Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Wilmington NC
323 am EDT sun Mar 29 2015

Synopsis...
a cold airmass will remain across the area through Sunday as the
center of high pressure moves by. A weak cold front will pass
through Monday bringing a chance for showers. A very weak but dry
front will move through Wednesday. A warming trend is expected
late next week ahead of a stronger cold front.

&&

Near term /through tonight/...
as of 3 am Sunday...a cold trough along the East Coast is
threatening to tie or break record lows in the next few hours.
Surface high pressure over West Virginia is keeping enough
pressure gradient over the coastal Carolinas now to generate 5-10
miles per hour winds and is precluding a nocturnal surface inversion. Just
before daybreak winds may become very light or calm creating a
narrow window for rapid temperature falls as the nocturnal
inversion strengthens.

Record lows for this morning (sunday morning March 29)

Wilmington 31 in 2011
Florence 28 in 1966
North Myrtle Beach 31 in 2013

Residual cold advection will turn neutral by daybreak...with warm
advection developing by late morning at the 850 mb level. Full
sunshine should allow highs to reach 52-55 across southeast North Carolina
and 55-58 across NE South Carolina...except several degrees cooler
at the beaches with a weak seabreeze.

With the high just starting to push offshore at sunset and excellent
radiational cooling this evening look for temperatures to plunge
into the upper 30s and lower 40s by 9 PM. Low temperatures should
occur around midnight...but a strengthening low level jet plus
increasing cloudiness will help erode the nocturnal inversion after
2 am...producing a rising temperature curve. The 00z GFS is the
fastest model with sufficient moisture return to warrant any weather or
probability of precipitation. The bulk of other models plus the sref ensembles indicate the
forecast area should remain dry through daybreak Monday morning.

&&

Short term /Monday through Tuesday night/...
as of 3 am Sunday...weak cold front will move across the area later
Monday with showers developing ahead of the boundary. Although the
front is displaced well south of the parent low there is a subtle 500 mb
feature helping push the front across the area. Modest positive vorticity advection ahead of
the feature along with period of increased middle level moisture is
likely to generate at least some convection. However do think what
does develop will be on the weak/light side. Forecast soundings
never show precipitable water values rising above 1 inch and
indicate a stable layer around 8k feet. While low level convergence
and dynamics may be able to overcome the stable layer the lack of
moisture is apt to keep rainfall totals for any locations that do
see convection under a tenth of an inch. Will continue with
inherited high chance likely pop for Monday. Although temperatures will be
on a warming trend highs and lows will end up below climatology.

Progressive middle level pattern aloft on Tuesday will quickly move surface
high over the area and off the coast Monday night into Tuesday. There will
be a weak impulse dropping southeast in the middle level west-northwest
flow but it appears this feature will pass to the south. Should it
track a little farther north it may result in an increase in middle
cloud late Tuesday and Tuesday night but low level dry air should prevent
any precipitation from reaching the ground. Return flow on the
backside of the high along with westerly flow will result in temperatures
warmer but ultimately below climatology Tuesday and Tuesday night.

&&

Long term /Wednesday through Saturday/...
as of 3 am Sunday...middle level pattern will remain progressive for
the duration of the period. Deep westerly flow aloft will only be
disrupted for a short period of time on Thursday as winds aloft become
southwest ahead of a weak shortwave crossing the southern Continental U.S.. low
level return flow around departing surface high coupled with
increased moisture/dynamics associated with the shortwave will lead
to potential for showers Thursday afternoon and evening.

Region briefly dries out late Thursday night and first part of Friday ahead
of weak cold front dropping in from the north Friday night. Front will
take its timing crossing the region...due to the flat middle level
flow...but eventually a subtle 500 mb impulse moving through the Tennessee
Valley Sat will push the boundary south of the area in the
afternoon. Weak low level convergence and diurnal instability will
be able to tap into deeper moisture associated with the frontal
zone. Will maintain inherited chance to slight chance pop for the end of
the week and start of the weekend. Temperatures will run near to
above climatology through the period.

&&

Aviation /08z Sunday through Thursday/...
as of 06z...VFR conditions expected through the taf valid period.
No fog expected as temperature dewpoint spreads will be greater
than 10 degrees. Also north winds will be at or below 7 knots through sunrise.

North wind speeds after daybreak will increase some...but will become
light SW-west during the afternoon. Only scattered high clouds expected.
During the evening winds will become light and variable as
middle/high clouds increase from the west.

Extended outlook...tempo showers/MVFR Monday with a cold frontal
passage...and again Thursday with a warm frontal passage. Otherwise
VFR.

&&

Marine...
near term /through tonight/...
as of 3 am Sunday...high pressure over West Virginia is sinking
southeastward toward the Carolinas. A surge line moved south
across the area between midnight and 2 am...accompanied by an
increase in northerly winds. At the beaches gusts are reaching 15
knots while farther offshore at buoy 41037 (wrightsville beach
offshore buoy) winds are gusting to nearly 25 knots. This surge of
stronger northerly winds will last only until daybreak before
diminishing quickly during the morning hours.

A weak seabreeze will develop during the mid-afternoon...but since
the high will be virtually overhead and inland-to-marine air temperature
differences will remain small winds should remain 10 knots or less.
Behind this high this evening southerly winds will develop with a
gradual increase in speed anticipated overnight.

At the buoys seas currently range from 2-3 feet nearshore (1 foot
nearshore in the Lee of long bay) to over 4 feet out at The Frying
Pan Shoals buoy. Seas may increase a bit more through daybreak but
should diminish to 1-2 feet this afternoon under the high...then
will build to 2-3 feet overnight due to increasing southerly
winds.

Short term /Monday through Tuesday night/...
as of 3 am Sunday...high pressure will remain over the waters
through the period...with a cold front expected to cross from the
northwest Monday night. Ahead of the front gradient becomes pinched
with winds increasing to 20 to 25 knots for a brief period of time in
the afternoon. The front itself lacks significant cold advection
and the Post front gradient is rather unimpressive. Offshore flow
will be 10 to 15 Monday night into Tuesday with winds becoming light and
variable as the high moves overhead late in the period. Seas 2 to
3 feet will build to 3 to 5 feet late in the afternoon Monday before
dropping back to 2 to 3 feet late Monday night into Tuesday.

Only shot at headlines during the period will be with the strong
southwest flow Monday afternoon. Have low confidence in development of
Small Craft Advisory conditions so for now will continue to run Sans
headline...especially given the cooler sea surface temperatures and
expected warm advection.

Long term /Wednesday through Thursday/...
as of 3 am Sunday...light offshore flow will veer to northeast
Wednesday and southeast Wednesday night as surface high moves southeast from
the Great Lakes to off the middle Atlantic coast. Gradient will
remain weak with speeds 10 to 15 knots. Winds continue
veering...ending up southeast Thursday and south-southwest Thursday night.
Little change to the surface gradient is expected Thursday and speeds
will remain in the 10 to 15 knots range. Seas will generally run 2 to
3 feet through the period.

&&

Ilm watches/warnings/advisories...
SC...freeze warning until 10 am EDT this morning for scz017-023-024-
032-033-039-053>056.
NC...freeze warning until 10 am EDT this morning for ncz087-096-099-
105>110.
Marine...none.

&&

$$

Near term...tra
short term...iii
long term...iii
aviation...mrr/tra

National Weather Service Glossary of Abbreviations