186
FXUS61 KPHI 230818
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
418 AM EDT MON JUN 23 2025
SYNOPSIS
HOT HIGH PRESSURE ACROSS THE WESTERN ATLANTIC WILL BUILD WEST
INTO THE APPALACHIAN REGION EARLY THIS WEEK. THIS WILL RESULT IN
A SIGNIFICANT HEAT WAVE WITH NEAR RECORD BREAKING TEMPERATURES
FORECAST. THE HIGH PRESSURE SYSTEM WILL BEGIN TO WEAKEN AND
RETREAT TO THE SOUTH BY THE MIDDLE TO END OF THE WEEK, AND
TEMPERATURES WILL RETURN CLOSER TO NORMAL ALONG WITH INCREASING
CHANCES FOR SHOWERS AND THUNDERSTORMS TOWARD THE END OF THE
WEEK.
NEAR TERM /THROUGH TUESDAY/
SIGNIFICANT AND DANGEROUS HEAT TODAY AND TOMORROW, WITH POTENTIALLY
SOME OF THE HOTTEST TEMPERATURES IN OVER A DECADE IN SOME LOCATIONS.
A STRONG RIDGE OF HIGH HOT AND DRY PRESSURE WILL BUILD ACROSS THE
EASTERN US THROUGH TUESDAY. MID LEVEL HEIGHTS, THICKNESSES, AND 850
MB TEMPERATURES CONTRIBUTING TO THE HEAT WAVE WILL ALL PEAK DURING
THIS TIME FRAME. THE CENTER OF THE RIDGE WILL BE POSITIONED TO OUR
SOUTHWEST, WHICH SHOULD MAXIMIZE HEAT POTENTIAL LOCALLY. AT THE
SURFACE, WINDS WILL BE FROM THE WEST OR NORTHWEST. THIS WILL ADD A
COMPONENT OF DOWNSLOPING INTO THE TEMPERATURE EQUATION, HELPING TO
BOOST TEMPERATURES BY A COUPLE DEGREES. THE PATTERN IS CHECKING A
LOT OF BOXES FOR A SET UP CAPABLE OF PRODUCING FAIRLY WIDESPREAD 100
DEGREE TEMPERATURES IN OUR REGION, PERHAPS ONE OF THE MOST FAVORABLE
PATTERNS IN A FEW YEARS. HIGHS TODAY GET INTO THE UPPER 90S OR EVEN
TRIPLE DIGITS. TODAY WILL BE THE MOST HUMID OF THE HEAT WAVE, WITH
WIDESPREAD HEAT INDICES OF 105 TO 110 DEGREES. FLOW MAY BE WEAK
ENOUGH TO GENERATE A SEA-BREEZE, POTENTIALLY PROVIDING SOME RELIEF
TO THE IMMEDIATE COAST. HOWEVER, GUIDANCE DOES NOT HAVE THE SEA-
BREEZE PENETRATING THAT FAR INLAND GIVEN PREVAILING WEST/NORTHWEST
FLOW.
FOR TUESDAY, TEMPERATURES LOOK TO BE A BIT WARMER, WITH POTENTIAL
WIDESPREAD TRIPLE DIGITS, THOUGH THE PATTERN WILL FAVOR DEWPOINTS
MIXING OUT REASONABLY WELL INTO THE AFTERNOON HOURS. THIS WILL
RESULT IN LOWER HUMIDITY, BUT HIGHER TEMPERATURES, RESULTING IN HEAT
INDEX VALUES NOT VERY DIFFERENT THAN MONDAY. STILL LOOKING AT 100-
110 HEAT INDICES ACROSS THE BOARD. AGAIN, A SEA-BREEZE MAY TRY TO
GENERATE, BUT LIKELY WON'T GET TOO FAR INLAND. REGARDLESS OF THOSE
DETAILS, IT'S GOING TO BE VERY HOT BOTH DAYS!
