Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
704 am EDT Friday may 22 2015
low pressure will move away into the northern Atlantic today.
High pressure will build across the area today through Saturday
before sliding off the coast Sunday into early next week.
Near term /until 6 PM this evening/...
early this morng...low pressure was centered well off the Delaware CST...while
hi pressure was centered over the middle-MS valley. That low will track NE
away into the northern Atlantic today...while hi pressure remains west-northwest of the
area for much of today. Expect lots of sunshine and comfortable
temperatures in the lower to middle 70s.
Short term /6 PM this evening through Sunday/...
the models show a secondary cold front crossing the region this
eveng into tonight. Expect just some clouds with this front...esply
across the Northern Neck and Eastern Shore. Lows will range from the upper 40s
over the northwest/northern counties...to the middle to upper 50s southeast. Cool hi pressure
settles over the middle-Atlantic region on Sat. Another pleasant day
expected with lots of sunshine...as north-northeast winds become onshore late
in the day. Highs 70-75 inland/Piedmont...and in the middle to upper
60s near the water. Clear to partly cloudy Sat night with lows in
the upper 40s to middle 50s. The surface hi shifts into the Atlantic on
sun...resulting in a southerly flow over the region. Expect a little
more humidity and warmer temperatures ranging from the middle 70s to lower 80s.
Long term /Sunday night through Thursday/...
medium range begins with latest GFS/European model (ecmwf) remaining into good
agreement with upper level ridge centered over southeast Georgia/Florida Sun
night...building back north into the Middle Atlantic States Mon/Tue.
Latest GFS dampens the ridge somewhat by midweek...but has generally
trended to the stronger ridge solution of the European model (ecmwf). This pattern
will lead to warm/Summer-like weather through the entire period. A
weak warm front still prognosticated to lift north through the Ohio Valley
and northern middle Atlantic region late Sun night/Monday morning...but bulk of
precipitation should stay off to our north. Will maintain a 20% pop across the
far NE portions of the County Warning Area to account for this into midday Monday...but
will maintain a dry forecast elsewhere under partly cloudy skies.
From Mon-Tue...500 mb heights rise and bulk of thunderstorm activity
should continue to stay off to our north. Will keep a late
afternoon/evening 20% pop over just the far northern portions of the County Warning Area on
Tuesday...and generally a 20% pop in the late afternoon/evening over much of
the area Wednesday/Thursday (up to 30% far nw). Increasing humidity and high
temperatures warming back to 85-90 f Monday...and upper 80s to lower 90s
Tue-Thu...favoring European model (ecmwf) for highs (gfs highs only in middle-upper
80s well inland appears too cool in this pattern). Conditions
will generally be about 5 degrees cooler at the coast.
Aviation /12z Friday through Tuesday/...
VFR conds at all terminals with clearing trend well underway. Much
drier air moving in behind the cold front will mix out any
lingering scattered stratus over the next 2-3 hours. A clear to mostly
clear/sunny sky and VFR conditions expected Friday afternoon through the
latest observation reflect north-northwest winds ~15-20 knots across the waters this
morning, with gradually diminishing winds expected through late
morning as pressure gradient slackens steadily west/surface low pressure
system quickly ejecting NE towards the Canadian Maritimes through
tonight. High res models reflecting a few more gusts to ~25 knots
over northern coastal waters through middle-morning, so will allow
existing Small Craft Advisory to expire on time later this morning...expiring only
Lower Bay and sound with 7am issuance. Winds diminish to 10-15 knots
on average by aftn, with seas subsiding to 2-4 feet along the
coastal waters later today. Another brief northerly surge expected
late tonight/early Saturday as cool ~1030 mb high pressure builds
in from the north.
Anticipate another brief period of low end Small Craft Advisory conditions with
(dry) surface cold frontal passage late tonight, and expect flags will
likely be needed for this time frame once current Small Craft Advisory is dropped.
Gradient slackens quickly Saturday and expect winds to again drop
off quickly Saturday and Saturday night as the high shifts off the
coast for the latter half of the Holiday weekend. Resultant surface
flow backs to the S/southeast for later Sat through Monday avgg at or below 15
Marine...Small Craft Advisory until 10 am EDT this morning for
Small Craft Advisory until 7 am EDT this morning for anz633-