Scientific Forecaster Discussion
fxus61 kphi 170714
Area forecast discussion
National Weather Service Mount Holly New Jersey
314 am EDT Tue Sep 17 2019
a weak cold front will continue to move south across Delmarva this
morning. High pressure across southern Canada will then build southward
into New England through Thursday and then across the middle Atlantic
Friday. The high will then push offshore this weekend. Low pressure
will move through Canada next week and an associated cold front
will approach our area next Monday.
Near term /until 6 PM this evening/...
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 /6 PM this evening through 6 am Wednesday/...
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/...
rather uneventful weather during the extended period since high
pressure will be across the area much of the time. We have a dry
forecast for Wednesday through Sunday and then slight chc or low
chc pops for next Monday when a cold front will approach.
Temperatures during this period will be below normal Wed/Thu,
then close to normal Fri. After that, readings will climb above
normal (by almost 10 degrees sun and mon). The upper high
pressure across the southeast will promote the high temperatures while
keeping most disturbances away from our area.
Aviation /07z Tuesday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Today...some MVFR ceilings are possible through about 12z. Once
those clouds dissipate however, there is 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 less.
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.
Wed/Wed night...Small Craft Advisory probable with a NE fetch ahead of the
building high. Not sure yet whether winds and seas will climb
fast enough yet to justify extending the Tue/Tue night Small Craft Advisory into
Wed yet. Seas will climb also with swells assd with Humberto.
Thu thru Sat night...Humberto swells will likely force a long
term Small Craft Advisory flag for the ocean. Sub-Small Craft Advisory for Delaware Bay. Fair
a moderate risk of rip currents is anticipated through this
evening as northeasterly winds increase to 15-20 kts 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.