EXTREME HEAT WARNINGS AND HEAT ADVISORIES REMAIN IN EFFECT AS
PREVIOUSLY ISSUED. AROUND THE DELAWARE VALLEY, LEHIGH VALLEY, AND
NORTHERN NEW JERSEY, TEMPERATURES COULD BE THE HOTTEST OBSERVED IN
OVER A DECADE. THERE WILL BE LITTLE RELIEF OVERNIGHT AS TEMPERATURES
TONIGHT ARE EXPECTED TO BE AROUND 75 TO 80 DEGREES. HEAT TENDS TO HAVE
CUMULATIVE EFFECTS ON THE BODY AND WE ARE CURRENTLY FORECASTING 3
CONSECUTIVE DAYS OF 95+ AND 5-6 DAYS OF 90+ TAKING INTO ACCOUNT
TEMPERATURES THIS PAST WEEKEND. TAKE FREQUENT BREAKS IF OUTSIDE,
AND DRINK PLENTY OF FLUIDS.
SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/
DANGEROUS HEAT AND HUMIDITY CONTINUES THROUGH MID-WEEK AS THIS
SIGNIFICANT HEAT WAVE PERSISTS. THE EXTREME HEAT WARNINGS REMAIN IN
EFFECT AND THE HEAT ADVISORIES FOR THE POCONOS, SOUTHERN NEW JERSEY,
AND THE DELMARVA (WITH THE EXCEPTION OF THE COASTAL STRIP) WERE
EXTENDED INTO WEDNESDAY.
VERY WARM OVERNIGHT LOW TEMPERATURES IN THE MID 70S TO LOW 80S AGAIN
TUESDAY NIGHT PERPETUATE OUR HEAT RISK ANOTHER DAY, OFFERING LITTLE
RELIEF. BY WEDNESDAY, THE RIDGE WILL BEGIN TO WEAKEN SOME AND
RETREAT AWAY FROM OUR AREA, BUT TEMPERATURES WILL REMAIN HOT WITH
AFTERNOON HIGHS SQUARELY IN THE MID TO UPPER 90S ACROSS MOST OF THE
REGION. WEST TO NORTHWEST DOWNSLOPE FLOW WILL HELP KEEP TEMPERATURES
HIGH, BUT ALSO FAVOR DEWPOINTS MIXING OUT DURING THE DAYTIME HOURS.
ADDITIONALLY, SOME ISOLATED TO AFTERNOON SHOWERS AND THUNDERSTORMS
COULD SLOW DOWN THE DAYTIME HEATING SLIGHTLY WITH A COMBINATION
OF RAIN- COOLED AIR AND CLOUD COVERAGE. WITH THE HIGH
RETREATING SLIGHTLY TOO, NIGHTTIME LOWS WEDNESDAY NIGHT WILL BE
A FEW DEGREES COOLER, THOUGH STILL ABOUT 10 DEGREES ABOVE CLIMO
IN THE LOW TO MID 70S.
HEAT TENDS TO HAVE CUMULATIVE EFFECTS ON THE BODY AND WE ARE
CURRENTLY FORECASTING SEVERAL CONSECUTIVE AFTERNOONS OF 95+ WITH
LITTLE RELIEF DURING THE NIGHTTIME HOURS THANKS TO LOWS IN THE UPPER
70S TO AROUND 80. TAKE FREQUENT BREAKS IF OUTSIDE, AND DRINK PLENTY
OF FLUIDS.
LONG TERM /THURSDAY THROUGH SUNDAY/
THE UPPER-LEVEL RIDGE WILL CONTINUE TO WEAKEN AND FLATTEN OUT/ERODE
TOWARD THE END OF THE WEEK, ESPECIALLY ON THE NORTHERN PERIPHERY.
WHILE THE HEAT AND HUMIDITY WILL REMAIN, IT WILL BE NOT NEARLY AS
OPPRESSIVE AS EARLIER IN THE WEEK. HIGH TEMPERATURES WILL REMAIN IN
THE UPPER 80S TO LOW 90S THURSDAY, AND SHOULD BE LARGELY IN THE
UPPER 70S TO MID 80S FOR FRIDAY. IN ADDITION, A SURFACE TROUGH
SHOULD BECOME BETTER DEFINED AND INTRODUCE A BIT MORE CLOUDS AND
ALSO THE POTENTIAL FOR SOME SCATTERED DIURNALLY DRIVEN CONVECTION.
