181
FXUS61 KPHI 301659
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1259 PM EDT WED JUL 30 2025
SYNOPSIS
HIGH PRESSURE WILL BEGIN TO SHIFT OFFSHORE THROUGH TODAY, WITH
DANGEROUSLY HOT AND HUMID CONDITIONS PERSISTING. A SLOW MOVING
COLD FRONT WILL PUSH THROUGH THE REGION BEGINNING LATE TONIGHT
THROUGH THURSDAY NIGHT, BRINGING WIDESPREAD SHOWERS AND STORMS.
HIGH PRESSURE WILL THEN BUILD FROM THE NORTH INTO THE WEEKEND,
WITH BELOW NORMAL TEMPERATURES, MUCH DRIER AND PLEASANT
CONDITIONS EXPECTED INTO EARLY NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
VERY HOT AND HUMID CONDITIONS EXPECTED TO CONTINUE TODAY, ALONG
WITH A CHANCE FOR SOME ISOLATED SEVERE THUNDERSTORMS IN EASTERN
PA AND NORTHERN NJ. A HEAT ADVISORY REMAINS IN EFFECT FOR
PORTIONS OF THE AREA.
THE RIDGING TO OUR SOUTHWEST WILL BEGIN TO WEAKEN AND SHIFT
EASTWARD TODAY INTO TONIGHT. THE WEAK SURFACE HIGH PRESSURE IN
PLACE ACROSS THE AREA WILL ALSO START PUSHING OFFSHORE, WITH
SOUTHWESTERLY RETURN FLOW DEVELOPING LATER TODAY. THE JET STREAK
TO OUR NORTH WILL ALSO SHIFT EAST, SHIFTING US FROM AN UPPER
SUBSIDENCE TO UPPER DIFFLUENCE REGIME INTO TONIGHT. MEANWHILE, A
SLOW MOVING COLD FRONT IS EXPECTED TO SINK SOUTHWARD INTO THE
AREA OVERNIGHT, REACHING NEAR THE I-78 CORRIDOR BY DAYBREAK
THURSDAY.
THERE HAS BEEN NO SIGNIFICANT CHANGE TO THE FORECAST REGARDING
TODAY'S HEAT AND HUMIDITY. FORECAST HIGH TEMPERATURES ARE MOSTLY
IN THE MID TO UPPER 90S. EVEN THE SOUTHERN POCONOS, HIGHER
ELEVATIONS OF NW NJ, AND THE IMMEDIATE COAST SHOULD GET INTO THE
UPPER 80S TO LOW 90S AGAIN TODAY. THE WEAK HIGH PRESSURE
SHIFTING OFFSHORE WILL RESULT IN SOME MODEST SOUTHWESTERLY
RETURN FLOW AHEAD OF THE COLD FRONT. THIS WILL KEEP THE
DANGEROUSLY HOT AND HUMID CONDITIONS IN PLACE. RESULTING HEAT
INDICES REMAIN IN THE 100-105 DEGREE RANGE. THE HEAT ADVISORY
REMAINS IN EFFECT THROUGH 8 PM TODAY AS PREVIOUSLY ISSUED FOR
ALL COUNTIES WHERE CRITERIA IS 100+. AN EXPANSION OF THE
ADVISORY FARTHER SOUTH WAS CONSIDERED FOR OUR SOUTHERN COUNTIES,
HOWEVER THE FORECAST CURRENTLY SUPPORTS HEAT INDICES REMAINING
LARGELY BELOW THE 105 DEGREE CRITERIA.
THE APPROACHING FRONT AND LESSENING SUBSIDENCE MAY ALLOW FOR
SOME ISOLATED THUNDERSTORMS TO DEVELOP THIS AFTERNOON AND
EVENING, ESPECIALLY NEAR/NORTHWEST OF I-78. COVERAGE SHOULD BE
LIMITED (20-30% POPS IN THE FORECAST), BUT ANY STORMS THAT DO
DEVELOP COULD BECOME SEVERE WITH DAMAGING WINDS BEING THE MAIN
THREAT. THIS WILL BE DUE TO FAIRLY HIGH DCAPE IN PLACE FROM
STEEP LOW LEVEL LAPSE RATES AND MID LEVEL DRY AIR. SHEAR WILL BE
MODEST AROUND 20-30 KTS, BUT ANY STORMS WILL BECOME OUTFLOW
DOMINANT VERY QUICKLY AND SHOULD BE FAIRLY TRANSIENT AND
DISORGANIZED IN NATURE. A MARGINAL RISK (1/5) FOR DAMAGING WINDS
REMAINS IN PLACE FROM SPC.
