579
FXUS61 KPHI 030900
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
500 AM EDT FRI JUL 3 2026
WHAT HAS CHANGED
THE AVIATION SECTION HAS BEEN UPDATED FOR THE 06Z TAFS.
KEY MESSAGES
1. DANGEROUS HEAT AND HUMIDITY WILL CONTINUE ACROSS THE REGION
THROUGH SATURDAY. ALL TIME RECORD HIGH TEMPERATURES COULD BE
CHALLENGED AGAIN TODAY WITH WIDESPREAD TRIPLE DIGIT
TEMPERATURES.
2. THERE IS THE POTENTIAL FOR MORE AFTERNOON AND EVENING
THUNDERSTORMS STARTING ON FRIDAY AND LASTING THROUGH THE HOLIDAY
WEEKEND.
DISCUSSION
KEY MESSAGE 1...DANGEROUS HEAT AND HUMIDITY WILL CONTINUE
ACROSS THE REGION THROUGH SATURDAY. ALL TIME RECORD HIGH
TEMPERATURES COULD BE CHALLENGED AGAIN TODAY WITH WIDESPREAD
TRIPLE DIGIT TEMPERATURES.
STRONG MID-LEVEL RIDGING ACROSS THE MISSISSIPPI VALLEY, GREAT
LAKES, AND OHIO VALLEYS HAS BUILT EASTWARD INTO THE NORTHEAST
AND MID ATLANTIC AND WILL PERSIST INTO THE HOLIDAY WEEKEND. THE
FLOW WILL SHIFT MORE WEST TO NORTHWEST TODAY. THE RIDGE WILL
FINALLY START TO BREAK AND RETREAT SOME STARTING SATURDAY, AND
ESPECIALLY INTO SUNDAY.
HIGH TEMPERATURES ARE FORECAST TO RANGE BETWEEN 100 TO 105
DEGREES IN MOST AREAS AGAIN TODAY. THE SHIFT TO A MORE WEST TO
NORTHWEST FLOW ALOFT WILL ALLOW FOR BETTER MIXING OUT OF
DEWPOINTS DURING THE AFTERNOON, AND ALSO A COMPONENT OF
DOWNSLOPING (ADIABATIC WARMING) FROM THE APPALACHIANS. THIS
PHENOMENON SHOULD BE A LITTLE STRONGER TODAY AND DEWPOINTS
SHOULD MIX OUT A FAIR AMOUNT IN THE AFTERNOON. THIS SETUP WILL
SUPPORT TEMPERATURES CLIMBING ABOVE 100 DEGREES ACROSS MOST NON
MOUNTAINOUS INLAND AREAS AS DEWPOINTS MIX OUT INTO THE MID TO
UPPER 60S DURING THE AFTERNOON HOURS. RESULTING FORECAST HEAT
INDICES ARE MOSTLY IN THE 105-110 DEGREE RANGE, THOUGH
LOCALIZED VALUES UPWARDS OF 115 DEGREES ARE POSSIBLE AGAIN IF
DEWPOINTS STAY CLOSER TO 70 DEGREES.
TODAY WILL LIKELY END UP BEING THE HOTTEST SOUTH OF I-78 BY A
DEGREE OR TWO DUE TO AFOREMENTIONED METEOROLOGICAL FACTORS.
THIS WILL BE ESPECIALLY THE CASE FOR COASTAL AREAS AND DELMARVA,
WHERE THE STRONGER WEST TO NORTHWEST LOW LEVEL FLOW SHOULD KEEP
THE MARINE LAYER OFFSHORE A BIT LATER INTO THE DAYTIME HOURS
BEFORE THE SEA BREEZE DEVELOPS. SEE THE CLIMATE SECTION BELOW
FOR MORE INFORMATION ON RECORD TEMPERATURES.
TEMPERATURES WILL BEGIN TO 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 AROUND 100
DEGREES, HOTTEST ALONG AND SOUTHEAST OF I-95. ANOTHER DAY OF
WEST TO NORTHWEST FLOW OF SIMILAR MAGNITUDE SHOULD ONCE AGAIN
SUPPORT THE IMMEDIATE COASTLINE WARMING UP CONSIDERABLY BEFORE
THE SEA BREEZE DEVELOPS. ELSEWHERE, A GRADUALLY WEAKENING RIDGE
ALOFT WILL RESULT IN THE SLIGHTLY COOLER TEMPERATURES.