THIS WILL INCLUDE A THREAT OF LOCALIZED SEVERE THUNDERSTORMS. A BACK
DOOR COLD FRONT WILL DRAW NEAR BY THURSDAY, BUT THERE IS A DECENT
AMOUNT OF UNCERTAINTY WITH HOW QUICKLY IT WILL DROP SOUTH GIVEN THE
STRENGTH OF THE RIDGE. DUE TO THIS FRONT, THERE IS AN INCREASING
CHANCE (40-60%) OF SHOWERS AND THUNDERSTORMS THURSDAY. WE SHOULD
FINALLY BE BELOW ANY HEAT HAZARD CRITERIA BY THURSDAY, AND
ESPECIALLY BY FRIDAY.
THE WEEKEND WILL BE MORE SEASONABLE WITH HIGHS LARGELY IN THE 80S
AND LOWS FALLING BACK INTO THE MID 60S TO LOW 70S. WE CAN ALSO EXPECT
SOME SHOWERS AND THUNDERSTORMS THROUGH SUNDAY.
AVIATION /08Z MONDAY THROUGH FRIDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH 12Z...PRIMARILY VFR. REMOVED RESTRICTIONS OF FOG FOR NOW
AS PROBABILITY IS ONLY AROUND 10-15% AND MAINLY FOR
KACY/KMIV/KTTN/KABE. SEEING A MARINE LAYER DEVELOPING ON
SATELLITE THAT IS TRYING TO PUSH INLAND, THOUGH CLOUD BASES IN
UPSTREAM OBSERVATIONS SEEM TO BE ABOVE FL050. WINDS
WEST/SOUTHWEST AROUND 5 KT, BECOMING MORE NORTHWESTERLY LATE
TONIGHT, STILL GENERALLY LIGHT. MODERATE CONFIDENCE IN
PREVAILING VFR.
TODAY...VFR. N-NW WINDS 5 TO 10 KT, BECOMING W-SW IN THE
AFTERNOON. WINDS BECOME S AT KACY AFTER 17Z BEHIND SEA BREEZES.
HIGH CONFIDENCE IN PREVAILING VFR, MODERATE CONFIDENCE IN TIMING
OF SEA-BREEZE AND HOW FAR INLAND IT PUSHES.
TONIGHT...VFR. WEST/SOUTHWEST WINDS 5 KT OR LESS. HIGH
CONFIDENCE.
OUTLOOK...
TUESDAY THROUGH TUESDAY NIGHT...VFR. NO SIGNIFICANT WEATHER.
WEDNESDAY THROUGH FRIDAY...PREVAILING VFR, THOUGH CHANCES OF A
SHOWER/THUNDERSTORM INCREASE (30-60%), ESPECIALLY FOR THURSDAY
AND FRIDAY.
MARINE
NO MARINE HEADLINES EXPECTED THROUGH TUESDAY. WINDS GENERALLY OUT OF
THE SOUTH AROUND 10 KT WITH 2 FOOT SEAS.
OUTLOOK...
MONDAY NIGHT THROUGH FRIDAY...NO MARINE HEADLINES EXPECTED.
INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS BY THURSDAY AND
FRIDAY, OTHERWISE FAIR WEATHER.
RIP CURRENTS...
FOR MONDAY, W TO NW WINDS OF 5 TO 10 MPH WILL TURN S IN THE
AFTERNOON BEHIND DEVELOPING SEA BREEZES. A WEAK E TO ESE SWELL
AROUND 1 FEET WILL BE OF LITTLE CONSEQUENCE. SINCE WINDS WILL
BE FAIRLY LIGHT AND BREAKING WAVES AROUND 1 FEET, THERE WILL BE
A LOW RISK FOR THE DEVELOPMENT OF DANGEROUS AND LIFE
THREATENING RIP CURRENTS FOR THE JERSEY SHORE AND FOR DELAWARE
BEACHES.