ANOTHER VERY WARM AND HUMID NIGHT FORECAST TONIGHT AHEAD OF THE
COLD FRONT WITH LOWS IN THE UPPER 60S TO MID 70S. SOME
SCATTERED SHOWERS/STORMS COULD PERSIST OR REDEVELOP OVERNIGHT AS
THE FRONT STARTS TO PUSH INTO THE AREA FROM THE NORTH AFTER
MIDNIGHT. SOME LOCALLY HEAVY RAINFALL COULD RESULT, PERHAPS SOME
ISOLATED AMOUNTS IN THE 1-2" RANGE NORTH OF I-78. THE GREATER
FLASH FLOOD THREAT SHOULD HOLD OFF UNTIL THE DAYTIME THURSDAY
THOUGH.
SHORT TERM /THURSDAY THROUGH FRIDAY/
WIDESPREAD SHOWERS AND THUNDERSTORMS ARE FORECAST ON THURSDAY,
WHICH WILL POSE A RISK OF FLASH FLOODING. MUCH COOLER, BREEZY,
AND SHOWERY CONDITIONS ARE EXPECTED TO FOLLOW ON FRIDAY.
THE RIDGING TO OUR SOUTHWEST WILL CONTINUE TO SHIFT EASTWARD
THROUGH THURSDAY, WITH HIGH PRESSURE REMAINING OFFSHORE AT THE
SURFACE. BROAD UPPER DIFFLUENCE WILL REMAIN IN PLACE ALOFT
THROUGH FRIDAY. MEANWHILE, A SLOW MOVING COLD FRONT IS EXPECTED
TO PUSH GRADUALLY SOUTHWARD THURSDAY THROUGH THURSDAY NIGHT.
THIS SHOULD RESULT IN SOME WEAK CYCLOGENESIS IN THE MID ATLANTIC
REGION AS THE FRONT WORKS ITS WAY SOUTH, WITH THE SURFACE LOW
PASSING OFFSHORE ON FRIDAY.
THERE REMAINS A THREAT OF FLASH FLOODING FOR THURSDAY AFTERNOON
AND EVENING, AS WIDESPREAD SHOWERS AND THUNDERSTORMS ARE
ANTICIPATED TO DEVELOP WITHIN THE VICINITY OF THE SLOW MOVING
FRONTAL BOUNDARY. POPS WERE REMAIN NEAR 70-80% FOR THE ENTIRE
AREA, PEAKING FROM NORTH TO SOUTH AS THE FRONT MOVES GRADUALLY
SOUTHWARD THROUGH THURSDAY NIGHT. AS DIURNAL INSTABILITY BUILDS
AHEAD OF THE FRONT INTO THE AFTERNOON, PWATS WILL INCREASE INTO
THE 2.0-2.5 INCH RANGE. MEAN LAYER FLOW WILL BE ROUGHLY PARALLEL
TO THE FRONTAL BOUNDARY, WHICH COULD SUPPORT TRAINING
CONVECTION. THE LATEST GUIDANCE HAS TRENDED A BIT FASTER WITH
THE FRONTAL AND CONVECTIVE PROGRESSION, WHICH COULD LIMIT A MORE
WIDESPREAD FLASH FLOOD POTENTIAL. CYCLOGENSIS NEARBY COULD ALSO
INTRODUCE SOME FRONTOGENETIC FORCING INTO THE EQUATION AS WELL.
THE SYNOPTIC ASPECTS OF THIS SETUP WILL PROBABLY LEAD TO
CONVECTION CONTINUING INTO THE OVERNIGHT PERIOD AS WELL.
EXACT DETAILS ON THE EVOLUTION OF THE CONVECTION AND FLASH
FLOOD THREAT REMAIN UNCLEAR, AS THE MESOSCALE DETAILS REMAIN TO
BE SEEN. OUR CURRENT RAINFALL FORECAST RANGES FROM AROUND 1-2"
ACROSS THE AREA, BUT LOCALLY HIGHER AMOUNTS OF 3" OR GREATER ARE
CERTAINLY POSSIBLE. THE FLASH FLOOD THREAT WILL ULTIMATELY
DEPEND ON WHERE THE HEAVIEST RAIN SETS UP, AND HOW QUICKLY
CONVECTION IS PROPAGATING. THE HIGHER THREAT FOR FLASH FLOODING
WILL PROBABLY END UP BEING IN THE USUAL LOCATIONS NEAR AND
NORTHWEST OF I-95. WPC HAS MAINTAINED A SLIGHT RISK OF EXCESSIVE
RAINFALL LEADING TO FLASH FLOODING FOR THE ENTIRE AREA. A FEW
ISOLATED SEVERE THUNDERSTORMS WITH DAMAGING WINDS ARE POSSIBLE
AS WELL, BUT THE MAIN THREAT WILL BE THE FLASH FLOODING
POTENTIAL. REMAIN ALERT FOR UPDATES TO THE FORECAST REGARDING
THESE THREATS.
