Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 280327
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1127 PM EDT SAT AUG 27 2016

.SYNOPSIS...
High pressure centered over southern Quebec this afternoon will
drift to the east. The high will continue to influence our weather
into Sunday. A frontal boundary approaching from the northwest is
forecast to arrive during the afternoon and evening hours on
Monday. The front is expected to stall and slowly dissipate on
Tuesday on Wednesday. A cold front from the northwest is
anticipated to pass through our region early on Thursday followed
by high pressure for Friday and Saturday.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Surface high pressure ridge axis will be just northwest of I-95,
maintaining a low-level easterly flow near and to the southeast
of this area. Temperature-Dewpoint depressions over the southern
two thirds of Delaware and portions of southeast New Jersey have
decreased significantly this evening. A general consensus of the
short range guidance indicates the surface layer will saturate,
under a strong radiation (long wave cooling) inversion, as skies
clear from resultant large scale subsidence within the mid level
ridge. We expect winds to decouple just enough over portions of
Delaware and southern NJ to allow patchy fog to develop. Given the
dry low level air in place above the developing radiation
inversion, as evidenced by the absence of low clouds offshore in
the last visible satellite of the day, we do not expect much in
the way of low cloudiness to develop overnight. Interestingly, the
warmer than normal Sea Surface Temperatures (SSTs) may be playing
a role in this.

The main change with this update was to add patchy fog for the
aforementioned areas. We also made some minor updates both the
overnight temperatures and dew points.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
High pressure will continue to influence our weather for Sunday.

Any patchy fog will clear early in the morning and another
relatively sunny day will had across the region. Easterly winds
will be light through the day, around 10 mph or less.

Temperatures will be similar to today, with highs into the mid to
upper 80s to around 90 across the region. With an easterly flow in
place, shore points will be slightly cooler and remain in the
upper 70s to lower 80s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
A mid level short wave trough is anticipated to move across New
York State and New England during the afternoon and evening hours
on Monday. It should push a surface frontal boundary into our
region at that time. The guidance continues to suggest only a
limited potential for precipitation. A band of precipitable water
values around 1.7 inches is forecast to precede the front and
there should be marginal instability. We will keep the mention of
a slight chance of showers and thunderstorms.

It appears as though the boundary will dissipate slowly over or
near Maryland, Delaware and southern New Jersey. Drying is
expected to work its way into our region from the north for
Tuesday so we are not anticipating any precipitation at that time.

Temperatures are forecast to remain above normal for Monday,
Tuesday and Wednesday with highs around 90 and lows ranging from
the middle 60s to the lower 70s. Readings will be lower than those
values in the elevated terrain of the Poconos and northwestern New
Jersey.

A cold front is expected to approach from the northwest on
Wednesday. It looks as though our best chance of showers and
thunderstorms during the coming week will be on Wednesday
afternoon into Wednesday night in advance of the front. The
boundary should pass through our region early on Thursday.

High pressure is forecast to build from Ontario and the Great
Lakes on Thursday to the northeastern states on Saturday. The air
mass will be noticeably cooler and less humid than the one that it
will be replacing.

&&

.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Overnight...Predominantly VFR conditions. Easterly winds will
decrease to less than 5 knots at most locations. Latest guidance
indicates that patchy fog will be the primary concern, mainly at
ACY and MIV. There could also be some low clouds at these sites,
and we added SCT005 to SCT007, as conditions are not favorable
for the development of widespread low clouds.

Sunday...Predominantly VFR conditions. Light southeast winds
around 10 knots or less.

OUTLOOK...
Sunday night through Wednesday morning...Mainly VFR. Late night
and early morning visibility restrictions are possible.

Wednesday afternoon into Wednesday night...Mainly VFR. However,
there is a chance of showers and thunderstorm.

Thursday...Mainly VFR.

&&

.MARINE...
Sub-advisory conditions are expected to continue on the area
waters through Sunday. Easterly winds around 10 to 15 knots across
the area waters. Seas around 2 feet tonight, increasing to 2 to 4
feet on Sunday as we start to see the swells arrive from distant
Tropical Storm Gaston.

OUTLOOK...
Sunday night through Thursday...No marine headlines are
anticipated.

