011
FXUS61 KPHI 181900
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
300 PM EDT MON MAY 18 2026
WHAT HAS CHANGED
HEAT ADVISORY EXPANDED TO MOST OF EASTERN PENNSYLVANIA AND NORTHERN
TO SOUTHERN NEW JERSEY.
SMALL CRAFT ADVISORY ISSUED FOR THE NEW JERSEY ATLANTIC COASTAL
WATERS.
KEY MESSAGES
1. HOT AND MORE HUMID CONDITIONS CONTINUE, WITH RECORD SETTING EARLY
SEASON HEAT PROBABLE, THROUGH WEDNESDAY.
2. A COLD FRONT WILL BRING SOME SHOWERS AND THUNDERSTORMS TO THE
REGION WEDNESDAY THROUGH THURSDAY, THEN MUCH COOLER TEMPERATURES BY
THE END OF THIS WEEK.
DISCUSSION
KEY MESSAGE 1...HOT AND MORE HUMID CONDITIONS CONTINUE, WITH RECORD
SETTING EARLY SEASON HEAT PROBABLE, THROUGH WEDNESDAY.
A STRONG UPPER-LEVEL RIDGE CENTERED OFF THE SOUTHEAST U.S. COAST
WILL REMAIN IN PLACE THROUGH LATE TUESDAY BEFORE IT STARTS TO
FLATTEN ON ITS NORTHWEST SIDE DURING WEDNESDAY. THIS ALONG WITH
SURFACE HIGH PRESSURE ANCHORED IN THE WESTERN ATLANTIC WILL DRIVE A
SOUTH TO SOUTHWEST FLOW OF EARLY SEASON (ANOMALOUS) HEAT ACROSS OUR
AREA INTO WEDNESDAY.
TEMPERATURES ARE FORECAST TO PEAK INTO THE 90S FOR MANY AREAS AGAIN
TUESDAY AND WEDNESDAY, EXCEPT COOLER ALONG THE COASTS AND THE HIGHER
TERRAIN. WHILE THE SURFACE DEW POINTS WILL LIKELY MIX OUT SOME
DURING PEAK HEATING DUE TO THE DRIER GROUND AND BOUNDARY LAYER (LOW
EVAPOTRANSPIRATION), THIS STRETCH OF EARLY SEASON HEAT, WITH RECORD
BREAKING HIGH TEMPERATURES PROBABLE, WILL HAVE POTENTIALLY GREATER
IMPACTS. FOR THIS REASON, OPTED TO EXPAND THE HEAT ADVISORY TO THE
AREAS WHERE THE HEAT INDEX CRITERIA STARTS AT 100F (THE URBAN I-95
CORRIDOR CRITERIA STARTS AT 96F THROUGH JUNE). WHILE IT WILL
PROBABLY FALL A LITTLE SHORT FOR SOME AREAS, THE POTENTIAL GREATER
IMPACTS (LACK OF ACCLIMATION) IS DRIVING OUR DECISION. WHERE THE
WIND TURNS MORE FROM THE SOUTH AND ESPECIALLY SOUTHEAST WILL RESULT
IN QUITE A BIT OF COOLING DUE TO THE CHILLY OCEAN AND THEREFORE DID
NOT INCLUDE THE IMMEDIATE COASTAL ZONES IN THE HEAT ADVISORY. PEAK
HEAT INDICES WILL BE 95 TO NEARING 100 DEGREES, WITH THE CORE OF THE
HEAT SHIFTING A BIT MORE SOUTH AND EAST DURING WEDNESDAY AS A STRONG
COLD FRONT STARTS TO ARRIVE. BASED ON THIS, PORTIONS OF THE HEAT
ADVISORY FOR AREAS FARTHER NORTH AND WEST OF I-95 ONLY GOES THROUGH
TUESDAY. HIGH TEMPERATURES ON WEDNESDAY WILL DEPEND ON HOW QUICKLY
CLOUD COVER ARRIVES ALONG WITH SHOWERS AND SOME THUNDERSTORMS.
