Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
FXUS61 KPHI 311555
Area Forecast Discussion
National Weather Service Mount Holly NJ
1155 AM EDT WED AUG 31 2016
A cold front over the eastern Great Lakes will move through the
mid Atlantic states tonight into Thursday morning. High pressure
will build southeast into the Great Lakes and New England Friday
through Sunday. Tropical Depression Nine, currently in the Gulf
of Mexico, is expected to move northeast along the southeastern
coast on Friday and then continue northeastward off the coast, but
will continue to be monitored. High pressure will move into the
area early next week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Clouds continue to build into northern areas, mainly north of
I-80, as a cold front approaches from the west. For the rest of
the CWA, mostly sunny skies for much of the afternoon, giving way
to partly sunny skies as that front pushes east.
Hot weather continues. Showers and scattered gusty thunderstorms
could move east northeastward into the Poconos late in the day.
Currently only about 250-300 J/kg of MUCAPE and 30-35 KT 0-6 km
bulk shear. Possible burst of 40 kt wind vcnty the Poconos after
Forecasted 92 in PHL today. EC 18z 2m temps (86) and the 00z/31
GFS 2m has 89 as does the 06z NAM. NAM bl temp of 29C at 21z
should give us a 91 or 92 max. No rain since the 21st permits
larger diurnals, especially upside in the urban areas. presuming
it reaches 90F today at KESN and KPHL, this would be D6 of the
modest heat wave and the last of this heat wave for PHL and ESN
but certainly not last of the season per multiple model cycles of
day 8-14 ensemble 2m temps and 500mb height anomalies. See
climate section of a sampling of records next Wed-Fri that may be
So max temps today about 7 to 9F above normal.
The fcst elements were basically a 50 50 blend of the 00z/31
gfs/nam mos guidance except temps adjusted higher per the
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
As a cold front sags southward and the winds to the north of the
front probably turn north, convergence will increase considerably,
especially after midnight. so despite this cfp being in the middle
of the night, am expecting an active late night with groups of
heavy showers in the pwat of 1.8" and possibly isolated
The fcst elements were basically a 50 50 blend of the 00z/31
gfs/nam mos guidance. POPS were a mix of sref blended within the
overall categorical event for most of our area. Min temps are
forecast 7 to 9 above normal.
.LONG TERM /THURSDAY THROUGH TUESDAY/...
A cdfnt will be movg thru the area at the start of the extendd pd
and rain chcs will be present, mainly erly. A tstm can not be
ruled out, though there isn`t much to work with. There is
virtually no CAPE or UVV and LI`s are marginal at best.
Behind the front, High pressure builds down from Canada into the
Grtlks and then shifts ewd into New Eng for the weekend.
It is this high pres that will play a key role in the movement of
what is now Tropical Depression 9, which is now located in the
The guid is in genly good agreement bringing the sys acrs FL and
then alg or close to the sern cst. After that there is a bit more
divergence as the sys moves newd. The latest global mdl runs have
seemingly come into a better agreement with a bit of a more ewd
shift than the prev guid keeping the low well of the NJ and DE
csts as it moves newd Sat into Sun. If this track were to come to
fruition, there cud be some 20 to 30 kt wind at the shore and
elevated seas and rip current risk, but not much else. As always,
please see the latest NHC advisories for the latest information.
Once this system moves by, high pressure will build in for the
remainder of the pd.
Behind the cfp on Thu, temps look to be aob nrml for all or most
of the pd. Its been awhile since we have been able to say that!
Welcome to September, folks.
.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Lingering LIFR conditions at KMIV should give way to VFR
conditions by 14Z. VFR otherwise. South-southwest winds increase
to 5-10 knots, however becoming southeast at ACY in the afternoon.
A cold front will approach later in the day. It appears that the
showers/thunderstorms only develop in eastern PA after 20z.
Tonight...VFR to start, with some MVFR or IFR restrictions possibile
in any heavier showers or isolated thunderstorms. Southwest winds
around 10 knots shifting to light north. chance IFR cigs parts of
the area after 06z/01 in the light northerly flow, particularly
northwest of I-95 inclusive of KPHL/KPNE/KTTN/KRDG/KABE.
Thu...Mainly VFR, though some MVFR is psbl in heavier SHRA or any
TSRA. Moderate confidence.
Thu night through Fri night.. VFR. High confidence.
