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000
FXUS61 KPHI 240100
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
900 PM EDT Sat Sep 23 2017

.SYNOPSIS...
High pressure remains entrenched over the Northeast before weakening
by the middle of the week. Hurricane Maria will track northward over
the Atlantic waters, approaching the Coastal Carolinas on Wednesday,
then curving out to sea on Thursday as a cold front passes through
the region. High pressure builds east to close out the week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
No changes to the forecast tonight other than hourly temperature
and dewpoint adjustments. This will be the main challenge into
the evening hours as temperatures will rapidly drop in some
areas as the sun sets, and not as quickly in others. Under clear
skies, temperatures will drop into the low/mid 60s in most
areas.

Otherwise, high pressure will remain nearby tonight and fair
weather is expected tonight. There could be a few patches of
ground fog overnight, confid in this is low however. Winds will
become light and variable through the night.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
The surface high will remain just west of the region Sunday while
the upper high remain overhead. A continuation of fair weather along
with very warm temperatures is expected. We expect high temperatures
to be around 90 degrees in many areas, a bit cooler at the shore and
in the Poconos. Humidity levels will be a little higher, but overall
not too uncomfortable. Winds will be light from the NE during the
morning then E or SE during the afternoon.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Monday...Surface high remains over the region. As a result
expect continued dry and very warm weather. We could get close
to record highs at inland locations (see climate section for
the current record highs for those days). Forecast is a few
degrees above most guidance as the increasing thicknesses and
abundant sunshine should win out over the light northerly flow.
Closer to the coast however, a light onshore flow could temper
the warming trend.

Tuesday...Surface high weakens. As it does so, we could have
some showers develop, primarily diurnally driven (rain
associated with the low over eastern Canada will stay well to
our northwest.

Wednesday...depending on how close Hurricane Maria gets to the
Outer Banks during this period, we may see some outer rain bands
reach the Coastal Plains in our area. The center of Maria is
expected to stay well to our south (by a few hundred miles)
through this period. Please see the forecast discussion from the
National Hurricane Center for the latest information on the
track.

Thursday...There are two things to watch through this period. First,
the cold front still looks on track to propagate through our region
late Wednesday night into Thursday. That will bring us back to near
normal temperatures (although depending on how quickly it moves
through, we may not notice it until Friday). The other thing we will
be watching is the eventual track of Maria. Nearly all guidance
continues to show the storm taking a hard turn to the right
during this period in response to the cold front moving off
shore. If this trend continues, even tropical storm force winds
should stay well south of our region.

Friday and Saturday...Cooler and drier air should settle in
over the region. Temperatures through this period are likely to
be near or slightly below normal (in stark contrast to the
beginning of the week).

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

High pressure across the area will ensure a continuation of VFR
conditions with few clouds through Sunday. Winds will become
light and variable/calm for most areas this evening and
overnight. Any direction will vary between NW and NE. Winds on
Sunday may become NE or E by afternoon, but remain under 10
knots. It appears to be too dry to support anything more than
patchy fog overnight. We will keep it out of the tafs at this
time.

Outlook...

Monday...mostly VFR conditions are expected.

Tuesday and Wedensday...mostly VFR conditions expected. There is a
chance for showers both days (if any showers move over a TAF
site, MVFR or lower conditions are possible). Northeasterly
wind up to 10 KT possible.

Thursday...A cold front will bring a shift to northwesterly
winds and a slight chance for showers. Otherwise, mostly VFR
conditions are expected.

&&

.MARINE...
We will continue with the SCA for hazardous seas across the
southern waters and drop it further north. The wave heights
continue to slowly decrease and are mostly around 3-4 ft north
and around 5 ft south attm. Guidance shows that this decreasing
trend will continue into the evening and then slowly reverse Sunday.
Eventually, the SCA flag will return to the northern waters later
Sunday when seas could reach 5 to 6 ft again. Overall, a long period
swell with the offshore tropical systems and some minor winds waves
too. Fair weather tonight and Sunday.

Outlook...
Monday through Wednesday...An SCA will likely be needed for the
entire period on the ocean waters as elevated seas due to
swells associated Hurricane Maria will be observed through this
time. Seas will gradually build to 8-12 feet by Wednesday. Gusts
up to 25 KT will be possible especially on the Delaware Coastal
waters Tuesday and Wednesday. Elevated waves will be possible
at the mouth of the Delaware Bay. Otherwise, winds and waves
should stay below SCA criteria on the Bay.

Thursday...A cold front will bring a shift to northwesterly
winds and gusts above 25 KT likely on the Atlantic Coastal
waters. In addition, seas will likely still be elevated due to
swells from Maria.

Rip Currents...

Sunday...A MODERATE risk for dangerous rip currents is expected
for Sunday.

Monday...a 5 or 6 foot SE swell of 15 seconds is expected to be
dominant and could result in a high risk.

Tuesday...an 8 foot 15 second swell should be dominant by that
time. If this trend continues, this would result in a high risk.

Wednesday...around an 11 to 13 foot SE swell at 15 seconds. This
would mean a high risk.

Thursday the 28th...still a 10 foot SE swell at 14 seconds. This
would mean a high risk.

Friday...maybe down to 5 or 6 feet and a moderate or high risk.

&&

.CLIMATE...
Todays high temp of 89 at ABE is the warmest there since August
22...when it reached 91. So far nothing higher than ydy at
PHL/ILG.

With high temperatures making a run at 90 Sunday and Monday across
portions of the region, some record high temperatures may be tied or
broken. The highest chances are for inland locations as onshore flow
may slightly temper the warming trend at ACY and GED.

Here are the records for both days.

Sunday

ACY-92(2010)
PHL 95(1970)
ILG-92(2010)
ABE-92(1970)
TTN-92(1970)
GED-97(2010)
RDG-95(1970)
MPO-85(2010)

Monday

ACY-91(1970)
PHL-92(1970)
ILG-93(1970)
ABE-92(1970)
TTN-92(1970)
GED-92(2010 and 1970)
RDG-92(1970)
MPO-85(1970)

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory for hazardous seas until 6 PM EDT Sunday
     for ANZ452>455.
-- End Changed Discussion --

&&

$$
Synopsis...Johnson
Near Term...Robertson/O`Hara
Short Term...O`Hara
Long Term...Johnson
Aviation...Johnson/Robertson/O`Hara
Marine...Johnson/O`Hara
Climate...