EITHER WAY, WE WILL HAVE A HIGH LAUNCHING PAD FOR TEMPERATURES TO
START WEDNESDAY AND IT WILL STILL BE RATHER HOT.
TEMPERATURES AT NIGHT WILL BE QUITE WARM BY MID MAY STANDARDS.
LOWS WILL ONLY BE IN THE MID 60S TO LOW 70S, WHICH WILL
CHALLENGE DAILY WARMEST LOW TEMPERATURE RECORDS FOR MAY 19TH.
AS A SIDE NOTE, ISOLATED CONVECTION HAS DEVELOPED OVER THE CENTRAL
APPLACHIANS THIS AFTERNOON AND THIS ACTIVITY WILL MOVE TO THE NORTH
AND NORTHEAST INTO THIS EVENING. GIVEN THE PRESENCE OF THE RIDGE
FARTHER EAST, THE CHANCE FOR ANY OF THIS TO MAKE IT TO PARTS OF OUR
FAR WESTERN ZONES THIS EVENING IS VERY LOW AT THE CURRENT TIME AND
THEREFORE WENT WITH A DRY FORECAST.
KEY MESSAGE 2...A COLD FRONT WILL BRING SOME SHOWERS AND THUNDERSTORMS
TO THE REGION WEDNESDAY THROUGH THURSDAY, THEN MUCH COOLER TEMPERATURES
BY THE END OF THIS WEEK.
AS MENTIONED ABOVE, A COLD FRONT WILL APPROACH THE AREA WEDNESDAY
AND BRING AN END TO THE STRETCH OF ABOVE NORMAL TEMPERATURES BY
THURSDAY. SHOWERS AND THUNDERSTORMS WILL ACCOMPANY THIS FRONT AS IT
PASSES THROUGH THE REGION. RECENT GUIDANCE TRENDS CONTINUE TO SHOW
THE FRONT MOVING THROUGH DURING THE SECOND HALF OF WEDNESDAY INTO
WEDNESDAY NIGHT. GIVEN THIS TIMING, THERE IS THE THREAT FOR STRONG
TO SEVERE THUNDERSTORMS. THERE REMAINS UNCERTAINTY IN THE MORE
SPECIFIC DETAILS AND SOME TIMING VARIATIONS REMAIN. REGARDING THE
THREAT FOR STRONG TO SEVERE THUNDERSTORMS, THE COLD FRONT WILL BE
MOVING INTO AN AIR MASS THAT WILL FEATURE PLENTY OF INSTABILITY. THE
BETTER SHEAR AND FORCING LOOK TO BE TO OUR NORTH, BUT BULK SHEAR
VALUES WILL BE SUPPORTIVE OF SOME STORM ORGANIZATION ALONG WITH SOME
SUPPORTIVE LAPSE RATES. ALL OF THIS SAID, THE POTENTIAL IS THERE FOR
ISOLATED STRONG TO SEVERE THUNDERSTORMS. THE PRIMARY CONCERNS WITH
ANY STRONG TO SEVERE THUNDERSTORM WOULD BE DAMAGING WIND GUSTS AND
LARGE HAIL. GENERAL RAINFALL ACCUMULATION FROM THIS FRONTAL PASSAGE
LOOKS AROUND 0.25" OR LESS. HOWEVER, GIVEN THIS CONVECTION AND PWAT
VALUES REACHING TO 1.5-2.0", LOCALIZED HIGHER AMOUNTS ARE CERTAINLY
POSSIBLE WITH ANY HEAVIER POCKETS OF RAIN.
AS THE FRONT SINKS SOUTH INTO THURSDAY MORNING, IT THEN LOOKS TO
LINGER NEAR OR JUST SOUTH OF THE AREA THROUGH THE REMAINDER OF THE
DAY THURSDAY. THIS WILL LEAD TO THE POTENTIAL FOR MORE RAIN SHOWERS,
PARTICULARLY FOR OUR SOUTHEASTERN ZONES. AN UNSETTLED PATTERN LOOKS
TO CONTINUE TO TAKE SHAPE FOR FRIDAY AND INTO THE WEEKEND.
