Area Forecast Discussion
Issued by NWS Wilmington, NC

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949
FXUS62 KILM 301734
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
134 PM EDT Fri Sep 30 2016

.SYNOPSIS...
A stationary front will waver along the coast through this
weekend. Periods of showers with an isolated thunderstorm are
possible along this front. Weak high pressure will build in
early next week. Hurricane Matthew may bring increasing waves
by the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 10 AM Friday...Periods of torrential rainfall to prevail
along the SE NC coast and around Cape Fear through the remainder
of the morning. Radar trends shows a `back-edge` to the convection
with a very low echo-count from the mosaic of radars off SC and
north FL presently. While convective development over land is
expected this afternoon as diurnal warming starts to brings
destablization with a nearly tropical air mass, the stream of
scattered downpours off the Atlantic should begin to wane in
coverage after midday. Several cell mergers off the SSE into the
line of coastal convection have spun up SRM couplets briefly and
this will be closely monitored near the coast north of Cape Fear
especially this morning.

Isolated to scattered land convection should reform generally along
and east of a line from GGE to MYR to CPC to EYF this afternoon but
highest rain rates confined mainly across Brunswick, New Hanover,
and Pender counties. A lull however in rain coverage and intensity
expected into early afternoon prior to some redevelopment.

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
As of 415 AM Friday...The cutoff low begins to very slowly fill as
it lifts to the north reaching the Eastern Great Lakes by the end
of this short term period. The direct affect from this cutoff low
will lessen with time. Models in agreement with the stalled sfc
front lying along or just off the coastline of the Carolinas. And
the dry air extending just shy of the immediate coast. Thus the
challenge of fcsting daily sfc temps and dewpoints. The moist air
will extend from the stalled front and offshore. The main
baroclinic zone and associated convection, to lie offshore from
SW to NE, parallel to the Carolina coastlines. Have indicated low
pops for the immediate coast to account for any onshore movement of
pcpn each night, and any development along the stalled front
during each day. As for temps, stayed closed to a consensus
amongst the avbl Mos Guidance with a slightly higher bias for max
temps each day. This will result in daily max temps a category
higher than climo norms and daily Mins 1 to 2 categories above the
norms.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 3 AM Friday...Temperatures will be quite seasonable to
slightly mild and rain chances minimal through the long term.
Moisture associated with frontal remains lingering offshore on
Monday and low level onshore flow could advect the stray shower to
mainly coastal areas. Weak upper troughiness may aid the coverage of
showers even though mid levels probably dry. Beyond Monday this
troughiness gets replaced by a slowly amplifying ridge and this
should cut down on the already paltry radar coverage. This low
coverage will be confined to coastal areas while inland zones stay
dry. Low level moisture trapped beneath the inversion will favor a
bit more in the way of clouds than `normal` through the period.
Currently it appears that Matthew stays far enough east to only have
marine effects locally. The GFS has been a very fast outlier from
other guidance though now Canadian is even faster. The EC has
shifted a bit farther east from previous runs. The overnight RI is
allowing convection to wrap around the center and so models may show
some improvement with the system stacking in the vertical.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
As of 18Z...Cold front slowly approaching from the W/SW will bring
increased drying to the inland terminals, but showers and
thunderstorms are again possible at the coast.

Thunderstorms with periods of heavy rainfall have affected ILM this
morning, and guidance suggests that more thunderstorms will develop
this aftn, potentially impacting the Myrtles. Have included a tempo
group for MVFR at ILM/CRE/MYR for short duration thunderstorms, but
expect both coverage and intensity to be less than experienced this
morning. Convection is forecast to wane with loss of heating.
Inland, the cold front will bring drier air into FLO/LBT, and sky
conditions will remain primarily VFR but a shower or two is possible
at LBT through this aftn. Winds will be generally from the S/SW
around 10 kts today.

While sky conditions will improve and convection will wane tonight,
the environment remains moist so fog becomes a possibility. At the
coast, winds are expected to remain too strong for fog, and
crossover temps at FLO will likely not be reached. That leaves LBT
as the most likely place for vsby restrictions overnight. Any
restrictions will erode after daybreak on Saturday, with VFR
expected inland and potentially more showers/tstms developing at the
coast.

EXTENDED OUTLOOK...Primarily VFR. Isolated to scattered afternoon
showers through much the period, although limited in strength and
coverage due to dry air aloft.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 10 AM Friday...Sfc cold front across the inland Carolinas
will push to the coast late tonight and likely stall along the
immediate coast or just offshore Sat and subsequent periods. This
will be the dividing line for pcpn coverage. East of the front
pcpn will be more numerous and potent, and west of the front
isolated in coverage. Looking at S winds at 10 to 15 kt today and
SW 10 to 15 kt tonight, with speeds lower within the actual
frontal zone. Significant seas will be a healthy 3 to possibly 4
ft, and comprised of mainly wind driven waves at 4 to 6 seconds.
An underlying 1 foot ESE ground swell at 10-11 second periods will
be present.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 415 AM Friday...This time period will feature a stalled
frontal boundary either along the immediate coast of the Carolinas
or just offshore and parallel to the coastline. Thus the challenge
of either keeping winds from the S-SW or eventually having winds
become nearly variable in direction during this period. As
always, will try to acknowledge a dominate wind direction in lieu
of going variable. The sfc pg remains rather semi-relaxed thruout
this period, yielding either 5-10 kt or 10-15 kt. The latter will
occur at the beginning of this period and becoming 10 kt or less
as this period progresses. Significant seas will run around 3 ft
thruout this period. Wind driven wave input into the significant
seas will lower during this period. However, an easterly 2 to
possibly 3 foot ground swell at 10 to 12 second periods will
become the dominate input into the significant seas equation
during the day on Saturday and persisting thru Sunday night.
This illustrated nicely by Wavewatch3.

LONG TERM/MONDAY THROUGH TUESDAY/...
As of 3 AM Friday...A northeasterly wind wave and increasing ESE
ground swell energy to cause a gradual rise in seas over the long
term. Tough to say how high the wind speed and resulting short
period seas get though as most model guidance is seemingly too
fast with Matthew. Winds may end up being reduced this period
assuming the slow movement of the currently favored EC model comes
to pass. The aforementioned swell energy is less related to
Matthew and more energy from the long fetch developing. Any
Matthew swells (and there will be some!) may be slated for just
beyond the long term.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.

&&

$$
SYNOPSIS...MBB
NEAR TERM...DCH
SHORT TERM...DCH
LONG TERM...MBB
AVIATION...JDW
MARINE...



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