968
FXUS61 KPHI 300836
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
436 AM EDT Tue Jun 30 2026

.WHAT HAS CHANGED...
Extreme Heat Warning issued for all of southeastern
Pennsylvania, northern Delaware, and portions of New Jersey.

Confidence continues to increase in a prolonged period of
dangerously hot conditions beginning Wednesday and into the
holiday weekend.

&&

.KEY MESSAGES...
1. A warming trend in temperatures is expected to continue
through today. There is some potential for a few thunderstorms
mainly along and north of I-78 this afternoon and evening. There
is also potential for isolated thunderstorms across much of the
area on Wednesday.

2. Dangerous heat and humidity will build over the Northeast
and Mid Atlantic Wednesday through Saturday. All time record
high temperatures could be challenged Thursday and Friday.

3. There is the potential for afternoon and evening
thunderstorms starting on Friday and lasting into the holiday
weekend.

&&

.DISCUSSION...
KEY MESSAGE 1...A warming trend in temperatures is expected to
continue through today. There is some potential for a few
thunderstorms mainly along and north of I-78 this afternoon and
evening. There is also potential for isolated thunderstorms
across much of the area on Wednesday.

A strengthening ridge of high pressure to our west will result
in a warming trend in temperatures locally through today. Highs
will be mainly in the upper 80s to low 90s this afternoon. With
a lack of low level moisture return locally until later tonight,
dewpoints are anticipated to mix out in the afternoon. So
although it`ll be quite warm, humidity won`t be too oppressive
until the heat ramps up on Wednesday. Lows in the mid 60s to low
70s tonight.

For this afternoon and evening, we could get some MCS activity
coming into our region out of the eastern Great Lakes and
southern Ontario region amid the northwesterly flow aloft.
Latest CAMs suggest this MCS`s remnants will stay mainly north
of our area across Upstate New York and the Hudson Valley, but
CAMs sometimes tend to place MCSs too far north. Will have to
monitor this system as it progresses south today. Greatest
chances of any thunderstorms will be focused mainly along and
north of I-78 after 2 PM this afternoon through the evening.
Some additional convection could develop later tonight as well.
SPC`s MARGINAL risk area is currently just to our north, so
we`ll continue to monitor the potential for any storms to drift
south into our area. Damaging winds and frequent lightning
would be the main threat with any thunderstorms today through
tonight.

For Wednesday, instability is forecast to be high (potentially
3000 J/kg or greater) across the area, especially along and
northwest of I-95 by the afternoon hours. Due to the strong
subsidence and ridging building in from the west, there will
also be a lot of mid level dry air contributing to high DCAPE
(1000-1500 J/kg). Latest CAMs are hinting at potential for some
convective initiation within this environment, despite the
strong subsidence. While coverage of any thunderstorms would be
very isolated, any storms that do form could be capable of
producing strong microbursts with damaging winds. SPC has
highlighted our northern CWA in a MARGINAL (level 1 out of 5)
risk for severe thunderstorms.


KEY MESSAGE 2...Dangerous heat and humidity will build over the
Northeast and Mid Atlantic Wednesday through Saturday. All time
record high temperatures could be challenged Thursday and
Friday.

Strong mid-level ridging is developing across the Mississippi
Valley, Great Lakes, and Ohio Valleys early this week. Ridging
will then build eastward into the Northeast and Mid Atlantic by
Wednesday and persist into the holiday weekend. A west to
southwest flow on Wednesday will shift more west to northwest by
Friday. The ridge will finally start to break and retreat some
starting Saturday into Sunday.

High temperatures will climb into the mid and upper 90s on
Wednesday, and then from 100 to 105 degrees on Thursday and
Friday. With a south to southwest flow on Wednesday, dewpoints
are less likely to mix out significantly in the afternoon.
Resulting heat indices are forecast to range mainly from around
100-105 degrees. By Thursday and especially Friday, the shift to
a more west or northwest flow will allow for better mixing out
of dewpoints during the afternoon, and also a component of
downsloping (adiabatic warming) from the Appalachians. This will
support temperatures climbing above 100 degrees as dewpoints
mix out into the mid 60s during the afternoon hours. Resulting
forecast heat indices are mostly in the 105-110 degree range.
This is indeed the type of synoptic pattern that could challenge
all time record high temperatures in our region. See the
Climate section below for more information on record
temperatures.