DEWPOINTS SHOULD MIX OUT AGAIN INTO THE UPPER 60S TO NEAR 70
DEGREES BY AFTERNOON, WHICH RESULTS IN 100-108 DEGREE HEAT
INDICES.
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. IT WILL STILL BE QUITE HUMID THOUGH, WITH
HEAT INDICES GETTING INTO THE MID 90S TO LOW 100S FROM THE
PHILLY METRO AND SOUTH. BY MONDAY, IN THE WAKE OF A COLD FRONT,
TEMPERATURES LOOK TO TOP OUT IN THE MID 80S FOR MOST LOCATIONS,
THOUGH SLIGHTLY COOLER IN THE POCONOS AND SLIGHTLY WARMER
ACROSS DELMARVA. EVEN WITH THIS IMPROVEMENT, HEAT RELATED
IMPACTS MAY CONTINUE BEYOND SATURDAY, ESPECIALLY FOR THE URBAN
CORRIDOR AND DELMARVA. ALL THIS BEING SAID, INCREASING SHOWER
AND THUNDERSTORM CHANCES DO COMPLICATE THE TEMPERATURE FORECAST
SOME FOR THIS TIME PERIOD.
CONFIDENCE REMAINS HIGH FOR 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
WARNING FOR OUR ENTIRE FORECAST AREA (EXCLUDING THE NEW JERSEY
BARRIER ISLANDS) REMAINS IN EFFECT THROUGH 8 PM SATURDAY. THE
HOTTEST CONDITIONS ARE FORECAST TO OCCUR THROUGH TODAY SOUTH OF
I-78. WHILE HEAT INDICES MAY FALL JUST SHY OF WARNING CRITERIA
BY SATURDAY, IMPACTS WILL LIKELY BE WORSENED BY THE MULTIPLE
DAYS OF HEAT AND BUSY OUTDOOR HOLIDAY FESTIVITIES. IT IS LOOKING
LESS PROBABLE THAT ANY HEAT HEADLINES WILL BE NEEDED FOR
SUNDAY, BUT WE'LL CONTINUE TO MONITOR THIS.
A HEAT ADVISORY REMAINS IN EFFECT FOR THE NEW JERSEY SHORE
(BARRIER ISLANDS), INCLUDING COASTAL OCEAN, COASTAL ATLANTIC,
AND COASTAL CAPE MAY COUNTIES. THE STRONG SOUTHERLY COASTAL JET
AND RESULTING LOCAL UPWELLING OF COOLER OCEAN TEMPERATURES
SHOULD PREVENT THE ISLANDS FROM GETTING TOO HOT DURING THE
AFTERNOONS, THOUGH THE WIND DIRECTION WILL BE MORE SOUTHWESTERLY
TODAY AND SATURDAY. THIS SHOULD ALLOW FOR TEMPERATURES TO RISE
INTO THE MID 90S TO POTENTIALLY NEAR 100 DEGREES BEFORE THE SEA
BREEZE DEVELOPS, RESULTING IN DAILY MAXIMUM HEAT INDICES
THROUGH SATURDAY FROM 95 TO 105 DEGREES. THE ADVISORY IS ALSO IN
EFFECT THROUGH 8 PM SATURDAY. THE HOTTEST CONDITIONS ARE
FORECAST TO OCCUR TODAY IN THIS AREA AS WELL. THE EXTREME HEAT
WARNING REMAINS IN EFFECT FOR COASTAL MONMOUTH COUNTY.
THE MID-LEVEL RIDGE WILL BREAK AND RETROGRADE BACK TOWARDS THE
SOUTH AND WEST BEGINNING SATURDAY, AND A MID-LEVEL TROUGH WILL
DIG SOUTHEASTWARD ACROSS PORTIONS OF NEW ENGLAND WITH ENHANCED
NORTHWESTERLY MID-LEVEL FLOW ACROSS THE REGION. IN ADDITION TO
THE PATTERN CHANGE ALLOWING FOR COOLING TEMPERATURES, SHOWER AND
THUNDERSTORM CHANCES WILL INCREASE FOR THE HOLIDAY WEEKEND (SEE
KEY MESSAGE 2 BELOW).