THE SILVER LINING WITH THE FRONTAL PASSAGE, INCREASED CLOUD
COVER, AND CONVECTION WILL BE LOWER TEMPERATURES THURSDAY,
ESPECIALLY FOR OUR NJ AND PA COUNTIES. FORECAST HIGHS ARE MOSTLY
IN THE 80S, AND NEAR 90 DEGREES IN THE PHILLY METRO AND SOUTH
INTO DELMARVA. IT WILL STILL BE QUITE HUMID, ESPECIALLY AHEAD OF
THE FRONT, BUT NO HEAT HEADLINES ARE EXPECTED.
BY FRIDAY, THURSDAY'S FRONTAL BOUNDARY SHOULD BE SOUTH OF THE
FORECAST AREA AS THE WEAK SURFACE LOW SLIDES OFFSHORE ALONG IT.
DIFFLUENCE WILL REMAIN IN PLACE ALOFT AS CANADIAN HIGH PRESSURE
BEGINS TO BUILD IN FROM THE NORTH. THIS SETUP WILL RESULT IN
CLOUDY SKIES FRIDAY ALONG WITH AN UNUSUALLY BREEZY NORTHEAST
WIND BY MID SUMMER STANDARDS. LINGERING SHOWERS AND DRIZZLE CAN
ALSO BE EXPECTED, ESPECIALLY ACROSS THE COASTAL PLAIN. NORTHEAST
WINDS 10-20 MPH WITH GUSTS NEAR 30 MPH POSSIBLE. HIGH
TEMPERATURES FRIDAY WILL BE IN THE LOW TO MID 70S, THOUGH SOME
COOLER SPOTS NORTH OF PHILLY COULD EVEN BE STUCK IN THE UPPER
60S ALL DAY.
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
THE HOT, HUMID, AND STORMY WEATHER WILL FORTUNATELY BY FOLLOWED
BY VERY PLEASANT AND DRY CONDITIONS OVER THE WEEKEND AND INTO
EARLY NEXT WEEK.
DRIER AIR WILL FINALLY START TO WORK INTO THE AREA FROM THE
NORTH FRIDAY NIGHT AND ESPECIALLY BY SATURDAY AS HIGH PRESSURE
TAKES HOLD OF THE REGION. HIGHS SATURDAY WILL BE NEAR 80 DEGREES
AND DEWPOINTS WILL BE IN THE 50S, PERHAPS EVEN MIXING OUT INTO
THE UPPER 40S IN SOME SPOTS. LOW TO MID 80S FORECAST FOR SUNDAY
THROUGH TUESDAY HIGH TEMPERATURES, THOUGH WITH SIMILARLY DRY AND
COMFORTABLE DEWPOINTS AND HUMIDITY LEVELS. LOWS IN THE PERIOD
WILL RANGE FROM THE MID 50S AND 60S. ABOUT AS PERFECT AND NICE
AS MID SUMMER WEATHER GETS!
AVIATION /18Z WEDNESDAY THROUGH MONDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
REST OF TODAY...VFR. LOW CHANCE FOR A SHRA/TSRA TO IMPACT
KRDG/KABE/KTTN. WILL CARRY VCTS AT KRDG/KABE THROUGH LATE
AFTERNOON. S-SW WINDS 5 TO 10 KT. LOW CONFIDENCE ON A SHRA/TSRA
PASSING DIRECTLY OVER THOSE NORTHERN TERMINALS
TONIGHT...VFR. THERE IS THE POTENTIAL FOR VSBY RESTRICTIONS IN
FOG AFTER 08Z. S-SW WINDS 5 TO 10 KT, BECOMING LGT/VRB BY 06Z.
LOW CONFIDENCE ON FOG FORMATION LATE TONIGHT.
THURSDAY...ANY MORNING FOG LIFTS AND DISSIPATES FROM 12Z-13Z.
VFR UNTIL 18Z, THEN SUB-VFR IN SHRA/TSRA. POTENTIAL FOR HEAVY
RAIN. SE TO E WINDS 5 TO 10 KT. MODERATE CONFIDENCE.
OUTLOOK...
THURSDAY NIGHT...CEILING AND VISIBILITY RESTRICTIONS LIKELY.
NUMEROUS SHOWERS AND THUNDERSTORMS ACROSS THE AREA.
