Area Forecast Discussion
Issued by NWS Mt. Holly, NJ-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KPHI 232241
Area Forecast Discussion
National Weather Service Mount Holly NJ
641 PM EDT SAT JUL 23 2016
A very weak front will cross Delmarva this evening. High pressure
will build over the area later tonight and through the day Sunday. A
weak cold front will cross the region Monday. High pressure will
return for the middle part of the week. Another front may affect the
area Thursday and Thursday night.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --Impressive thunderstorms developed late this afternoon in extreme
southeast Pennsylvania, extreme northeast Maryland, and far
northern Delaware...before moving into southern New Jersey. These
thunderstorms formed along a surface trough that was positioned
over the coastal plain of New Jersey, extending into extreme
southeast Pennsylvania. Hot, muggy air was positioned south of
this trough, and less hot and less muggy air, as evidenced by
dewpoints in the 50s, was positioned north of this trough.
Thunderstorm activity is expected to slowly wane this evening
before ending late this evening. With the continual loss of
daytime heating, it appears the worst of the storms should be
behind us, but scattered rain showers are still possible through
the evening hours. Recent 88D imagery shows the outflow boundary
from some of these thunderstorms moving north in northern
Montgomery, Bucks, and Mercer Counties.
Showers and thunderstorms have cooled portions of the Philly metro
area late this afternoon and early this evening. As of 600 pm,
heat indices were below 100 north of the C&D canal, but over 100
(and in some cases over 110 degrees) over southern Delaware.
Temperatures will gradually temper themselves with the setting sun
down south. The Heat Advisory will be allowed to expire at 8 PM
this evening...with the Excessive Heat Warning continuing until
600 PM Monday for the urban corridor around Philadelphia.
Low temperatures are expected to range from the mid 60s in
northeast PA and northwest NJ to mid 70s in the urban areas and
the coastal plain.
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.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
The cold front will move south of the area by morning. The airmass
will be only slightly cooler behind the front. In northeast PA and
northwest NJ, where CAA is a bit more robust high temperatures will
be about 3-5 degrees lower than today. Farther south, expect only a
1-3 degree difference between tomorrow and today. However, drier air
will works its way into the region behind the cold front, so it
shouldn`t be too humid outside of the southern DE and adjacent
eastern MD (where dewpoints will still be around 70F).
Forecast soundings show a subsidence inversion that should cap
convection with us located underneath the ridge. The forecast was
kept dry accordingly. Winds will be light and variable through the
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
No huge changes foreseen in the summer-like pattern with upper
heights remaining high across much of the U.S. The storm track will
be across southern Canada with short waves and weak low pressure
systems moving across the area. The weakening cold fronts associated
with these features will cross the area thru the week. The best chc
for showers and tstms will center around both Mon and Thu. We have
kept pops in the chc range for these periods with mostly dry or slgt
chc pops for other periods. The exact timing will depend on the
individual waves which the models have difficult resolving by the
end of the extended period. Pretty much all of the major models have
precip somewhere across the area Monday. SPC has a marginal risk for
SVR storms across much of area then.
The above normal temperatures will continue thru much of the week.
Monday will likely be the hottest day with readings in the mid/upper
90s and heat index values in the 100s. The temperatures and dew
points will be lower for Tue and Wed, but still in the
uncomfortable/marginally unsafe range with heat index values 95-100
over the urban areas.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Predominately VFR thru Sunday, except briefly IFR if a
thunderstorm happens to move over an airport before sunset. Some
patchy fog may develop across mainly the southern portions of the
area later tonight, especially if any precipitation falls at any
of the terminals.
W-NW winds will continue to gust to 20 kt early this evening before
becoming light and variable tonight. Winds AOB 10 kt on Sunday.
VFR much of the time. Scattered (mostly) late afternoon and
evening showers and thunderstorms may limit cigs/vsbys at times
through the period.
S-SWly winds will be strongest early this evening in our coastal
waters off S NJ and DE. Winds could be sustained near 20 kt but
the potential to mix down higher gusts is minimal with a hot
airmass residing over the relatively cooler waters. While there
could be a few gusts near 25 kt early this evening nearshore, do
not expect conditions will warrant a SCA.
Winds will be light tonight and Sunday with high pressure building
Medium-period sly swells will persist today and tomorrow. Wave
heights should subside in the 2-3 ft range through the remainder of
Mostly a period of sub-sca conditions expected. scattered showers
and thunderstorms will create locally higher winds and seas
through the period.
Record high temperatures today through Thursday are below.
Site 23rd 24th 25th 26th 27th 28th
---- ---- ---- ---- ---- ---- ----
PHL... 101-2011 98-2011 96-1899 101-1892 101-1940 100-1941
ABE... 99-1955 95-1999 95-1999 98-1940 98-1955 97-1949
ACY... 105-2011 100-2011 99-2010 96-2011 99-2005 98-1999
ILG... 100-2011 98-2011 96-1987 99-1894 100-1894 101-1894
TTN... 104-2011 98-1910 97-1999 99-1892 100-1894 101-1894
GED... 104-2011 99-2011 99-2010 97-2012 98-2005 99-1949
RDG... 100-2011 96-2010 96-1999 99-1940 98-1955 99-1941
MPO... 91-1955 91-1914 90-1999 89-1949 91-1955 93-1949
PA...Heat Advisory from 11 AM to 6 PM EDT Monday for PAZ060>062-101-
Excessive Heat Warning until 6 PM EDT Monday for PAZ070-071-
NJ...Heat Advisory from 11 AM to 6 PM EDT Monday for NJZ007>010-
Heat Advisory until 8 PM EDT this evening for NJZ012>014-016-
Excessive Heat Warning until 6 PM EDT Monday for NJZ015-
DE...Heat Advisory from 11 AM to 6 PM EDT Monday for DEZ002>004.
Heat Advisory until 8 PM EDT this evening for DEZ002>004.
Excessive Heat Warning until 6 PM EDT Monday for DEZ001.
MD...Heat Advisory from 11 AM to 6 PM EDT Monday for MDZ008-012-015-
Heat Advisory until 8 PM EDT this evening for MDZ008-012-015-