Area Forecast Discussion
Issued by NWS Wilmington, NC-- Highlight Changed Discussion --
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FXUS62 KILM 310115
Area Forecast Discussion
National Weather Service Wilmington NC
915 PM EDT TUE AUG 30 2016
Tropical Depression Eight is expected to make its closest
approach to land tonight near the Outer Banks. It may become a
weak tropical storm before accelerating to the ne, away from the
nc mainland during Wednesday. A cold front will drop to the
forecast area Friday. Its passage will be delayed until early
Saturday, due to a tropical cyclone potentially affecting all or
portions of the region late Thursday Night thru Friday Night. This
tropical cyclone will accelerate to the NE, away from the region
early Saturday. The cold front will then push through and offshore
allowing dry Canadian high pressure accompanied with at or below
seasonable temperatures to overspread the region during this
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
-- Changed Discussion --As of 900 PM Tuesday...With the days heating overwith, what
ongoing convection that is left should dissipate quickly with the
loss of the days instability. No additional forcing identified for
this evening and overnight to keep POPs up over inland areas.
However, along the coast mainly south of Cape Fear during the pre-
dawn Wed hours, isolated nocturnal convection may develop over
the adjacent Atl waters and could push onshore given the weak
progged flow from the sfc thru 7h overnight into early Wed. The
latest near term models, RAP, HRRR and the HighresWRF are not
nearly as robust in pushing pcpn activity onshore overnight like
the previous several nights. The 3 models do agree on pcpn
activity filling in from the south to north across the FA and
adjacent local waters during daylight Wed morning as a sfc trof
or low and associated mid-level vort or s/w moves northward from
off the GA coast. Will trend POPs upward after sunrise Wed.
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.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
As of 3 PM Tuesday...The last hurrah of the upper disturbance that
sat near Savannah, GA for quite a while comes on Wednesday as the
weakening system lifts northeastward. Rain should spread up the
coast and may not penetrate very far inland. The extent of inland
rain may hinge slightly upon how much of a surface reflection runs
up the coast and where. Will cap POPS at slight far west and solid
chance along the coast in deference to models like the GFS that keep
just about all of the rain offshore. Rain chances should become a
bit more uniform across the area on Thursday as the Atlantic
moisture continues to feed into the coast and a cold front impinges
upon the area from the northwest.
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 3 PM Friday...Early portion of the forecast hinges upon the
track and evolution of the what is currently TD 9. Guidance
continues to insist on 9 moving northeast across northern FL and
then moving up the southeast coast Fri into Fri night ahead of a
shortwave trough dropping into the southeast. The proximity to the
coast is the main concern and will determine how much impact this
system has on the local area. The main concern at this point is not
so much the wind but potential rainfall. As far as winds go the
worst case scenario right now would be speeds in the 40 to 50 mph
range. However, there could be potential for a significant amount of
rain with this system regardless of its classification. Current
rainfall forecast from WPC is less than 2 inches but there is likely
to be a very sharp gradient given deep dry air being spread in from
the west by the shortwave. If the system ends up closer to the coast
there is potential for rainfall amounts more than double the current
forecast which could lead to significant flooding in some areas.
The remainder of the period will be dry with temperatures slightly
below climo as cool, dry Canadian air mass builds over the region.
Surface and mid level high pressure will ensure a quiet start to
next week. Northeast flow will be continued and the guidance is
trying to develop some weak coastal showers late in the period but
given the abundance of dry air and possible subsidence under the mid
level ridge not ready to add anything mentionable to the forecast.
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
As of 00Z...Potential for MVFR in any heavy downpours on
Wednesday. Otherwise expect VFR through the valid TAF period with
isolated showers and thunderstorms on Wednesday.
Latest radar imagery continues to illustrate a downward trend in
isolated convection coverage this evening. Thus, anticipate quiet
conditions to prevail tonight through the overnight hours with
winds becoming light and variable and SCT/BKN mid to high clouds.
Would not entirely rule out FEW/SCT low cigs meandering near
KILM/KLBT overnight, but confidence is low attm. On Wednesday,
expect VFR with isolated showers in the morning along the coast
and easterly winds around 5 to 10 kts. Into the afternoon hours,
isolated showers and thunderstorms are expected.
EXTENDED OUTLOOK...There is uncertainty with the potential of what
could become widespread MVFR conditions in rain and low ceilings
near the coast Friday as a tropical storm moves well offshore.
Breezy north winds could also occur.
-- Changed Discussion --NEAR TERM /THROUGH TONIGHT/...
As of 915 PM Tuesday...Rather noisy sfc pressure pattern and
a relaxed gradient to occur over the ILM waters tonight. This due
to TD 8 exiting to our northeast and a sfc trof or low off the GA
Coast beginning to move northeast. This will produce a variable
wind direction less than 10 kt, possibly as low as 5 kt. In lieu
of forecasting a variable wind direction, will identify or trend
what directions may become overnight into daytime Wed.
Significant seas will run 2 to 4 ft. The majority if not all of
the sig. seas will be driven by the 11 to 13 second period
Gaston easterly Swell...accompanied with a 1 foot or less wind
Showers and tstorms will be more isolated in coverage compared
to the previous nights. However, by and after sunrise Wed, pcpn
activity just south of the area waters will begin to spread
northward due to the approaching sfc trof/low off GA coast.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 3 PM Tuesday...Surface troughiness and perhaps even a
weakly closed wave of low pressure to parallel the coast most of
Wednesday. The strength of the low is poorly agreed upon by models
and will affect the wind direction slightly though a predominant
onshore flow is expected. Wind remains light on Thursday and will
turn to the southwest as a cold front approaches from the
northwest. Depending on the speed of TD9 the period may end in
increasing winds and a turn to the southeast.
SHORT TERM /FRIDAY THROUGH SUNDAY/...
As of 3 PM Friday...Deteriorating conditions seem to be a given
Fri morning as the system currently known as TD 9 moves across
northern FL and up the southeast coast. There is still a lot of
uncertainty with respect to the development, evolution, and track
of the system but at the very least there is potential for strong
northeast winds Fri and Fri night along with torrential rain and
significantly decreased visibilities. Additionally an extended
period of increasing northeast flow will build seas well above sca
thresholds. So while the nature of potential headlines remains a
question it is almost certain that some form of headline will be
needed. The system exits northeast Sat morning with high pressure
building in from the west for the remainder of the period. North
to northeast flow will be maintained through Sun but with speeds
under 15 kt from Sat afternoon on. Seas may remain elevated into
Sat evening, warranting a SCA headline, due to continuation of
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SC...High Rip Current Risk through Wednesday evening for SCZ054-056.
NC...High Rip Current Risk through Wednesday evening for NCZ106-108-