AVIATION /18Z MONDAY THROUGH SATURDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
REST OF THIS AFTERNOON...VFR. SOUTH TO SOUTHWEST WINDS AROUND 10
KNOTS WITH SOME LOCAL GUSTS 15-20 KNOTS AT TIMES (SOUTHEAST WINDS
ESPECIALLY AT KILG, KMIV AND KACY. MODERATE CONFIDENCE.
TONIGHT...VFR. SOUTH TO SOUTHWEST WINDS 5-10 KNOTS, BECOMING LOCALLY
LIGHT AND VARIABLE. HIGH CONFIDENCE.
TUESDAY...VFR. SOUTHWESTERLY WINDS 5-8 KNOTS INCREASING TO 10-15
KNOTS, WITH SOME AFTERNOON GUSTS UP TO 20 KNOTS. MODERATE
CONFIDENCE.
OUTLOOK...
WEDNESDAY THROUGH THURSDAY...SUB-VFR WITH RAIN SHOWERS AND
THUNDERSTORMS WEDNESDAY AFTERNOON AND EVENING. RAIN SHOWERS MAY
CONTINUE INTO THURSDAY.
FRIDAY THROUGH SATURDAY...SUB-VFR WITH RAIN SHOWERS MOVING THROUGH.
MARINE
SMALL CRAFT ADVISORY ISSUED FOR THE NEW JERSEY ATLANTIC COASTAL
WATERS TUESDAY AFTERNOON AND TUESDAY EVENING. SOUTHERLY FLOW WILL
INCREASE TONIGHT AND ESPECIALLY DURING TUESDAY. A HOT AIR MASS WILL
BE MOVING OVER THE CHILLY WATER AND THIS VERTICAL MIXING WILL BE
REDUCED, HOWEVER GIVEN THE STRENGTH OF THE FLOW THERE SHOULD BE A
PERIOD OF WIND GUSTS TO AROUND 25 KNOTS AND SEAS BUILDING TO ABOUT 5
FEET. IT LOOKS TO BE MORE MARGINAL FOR THE DELAWARE ATLANTIC COASTAL
WATERS AND THEREFORE HELD OFF ON ISSUING AN ADVISORY. FOR DELAWARE
BAY, THE CONDITIONS SHOULD CONTINUE TO REMAIN BELOW SMALL CRAFT
ADVISORY CRITERIA THROUGH TUESDAY NIGHT.
OUTLOOK...
WEDNESDAY...SMALL CRAFT ADVISORY CONDITIONS POSSIBLE. SEAS LESSEN BY
WEDNESDAY MORNING BUT ELEVATED WINDS OUT OF THE SOUTHWEST REMAIN
THROUGH THE DAY WEDNESDAY WITH GUSTS NEAR 20-25 KT. RAIN SHOWERS
MOVE IN WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. THERE IS ALSO THE
POTENTIAL FOR ISOLATED THUNDERSTORMS WEDNESDAY AFTERNOON INTO EARLY
WEDNESDAY NIGHT.
THURSDAY...CONDITIONS EXPECTED TO BE BELOW SMALL CRAFT ADVISORY
CRITERIA BUT SHOWERS MAY LINGER.
FRIDAY THROUGH SATURDAY...SMALL CRAFT ADVISORY CONDITIONS EXPECTED
AS SEAS REACH 4-6 FEET. THERE IS THE CHANCE FOR SOME RAIN
SHOWERS.
RIP CURRENTS...
THIS AFTERNOON, SOUTH-SOUTHEAST WINDS WILL BE 10 TO 15 MPH WITH
BREAKING WAVES OF 1 TO 2 FEET. THERE WILL BE A SOUTHEASTERLY
SWELL WITH A PERIOD OF AROUND 8 SECONDS. AS A RESULT, THERE IS A
MODERATE RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS AT
THE JERSEY SHORE AND A LOW RISK AT DELAWARE BEACHES WHERE WINDS
WILL BE MORE SHORE PARALLEL.