FOR TUESDAY, NW WINDS OF 5 TO 10 MPH TURN S IN THE AFTERNOON
BEHIND DEVELOPING SEA BREEZES. A WEAK E TO ESE SWELL AROUND 1
FEET WILL BE OF LITTLE CONSEQUENCE. WITH LIGHT WINDS AND
BREAKING WAVES AROUND 1 FEET, THERE WILL BE A LOW RISK FOR THE
DEVELOPMENT OF DANGEROUS AND LIFE THREATENING RIP CURRENTS FOR
THE JERSEY SHORE AND FOR DELAWARE BEACHES.
FOR SPECIFIC BEACH FORECASTS, VISIT WEATHER.GOV/BEACH/PHI
TIDES/COASTAL FLOODING
WITH THE NEW MOON APPROACHING ON JUNE 25TH, ASTRONOMICAL TIDES
ARE EXPECTED TO INCREASE. SPOTTY MINOR TIDAL FLOODING IS
ANTICIPATED FOR THE IMMEDIATE COASTLINE AND BACK BAYS AS WELL AS
WITHIN DELAWARE BAY BEGINNING WITH THE HIGH TIDE ON MONDAY
NIGHT. CANNOT RULE OUT THE NEED FOR ADVISORIES LATER THIS WEEK
AS ASTRO TIDES PEAK. NO TIDAL FLOODING IS EXPECTED WITHIN THE
TIDAL DELAWARE RIVER OR CHESAPEAKE BAY.
CLIMATE
NEAR RECORD BREAKING HEAT IS EXPECTED ACROSS THE AREA THROUGH
THE MIDDLE OF THE UPCOMING WEEK. WE ALREADY ARE SETTING RECORDS,
WITH PHILADELPHIA (PHL) TYING THEIR RECORD WARMEST LOW
TEMPERATURE FOR JUNE 22ND, AND ATLANTIC CITY AIRPORT (ACY)
SETTING A NEW RECORD WARM LOW. FURTHER RECORDS ARE EXPECTED TO
FALL INTO THE WEEK. BELOW IS A LOOK AT THE LAST 100 DEGREE DAY,
DAILY RECORD HIGH MAXIMUM AND MINIMUM TEMPERATURE FOR ALL OF
OUR CLIMATE SITES.
MOST RECENT 100 DEGREE DAY
SITE DATE/TEMPERATURE
ALLENTOWN (ABE) JULY 22, 2011/104
AC AIRPORT (ACY) JULY 21, 2019/100
AC MARINA (55N) JULY 5, 1999/101
GEORGETOWN (GED) JULY 21, 2019/100
MOUNT POCONO (MPO) JULY 3, 1911/103
PHILADELPHIA (PHL) JULY 18, 2012/100
READING (RDG) JUNE 22, 2024/101
TRENTON (TTN) JULY 18, 2012/100
WILMINGTON (ILG) JULY 18, 2012/101
RECORD HIGH TEMPERATURES
JUNE 23
SITE RECORD/YEAR
ALLENTOWN (ABE) 96/2024
AC AIRPORT (ACY) 98/1988 & 2024
AC MARINA (55N) 91/1909
GEORGETOWN (GED) 100/1988
MOUNT POCONO (MPO) 90/1954
PHILADELPHIA (PHL) 98/2024
READING (RDG) 98/2024
TRENTON (TTN) 97/1894
WILMINGTON (ILG) 100/1894
RECORD WARMEST LOW TEMPERATURES
JUNE 23
SITE RECORD/YEAR
ALLENTOWN (ABE) 71/2017 & 2024
AC AIRPORT (ACY) 75/2024
AC MARINA (55N) 74/2010
GEORGETOWN (GED) 76/1988
MOUNT POCONO (MPO) 69/2024
PHILADELPHIA (PHL) 76/1888
READING (RDG) 77/2024
TRENTON (TTN) 74/2017 & 2024
WILMINGTON (ILG) 75/2024
