Area forecast discussion 
National Weather Service Mount Holly New Jersey 
629 am EDT Tuesday Aug 30 2016 

high pressure across New York and New England will build across our 
region today and then move offshore tonight. Tropical Depression 
Eight is expected to pass well to our southeast on Wednesday as a 
strong cold front approaches from the northwest. The front is 
anticipated to pass through our region early on Thursday followed by 
high pressure for Friday into the upcoming Holiday weekend. 


Near term /until 6 PM this evening/... 
today...forecast 90f at phl...since the 00z/30 GFS 2m temp has 88-89f 
from SW New Jersey through phl and all of Montgomery County PA with cooler 
values to the northeast. Usually can add 2-3f to GFS 2m temps on 
p-msunny days. The 00z/30 NAM looks a little moist biased and a 
degree cooler than the GFS. 00z/30 NAM 28c bl temp can barely 
make 90 (and its 06z vsn is about 27c) so its support for 90f is 
less than the GFS. It hasn't rained since the 21st so less energy 
is needed to evaporate, making it easier to rise a degree or 2 
warmer than expected. 00z/30 European model (ecmwf) 2m temp is 85 at phl which 
would favor 89f. So am fcstg phl and esn day5 of heat wave but 
with a little less than average confidence. If it does make 90 
today at phl, then we're on our way to a record equaling 17, 90 
degree days that would occur with tomorrows 90. 

A sunny start but easterly boundary layer winds permit enough 
increase in moisture to probably develop a sct-bkn deck of clouds 
in much of New Jersey and coastal de this afternoon. The wind turns east 
but gusts remain under 15 mph. 

Of interest is multiple model guidance allowing for low top 
convection in the leftover boundary moisture anywhere from S Delaware 
to se New Jersey. I dont think it will occur but I do have low pop and 
called it sprinkles in the period of roughly 18z-21z. Presuming 
the generating mechanism is ocean/land Ely flow sfc convergence in 
the convectively unstable boundary layer. 

Forecast elements were generally 50 50 blended 00z/30 GFS/NAM MOS 
except raised the temp guidance 1-3f to better equate to 2m temp 
relationship. Max temps about 7f above normal. 


Short term /6 PM this evening through 6 am Wednesday/... 
the sct-bkn clouds in New Jersey may skirt phl-ttn this evening as the 
guiding cloud layer wind turns south and advances what remains of 
the evening cu/SC cloudiness, into nnj while elsewhere it turns 
clear. Surface winds should become nearly calm and the resultant 
cooling will probably allow patchy dense fog in the Countryside 
toward dawn Wednesday. 

Forecast elements were a 50 50 blend of the 00z/30 GFS/NAM MOS 
with no modification of the temps. Min temps about 6f above 


Long term /Wednesday through Monday/... 
a mostly dry period with the best opportunity for showers and sct 
tstms will be Wed night thru Thu night as an upper trough and cold 
front move across the area. Pops for these periods mostly in the 
chc range attm. Depending on the track of tropical systems, there 
could be some showers near the coastal areas Mon, so we have slgt 
chcs then, low confid. 

Temperatures well above normal Wed before cold front swings thru 
Thu and brings readings back to normal or a little below normal 
for Thu-sun. There are signals that temps may trend back above 
normal next week, and we have above normal temps in there for Mon 


Aviation /12z Tuesday through Saturday/... 
the following discussion is for kphl, kpne, kttn, kabe, krdg, 
kilg, kmiv, kacy and surrounding areas. 

Today...VFR with sct clouds aoa 4500 ft developing late morning/early 
afternoon, particularly kacy/kmiv where an afternoon sprinkle may 
occur in a broken deck near 5000 ft. A light north wind this morning 
turns easterly midday. 

Tonight...VFR with sct-bkn clouds near 5000 ft grazing kphl-kttn 
this evening as they edge north. Patchy shallow IFR stratus fog 
possible kacy/kmiv/kttn after 06z/31. Wind becoming nearly calm. 

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 with a chance of showers. 

Thursday night through Saturday...mainly VFR. 


no marine headlines through tonight. 

Wave heights 3 to 4 ft as an ESE swell of 3 ft continues to our 
shores from the slowly departing central Atlantic Hurricane 

There is a chance that wave will rise to near 5 feet today and if 
they get to 5.2 or higher and are expected to last for several 
hours we would then issuance an sca, the long period swell making 
wave steepness less than for a shorter period equivalent wave 

Winds northeast gusting 15-20 kt early today turn east by 
afternoon and continue tonight as light easterly. 

Water temps are generally in the 70s..above normal. 


Wednesday through marine headlines are anticipated 
for Wed - Fri night. Then Small Craft Advisory flag possible Sat. For seas with 
4-6 ft expected on the ocean. Through the period, long period 
swells may create rough conditions in and around the inlets along 
the coasts of New Jersey and Delaware. 

Rip currents... 
with the 3-4 foot long period swells across the ocean and a northeast 
to east flow, the rip current risk for today is moderate. If the 
onshore easterly winds increase a bit more than forecast or the 
waveheights are slightly higher than the 3-4 ft forecast, then we 
would upgrade to a high risk but for now we think a moderate risk 
for the formation of dangerous rip currents is reasonably accurate. 

Wednesday: GFS and tropical modeled swell/period wave groups strongly 
suggest another day of moderate risk for the formation of dangerous 
rip currents. 

The beach hazards statement (thank you for disseminating) was 
reissued at 431 am for not only the Gaston swells but then a 
probable renewal of moderate to high risk rip current formation 
conditions between Friday and Labor Day. This in part based on 
nhcs outlook compared with the cyclic continuity of GFS/ec 
operational model cycles. 

Thursday: rc risk probably eases back to low enhanced, but it may 

Friday-sunday: rc 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. 

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). 


this section is up to date through 3 am today-Tuesday August 30. 

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

Regarding whether August can tie its record of 17 90f days. Its 
possible. Today is the critical day for extending the heat wave. 
The record of 17 was set in 1995. The mean for the month is only 
5. Tomorrow reaching 90 at phl looks to be relatively easy. 

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 
with very little chance of slipping to #2. 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. 78.8 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... 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 29th. 

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 39 21 15 5 17-1995 55-2010 

Ilg 33 20 14 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 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 so far, the 12th driest Summer...again this presumes no further 
measurable rain in August. 


Phi watches/warnings/advisories... 
New Jersey...beach hazards statement through Wednesday evening for njz014- 
Delaware...beach hazards statement through Wednesday evening for dez004. 


near term...drag 
short term...drag 
long term...O'Hara 
marine...drag/O'Hara 628a 

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