773
FXUS61 KPHI 211012
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
612 AM EDT SUN JUN 21 2026
WHAT HAS CHANGED
UPDATED AVIATION SECTION FOR 12Z TAFS.
KEY MESSAGES
1. MOSTLY TRANQUIL TODAY AND TONIGHT.
2. A SYSTEM MOVES IN MONDAY INTO MONDAY NIGHT BRINGING THE
THREAT FOR HEAVY RAINFALL WITH AN ASSOCIATED FLOODING RISK ALONG
WITH AT LEAST SOME THREAT FOR SEVERE WEATHER.
DISCUSSION
KEY MESSAGE 1...MOSTLY TRANQUIL TODAY AND TONIGHT.
HIGH PRESSURE WELL TO THE SOUTH/WEST ACROSS THE LOWER OHIO
VALLEY WILL CONTINUE TO WEAKEN TODAY. IT WILL PROVIDE MOSTLY
DRY WEATHER AND COMFORTABLE TEMPERATURES TODAY AND TONIGHT.
THERE IS ONE MORE WEAK SHORTWAVE IN THE WEST TO NORTHWEST FLOW
ALOFT AND IT WILL LIKELY RESULT IN SOME ADDITIONAL SHOWERS OR A
LOW-TOPPED THUNDERSTORM IN THE NORTHERN AREAS AGAIN THIS
AFTERNOON.
KEY MESSAGE 2...A SYSTEM MOVES IN MONDAY INTO MONDAY NIGHT
BRINGING THE THREAT FOR HEAVY RAINFALL WITH AN ASSOCIATED
FLOODING RISK ALONG WITH AT LEAST SOME THREAT FOR SEVERE
WEATHER.
FORECAST GUIDANCE CONTINUES TO INDICATE AN UNSETTLED START TO
THE WEEK WITH LOW PRESSURE IMPACTING THE AREA BUT THERE REMAIN
DIFFERENCES IN THE DETAILS OF HOW ALL THIS WILL PLAY OUT. THE
MAIN QUESTION CONTINUES TO BE THE EXACT TRACK OF THE LOW, WHICH
WILL HAVE NOTABLE CONSEQUENCE ON SPECIFIC IMPACTS.
THE MAIN TAKEAWAY THOUGH IS THAT IS THAT MOST AREAS WILL SEE AT
LEAST SOME SHOWERS AND THUNDERSTORMS MONDAY AFTERNOON INTO THE
EVENING, POTENTIALLY EVEN LASTING INTO THE OVERNIGHT. CONSENSUS
GUIDANCE SHOWS PWAT VALUES (1.75- 2.00") NEAR THE CLIMATOLOGICAL
MAXIMA, SETTING UP THE RISK FOR HEAVY RAINFALL. NBM
PROBABILITIES FOR 1+ INCHES OF RAIN WITH THE SYSTEM ARE IN THE
60-80 PERCENT RANGE FOR AREAS ALONG AND NORTH OF THE I-95
CORRIDOR AND GENERALLY IN THE 25 TO 50 PERCENT RANGE FARTHER
SOUTH. FOR 2+ INCHES, THESE PROBABILITIES ARE AS HIGH AS 30 TO
50 PERCENT OVER NE PA INTO NW NJ, GENERALLY AROUND 10 TO 25
PERCENT NEAR THE I-95 CORRIDOR, AND LESS THAN 10 PERCENT FARTHER
SOUTH. IT IS WORTH NOTING THOUGH THAT FORECAST MODELS
NOTORIOUSLY STRUGGLE WITH QPF, ESPECIALLY WHEN IT INVOLVES
CONVECTION. LOOKING AT THE DIFFERENT DETERMINISTIC MODELS, THERE
ARE INDICATIONS THAT SOME PARTS OF OUR AREA COULD SEE 2-3+
INCHES OF RAIN BUT THE QUESTION IS NOT JUST IF THIS OCCURS BUT
IF SO, WHERE. IF THE LOW TRACKS FARTHER NORTH, THIS WOULD TEND
TO KEEP THE HEAVIEST RAIN GENERALLY FAVORED FOR NE PA INTO NW NJ
WITH MORE OF A SEVERE WEATHER THREAT SOUTH OF THESE AREAS.
HOWEVER A TRACK FARTHER SOUTH NEAR DELMARVA / SE PA / SOUTHERN
NJ COULD UNFORTUNATELY MEAN THAT THE HEAVIEST RAIN WOULD BE
TARGETED NEAR THE I-95 CORRIDOR. WE'RE STILL IN A REGION-WIDE
DROUGHT THOUGH SO THAT COULD MITIGATE THE FLOOD THREAT SOME. AT
THIS TIME THE WEATHER PREDICTION CENTER HAS AREAS FROM THE I-95
CORRIDOR NORTHWARD IN A SLIGHT RISK (LEVEL 2 OUT OF 4) FOR
EXCESSIVE RAINFALL MEANING SCATTERED INSTANCES OF FLASH FLOODING
WILL BE POSSIBLE. FARTHER SOUTH, THE RISK IS MARGINAL (LEVEL 1
OUT OF 4) MEANING ANY FLASH FLOODING WILL BE MORE ISOLATED IF IT
OCCURS. THE STORM PREDICTION CENTER HAS MAINTAINED A SLIGHT
RISK (LEVEL 2 OUT OF 5) FOR AREAS SOUTH OF PHILADELPHIA WITH A
MARGINAL RISK (LEVEL 1 OUT OF 5) FOR AREAS NORTH OF THERE
REGARDING THE POTENTIAL FOR SEVERE THUNDERSTORMS. AS OF NOW,
DAMAGING WIND GUSTS ARE THE PRIMARY THREAT HOWEVER WILL NEED TO
WATCH THE TRACK OF THE LOW AND WARM FRONT AS SHEAR PROFILES WILL
BE STRONGER NEAR IT, ALTHOUGH INSTABILITY IS STILL MORE
UNCERTAIN.
