Scientific Forecaster Discussion
fxus61 kphi 210120
Area forecast discussion
National Weather Service Mount Holly New Jersey
920 PM EDT Fri Sep 20 2019
high pressure will slide southward tonight and then offshore through
the weekend. A cold front will approach from the west on Monday,
crossing the area Monday night. High pressure will return for the
Near term /until 6 am Saturday morning/...
temperatures dropping off fairly quickly due to radiational
cooling from clear skies and light winds. Some patchy fog is
possible in the predawn hours, mainly away from the urban
Short term /6 am Saturday morning through Sunday/...
dry weather will continue through Saturday and Saturday night
as high pressure remains to our south and a surface trough
remains across the area. Temperatures will warm well above
normal starting Saturday as ridging aloft builds across the East
Coast and return flow brings in warmer, more moist air.
Vertical moisture remains limited, so precipitation is not
expected through Saturday night, regardless of any short
By Sunday, the ridge aloft breaks down while the high pushes
offshore of the mid-Atlantic coast and the weak surface trough
remains near the area. This will allow for the return flow to
continue through Sunday. Very warm temperatures and increasing
moisture are expected through Sunday. Later Sunday, there is a
chance some showers may develop to our west, but they are
expected to stay out of our area and remain near the surface
trough as it drifts westward through the day.
Long term /Sunday night through Friday/...
not much change in the extended period as we are largely dominated
by high pressure. Main opportunity for precipitation will be with
the frontal passage on Monday night.
A cold front will approach the region from the west on Monday,
crossing through the area Monday night. Low level moisture will be
on the rise in the return flow around the departing high pressure.
Flow looks to be pretty progressive with the front working through
the area Monday night and then offshore by Tuesday morning. Some
instability may develop head of the front with the best forcing
right in front of and along the boundary. Only will mention a slight
chance of thunder, mainly during the afternoon, with it waning once
we head into the evening and lose the diurnal component.
Once the front moves through, high pressure starts to build back
into the region. There may be a weak front that moves through on
Thursday but most guidance shows little moisture around and it may
not be much more than a wind shift across our area.
Aviation /01z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Tonight...mostly VFR conditions expected. Patchy fog may
develop for a few locations, mainly rdg, miv, and Acy. Will
carry tempo groups with MVFR visibility. Light/vrb winds.
Saturday...VFR. Light and variable winds early, increasing out
of the southwest 5-10 knots during the day.
Saturday night...mostly VFR conditions expected. Patchy fog may
develop for a few locations, mainly rdg, miv, and Acy. Southwest
winds 5-10 knots or less early this evening, then light and variable
Sunday...VFR conditions expected. Light and variable winds early,
increasing out of the southwest 5-10 knots during the day, with
gusts 15-20 knots possible.
Monday...mainly VFR expected. MVFR or lower possible in scattered
showers. Southwest winds around 5 to 10 knots with some gusts around
15 to 20 knots (more likely closer to kacy). Winds will turn to the
west and then northwest late behind a cold frontal passage.
Tuesday...mainly VFR expected. Northwest winds around 5 to 10 knots.
Wednesday...mainly VFR expected. Light westerly winds.
tonight...Small Craft Advisory continues on the Atlantic Ocean
coastal waters through tonight with seas around 5-6 feet.
Saturday...the Small Craft Advisory will continue into the
first half of the day, before dropping during the afternoon as
Saturday night...conditions expected to remain below advisory levels
Sunday...winds increase through the day Sunday and may reach
advisory levels by late afternoon.
Sunday night through Monday night...seas may start to build to
around 5 feet Sunday night, continuing through Monday night. A Small
Craft Advisory will likely be needed for the ocean waters.
Tuesday through Wednesday...seas subside into Tuesday morning,
falling below advisory levels and remaining sub-advisory through
A high risk for the development of dangerous rip currents
continues through Saturday as the long period swells and high
seas continue. A rip current statement (under the coastal
hazard message) is carrying the related info.
New Jersey...high rip current risk through Saturday evening for njz014-
Delaware...high rip current risk through Saturday evening for dez004.
Marine...Small Craft Advisory until 4 PM EDT Saturday for anz452>455.
Small Craft Advisory until noon EDT Saturday for anz450-451.