KEY MESSAGE 2...THERE IS THE POTENTIAL FOR MORE AFTERNOON AND
EVENING THUNDERSTORMS STARTING ON FRIDAY AND LASTING THROUGH THE
HOLIDAY WEEKEND.
THE MID-LEVEL RIDGE LOOKS TO BREAK DOWN AND RETROGRADE BACK TO
THE SOUTH AND WEST STARTING LATER TODAY, AND THIS WILL ALLOW A
MID- LEVEL TROUGH TO DIG SOUTHEASTWARD INTO NEW ENGLAND. WITH
SEVERAL SHORTWAVES RIDING OVER THE TOP OF THE RIDGE AND INTO THE
LOCAL AREA, THIS WILL SUPPORT INCREASING COVERAGE OF AFTERNOON
AND EVENING SHOWERS AND THUNDERSTORMS STARTING LATE THIS
AFTERNOON, BUT ESPECIALLY ON SATURDAY AND SUNDAY. CURRENTLY,
POPS ARE AROUND 10-25% THIS AFTERNOON AND EVENING AND GENERALLY
30-60% ON SATURDAY. ACTIVITY BECOMES MORE WIDESPREAD ON SUNDAY
AND MONDAY, WITH POPS AROUND 60-90% FOR MOST OF THE AREA.
SPC HAS HIGHLIGHTED PORTIONS OF OUR AREA IN A SLIGHT RISK
(LEVEL 2 OUT OF 5) FOR SEVERE THUNDERSTORMS TODAY, SATURDAY, AND
SUNDAY. AS INDICATED BY THE POP FORECAST ABOVE, COVERAGE OF
STORMS IS ANTICIPATED TO BE RELATIVELY LOW TODAY, MAINLY
ISOLATED TO SCATTERED IN NATURE AT BEST. COVERAGE AND
ORGANIZATION OF STORMS SHOULD BE A BIT GREATER ON SATURDAY
THOUGH. DAMAGING WINDS WILL BE THE MAIN THREAT WITH ANY
THUNDERSTORM DEVELOPMENT. ON SUNDAY, THE SEVERE WEATHER THREAT
MAY BEGIN TO BECOME CONFINED MAINLY TO DELMARVA WHERE
DESTABILIZATION IS GREATEST AHEAD OF AN APPROACHING COLD FRONT.
WITH THAT BEING SAID, THE ENTIRE AREA COULD SEE SHOWERS AND A
FEW STORMS.
WHILE THERE IS STILL SOME UNCERTAINTY IN THE DETAILS OF THE
THUNDERSTORM ACTIVITY FRIDAY AND INTO THE WEEKEND, IT IS
IMPORTANT TO POINT OUT THAT ANY HOLIDAY WEEKEND FESTIVITIES
COULD BE IMPACTED BY THUNDERSTORMS (IN ADDITION TO THE EXTREME
HEAT).
AFTER THE COLD FRONT MOVES THROUGH ON SUNDAY, IT MAY STALL FOR
A PERIOD NEAR OR JUST SOUTH OF THE REGION BEFORE HIGH PRESSURE
BEGINS TO BUILD BACK IN BY MID-WEEK. THIS, IN COMBINATION WITH A
MID-LEVEL IMPULSE MOVING EASTWARD ACROSS THE REGION, IS
EXPECTED TO LEAD TO SCATTERED TO WIDESPREAD SHOWERS AND A FEW
STORMS SUNDAY NIGHT THROUGH MONDAY NIGHT. THEREAFTER, DAILY
CHANCES FOR ISOLATED, PRIMARILY DIURNALLY DRIVEN CONVECTION,
COULD CONTINUE INTO THE MIDDLE OF NEXT WEEK.
AVIATION /08Z FRIDAY THROUGH TUESDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH 12Z...VFR. SOUTHWEST WINDS 5-10 KTS BECOMING MORE WEST-
NORTHWEST BY 09Z. HIGH CONFIDENCE.
