Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
1007 am EDT sun Mar 9 2014
warm and dry weather will continue through Tuesday. A weak and
dry cold front will pass from north to south today. A developing
low pressure system will pass north of the area Wednesday with a
strong cold front passing Wednesday night. High pressure
accompanied with dry conditions and cooler temperatures for Thursday
and Friday. A weak coastal trough may develop late in the week.
Near term /through tonight/...
as of 1000 am Sunday...a fair amount of clouds increasing across the
coastal Carolinas this morning as weak dry cold front drops
south. Model pcp water values show concentrated moisture up close
to an inch in band along and just ahead of the front as it
progresses south southeast through today. Looking at sounding data
and moisture profiles...this moisture was mainly confined to the
middle to upper levels. Although expect some lower strato cumulus to
develop as well as lift increases into this afternoon...but not
enough to warrant any pcp. Models in fairly good consensus
bringing wind shift to northwest through the Pee Dee region by around
noon and slowly dropping south through the afternoon.
These clouds will slow the warming process...but with temperatures
already in the and an increasing downslope component to the
wind...expect temperatures to rise into the upper 60s most places. The
clouds and slight cold air advection this afternoon could offset the warming to prevent
most temperatures to remain below 70. Places across northeast South
Carolina coast will have the best chance as the front will reach
there last. The westerly winds will help to keep any sea breeze
pinned along the coast keeping beaches cooler as water temperatures
remain near 50.
the forecast area will remain under a rather low amplitude
longwave upper trough this forecast period. Middle level short wave trough ie.
Clipper type system...to remain north of the ilm County Warning Area as it pushes
off the NE-states and middle-Atlantic coast this afternoon. At the
surface...the cold front associated with this clipper to drop
southward across the forecast area during today. The front will become
oriented parallel with the middle to upper flow... from west-northwest to
east-southeast...and thus stall since no available dynamics to keep it
progressing. No precipitation associated with this front.
For tonight...weak high pressure to prevail after the cold front passage
earlier. Some decent radiational cooling possible and will
indicate lows at or below the lowest mins available via MOS
guidance. Fog could become an issue tonight...especially if enough
low level moisture is available. But with 2 solid days of
insolation...would think the majority of this low level moisture
will have dissipated. Something to monitor for now...will continue
with a fog-less forecast for now. Skies tonight will be mostly
clear as drier air associated with west-northwest-northwest downslope flow aloft
scours out any remaining moisture aloft.
Short term /Monday through Tuesday night/...
as of 3 am Sunday...surface high over the Gulf Coast at the start of
the period will move east across Florida Monday night and east of the
Bahamas Tuesday. Middle level pattern remains flat into late Tuesday before a
southern stream shortwave induces some amplification over the
southeast. Deep westerly flow aloft Monday and Tuesday will keep the region
dry with minimal clouds and temperatures above climatology. Later Tuesday some
upper level moisture ahead of the southern stream shortwave may
spread over the area in the form of cirrus but this will likely be
too late to impact Tuesday highs. Moisture continues to increase Tuesday
night as the wave opens up and a northern stream shortwave becomes
dominant. Given the moist environment think enough positive
vorticity advection will exist ahead of the rapidly weakening wave
to generate some isolated showers. Plan to maintain inherited chance
pop Tuesday night with highest values during the last 6 hours of the
Long term /Wednesday through Saturday/...
as of 3 am Sunday...period begins unsettled with weakening southern
stream system moving off the coast ahead of a strengthening system
moving into the middle Atlantic. The northern stream shortwave moving
through the Ohio Valley Wednesday and driving the surface cyclogenesis will
help push a cold front across the area Wednesday night. Precipitation chances
continue to look marginal at best as the bulk of the forcing and
moisture associated with the strengthening northern system remains
displaced west and north of the forecast area. Additionally the
remains of the exiting southern stream shortwave may generate weak
subsidence over the region and the waves exit helps cut off the
already limited Gulf moisture feed. Plan to maintain inherited middle
to high chance pop with no mention of thunder and limited quantitative precipitation forecast.
