Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
659 am EDT Thursday Oct 23 2014
dry weather will continue through the weekend and into much of next
week. High pressure building in from the northwest will bring cool
temperatures today. Seasonable temperatures during the weekend will
rise above normal next week as high pressure moves offshore.
Near term /through tonight/...
as of 600 am Thursday...water vapor imagery tells the story this
morning...high and dry. Precipitable water values will be near a
half inch or less through the period. At the surface...high
pressure will continue to build across the eastern Carolinas from
the northwest and west this period. Significant subsidence is expected to
inhibit the development of cloud cover through the day and we are
forecasting a sunny day. Cyclonic flow aloft will gradually abate
as upper low off the New England coast moves slowly to the
northeast. Flat to subtle ridging will develop tonight. A weak
middle-level disturbance embedded in the flow may bring some cirrus
to the area late tonight.
The airmass will begin to modify later today and this modification
process will become noticeable in the coming days. We expect highs
today will be near those of Wednesday...warmest across southern and
western zones...lower 70s. The coolest readings will be found along
the coast and across southeast North Carolina where the residual
cyclonic flow will hang on longest. Upper 60s will be most common
along the grand strand and Cape Fear coast through Whiteville and
Lumberton and points north. Lows tonight will be in the lower 40s.
Middle 40s will be more common along the immediate coast.
Short term /Friday through Saturday night/...
as of 300 am Thursday...weak shortwave drops southeast into the area
Friday as stacked low off the New England coast heads toward the
Canadian Maritimes. Shortwave has almost no moisture to work with
due to prolonged deep northwest flow...evidenced by precipitable
water values well under half an inch. There will be a slight
increase in moisture around 500 mb which may manifest as some clouds
as the wave passes but otherwise clear skies are expected. Weak
front trails the shortwave later Sat with no significant air mass
change in the boundaries wake. Highs near climatology Friday will climb above
climatology Sat on the back of abundant sunshine...subsidence...and subtle
middle level warm advection. Lows run below normal Friday night with
potential for some radiational cooling. Boundary layer winds will
remain elevated Sat night so despite clear skies and deep dry air
mixing will keep lows near to slightly above climatology.
Long term /Sunday through Wednesday/...
as of 300 am Thursday...middle level pattern will complete the transition
from amplified to zonal sun as dry front exits the region.
Progressive flow will quickly move surface high west of the area on
sun overhead Monday and off the coast Tuesday. However the deep westerly
flow combined with middle level ridging will keep the column dry.
Abundant dry air will limit cloud cover...especially early in the
period...and all but rule out precipitation. Low level return flow develops
Tuesday with surface high shifting offshore. Middle level ridge axis shifts
east Tuesday night into Wednesday with flow aloft becoming southwest.
Development of return flow will lead to an increase in cloud cover
late in the period but precipitation chances remain near zero. Subsidence
and ample sunshine early in the period combined with return flow
during the second half of the period will keep highs above climatology
through Wednesday. Lows start out below climatology...with deep dry air and
light winds allowing for radiational cooling. Development of low
level southerly flow Tuesday will push lows near to slightly above climatology
for the end of the period.
Aviation /12z Thursday through Monday/...
as of 12z...as high pressure continues to build into the area...high
confidence for VFR through the taf period continues. Nearly clear
skies with northwest winds at or below 10 kts will prevail
today...becoming light and variable after sunset.
Extended outlook...expect VFR.
near term /through tonight/...
as of 600 am Thursday...the pressure gradient between strong low
pressure off the New England coast and high pressure slowly
building into the southeast from the west and northwest will
remain a little tight into this morning. The result...north-northwest to northwest
winds up to 20 knots with gusts as high as 25 knots. Thus...will continue
a small craft should exercise caution headline through middle
morning. The pressure gradient will slowly slacken beginning later
this morning...allowing wind speeds to diminish. The direction
will very slowly veer to north tonight. Seas will be up to 3 to 4
feet through tonight.
Short term /Friday through Saturday night/...
as of 300 am Thursday...surface high will build in from the west
Friday...resulting in northwest flow. Gradient will be of limited
strength with speeds 10 to 15 knots. Shortwave moving southeast across
the area Friday night into Sat may kick up northwest winds a bit for
Sat with another round of increased winds possible later Sat night
as dry cold front pushes across the area. Winds will remain under 15
knots thought the period...though gusts to 20 knots are possible Sat
night. Seas start out around 2 to 3 feet but drop to 1 to 2 feet by
midday and remain 1 to 2 feet into Sat before increased northwest flow
Sat night causes some 3 feet seas near 20 nm.
Long term /Sunday through Monday/...
as of 300 am Thursday...northwest flow peaks around 15 knots early sun
then slowly weakens during the day...becoming light and variable Sun
night into Monday as surface high shifts off the NC coast. East to
southeast flow will develop during Monday with speeds 10 knots or less.
Seas 1 to 3 feet on sun subside to 1 to 2 feet by Monday morning.