RECORD HIGH TEMPERATURES
JUNE 24
SITE RECORD/YEAR
ALLENTOWN (ABE) 98/1923
AC AIRPORT (ACY) 99/2010
AC MARINA (55N) 95/2002
GEORGETOWN (GED) 97/2010
MOUNT POCONO (MPO) 92/1914
PHILADELPHIA (PHL) 99/1923
READING (RDG) 98/1908 & 1923
TRENTON (TTN) 98/1894
WILMINGTON (ILG) 102/1894
RECORD WARMEST LOW TEMPERATURES
JUNE 24
SITE RECORD/YEAR
ALLENTOWN (ABE) 71/2010
AC AIRPORT (ACY) 72/1951, 2013, 2017 & 2024
AC MARINA (55N) 72/1924, 2002, 2010, 2011, 2013 & 2020
GEORGETOWN (GED) 74/2010
MOUNT POCONO (MPO) 66/1960, 1964 & 2002
PHILADELPHIA (PHL) 75/1909, 1921, 1994 & 2020
READING (RDG) 73/1909, 1994 & 2010
TRENTON (TTN) 76/1894 & 2010
WILMINGTON (ILG) 74/1994
RECORD HIGH TEMPERATURES
JUNE 25
SITE RECORD/YEAR
ALLENTOWN (ABE) 98/1923
AC AIRPORT (ACY) 96/1997
AC MARINA (55N) 95/1952
GEORGETOWN (GED) 96/1952
MOUNT POCONO (MPO) 91/1952
PHILADELPHIA (PHL) 98/1952
READING (RDG) 99/1943
TRENTON (TTN) 99/1997
WILMINGTON (ILG) 98/1894
RECORD WARMEST LOW TEMPERATURES
JUNE 25
SITE RECORD/YEAR
ALLENTOWN (ABE) 74/1923 & 1976
AC AIRPORT (ACY) 80/1950
AC MARINA (55N) 75/1997 & 2002
GEORGETOWN (GED) 75/2019
MOUNT POCONO (MPO) 69/1952
PHILADELPHIA (PHL) 76/1909, 1976 & 2002
READING (RDG) 75/1943 & 1949
TRENTON (TTN) 75/1976
WILMINGTON (ILG) 75/1976
PHI WATCHES/WARNINGS/ADVISORIES
PA...EXTREME HEAT WARNING UNTIL 8 PM EDT WEDNESDAY FOR PAZ060>062-
070-071-101>106.
HEAT ADVISORY UNTIL 8 PM EDT WEDNESDAY FOR PAZ054-055.
NJ...EXTREME HEAT WARNING UNTIL 8 PM EDT WEDNESDAY FOR NJZ001-
007>010-012-013-015-017>020-027.
HEAT ADVISORY FROM 8 AM THIS MORNING TO 8 PM EDT WEDNESDAY FOR
NJZ016-021>023.
HEAT ADVISORY FROM 8 AM THIS MORNING TO 8 PM EDT TUESDAY FOR
NJZ014-024>026.
DE...EXTREME HEAT WARNING UNTIL 8 PM EDT WEDNESDAY FOR DEZ001.
HEAT ADVISORY FROM 8 AM THIS MORNING TO 8 PM EDT WEDNESDAY FOR
DEZ002-003.
HEAT ADVISORY FROM 8 AM THIS MORNING TO 8 PM EDT TUESDAY FOR
DEZ004.
MD...HEAT ADVISORY FROM 8 AM THIS MORNING TO 8 PM EDT WEDNESDAY FOR
MDZ012-015-019-020.
MARINE...NONE.
SYNOPSIS...MJL/STAARMANN
NEAR TERM...HOEFLICH
SHORT TERM...MJL/STAARMANN
LONG TERM...MJL/STAARMANN
AVIATION...HOEFLICH/MJL
MARINE...HOEFLICH/MJL
TIDES/COASTAL FLOODING...
CLIMATE...
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