IN TERMS OF TIMING, THE TREND IS FOR THE SYSTEM TO BE A BIT
SLOWER MEANING SHOWERS/STORMS MAY NOT REALLY MOVE IN UNTIL THE
AFTERNOON BUT WOULD LINGER THROUGH THE EVENING AND POTENTIALLY
OVERNIGHT AS WELL. THE SEVERE WEATHER THREAT SHOULD BE
DIMINISHING THROUGH THE EVENING BUT THE FLOOD THREAD MAY LAST
INTO THE OVERNIGHT.
TUESDAY STILL LOOKS LIKE IT COULD SEE SOME ADDITIONAL SHOWERS
AND STORMS, MORE SCATTERED IN NATURE, DUE TO THE SYSTEM'S SLOWER
MOVEMENT WITH A FINAL PIECE OF THE UPPER LEVEL TROUGH MOVING
THROUGH. THIS SHOULD BE FOCUSED NEAR AND S/E OF THE URBAN
CORRIDOR WITH THE SEVERE WEATHER AND FLASH FLOODING THREAT
LOOKING LOW BY THIS TIME.
AVIATION /10Z SUNDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TODAY AND TONIGHT...VFR. A SHOWER POSSIBLE DURING THE
AFTERNOON, BEST CHANCE AT KABE. WEST-NORTHWEST WINDS AROUND 10
KNOTS WITH SOME GUSTS 15-20 KNOTS. WINDS MAY BECOME WEST OR EVEN
WEST- SOUTHWEST DURING THE AFTERNOON MAINLY AT KACY. GUSTS
DIMINISH IN THE EVENING AND WINDS LIKELY GO LIGHT/VARIABLE FOR A
TIME OVERNIGHT BEFORE SWITCHING EASTERLY TOWARD MORNING.
MODERATE CONFIDENCE.
OUTLOOK...
MONDAY AND MONDAY NIGHT...SUB-VFR CONDITIONS WITH SHOWERS AND
SOME THUNDERSTORMS LIKELY MAINLY FOR THE AFTERNOON AND EVENING
PERIODS.
TUESDAY...SCATTERED SHOWERS/STORMS COULD BRING BRIEF
RESTRICTIONS TO THE I-95 TAF SITES AND POINTS S/E OF THERE. VFR
SHOULD PREVAIL FARTHER NORTH.
WEDNESDAY...VFR. NO SIGNIFICANT WEATHER.
THURSDAY...CHANCES FOR SHOWER/STORMS RETURN (30 TO 50 PERCENT
CHANCES) AND THESE COULD BRING BRIEF RESTRICTIONS.
MARINE
MOSTLY FAIR WEATHER EXPECTED THROUGH TONIGHT. A BRIEF SHOWER
POSSIBLE.
OUTLOOK...
MONDAY THROUGH MONDAY NIGHT...SCA IN EFFECT WITH SOUTHERLY WIND
GUSTS INCREASING TO AROUND 30 KT WITH SEAS 4 TO 7 FEET.
TUESDAY...SCA CONDITIONS COULD LINGER EARLY.
WEDNESDAY THROUGH THURSDAY...SUB SCA CONDITIONS.
RIP CURRENTS...
FOR TODAY, WESTERLY WINDS DIMINISH TO AROUND 10 MPH, BECOMING
SOUTHWESTERLY TONIGHT. ONSHORE SWELLS WILL REMAIN WEAK AROUND 1
TO 2 FEET WITH A 7 SECOND PERIOD. BREAKING WAVES IN THE SURF
ZONE WILL BE AROUND 1 FOOT OR LESS. THEREFORE, A LOW RISK FOR
THE DEVELOPMENT OF DANGEROUS RIP CURRENTS IS FORECAST FOR ALL
BEACHES ON SUNDAY.
FOR MONDAY, SOUTH-SOUTHEASTERLY WINDS WILL INCREASE TO AROUND
15-20 MPH. SOUTH-SOUTHEASTERLY ONSHORE SWELLS WILL INCREASE TO
AROUND 2 TO 3 FEET WITH A 6 SECOND PERIOD. BREAKING WAVES IN THE
SURF ZONE WILL GENERALLY BE 1 TO 3 FEET. THERE, A MODERATE RISK
FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS IS FORECAST FOR
ALL BEACHES EXCEPT DELAWARE BEACHES WHERE THE BREAKING WAVES IN
THE SURF ZONE WILL GENERALLY BE 1 TO 2 FEET THAT WILL LEAD TO A
LOW RISK FOR DEVELOPMENT OF DANGEROUS RIP CURRENTS.
FOR SPECIFIC BEACH FORECASTS, VISIT WEATHER.GOV/BEACH/PHI
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 3 PM MONDAY TO MIDNIGHT EDT MONDAY
NIGHT FOR ANZ430-431.
SMALL CRAFT ADVISORY FROM NOON MONDAY TO 6 AM EDT TUESDAY FOR
ANZ450>455.
DISCUSSION...FITZSIMMONS/GORSE/OHARA/RCM
AVIATION...FITZSIMMONS/GORSE/OHARA/RCM
MARINE...FITZSIMMONS/MJL/RCM
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