Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
FXUS61 KPHI 270804
Area Forecast Discussion
National Weather Service Mount Holly NJ
404 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 just below on Friday.
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 was in sharp disagreement with
the 00z/27 ECMWF, GGEM WPC and continuity Tuesday and Wednesday
and therefore 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 slight 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 /08Z 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
This climate section will update between 445 and 5am with
extensive confirming information of climate projections posted
this past week and add some precipitation departure information.
Near Term...O`Hara 404
Short Term...O`Hara 404
Long Term...Drag 404