FRIDAY...CEILING AND VISIBILITY RESTRICTIONS LIKELY PREVAILING.
PERIODS OF SHOWERS AND DRIZZLE. GUSTY NORTHEAST WINDS.
FRIDAY NIGHT THROUGH SUNDAY...CONDITIONS IMPROVING TO VFR. NO
SIGNIFICANT WEATHER.
MARINE
NO MARINE HAZARDS EXPECTED THROUGH TONIGHT. SOUTH TO SOUTHWEST
WINDS 5-15 KTS. GUSTS NEAR 20 KTS POSSIBLE THIS AFTERNOON AND
EVENING. SEAS 1-2 FEET.
OUTLOOK...
THURSDAY AND THURSDAY NIGHT...WINDS AND SEAS BUILDING, BUT
SHOULD REMAIN BELOW ADVISORY CRITERIA. NUMEROUS SHOWERS AND
THUNDERSTORMS.
FRIDAY AND FRIDAY NIGHT...ADVISORY CONDITIONS LIKELY. GALE
FORCE WIND GUSTS POSSIBLE. NORTHEAST WINDS 20-25 KTS WITH GUSTS
30-35 KTS POSSIBLE. SCATTERED SHOWERS, STORMS, AND DRIZZLE.
SATURDAY...CONDITIONS IMPROVING WITH LESSENING WINDS AND SEAS,
THOUGH SEAS NEAR 5 FEET LIKELY LINGERING INTO THE NIGHT.
SUNDAY...CONDITIONS SHOULD FALL BELOW ADVISORY CRITERIA.
RIP CURRENTS...
FOR TODAY, THE SURFACE WINDS WILL BE MORE FROM THE SOUTH AND
SOUTHWEST NEAR 10 TO 15 MPH. BREAKING WAVES IN THE SURF ZONE
WILL CONTINUE TO BE 1 TO 2 FEET WITH A PERIOD AROUND 8 SECONDS.
A LOW RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS IS
EXPECTED FOR ALL BEACHES.
FOR THURSDAY, WINDS WILL TURN SOUTHEASTERLY NEAR 10 TO 15 MPH.
BREAKERS WILL REMAIN 1 TO 2 FEET WITH A PERIOD REMAINING AROUND
8 SECONDS. A LOW RISK FOR THE DEVELOPMENT OF DANGEROUS RIP
CURRENTS CONTINUES FOR ALL BEACHES.
FOR SPECIFIC BEACH FORECASTS, VISIT WEATHER.GOV/BEACH/PHI
CLIMATE
SEVERAL DAYS OF HIGH HEAT COMMENCED MONDAY AND WILL CONTINUE
THROUGH TODAY. NO RECORDS WERE REACHED MONDAY. TWO RECORD HIGHS
(PHL/ACY) WERE TIED ON TUESDAY, AS WELL AS A RECORD WARMEST LOW
SET AT THE AC MARINA. HERE'S A RUNDOWN OF RECORD WARMEST HIGH
AND LOW TEMPERATURES FOR TODAY.
RECORD WARMEST HIGH TEMPERATURES
SITE WEDNESDAY 7/30
AC MARINA (55N) 99 IN 2002
AC AIRPORT (ACY) 96 IN 2002
ALLENTOWN (ABE) 97 IN 1940
GEORGETOWN (GED) 99 IN 1949
MOUNT POCONO (MPO) 90 IN 1954
PHILADELPHIA (PHL) 98 IN 1988
READING (RDG) 97 IN 1940
TRENTON (TTN) 98 IN 1999
WILMINGTON (ILG) 97 IN 1954
RECORD WARMEST LOW TEMPERATURES
SITE WEDNESDAY 7/30
AC MARINA (55N) 79 IN 2020
AC AIRPORT (ACY) 76 IN 2015
ALLENTOWN (ABE) 74 IN 2024
GEORGETOWN (GED) 78 IN 2009
MOUNT POCONO (MPO) 68 IN 1909
PHILADELPHIA (PHL) 80 IN 2002
READING (RDG) 75 IN 1933
TRENTON (TTN) 78 IN 1894
WILMINGTON (ILG) 75 IN 2019
PHI WATCHES/WARNINGS/ADVISORIES
PA...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR PAZ054-055-
060>062-070-071-101>106.
NJ...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR NJZ001-007>010-
012>015-017>020-026-027.
DE...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR DEZ001.
MD...NONE.
MARINE...NONE.
SYNOPSIS...STAARMANN
NEAR TERM...STAARMANN
SHORT TERM...STAARMANN
LONG TERM...STAARMANN
AVIATION...MPS/STAARMANN
MARINE...STAARMANN
CLIMATE...
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