RIP CURRENTS...
A moderate risk for the formation of dangerous rip currents is
forecast for Sunday along the NJ shore and Delaware beaches.

East-northeast winds are expected to increase during the day,
with waves in the surf zone building 3 to 4 feet. A dominant,
longer period swell around 10 seconds, is also anticipated to
to reach the coast later in the day. Low tide occurs late in
the morning, and the rip current risk may be attenuated into
the early afternoon. Complicating matters, the long period
swells from Tropical Cyclone Gaston should arrive late Sunday
as the cyclone nears 55 degrees west longitude.

However, the long period 12 to 15 second swells are forecast to
become more pronounced along the coasts of New Jersey and Delaware
on Monday and Tuesday, even as Gaston makes its turn northeast.
Momentum in the swells reaching our coast due to the original
westward motion of the tropical system should result in an
enhanced threat for the development of dangerous rip currents for
much of the week.

Presuming these swells occur as outlined above, this will
eventually impact beach behavior. Follow the advice of local
lifeguards who will be observing and your safety net. This is not
a time to swim on your own without lifeguard presence.
Additionally waders are cautioned not to turn their backs to the
waves when coming out of the water. Wave knock down can result in
upper torso injury.

&&

.CLIMATE...
This section is up to date through 11 PM this Saturday evening
August 27.

A top 4 warmest August appears assured most of our forecast area
with record monthly warmth likely at PHL.

A top 3 warmest June-July-August for Philadelphia, Allentown and
possibly Atlantic City.

Philadelphia is on its way for its warmest August on record
(dating back to 1874). More than 4 degrees above normal.

This Philadelphia August ranking includes our forecast temps (SFT
specific values) through the 31st. The 30 year normal is 76.6
Records date back to 1874.

1. ~81.0 2016
2. 79.9 1980
3. 79.8 2001 and 1995

Regarding whether August can tie its record of 17 90F days. Its possible
but not probable. Foresee an additional 3 to 4 more 90 degree days
to add onto the 13 we have so far this month. The record of 17 was
set in 1995. The mean for the month is only 5.

Allentown will probably rank #2 warmest August. Records date back
to 1922. Normal is 71.7 and we are projecting a positive departure
of around 5 degrees.

1. 78.2 1980

2. 76.7 2016

3. 76.0 1937

Atlantic City records date back to 1874. The August monthly normal
is 74.4 and we`re projecting a positive departure of nearly 4 degrees.
As it stands, Atlantic City will rank #1 or #2 warmest August with
very little chance of slipping to #3. The forecast and climate for
Atlantic City has greater variability than Allentown and Philadelphia
due to proximity to water on sea breeze days and notable
radiational cooling on some nights.

1. 78.2 2016

2. 77.9 2005

3. 77.1 2009

Seasonal: This summer 2016 for Philadelphia will probably be the
2nd warmest June-July-August (JJA) in the period of record dating
back to 1874.

1. 79.6 2010
2. 78.9 2016
3. 78.6 1995
4. 78.3 1994

Allentown seasonal avg is projecting 75.0 or a ranking of around
#2 in the por.

1 75.3 1949

2 75.0 2016

3 74.6 2005 and 1980

Atlantic City seasonal average is projecting 75.8...4th warmest
in the por.

1. 77.5 2010

2. 77.0 2011

3. 75.9 2005

4. 75.8 2016

5. 75.5 2008

90 degree days through the 27th.

season       mean  Aug  Aug       Aug      Season
                        mean      rer      rer

abe  32      17    11   4         16-1980  41-1966

acy  27      10    10   3         11-2010  46-2010

phl  37      21    13   5         17-1995  55-2010

ilg  32      20    13   5         23-1895  59-1895


Rainfall: Uncertainty exists below.

Presuming no further measurable rain this month of August...the
current ACY value of 1.10 would rank the 6th driest August on
record,  after a 6th wettest July.

For Philadelphia, the June-August seasonal total of 7.45 inches is
the 12th driest summer...again this presumes no further measurable
rain in August.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$
Synopsis...Franck/Iovino
Near Term...Franck/Meola
Short Term...Meola
Long Term...Iovino
Aviation...Franck/Iovino/Meola
Marine...Franck/Iovino/Meola
Climate...Drag 1127P



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