Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Wakefield Virginia
402 PM EDT sun Apr 20 2014

Synopsis...
low pressure off the southeast coast...will track slowly northeast
into the Atlantic through Monday...as high pressure builds eastward
across New England and off the coast. A cold front will cross the
area Tuesday afternoon into Tuesday night. High pressure returns
for Wednesday and Thursday.

&&

Near term /until 6 am Monday morning/...
low pressure remains off the southeast Continental U.S. CST this afternoon...while surface hi pressure
has settled over eastern new eng. Combination of that low and surface hi
pressure to the north-northeast will result in continued low level flow from the NE
through tonight. Worst of the weather continues to be confined to coastal NE
NC...where clouds...gusty NE winds (to 30-40 kt) and intermittent
light rain (50-70% probability of precipitation...at least this eve) continuing. Also...carrying
hi surf advisory from beaches on northern NC Outer Banks as surf waves
average close to 8 feet (minor beach erosion possible as well). Keeping broken clouds
across southeast Virginia/interior NE NC...W/ probability of precipitation 15-40%. Xcpg some push of the
cloudiness/precipitation to the north early tonight...before beginning to retreat back
south-southeast. Elsewhere...mnnly clear...breezy inland/windy at the CST. Low temperatures
from the u30s inland to M/u40s at the CST in southeast Virginia/NE NC.

&&

Short term /6 am Monday morning through Wednesday/...
upper level ridge builds over the region later tonight through Monday with low pressure
continuing to (sloly) move out to sea. Improving conds expected
over coastal NE NC (albeit very sloly)...W/ clr-p/cloudy weather elsewhere.
Cold front tracking into the Ohio Valley Monday evening...will push east and over the
mountains Tuesday morning. That front will bring incrsg clouds from west-east Tuesday...along
with the next chance for rain. Most of if not all rain may hold off
until afternoon west...and toward lt afternoon/evening east on Tuesday. Will maintain a slight
chance of a thunderstorm...though dynamics weakening with time...as the fnt
enters the region.

Hi temperatures Monday from 55 to 60f right along the CST...to ranging through
the 60s to near 70f inland. Low temperatures Monday night ranging from the m40s to
around 50f. Hi temperatures on Tuesday ranging from the M/u70s inland...to
the u60s to l70s at the CST.

The cold front pushes out to sea Tuesday night...W/ significant drying and a period of
cooling thereafter (fm after mdngt Tuesday night through wed). Maintaining
30-40% probability of precipitation eastern portion of the forecast area Tuesday evening...15-25% elsewhere...then
clearing after mdngt as winds become northwest. Near seasonable/clr-pcldy weather
expected Wednesday west/ gusty northwest winds...mainly eastern portion.

Low temperatures Tuesday night from the m40s northwest to l50s southeast. Hi temperatures Wednesday from the
m60s to around 70f.

&&

Long term /Wednesday night through Sunday/...
progressive flow will result in near seasonable normal temperatures and
generally dry conditions through the extended period forecast. A
cold front will bring a chance of showers to the region Friday
afternoon into Friday night.

