Special Marine Warning 71, NWS Philadelphia/Mount Holly

Area Forecast Discussion
National Weather Service Mount Holly NJ
807 PM EDT Sat Jul 4 2026

.WHAT HAS CHANGED...
Excessive Heat headlines have expired.

Updated Aviation section for 00Z TAFs.

Severe Thunderstorm Watch #459 is in effect for the entire
County Warning area until 11PM.

&&

.KEY MESSAGES...
1. Dangerous heat and humidity will continue across the region
through today. The heat will start to break Sunday and especially
Monday.

2. Showers and thunderstorms are expected to impact the area
late this afternoon into this evening and have the potential to
produce severe weather and localized flash flooding. Additional
rounds of showers and thunderstorms are expected Sunday and
Monday with a continuing threat for both severe weather and
flash flooding.

&&

.DISCUSSION...
KEY MESSAGE 1...Dangerous heat and humidity will diminish
overnight. Heat will continue to diminish Sunday and especially
Monday.

The excessive heat and heat advisory headlines have been taken
down at 8 PM. While still very hot across NJ, the approaching
thunderstorms and rains will being cooler conditions overnight.
It will be notably cooler temperatures are expected across the
region on Sunday, with high temperatures generally in the upper
80s across most of eastern PA and NJ, and low 90s for the urban
corridor as well as Delmarva. However the cumulative impacts of
the heat are still going to likely take a toll of the region.
With dewpoints remaining in the upper 60s to mid 70s, with heat
indices getting into the mid 90s to low 100s from the Philly
metro and south. We will consider more Heat headlines (likely
Advisories) later tonight.

By Monday, with a frontal boundary draped across the area, much
cooler temperatures are expected. Placement of the front is uncertain,
but north of the front temperatures will likely only be in the mid
70s, and low to mid 80s to the south. South of the front where temperatures
are still fairly warm, the forecast remains complicated by the potential
for widespread showers and storms.

KEY MESSAGE 2...Showers and thunderstorms are expected to impact the
area this evening and have the potential to produce severe weather
and localized flash flooding. Additional rounds of showers and
thunderstorms are expected Sunday and Monday with a continuing
threat for both severe weather and flash flooding.

Severe Thunderstorm Watch #459 is in effect for the entire
County Warning area until 11PM.

The mid-level ridge over the area will continue breaking down
this afternoon and evening as a mid and upper level trough
pivots across eastern Canada. Strong vertical mixing has
already set the stage with substantial instability across the
region. The CU field is beginning to bubble up across to the
south and towards the north showing that conditions for Severe
weather are developing rapidly across the area. ML CAPE values
are progged to once again reach 2000+ j/kg with increasing
amounts of shear compared to Friday. 0-3/0-6 km shear values
look to be upwards of 30/40 knots by later today. Steep low and
mid-level lapse rates will result in very high DCAPE values
already showing up on SPC's meso A website. Damaging winds will
be the biggest threat but PWATs close to 2 inches will also
support at least a localized flash flooding threat. The biggest
change in the guidance was that we're expecting the storms to
trigger maybe an hour or so later than initially forecast this
morning with the main threat still in the 7 - 11pm time frame.
We certainly can't rule out any isolated convection that
develops ahead of the more significant forcing so the overall
time of concern is from 3pm to 11pm. Heading into the overnight
period, the threat of severe weather reduces however there is
some signal of potential training of storms leading to heavy
rainfall over the urban corridor. Will be paying very close
attention to rainfall rates as flash flooding is an increasing
concern.

On Sunday, the severe weather threat is generally anticipated to
remain from mainly the Philly metro and points south, but this
will be dependent on frontal placement. However, widespread
showers and storms are also expected north of the front. In
fact, model guidance is indicating PWATs potentially exceeding 2
inches, which is above the 90th percentile for this time of
year and near the daily observed maximum. CAPE also looks to be
tall and "skinny", another setup that favors heavy rainfall.
Given these factors, rainfall rates in storms could exceed 1 to
2 inches per hour and it's possible storms may also train over
the same areas. The WPC has continues to indicated a Slight Risk
(2 of 4) for the I-95 corridor and points west both Sunday and
Monday, with a Marginal Risk (1 of 4) for the remainder of the
area. Storms could last into a good portion of the night Sunday
night. The severe threat should diminish by the overnight but
the flash flood threat may continue.

