Area Forecast Discussion
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FXUS61 KPHI 301330
Area Forecast Discussion
National Weather Service Mount Holly NJ
930 AM EDT TUE 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/...
Forecast running on track, so will not make any significant
changes to the database. Will keep a high of 90F at PHL based on
previous forecast, as latest guidance shows no reason to change
Sunny skies initially, but easterly boundary layer winds permit
enough increase in moisture to probably develop a sct-bkn deck of
clouds into much of NJ 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 DE to
SE NJ. Will keep POPs capped below slight chance, but will carry
chance for sprinkles from around 18-21Z. Low probability of this
occurring. Presuming the generating mechanism is ocean/land ely
flow sfc convergence in the convectively unstable boundary layer.
Today...Forecast 90F at PHL...since the 00z/30 GFS 2m temp has
88-89F from SW NJ 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 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.
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 NJ 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 /14Z 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 Saturday...No marine headlines are anticipated
for Wed - Fri night. Then SCA 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.
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
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 75.8...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 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.
NJ...Beach Hazards Statement through Wednesday evening for NJZ014-
DE...Beach Hazards Statement through Wednesday evening for DEZ004.