Strong but brief cold advection follows the cold front for the
later half of Wednesday night and first part of Thursday. 850 temperatures drop below
zero and partial thickness values for Thursday suggest highs more typical
of early Jan and highs end up 10 to 15 degrees below climatology. Surface
high moves overhead Thursday night in what could be a strong radiational
cooling setup. 850 temperatures right around zero and partial thickness
suggest a freeze could be a threat for at least a portion of the
Increasing sun angle and longer days help quickly modify the air
mass and while Friday is likely to once again be below climatology highs
should end up several degrees warmer. By Friday night return flow is
firmly established with weak warm advection keeping lows closer to
climatology. Temperatures near to slightly above climatology Sat and Sat night with
potential for weak coastal trough development late in the period. At
this point does not appear the feature will be of strength to
warrant inclusion of pop in the forecast.
Aviation /11z Sunday through Thursday/...
as of 06z...VFR will prevail overnight as SW-west-southwest winds around 5 kts
should keep the boundary layer mixed enough to prevent any fog
formation. A weak cold front dropping southward...will reach the
forecast area later this morning...and south of the forecast area
by sunset. Winds will shift and veer to the west-northwest at 5 to 10 kts
during the daytime morning hours...and further veer to the northwest
around 10 knots by midday the front may be accompanied by scattered
middle-level clouds and/or low level scattered stratocu/cumulus
clouds during and after the cold front passage. But otherwise...its aviation
impacts will be limited with no precipitation expected. With decent winds
prognosticated at west-northwest 20 to 40 knots between 850-700mb via model time
height display...sea breeze development will be difficult. If its
able to form...it will likely be confined mainly along the
immediate coast...possibly and briefly backing the winds to the
S-SW across both myrtles during the middle-late afternoon. Overall...
surface winds are expected to become calm or variable 2 knots or
less. With favorable radiational cooling conditions shaping up for
early Monday...fog will likely become an issue across the
terminals...mainly after 06z Monday and just beyond the scope of this
Extended outlook...MVFR/IFR visibilities possible Monday morning from fog.
Otherwise expect VFR through Tuesday. Chance of showers and
associated ceilings with MVFR/IFR conditions on Wednesday. VFR on
near term /through tonight/...
as of 1000 am Sunday...cold frontal passage...from north to
south...to occur later this morning through sunset. Can expect
scattered cloudiness associated with this front...however with
limited dynamics and moisture available...expect a precipitation-free cold front passage.
SW to west winds will peak this morning ahead of the front...then
veer to the northwest at around 15 knots in the wake of the cold front passage as it makes
its trek southward. Winds will further diminish tonight as weak
high pressure and relaxed surface pg produce a somewhat variable wind
direction at 10 knots. Will try to identify a dominating wind
direction as additional 06z models become available. Significant seas
will also peak this morning...basically in the 2 to 4 foot
range...then slowly subside through tonight to around 2 feet. An
underlying 1.5 to 2.5 foot easterly ground swell at 10 to 12
second periods remains present and will definitely be a player
with sig seas through tonight.
Short term /Monday through Tuesday night/...
as of 3 am Sunday...light west to southwest flow will continue over
the waters through the period with a slight bump in speeds late Tuesday
and Tuesday night. High pressure over the Gulf Coast at the start of the
period will migrate well east of Florida Tuesday. Gradient will become more
defined as weakening system moves across the southeast. The result
will be wind speeds 10 knots or less Monday increasing to 10 to 15 knots late
Tuesday and Tuesday night. Seas 2 to 3 feet Monday into Tuesday build to 2 to 4 feet
for Tuesday night.
Long term /Wednesday through Thursday/...
as of 3 am Sunday...deepening low over the middle Atlantic region and
cold front approaching from the west will tighten the gradient
Wednesday...increasing southwest flow to a solid 20 knots with potential for
20 to 25 knots late in the day. Cold front pushes across the waters Wednesday
night with strong cold advection and pinched gradient keeping
northwest winds 20 to 25 knots through Wednesday night and during part of Thursday
morning. Ahead of the front seas build over 6 feet by Wednesday afternoon
but duration above 6 feet will be short lived given the anticipated
strong offshore flow Wednesday night. Gradient slowly weakens during Thursday
with winds gradually veering to northeast and dropping below 10 knots
Thursday night as high pressure drifts in from the west. Seas Thursday
steadily fall through the day...dropping from 3 to 5 feet in the
morning to 2 to 3 feet Thursday night.