Scientific Forecaster Discussion
fxus61 kphi 170635
Area forecast discussion
National Weather Service Mount Holly New Jersey
235 am EDT Tue Sep 17 2019
a weakening low pressure system will move into the mid Atlantic
region today, pushing a frontal boundary to our south. High
pressure builds across the northeast states on Tuesday into
Wednesday, then shifts southward across the mid Atlantic region
Thursday. The high is forecast to shift to our south Friday,
then offshore over the weekend.
Near term /through today/...
a cold front is making very slow progress south through our area
overnight. It is south of New Jersey/PA and should continue to sink
south of Delaware and NE Maryland through the morning. In the wake of the
front, high pressure will build in from the north. This will
keep persistent northeasterly flow for our region through the
day. Thanks to the Post-frontal cold air advection, temperatures
today should be about 5 to 10 degrees lower than Monday, with
highs mostly in the 70s across the area.
Short term /tonight/...
the surface high will continue to build south Tuesday night,
leading to more tranquil conditions overnight. Overnight lows
will be mostly in the 50s, with the possible exception of
coastal locations (with lows near 60), and the higher terrain
of the southern Poconos and northwest New Jersey which could drop into the 40s.
Despite the northeasterly flow, the risk for fog looks to be
relatively low as we should also see some dry air advection
today into tonight.
Long term /Wednesday through Monday/...
current long range forecast looks on track with a relatively
tranquil pattern through the weekend.
High pressure is forecast to build across New England Tuesday night
into Wednesday, then shift southward across the mid Atlantic region
on Thursday. The high is then expected to build to our south on
Friday, then offshore of the southeast states over the weekend. With
high pressure and its subsidence near the East Coast for the rest of
the week into the weekend, dry conditions are currently forecast,
although there will likely be periods of cloud cover at times.
A cold front will approach the area from the west on Monday, and a
pre-frontal trough may develop ahead of the front. There is a slight
chance that showers may accompany this trough and frontal passage
Temperatures will be near or slightly below normal Wednesday and
Thursday, before rising back above normal Friday, and especially
over weekend into Monday.
Aviation /06z Tuesday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Today...high confidence that VFR conditions will continue
through the day with decreasing mid level clouds through the
day. Winds should stay northeasterly 5 to 15 kt through the day.
However, in the late afternoon to early evening, winds could
veer to more easterly, but speeds by then should be 10 kt or
Tonight...VFR conditions continue overnight. Winds are expected
to be easterly and northeasterly with speeds below 10 kt.
Wednesday-Saturday...generally VFR conditions with light winds.
for the Delaware bay: winds and seas are expected to stay below
Small Craft Advisory criteria today and tonight.
For the Atlantic coastal waters: seas will continue to build
through the morning. Seas above 5 feet are expected for the
coastal waters adjacent to Delaware and the Delaware Bay by mid
day. Small Craft Advisory starts mid day and continues through at least tonight
(but will likely need to be extended later). For the rest of
the Atlantic coastal waters, expect the seas to stay just below
the 5 ft criteria into tonight. So have held off on an Small Craft Advisory for
these areas for now, but will continue to watch closely.
Wednesday-Thursday...Small Craft Advisory conditions likely as
wind gusts increase to around 25 knots and seas increase to 5-8
feet for portions of the Atlantic coastal waters.
Thursday night-Saturday...winds lower below advisory levels,
however, seas will average 6 to 10 feet for the Atlantic coastal
A moderate risk of rip currents is anticipated through this
evening as northeasterly winds increase to 15-20kts and seas
build to 4-5ft. An elevated risk of rip currents (e.G. Either
moderate or high) will likely persist through much of the week.
Marine...Small Craft Advisory from 11 am this morning to 6 am EDT
Wednesday for anz454-455.