Temperatures will abate somewhat on Saturday as the ridge
begins to break and retreat to the southwest. However, high
temperatures will still be in the mid 90s to near 100 degrees.
The prevailing flow direction will dictate how much mixing out
of dewpoints occur on Saturday. Currently, we have upper 60s to
near 70 degree dewpoints, which results in 100-105 degree heat
indices. Highs will remain in the low to mid 90s Sunday and
Monday as well, with heat indices still in the mid 90s to low
100s. So we certainly could see heat related impacts continuing
beyond Saturday despite a slight improvement in temperatures.

Given the increasing confidence in significant impacts from the
3 to 4 day excessive heat and humidity with heat indices
reaching into the 100-110 degree range each day, the Extreme
Heat Watch was upgraded to and Extreme Heat Warning for all of
southeastern Pennsylvania, northern Delaware, and portions of
New Jersey. This includes all areas where the previous watch was
effective beginning Wednesday afternoon through Saturday. While
heat indices may fall shy of warning criteria by Saturday,
impacts will likely be worsened by the multiple days of heat and
busy outdoor holiday festivities.

Elsewhere across far southern New Jersey, the New Jersey barrier
islands, and Delmarva, the Extreme Heat Watch remains in
effect beginning Thursday afternoon through Saturday. Within the
remaining watch area, heat indices up to 100 degrees are
possible on Wednesday, but the more notable heat won`t begin
until Thursday.

The mid-level ridge will break and retrograde back towards the
south and west beginning Saturday, and a mid-level trough will
try to slide down into the Northeast. This pattern change will
begin to favor slightly cooler temperatures and a break in the
extreme heat by Sunday and Monday, as well as the potential for
showers and thunderstorms for the holiday weekend (see Key
Message 3 below).


KEY MESSAGE 3...There is the potential for afternoon and
evening thunderstorms starting on Friday and lasting into the
holiday weekend.

The mid-level ridge looks to break down and retrograde back to
the south and west starting on Friday, and this will allow mid-
level troughiness to develop over the Northeast. With several
shortwaves riding over the top of the ridge and into the local
area, this may support afternoon and evening showers and
thunderstorms starting on Friday, but the better chances for
convection arrive on Saturday and Sunday. Currently, PoPs are
around 20-30% on Friday and 30-50% on Saturday and Sunday.

While details of this activity won`t become clear until later
this week, it is important to point out that any holiday weekend
festivities could be impacted by thunderstorms (in addition to
the extreme heat). The environmental setup would be favorable
for strong to severe thunderstorms, if any storms do develop.
We`ll continue to monitor this potential.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Through 12Z...There is a low chance of patchy fog developing
tonight. Due to the low confidence and patchy nature of any fog
development, no restrictions were put in the TAFs. Otherwise,
VFR. Winds less than 5 kts favoring a southerly direction,
locally calm. Low confidence in fog, high confidence otherwise.

Today...VFR. Winds shifting south to southwest and increasing
to near 10 kts with gusts up to 18 kts after 18Z. High
confidence.

Tonight...VFR. South to southwest winds remaining near 5-10 kts
overnight. High confidence.

Outlook...

Wednesday through Friday...VFR. Low chance (20%) of a
thunderstorm Wednesday and Friday, otherwise no significant
weather.

&&

.MARINE...
No marine hazards are forecast through most of today. However,
southerly winds will increasing to 15-20 kts. Winds as high as
25 kts north of Barnegat Light. Seas increasing to 2-3 feet by
evening. Winds and seas diminishing overnight.

A Small Craft Advisory was issued between 2 PM and midnight to
highlight the potential for winds up to 25 kts later this
afternoon and evening.

Outlook...