Sat and Sun...Will maintain VFR and a dry fcst durg this pd,
though there is still uncertainty in this timeframe regarding
tropical depression 9. Latest guid keeps the system out to sea
with minimal impacts across our region. However, if the track
shifts, impacts could be higher. There could be some nely gusts 20
to 30 kts on Sat and Sun mainly for KACY, with wind genly under
15 kts elsewhere. Low confidence.
No marine headlines anticipated through tonight. Easterly long
period (12 second) well modeled swell of nearly 4 feet persists
through tonight on the Atlantic waters (Gaston). Otherwise add a
wind wave of a foot or so and we have around 4 ft on the Atlantic
waters and around a foot on DE Bay. Southeast to south wind of 5 to
15 kt with afternoon gusts to 20 kt becomes light north from north
to south toward dawn Thursday. showers and isolated thunderstorms
Water temperatures are generally in the 70s, which is above normal.
Thu thru Fri...No marine headlines anticipated.
Sat thru Sun...Building seas and potentially increasing wind very
much dependent on the track and strength of what is now Tropical
Depression 9. There is still considerable uncertainty during this
time period, but latest consensus of the global models have pushed
east this cycle. Seas right now look to be above SCA criteria and
winds shud be SCA as well. Depending on the track and strength some
gales are psbl, though not in the fcst right now.
RIP CURRENTS...A 3 to 4 foot long period swell and an onshore wind
component is resulting in rough surf conditions. This is expected to
continue and therefore the rip current risk remains at moderate. A
Beach Hazards Statement remains in effect through this evening that
continues to highlight this hazard, and what is probably to come this
Thursday and Friday: Rip current risk probably eases back to low
"enhanced". Low does not mean NO risk! Please note that energetic
though slightly smaller swells will still be occuring.
Saturday-Monday: Rip current risk increases with cool boundary
layer wind transfer as high pressure develops to our north, with
an ensembled fairly extensive broad easterly fetch developing
south of New England. Likely to be moderate or higher risk
depending on the track and intensity of TD9. This system needs to
be monitored for Sunday-Monday impact. Our Beach Hazard Statement
has trimmed the guidance by 1 to 2 feet to basically ensure a
conservatively accurate outlook. Swell guidance tends to be
accurate, if initialized correctly. It has biases that we try to
In terms of safety, follow the advice of local lifeguards who will
be observing the waves and swimmers. There may be some beach
closures, all dependent on the reality that develops. 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 (dislocations/spinal cord injuries).
Some minor tidal flooding is possible late this week and the
weekend with the high tide cycles. However, this is highly dependent
on the track of TD 9. A track closer to the coast would increase
This section is up to date through 5 AM Today-Wednesday August 31.
A top 4 warmest August most of our forecast area with record monthly
warmth at PHL and ACY.
A top 2 warmest June-July-August for Philadelphia, Allentown and
# 4 at Atlantic City.
Philadelphia will establish 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. ~81.1 2016
2. 79.9 1980
August will equal its record of 17, 90F days. The record of 17 was
set in 1995. The mean for the month is only 5.
Allentown will 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. 76.6 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 warmest August.
1. 78.2 2016
2. 77.9 2005
Seasonal: This summer 2016 for Philadelphia will be the 2nd warmest
June-July-August (JJA) in the period of record dating back to
1. 79.6 2010
2. 78.9 2016
3. 78.6 1995
Allentown seasonal avg is projecting 75.0 or a ranking of around
#2 in the por.
1 75.3 1949
2 74.9 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 30th.
season mean Aug Aug Aug Season
mean rer rer
ABE 33 17 12 4 16-1980 41-1966
ACY 28 10 11 3 11-2010 46-2010
PHL 40 21 16 5 17-1995 55-2010
ILG 34 20 15 5 23-1895 59-1895
Rainfall: Some uncertainty exists regarding additional rainfall
in August, so this part of the climate is stated with caution.
Presuming no further measurable rain this month of August...the
current ACY value of 1.10 should rank the 6th driest August on
record, after a 6th wettest July.
For Philadelphia, the June-August seasonal total of 7.45 inches
is so far, the 12th driest summer...again this presumes no further
measurable rain in August.
There is a chance that following record max temperatures next Wed
and Thu may be challenged.
acy 94-1983 94-1939
phl 102-1881 96-1939 (we dont expect to challenge the 102 reading)
ilg 95-1983 95-1939
abe 91-2015* 97-1939
* equal previous years
NJ...Beach Hazards Statement until 8 PM EDT this evening for NJZ014-
DE...Beach Hazards Statement until 8 PM EDT this evening for DEZ004.