Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
321 PM EDT Tuesday Jul 29 2014
high pressure will build into and over the area from the northwest
through Wednesday...then slide off the coast on Thursday. A
frontal boundary will develop along the coast by Friday into the
Near term /through tonight/...
surface high pressure will cover the region into tonight. Meanwhile...a
broad upper trough will continue to dig into the eastern Continental U.S..
after a delightful evening...mainly clear to partly cloudy and
comfy conditions are expected tonight. Lows in the middle 50s to low
Short term /Wednesday through Friday/...
a trough aloft lingers over the eastern Continental U.S. Through Wednesday...
before weakening/shifting farther west by Thursday/Friday. Wednesday
will have continued subsidence keeping dry conditions in place
with a slight warming trend but still in the low/middle 80s for
highs. Lows Wednesday night in the upper 50s to middle 60s. Weak surface high
pressure will be off the coast for Thursday...with south-southeast low level flow
across the area. Only a very slight increase in humidity is
expected...otherwise partly to mostly sunny with high temperatures in the
middle to upper 80s. By Friday...Bermuda high pressure begins to
rebound across the western Atlantic with a frontal boundary
developing along the Virginia/NC coast. This feature will be the focus
for increased thunderstorm chances locally (especially aftn)...and thus
will carry solid chance probability of precipitation (30-40%). With plenty of clouds around
and precipitation possible...maximum temperatures Friday will likely be a touch cooler
than Thursday. Highs in the low/middle 80s.
Long term /Friday night through Tuesday/...
forecast rationale remains largely the same for medium range period.
Persistent upper level trough over the eastern third of the Continental U.S.
Will retrograde back west into the MS valley ahead of the building
western Atlantic ridge. This will allow for precipitable water values/deep layer
moisture ramping up through the period. Thus, scattered rain showers expected
through the period ahead of the advancing coastal front/inverted
trough, which will locate along/just off the mid-Atlantic/southeast
coast Saturday, eventually moving inland across the coastal plain by
Monday. Given that there is no significant forcing mechanism to key
in on, will lean towards climatology and use diurnally driven probability of precipitation
through the Sat-Tuesday time period. For temps, look for highs to remain
at or below climatology normal...generally ranging into the l-M 80s
Sunday/Monday...85 to 90 on Tuesday ahead of an approaching cold
front. Early morning lows in the 60s Sun morning, incrementally
increasing to u60s to around 70 by early Monday/Tuesday.
Aviation /19z Tuesday through Sunday/...
as of 17z...scattered to broken stratocu was present across portions of the
Middle Atlantic States. One band was moving off the coast while another
area of these clouds was developing from the west. Expect mainly scattered
clouds with bases of 3 to 4k feet which is forecast to clear off
toward sunset. Winds will be generally from the north and NE over southeast
portions of the area and northwest or north at ric and sby at 5 to 10 knots
Tuesday afternoon and around 5 knots or less from similar directions on
Wednesday. Winds go to calm or light and variable overnight.
Outlook...dry weather is forecast through Thursday. There will be a
a chance for mainly afternoon/evening thunderstorms Friday through Sunday. VFR is
expected outside of precipitation although patchy MVFR/IFR fog could develop
near sunrise beginning Friday.
Note: observations from ksby are not readily available due to a
communications problem. Return to service is unknown at this time.
However...current information may be obtained by calling into the
ASOS site directly. Amend not schedule will be appended to the ksby taf
until further notice.
latest observation reflect north-NE winds across the waters this aftn, with
slackening pressure gradient over the region as high pressure builds
in from the Ohio Valley. Light winds continue ~10 knots late this afternoon and
tonight. Seas 2-3ft, waves 1-2 feet. Winds remain at or below 10 knots Wednesday/ Wednesday
night as surface hi pressure remains overhead. Winds veer around to the
east-southeast by Thursday as the high slides offshore and low pressure passes well north
of the local area. Coastal front/inverted trough approaches from the
east by the weekend...with winds veering around to the S-SW late
Friday into the weekend with rain chances increasing again over the