly
above 6 ft over outer waters in northerly surge.
SC...High Rip Current Risk until 8 PM EDT this evening for SCZ054-
NC...High Rip Current Risk until 8 PM EDT this evening for NCZ106-