Wednesday through Friday...There is potential for marginal
advisory criteria to be met with winds increasing to near 20-25
kts with seas nearing 5 feet both Wednesday and Thursday
afternoon and evening, mainly north of Atlantic City.

Rip Currents...

For today, southerly winds increase to 15 to 25 mph with
breaking waves in the surf zone around 1-3 feet. There will
also be multiple swell groups and we`ll only be one day removed
from today`s Full Moon. For these reasons, we`ll go with a
MODERATE risk of dangerous rip currents for coastal Ocean County
south through Cape May County along the NJ shore. For coastal
Monmouth County and the Delaware Beaches we`ll continue with a
LOW risk.

For Wednesday, similar conditions to today can be expected, but
with slightly larger breaking waves. So we`ll continue to go
with a MODERATE risk of dangerous rip currents for coastal Ocean
County south through Cape May County along the NJ shore. And
for coastal Monmouth County and the Delaware Beaches we`ll
continue with a LOW risk.

For specific beach forecasts, visit weather.gov/beach/phi

&&

.CLIMATE...
Record breaking heat is forecast from Wednesday through
Saturday. Temperature records for our climate sites are listed
below:

All Time Record High Temperatures

Site                  Record / Date
Allentown (ABE)          105 / July 3, 1966
AC Airport (ACY)         106 / June 28, 1969
AC Marina (55N)          104 / August 7, 1918
Georgetown (GED)         104 / July 22 & 23, 2011
Mount Pocono (MPO)       103 / July 3, 1911
Philadelphia (PHL)       106 / August 7, 1918
Reading (RDG)            106 / July 22, 2011
Trenton (TTN)            106 / July 9, 1936 & July 22, 2011
Wilmington (ILG)         107 / August 7, 1918

All Time Record Warmest Low Temperatures

Site                  Record / Date
Allentown (ABE)           79 / July 15, 1995
AC Airport (ACY)          84 / July 23, 2011
AC Marina (55N)           82 / July 21, 2019
Georgetown (GED)          84 / July 23, 2011
Mount Pocono (MPO)        76 / July 12, 1952
Philadelphia (PHL)        83 / July 24, 2010 & July 23, 2011
Reading (RDG)             81 / August 7, 1918
Trenton (TTN)             84 / August 11, 1895
Wilmington (ILG)          84 / August 7, 1918

Record Number of Consecutive 100+ Degree Days

Site                  Record / Date
Allentown (ABE)       3 days / July 9-11, 1936 & July 2-4, 1966
AC Airport (ACY)      3 days / July 2-4, 1966 & July 22-24, 2011
AC Marina (55N)        1 day / Occurred multiple times
Georgetown (GED)      2 days / Most recent June 24-25, 2025
Mount Pocono (MPO)     1 day / July 3, 1911
Philadelphia (PHL)    3 days / July 2-4, 1966 & July 8-10, 1993
Reading (RDG)         3 days / Most recent July 21-23, 2011
Trenton (TTN)         3 days / Most recent July 21-23, 2011
Wilmington (ILG)      3 days / Most recent July 9-11, 1936

Record High Temperatures
                          July 1
Site                  Record / Year
Allentown (ABE)           98 / 2018
AC Airport (ACY)          99 / 1968
AC Marina (55N)           98 / 1968
Georgetown (GED)          99 / 2012
Mount Pocono (MPO)        88 / 1963, 1964, 1968, & 2018
Philadelphia (PHL)       102 / 1901
Reading (RDG)            101 / 1901
Trenton (TTN)             98 / 1898, 1901, & 1945
Wilmington (ILG)          97 / 1931 & 1963

Record Warmest Low Temperatures
                          July 1
Site                  Record / Year
Allentown (ABE)           74 / 1930
AC Airport (ACY)          77 / 1945
AC Marina (55N)           79 / 1945
Georgetown (GED)          76 / 1945
Mount Pocono (MPO)        67 / 1946, 1971, 2013, 2017, 2025
Philadelphia (PHL)        82 / 1901
Reading (RDG)             76 / 1968
Trenton (TTN)             77 / 1945
Wilmington (ILG)          75 / 2013