TODAY...VFR. WEST TO NORTHWEST WINDS 5-10 KTS EARLY, SHIFTING
WEST TO SOUTHWEST IN THE AFTERNOON. VERY LOW RISK OF ISOLATED
THUNDERSTORMS AFTER 20Z (ABOUT 10-20% CHANCE), BUT THE RISK IS
TOO LOW TO INCLUDE A TAF MENTION. HIGH CONFIDENCE OVERALL.
TONIGHT...VFR. SOUTHWEST WINDS NEAR 5 KTS SHIFTING WEST TO
NORTHWEST OVERNIGHT. HIGH CONFIDENCE.
OUTLOOK...
SATURDAY THROUGH TUESDAY...SCATTERED SHOWERS AND STORMS WILL BE
POSSIBLE EACH DAY. RESTRICTIONS WILL BE POSSIBLE WITH ANY
SHOWERS AND STORMS.
MARINE
NO MARINE HAZARDS EXPECTED THROUGH TONIGHT. SOUTH TO SOUTHWEST
WINDS 10-15 KTS. SEAS 1-3 FEET. 10-20% CHANCE OF A
THUNDERSTORM, OTHERWISE FAIR WEATHER AND HAZY.
OUTLOOK...
SATURDAY THROUGH MONDAY NIGHT...NO MARINE HAZARDS CURRENTLY
ANTICIPATED WITH WINDS UNDER 25 KT AND SEAS UNDER 5 FEET.
SCATTERED SHOWERS AND STORMS WILL BE POSSIBLE EACH DAY.
TUESDAY...WINDS WILL INCREASE OUT OF THE EAST AND GUSTS MAY
APPROACH 25 KT. SEAS MAY ALSO INCREASE TO ABOVE 5 FEET,
ESPECIALLY FOR NORTHERN MARINE ZONES. SCATTERED SHOWERS AND
STORMS WILL BE POSSIBLE.
RIP CURRENTS...
FOR TODAY, WINDS WILL START FROM THE NORTHWEST AT AROUND 10
MPH, THEN WILL TURN TO THE SOUTHWEST AT 10 TO 15 MPH WITH GUSTS
UP TO 20 MPH IN THE AFTERNOON. BREAKING WAVES WILL BE 1 TO 2
FEET. THERE WILL BE A LIGHT SOUTHERLY SWELL WITH A PERIOD AROUND
6 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.
ON SATURDAY, WINDS WILL BE FROM THE WEST TO SOUTHWEST AT 10 TO
15 MPH WITH GUSTS UP TO 20 MPH IN THE AFTERNOON. BREAKING WAVES
WILL BE AROUND 1 FOOT OR LESS. THERE WILL BE A LIGHT SOUTHEAST
SWELL WITH A PERIOD AROUND 6 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 SPECIFIC BEACH FORECASTS, VISIT WEATHER.GOV/BEACH/PHI
CLIMATE
RECORD BREAKING HEAT IS FORECAST THROUGH SATURDAY. ON THURSDAY,
JULY 2ND, DAILY RECORDS WERE TIED OR BROKEN AT THE ATLANTIC
CITY AIRPORT, MOUNT POCONO, PHILADELPHIA, READING, TRENTON,
WILMINGTON, AND GEORGETOWN. 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 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 UNTIL 8 PM EDT SATURDAY FOR PAZ054-055-
060>062-070-071-101>106.
NJ...EXTREME HEAT WARNING UNTIL 8 PM EDT SATURDAY FOR NJZ001-
007>010-012>023-027.
HEAT ADVISORY UNTIL 8 PM EDT SATURDAY FOR NJZ024>026.
DE...EXTREME HEAT WARNING UNTIL 8 PM EDT SATURDAY FOR DEZ001>004.
MD...EXTREME HEAT WARNING UNTIL 8 PM EDT SATURDAY FOR MDZ012-015-
019-020.
MARINE...NONE.
DISCUSSION...COOPER/RCM/STAARMANN
AVIATION...RCM/STAARMANN
MARINE...MPS/RCM/STAARMANN
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