TUESDAY, SOUTH-SOUTHWESTERLY WINDS OF 10-20 MPH WITH BREAKING
WAVES OF 2 TO 3 FEET. A SOUTHEASTERLY SWELL WILL REMAIN, THOUGH
THE PERIOD MAY BE SLIGHTLY SHORTER. FOR NOW, HAVE OPTED FOR A
MODERATE RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS FOR
ALL NJ AND DE BEACHES.
IMPORTANT TO NOTE THAT WHILE SURFACE TEMPERATURES INLAND WILL
BE IN THE UPPER 80S TO LOW 90S ON MONDAY, AND LOW TO MID 90S
TUESDAY, TEMPERATURES ALONG THE COASTS WILL MAINLY BE IN THE 70S
TO NEAR 80 DUE TO OCEAN TEMPERATURES IN THE 50S. THESE COLD
WATER TEMPERATURES CAN QUICKLY CAUSE HYPOTHERMIA AND PHYSICAL
INCAPACITATION TO ANYONE SUDDENLY IMMERSED IN THE WATER.
FOR SPECIFIC BEACH FORECASTS, VISIT WEATHER.GOV/BEACH/PHI
CLIMATE
NEAR RECORD BREAKING TEMPERATURES ARE FORECAST FROM TODAY THROUGH
WEDNESDAY. HIGH TEMPERATURES TUESDAY AND LOW TEMPERATURES
WEDNESDAY MORNING COULD CHALLENGE MONTHLY ALL TIME RECORDS FOR
MAY. RECORDS FOR OUR CLIMATE SITES ARE LISTED BELOW:
MONTHLY RECORD HIGH TEMPERATURES FOR MAY
SITE RECORD/DATE
ALLENTOWN (ABE) 97/MAY 19, 1962
AC AIRPORT (ACY) 99/MAY 29, 1969
AC MARINA (55N) 95/MAY 31, 1895 & MAY 23, 1925
GEORGETOWN (GED) 98/MAY 28, 1991
MOUNT POCONO (MPO) 94/MAY 22, 1911
PHILADELPHIA (PHL) 97/MAY 30 & 31, 1991
READING (RDG) 97/MAY 20, 1996
TRENTON (TTN) 99/MAY 23, 1911 & MAY 31, 1986
WILMINGTON (ILG) 98/MAY 10, 1895 & MAY 30, 1895
MONTHLY RECORD WARMEST LOW TEMPERATURES FOR MAY
SITE RECORD/DATE
ALLENTOWN (ABE) 71/MAY 31, 1975, MAY 28 & 31, 1991
AC AIRPORT (ACY) 73/MAY 24, 2004 & MAY 19, 2017
AC MARINA (55N) 73/MAY 30 & 31, 1987, & MAY 31, 1991
GEORGETOWN (GED) 74/MAY 23, 1953 & MAY 20, 2019
MOUNT POCONO (MPO) 68/MAY 21, 1996
PHILADELPHIA (PHL) 78/MAY 31, 1895
READING (RDG) 72/MAY 28 & 31, 1939, & MAY 31, 1991
TRENTON (TTN) 75/MAY 31, 1895
WILMINGTON (ILG) 75/MAY 30, 1895
RECORD HIGH TEMPERATURES
MAY 18
SITE RECORD/YEAR
ALLENTOWN (ABE) 96/1962
AC AIRPORT (ACY) 93/1987
AC MARINA (55N) 90/1987
GEORGETOWN (GED) 91/1974
MOUNT POCONO (MPO) 87/1962
PHILADELPHIA (PHL) 94/1962
READING (RDG) 96/1962
TRENTON (TTN) 96/1986
WILMINGTON (ILG) 94/1962
RECORD WARMEST LOW TEMPERATURES
MAY 18
SITE RECORD/YEAR
ALLENTOWN (ABE) 65/2017
AC AIRPORT (ACY) 70/2017