Record High Temperatures
                          July 2
Site                  Record / Year
Allentown (ABE)          102 / 1966
AC Airport (ACY)         100 / 1966
AC Marina (55N)           97 / 1968
Georgetown (GED)          99 / 1953
Mount Pocono (MPO)        93 / 1911
Philadelphia (PHL)       103 / 1901
Reading (RDG)            102 / 1966
Trenton (TTN)            100 / 1901
Wilmington (ILG)          98 / 1941 & 1966

Record Warmest Low Temperatures
                          July 2
Site                  Record / Year
Allentown (ABE)           75 / 2013
AC Airport (ACY)          79 / 2002
AC Marina (55N)           76 / 2012
Georgetown (GED)          77 / 1959
Mount Pocono (MPO)        70 / 1903
Philadelphia (PHL)        82 / 1901
Reading (RDG)             79 / 1901
Trenton (TTN)             79 / 1901
Wilmington (ILG)          75 / 1941 & 2014

Record High Temperatures
                          July 3
Site                  Record / Year
Allentown (ABE)          105 / 1966
AC Airport (ACY)         104 / 1966
AC Marina (55N)           99 / 1919
Georgetown (GED)         101 / 1954
Mount Pocono (MPO)       103 / 1911
Philadelphia (PHL)       104 / 1966
Reading (RDG)            103 / 1898 & 1966
Trenton (TTN)            102 / 1966
Wilmington (ILG)         102 / 1966

Record Warmest Low Temperatures
                          July 3
Site                  Record / Year
Allentown (ABE)           75 / 2018
AC Airport (ACY)          78 / 2018
AC Marina (55N)           76 / 1983, 2002, & 2018
Georgetown (GED)          79 / 1953
Mount Pocono (MPO)        69 / 2013
Philadelphia (PHL)        77 / 1876, 1901, &2002
Reading (RDG)             76 / 2018
Trenton (TTN)             76 / 1901 & 1966
Wilmington (ILG)          76 / 2002

Record High Temperatures
                          July 4
Site                  Record / Year
Allentown (ABE)          102 / 1949
AC Airport (ACY)         102 / 1966
AC Marina (55N)           99 / 1966
Georgetown (GED)         100 / 1966
Mount Pocono (MPO)        99 / 1911
Philadelphia (PHL)       103 / 1966
Reading (RDG)            100 / 1911 & 1966
Trenton (TTN)             99 / 1919, 1999, & 2010
Wilmington (ILG)         102 / 1966

Record Warmest Low Temperatures
                          July 4
Site                  Record / Year
Allentown (ABE)           75 / 1999
AC Airport (ACY)          75 / 1974, 1983, 1999, & 2002
AC Marina (55N)           79 / 2002
Georgetown (GED)          75 / 1999 & 2012
Mount Pocono (MPO)        70 / 2002 & 2013
Philadelphia (PHL)        79 / 1919
Reading (RDG)             78 / 1966
Trenton (TTN)             78 / 1966
Wilmington (ILG)          76 / 1999

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Extreme Heat Warning from noon Wednesday to 8 PM EDT Saturday
     for PAZ054-055-060>062-070-071-101>106.
NJ...Extreme Heat Warning from noon Wednesday to 8 PM EDT Saturday
     for NJZ001-007>010-012>020-027.
     Extreme Heat Watch from Thursday afternoon through Saturday
     evening for NJZ021>026.
DE...Extreme Heat Warning from noon Wednesday to 8 PM EDT Saturday
     for DEZ001.
     Extreme Heat Watch from Thursday afternoon through Saturday
     evening for DEZ002>004.
MD...Extreme Heat Watch from Thursday afternoon through Saturday
     evening for MDZ012-015-019-020.
MARINE...Small Craft Advisory from 2 PM this afternoon to midnight EDT
     tonight for ANZ450-451.

&&

$$

DISCUSSION...RCM/Staarmann
AVIATION...Staarmann
MARINE...Fitzsimmons/Staarmann