Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
124 PM EST Wednesday Nov 25 2015
high pressure becomes centered offshore of the New England coast
today through Friday. A cold front approaches from the northwest
by Saturday night.
Near term /through tonight/...
latest upper air analysis features upper trough axis shifting
farther offshore of the New England/mid-Atlantic coast, with broad
ridging building over the local area from Ohio/Tennessee River valleys.
At the surface...1036+mb high pressure over interior New England
continues to ridge SW across the Hudson Valley and through the
Dry weather and good conditions for last minute Holiday travelers today
across the region. Surface high to the north will continue to drift
toward Atlantic Canada today and tonight...building to ~1040mb
(~+2 St dev) through late tonight. Resultant breezy low level flow out
of the east-northeast will begin some weak warm air advection over our region, with temperatures
creeping slightly above tuesday's highs. Look for highs near climatology
normal today (55-60), with only some cirrus and some scant afternoon cumulus
along the coastal plain.
Continued clear to mostly clear tonight. Ongoing low level warm air advection tonight
will likely yield some areas of increasing low clouds/patchy fog
across the coastal plain late. Isentropic fields do indicate some
shallow isentropic lift building after midnight. Can't rule out
some widely scattered light rain showers over the northern Outer
Banks/coastal southeast Virginia...however, any sig precipitation should remain just
offshore and will therefore keep out mention for now.
Nevertheless, increasing clouds and onshore flow will allow for
temperatures that are a bit less chilly than the past few. Look for early
morning lows in the low 30s out in the Piedmont, middle to upper 30s
central sections, and 40s to near 50 along the coast.
Short term /Thursday through Saturday/...
mainly dry and pleasant for Thanksgiving day and into the start of
the long Holiday weekend. Surface high strengthens to ~1048mb (+3 St
dev) by 12z/Thursday as it slides off of eastern Maine and Atlantic
Canada. Low level winds shift to the east-se, which should continue low
level warm air advection, resulting in scattered- broken SC from time to time Thursday and Friday.
Models continue to feature development of a weak trough just off the
southeast coast. However any significant moisture / precipitation should stay southeast of
the local area and out over the Gulf Stream. Airmass modification
continues through the period with temperatures gradually warming each day
through the period.
Forecast will reflect dry conditions through Sat, with model timing
again slowing onset of cold front from the northwest until later Sat
afternoon/Sat night. Highs Thursday l-m60s. Lows Thursday night l40s- l50s.
Highs Friday M-u60s. Increasing clouds ahead of the front does temper
maxima a bit on Saturday, with highs falling back into the upper
50s to around 60 north...low to middle 60s central and southern
Long term /Saturday night through Tuesday/...
still no threat of winter weather anytime soon. A weak cold front washes
out as it passes through the local area on Saturday evening. Will
maintain slight chance probability of precipitation Sat night with the frontal passage. Behind the
front...surface high pressure builds over the New England
Sunday/Monday. Meanwhile...a flat upper ridge takes shape over the
southeast. Models indicate the chance for some overrunning precipitation to
return to the local area sun/Monday in this setup. However...there
are major discrepancies in the models with respect to the
timing/placement of this precipitation. Have kept chance probability of precipitation for much of the
area on Sunday as first wave of moisture moves by to the
north...then slight chance probability of precipitation Monday with precipitation expected to mainly
be west of the local area. Another round of rain is possible next
Tuesday ahead of a stronger cold front. Still mild Sat with highs
in the middle 50s northwest to middle 60s southeast. Cooler sun-Tuesday with highs from
the upper 40s to low 50s northwest...and 55-60 southeast.
Aviation /18z Wednesday through Monday/...
high pressure remains entrenched over the eastern third of the
country this afternoon and it will remain in place through 18z
Thursday. VFR conditions are expected through the period...however
with the flow becoming more easterly...expect to see some
additional low level moisture beginning to push to the west. Have
not added any clouds with this moisture overnight as lift looks
weak...but a few scattered clouds are possible.
Outlook...the area of high pressure remains in place into Saturday
with VFR conditions expected. A slow moving cold front will drop
southward into the region late on Saturday afternoon/early evening
and linger across the region through Monday. Expect possible MVFR
to IFR ceilings and visibilities with this front with light rain
generally benign marine conditions expected over the waters
today as surface high pressure resides over the region. NE-east winds
at or below 15kt with slightly more breezy conditions south of Cape
Charles Light this afternoon into this evening. Surface high
shifts offshore of the northern New England coast late tonight into
Thursday as a weak surface trough develops along the southeast coast...with the
trough lingering along the coast through Friday. This pattern
will allow NE-east winds to persist around 10-15kt during this time.
Building and persistent long period fetch will push seas above 5ft
by later Thursday into Friday...with Small Craft Advisory conditions expected. Winds drop off Friday
afternoon/night as the weak trough dissipates and stronger high pressure
builds across the eastern Great Lakes into New England. Seas are expected
to remain elevated Friday night into sun. Winds should increase again
Sat/sun as wind direction become more northerly...with the potential for
a period of Small Craft Advisory winds with a cold air advection surge behind a weak cold front.