AC MARINA (55N) 66/2017
GEORGETOWN (GED) 72/2017
MOUNT POCONO (MPO) 61/2017
PHILADELPHIA (PHL) 72/2017
READING (RDG) 67/1900, 1943, & 2017
TRENTON (TTN) 71/2017
WILMINGTON (ILG) 72/2017
RECORD HIGH TEMPERATURES
MAY 19
SITE RECORD/YEAR
ALLENTOWN (ABE) 97/1962
AC AIRPORT (ACY) 96/1962
AC MARINA (55N) 92/1998
GEORGETOWN (GED) 96/1962
MOUNT POCONO (MPO) 89/1962
PHILADELPHIA (PHL) 96/1962
READING (RDG) 96/1962
TRENTON (TTN) 96/1962
WILMINGTON (ILG) 95/1962
RECORD WARMEST LOW TEMPERATURES
MAY 19
SITE RECORD/YEAR
ALLENTOWN (ABE) 65/2017
AC AIRPORT (ACY) 73/2017
AC MARINA (55N) 68/1998
GEORGETOWN (GED) 73/2017
MOUNT POCONO (MPO) 60/1943
PHILADELPHIA (PHL) 74/1877
READING (RDG) 68/1962
TRENTON (TTN) 70/2017
WILMINGTON (ILG) 70/2017
RECORD HIGH TEMPERATURES
MAY 20
SITE RECORD/YEAR
ALLENTOWN (ABE) 92/1962 & 1996
AC AIRPORT (ACY) 96/1996
AC MARINA (55N) 93/1996
GEORGETOWN (GED) 95/1962
MOUNT POCONO (MPO) 89/1996
PHILADELPHIA (PHL) 94/1962 & 1996
READING (RDG) 97/1996
TRENTON (TTN) 94/1996
WILMINGTON (ILG) 96/1996
RECORD WARMEST LOW TEMPERATURES
MAY 20
SITE RECORD/YEAR
ALLENTOWN (ABE) 66/2019
AC AIRPORT (ACY) 68/1996
AC MARINA (55N) 69/1996
GEORGETOWN (GED) 74/2019
MOUNT POCONO (MPO) 61/1959
PHILADELPHIA (PHL) 71/2019
READING (RDG) 69/1959 & 1996
TRENTON (TTN) 68/1903, 1959, & 1962
WILMINGTON (ILG) 70/2019
PHI WATCHES/WARNINGS/ADVISORIES
PA...HEAT ADVISORY UNTIL 8 PM EDT WEDNESDAY FOR PAZ070-071-102-104-
106.
HEAT ADVISORY UNTIL 8 PM EDT TUESDAY FOR PAZ060>062-101-103-
105.
AIR QUALITY ALERT UNTIL MIDNIGHT EDT TONIGHT FOR PAZ060>062-
070-071-101>106.
NJ...HEAT ADVISORY UNTIL 8 PM EDT WEDNESDAY FOR NJZ015-017>019.
AIR QUALITY ALERT UNTIL 11 PM EDT THIS EVENING FOR NJZ001-
007>010-012-015-017>019.
HEAT ADVISORY UNTIL 8 PM EDT TUESDAY FOR NJZ007>010.
AIR QUALITY ALERT FROM 11 AM TO 11 PM EDT TUESDAY FOR
NJZ012>021-026-027.
HEAT ADVISORY UNTIL 8 PM EDT WEDNESDAY FOR NJZ012-013-020-027.
DE...HEAT ADVISORY UNTIL 8 PM EDT WEDNESDAY FOR DEZ001.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TUESDAY TO MIDNIGHT EDT TUESDAY
NIGHT FOR ANZ450>453.
DISCUSSION...GORSE/GUZZO
AVIATION...GORSE/GUZZO
MARINE...GORSE/GUZZO
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