Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
FXUS61 KPHI 270935
Area Forecast Discussion
National Weather Service Mount Holly NJ
535 AM EDT SAT AUG 27 2016
High pressure in southeast Canada is ridged down into the mid
Atlantic states this weekend, then shifts offshore next week. A
very weak frontal boundary from the northwest may arrive early in
the new week. A strengthening cold front approaching from the
northwest is anticipated to cross our area early on Thursday.
Great Lakes high pressure builds toward the mid Atlantic coast for
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
High pressure will settle across the area today with fair weather
expected. It will remain warmer than normal, like Friday, with
highs in the upper 80s to low 90s. The humidity levels will be a
little lower than Friday, so although it will be warm/hot, it
shouldn`t be unbearable to be outside today. Winds will be mostly
NE or E at around 10 mph. This will keep temperatures along the
shore and inland a bit cooler.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
More fair weather tonight as the High continues to move away far
N/NE. Skies will remain mostly clr and winds will be light. Low
temperatures will be mostly in the 60s, with some 70 degree temps
over the metro Philadelphia area. Lows across the srn Poconos will
be closer to 60 degrees, so overall, temperatures will be about 5
degrees above normal.
.LONG TERM /SUNDAY THROUGH FRIDAY/...
**a basically dry 6 day period with a possible modest 6 day heat
wave parts of the I-95 corridor and RDG-ABE**
500 MB: +2 standard deviation ridge overhead to start this 6 day period
progressively weakens during the middle and end of the week as a trough
develops across the ne USA with ridging to return eastward Labor Day
Temperatures: A top 4 warmest August and summer (June-July-August)
will come to close with calendar day average temperatures Sunday-
Wednesday 6 to 10 degrees above normal, then cooling Thursday to
maybe 2 to 5 above normal and finally normal or just below, on
Forecast basis: Unless otherwise noted, a 50 50 blend of the 00z/27
GFS/NAM MOS guidance Sunday-Monday, thereafter the 00z/27 GFS MEX
MOS for Monday night and 05z/27 WPC Guidance Tuesday-Friday.
The 00z/27 GFS operational cycle had some temperature disagreement
with the 00z/27 ECMWF, GGEM, WPC and continuity Tuesday and
therefore was not applied.
Sunday-Wednesday...Clear to partly cloudy, very warm to hot during
each afternoon. Light wind at night permits radiational cooling
in the countryside. Lowered blended gfs/nam mos guidance temps in
the non-urban areas Sunday night by 2F, especially since it hasnt
rained since the 21st. Did not have time to consider that cooling
adjustment For Monday night. Light onshore flow Sunday and Tuesday
afternoon will cool the coasts but a 6 day heat wave is possible
(Friday the 26th was the start if it happens) for some of the
interior including Berks County into the Lehigh Valley and parts
of the I-95 corridor. Confidence for a 6 day heat wave is average
to slightly below average with a 1 day interruption in 90 degree
warmth possible. Early morning haze and fog may eventually develop
during mid week, especially Wednesday morning. For now its only
a spotty prediction Monday and Tuesday.
Late Wednesday afternoon into early Thursday...A developing cold
front is expected to pass through our area and possibly trigger
scattered thunderstorms. This appears to be our primary hope for
any beneficial rain since the 21st. if we dont get it, it could be
quite a few days before it rains.
Thursday...turning cooler but still near or slightly above normal
with a gusty northwest wind developing.
Friday...Could be delightful for late summer with very dry air=low
humidity (dewpoints down close to 50).
.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
A decent period of flying weather today and tonight with high
pressure in control. Skies will be clear except for a few daytime cu
this afternoon. Wind speeds will be 10 knots or less. The wind
directions mostly North or Northeast this morning and then East or
Southeast this afternoon.
Sunday through Wednesday...VFR...mainly sct clouds aoa 5000 ft with
brief broken cigs near 5000 or 6000 ft. Late night and early morning
visibility restrictions are possible, especially Wednesday morning.
Small chance of a passing shower or thunderstorm early Monday.
Scattered Showers and thunderstorms are possible late Wednesday
night with the approaching cold front.
Winds: light southeast Sunday, light west to northwest Monday,
light and variable Tuesday, then on Wednesday southwest gusting 15
kt in the afternoon before shifting northwest at night.
No significant weather today or tonight. Winds will veer from
North early this morning to Northeast after sunrise. Wind speeds
will increase to 10-15 knots by mid-morning. Winds will then
continue to veer to East or a little Southeast tonight. Winds by
tonight will have subsided back to less than 10 knots for the most
part. Seas on the ocean will be 2 to 4 ft today and closer to 2 ft
Sunday through Wednesday...No marine headlines are anticipated.
Long period (12-15 second) 2 to 3 foot southeast swells from Gaston
will be rolling ashore in the Atlantic waters Monday through Wednesday.
Its possible these swells will briefly build to 4 feet Tuesday.
A Moderate risk for enhanced rip currents is expected today. The
swells from distant tropical systems have yet to arrive, but the
beginnings of this may be late this afternoon and early tonight.
Winds will be onshore today and will be 10-15 knots this morning.
This will create some enhanced surf conditions. The swell will
arrive late and may further create enhanced conditions.
The long period swells from Tropical Cyclone Gaston should arrive
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 northeastward. 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
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.
This section of the AFD will probably be omitted later today. It
will be rereviewed daily through Wednesday morning but unless
there is some sort of major change in the ranking...am not
anticipating a repost until Monday or Tuesday morning.
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 330 AM 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 3 to 5 more 90 degree days to
add onto the 12 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
at least 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.
1. 78.0 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
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 26th.
season mean Aug Aug Aug Season
mean rer rer
abe 31 17 10 4 16-1980 41-1966
acy 27 10 10 3 11-2010 46-2010
phl 36 21 12 5 17-1995 55-2010
ilg 31 20 12 5 23-1895 59-1895
Decided not to post dry rainfall statistics due to uncertainty regarding
shower amounts, if any Monday-Wednesday.
Long Term...Drag 535A