Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
316 am EDT Friday Jul 31 2015
low pressure off the southeast coast will slowly lift northeast
away from the area as a cold front moves into the area today.
The front will stall in the area over the weekend before
dissipating early next week. Bermuda high pressure will expand
westward Tuesday through Thursday.
Near term /through tonight/...
as of 3 am Friday...a weak cold front has moved into the northwest
corner of the forecast area. This front is expected to drift to
the coast this morning and then stall as it becomes intertwined
with the seabreeze boundary. The front is expected to aid in the
development of showers and thunderstorms. In fact...a few showers
were ongoing just upstream of the Pee Dee early this morning.
Other showers near the South Santee River have dissipated within
the last hour or so.
Along the coast...significant moisture will remain in the column
through tonight with precipitable water values topping 2.25 inches.
For our inland locations...precipitable water values will also top
2.25 inches and will be high into the middle and late evening hours.
However...some drying is expected to begin during the overnight and
early morning hours of Sat. In addition to frontal lift and surface
moisture convergence...the forecast area will be on the southern
periphery of a middle-level shortwave trough that will pivot across
eastern portions of North Carolina and Virginia during the later
afternoon and evening hours. Another shortwave will brush by to our north
Overall...the upper trough will begin to dig across the middle-Atlantic
and southeast...in between Atlantic ridging and a hot ridge centered
across The Four Corners. This type of pattern generally leads to
unsettled weather and we are expecting considerable shower and
thunderstorm activity. Will carry scattered to numerous showers and
thunderstorms with the greatest coverage centered around the
afternoon and early evening.
Heights and thicknesses will be lowering through the period and we
are expecting lower highs than on Thursday. There will be more in the way
of cloud cover and with considerable convection today...highs in
most locations will be in the lower to middle 90s. Some of the beaches
will not quite make it to 90 today. Lows tonight will be typical for
the last day of July...lower to middle 70s.
Short term /Saturday through Sunday night/...
as of 3 am Friday...weak front will remain stalled in the area
this weekend...though it will be quite hard to pick out at times.
Daily sea breeze will mask the location of the boundary with light
northerly flow at night becoming southeast once daytime heating
generates the sea breeze. Middle level trough axis will be over or
just west of the area during the period...with the combination of
middle level dry air and weak subsidence working against convection.
There will be an abundance of deep moisture just off the coast all
weekend...some of which will try and move onshore from time to time.
Best chance of this happening will be during the morning and early
afternoon hours Sat...before a slightly stronger middle level northwest
push is able to move the moisture a bit farther offshore. Will carry
slightly higher pop for Sat compared to sun...though both days will
remain in the chance category. It does appear there will be a couple
weak shortwaves crossing the area...one Sat afternoon with another
on sun. The problem for both will be the aforementioned lack of
moisture. What little convection is able to develop along the sea
breeze and lingering surface boundary/front could be enhanced by the
passage of such features. Temperatures will be near to slightly
above climatology through the period.
Long term /Monday through Thursday/...
as of 3 am Friday...middle level troughing Monday into Tuesday will briefly
make way as 500 mb ridge to the west expands east during the middle of
the week. Ridging aloft will be short lived however as another
shortwave/trough moves in from the west late in the period. Early
next week the bulk of the deep moisture will remain offshore as the
stalled surface boundary...along the coast...slowly dissipates.
Proximity of deeper moisture to the coast and presence of the
surface boundary warrants chance pop Monday with highest values at the
Ridging to the west expands east Tuesday into Wednesday with middle level
subsidence and dry air leading to a reduction in precipitation chances.
Building heights and middle level drying will push temperatures above
climatology during the middle of the week. Shortwave crossing the MS
valley Wednesday erodes ridging aloft which is replaced by troughing Wednesday
night into Thursday. Deep moisture and middle level troughing combined with
heating and convergence ahead of approaching cold front will lead to
an increase in precipitation chances as the period ends. Although hard to
time 7 days in the future there is certainly potential for shortwave
enhancement of convection on Thursday. Temperatures near to slightly
below climatology to end the period.
Aviation /07z Friday through Tuesday/...
as of 06z...radar was showing spotty convection across inland
zones associated with frontal boundary that will push across the
County Warning Area and stall off the southeast coast today. This front will become the
focal area for convection. For the rest of the early morning hours
VFR conditions to persist with some patchy fog around the
area...but will leave out of the forecast as confidence is low it
will impact any of the terminals directly. VFR early today with
some MVFR later in ceilings as convection fires up. As the weak
front clears the coast later today...VFR conditions to return.
Extended outlook...predominantly VFR through the period with a
chance afternoon rain showers/thunderstorms and rain through the weekend and on Monday.
near term /through tonight/...
as of 3 am Friday...weak low pressure off the North Carolina
coast will drift north of the area through tonight as a cold front
drifts to the coast and stalls...remaining west of the waters. SW
to west-southwest winds will dominate...although winds may become light and
variable for a brief time this morning with a front in close
proximity. The strongest winds are expected late afternoon and
this evening...up to 10 to 15 knots. Seas will be 2 to 3 feet through
early afternoon. Seas up to 4 feet will be more common later this
afternoon and tonight. A mainly weak 8 to 10 second southeast swell will
Short term /Saturday through Sunday night/...
as of 3 am Friday...weak front stalled in the area during the
weekend will keep the wind field light and somewhat variable.
During the day...as the sea breeze becomes more dominant southerly
flow will develop...with speeds of 10 to 15 knots. At night the front
will try and move offshore...which could result in brief period of
light offshore flow...5 to 10 knots. Seas around 3 feet Sat will run 3
to 4 feet on sun.
Long term /Monday through Tuesday/...
as of 3 am Friday...front stalled just inland from the coast Monday
morning will dissipate during the day as Bermuda high becomes the
dominant surface feature. Southwest flow Monday continue on Tuesday with
speeds 10 to 15 knots...slightly high near shore due to sea breeze
enhancement. Seas 3 to 4 feet with occasional 5 feet possible near 20
nm in the afternoon and evening.
as of 200 am Friday...minor coastal flooding is possible during
the nighttime high tide over the next few days. These higher than
normal tides are the result of the perigean Spring tide and full
moon which occurs today. Departures of plus 1/2 to 1 foot will be
enough to produce a brief period of minor coastal flooding. The
risk is highest for portions of the lower Cape Fear River to
include downtown Wilmington. However...this cycle...even the
beaches have a small risk. High tide tonight is about 800 PM at
the beaches and about 1030 PM in downtown Wilmington. A coastal
Flood Advisory will be issued by the National Weather Service if
coastal flooding is expected.