Unfortunately the aformentioned front is likely to remain
stalled near the area Monday as an upper level trough approaches
from the west. This will lead to additional widespread showers
and storms. The severe weather threat looks to be lower by this
time but the flash flood threat will remain elevated, especially
since the same areas have the potential of being hit with
multiple rounds of showers/storms over successive days.

Even into next Tuesday there could be more showers and storms before
the front should finally push south of the area by Wednesday
leading to the weather trending drier.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...Showers and storms likely to affect most TAF sites in
the evening bringing brief restrictions to IFR along with the
potential for strong wind gusts that could briefly exceed 40 to
45 knots. Showers/storms should largely be done by the overnight
period but can't rule out some localized fog/mist forming.

Outlook...

Sunday through Monday night...Scattered to widespread showers
and thunderstorms with sub-VFR conditions expected at times.

Tuesday through Wednesday...Primarily VFR. Isolated to
scattered showers and storms will be possible, especially in the
afternoon hours each day, which could lead to brief periods of
sub-VFR conditions.

&&

.MARINE...
Southwest winds 10-15 kt this afternoon, with some gusts up to 20
knots nearshore by mid to late afternoon with the increasing
seabreeze. Some heavy showers and strong to severe storms could
affect the waters this evening, leading to locally strong winds over
40 knots and reduced visibilities.

Outlook...

No marine headlines are currently anticipated through Wednesday,
with winds below 25 kt and seas remaining below 5 ft. Relatively
benign boating conditions are expected outside of thunderstorms.
However, a cold front drops into the area then stalls and slowly
weakens over the local waters. That front will be the focus for
additional showers and storms possible each day through Tuesday,
with activity being the most widespread Sunday afternoon/evening
and again on Monday afternoon. Reduced visibility and strong winds
remain possible with the strongest storms.

Winds back to the E-NE behind the front tomorrow afternoon and
evening through midweek. This will build seas slightly Monday
afternoon through Wednesday, especially north of Barnegat Light,
though again remaining below 5 ft.

Rip Currents...

For Sunday, winds will be from the east around 10 mph with gusts up
to 15 mph in the afternoon. Breaking waves will be around 1-2 feet
or less. There will be a weak southeast swell with a period around 8
seconds. This results in a LOW risk for the development of dangerous
and life threatening rip currents at the Jersey Shore and at
Delaware Beaches.

For Monday, winds remain east around 10 to 15 kt, with gusts to 20
kt in the afternoon. Resulting increasing NE wind wave could drive
an elevated MODERATE Rip Current Risk along the Jersey Shore, with
LOW risk persisting over the Delaware Beaches.

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

&&

.CLIMATE...
The record breaking heat is forecast to continue across our area
through today. 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 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...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

DISCUSSION...Cooper/Fitzsimmons/MPS/RCM/Staarmann/po
AVIATION...Cooper/Fitzsimmons/RCM/po
MARINE...Cooper/Fitzsimmons/MJL/MPS/RCM

Hazardous Weather Outlook
National Weather Service Mount Holly NJ
503 AM EDT Sat Jul 4 2026

MDZ012-015-019-020-050915-
Kent MD-Queen Annes-Talbot-Caroline-
503 AM EDT Sat Jul 4 2026

...EXTREME HEAT WARNING IN EFFECT UNTIL 8 PM EDT THIS EVENING...

This Hazardous Weather Outlook is for northeast Maryland.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Extreme Heat Warning.

In addition to the extreme heat, severe thunderstorms are possible
late this afternoon and evening.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Severe thunderstorms are possible Sunday afternoon and evening.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

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