Trough axis will push off the NE coast Wednesday night as an upper
level ridge builds eastward over the central-eastern Continental U.S.. at the surface...cool
Canadian high pressure will build southeastward from the Great Lakes into
the middle-Atlantic region Wednesday night-thurs. This will result in
another cool day Thursday (highs generally in the middle-upper 60s) as
flow remains NW-W. Surface high will slide over the local area Thursday-
late Thursday...locating offshore Thursday night. This will veer the
flow around to the south as the upper ridge axis builds overhead.
Medium range guidance is coming into better agreement...but
continue to struggle with the evolution of an upper trough over
the intermountain west into the northern plains Thursday-Thursday night.
However...guidance is in fairly good agreement with lifting a warm
front over the region in the amplifying flow. Trailing cold front
forecast to cross the region Friday afternoon. Westerly flow over the
Southern Plains into the Gulf states will limit the amount of moisture
advection into the region...especially east of the Appalachians.
Dewpoints only prognosticated to warm into the low-middle 50s Friday. Best
dynamics will also remain north of the local area as zonal flow
prevails over the local area. However...increasing speeds aloft
and small amplitude shortwaves will be enough to mention slight
chance-low end chance probability of precipitation along the front at this time. With the local
area in the warm sector Friday...temperatures will warm into the middle-upper
70s (near 80 inland). Warm temperatures combined with low level Theta-E
advection will maintain a marginally unstable airmass over the
region Friday afternoon. Thus will carry a slight chance of thunder.
Southern portion of the front will likely stall over the Carolinas Friday
night-Sat in westerly flow aloft. Cool Canadian high pressure will be
slow to build over the region as the trough remains over the NE
states through the weekend. This will result in another warm day Sat
with highs in the middle-upper 70s in westerly flow. Cooler Sunday as cool
Canadian high pressure finally builds southeastward over the region.

&&

Aviation /20z Sunday through Friday/...
strong low pressure now off the SC coast will continue to track
east-northeast off the coast through the taf period. This will help to
keep a tight pressure gradient and gusty winds over the local
area. Clouds will persist over the southern portions of the County Warning Area
with -ra and MVFR ceilings over NE NC affecting ecg. 3000-4000 feet ceilings
are possible for orf/phf through the afternoon and early evening as well
as a slight chance of sprinkles over orf. Winds will gust to 20-30kt
this afternoon/evening at phf- orf-ecg (and ~20kt at ric/sby).

Outlook: gusty winds diminish tonight...and while visibilities remain
VFR, expect low clouds will persist across coastal terminals. After
a brief period of MVFR possible across the coastal plain
(ecg/orf) late tonight, expect predominate VFR for Monday. Next
wxmaker arrives Tuesday as a cold front pushes across the region
Tuesday/Tuesday night. VFR conds return Wednesday as high pressure
builds into the region.

&&

Marine...
strong NE winds continue over the waters this afternoon as high
pressure remains ridged over the waters and low pressure resides
off the southeast coast. Pressure gradient over the southern waters between low
and high pressure remains quite strong...resulting in gusts
approaching gale force over the southern coastal waters...Currituck
Sound and Lower Bay. Mhx VAD wind profile shows 40-50 knots winds a
thousand foot off the surface with several elevated sites recording
winds in excess of 35-40 knots. Conditions will begin to change this
evening as high pressure pushes off the NE coast and low pressure
begins to slowly lift northeastward. Winds will back around to the north and
diminish slightly...averaging 20-30 knots. Gradient will also relax
slightly. However...seas will remain elevated...ranging from 7-10
feet (highest in the southern waters) tonight. Surface low will push farther
out to sea Monday as high pressure remains ridged over the waters.
Sub-Small Craft Advisory conditions expected over the Bay and eastern Virginia rivers by middle-
late Monday morning. Will hold onto Small Craft Advisory headlines for the mouth of
the Bay for waves 4+ feet through Monday as well as the sound for winds
20-25 knots. Seas will subside to 4-8 feet Monday. Flow becomes southerly Monday
night in advance of a cold front approaching from the west. Seas
will finally fall below 5 feet late Monday night-early Tuesday morning.
Cold front will cross the waters Tuesday afternoon with Small Craft Advisory
conditions again likely behind the front.

&&

Akq watches/warnings/advisories...
Maryland...none.
NC...high surf advisory until 6 am EDT Monday for ncz102.
Virginia...none.
Marine...Small Craft Advisory until 10 am EDT Monday for anz630>632-
635>638.
Small Craft Advisory until 4 PM EDT Monday for anz633-634.
Small Craft Advisory until 6 am EDT Tuesday for anz650-652-654-
656-658.

&&

$$
Synopsis...alb/tmg
near term...alb
short term...alb/tmg
long term...Sam
aviation...mam/jef
marine...Sam