014
FXUS61 KPHI 200514
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
114 AM EDT SUN SEP 20 2026
WHAT HAS CHANGED
FOR AVIATION INTERESTS, IT IS LOOKING MORE LIKELY THAT KMIV AND
KACY WILL KEEP PREVAILING VFR CONDITIONS UNTIL LATE IN THE DAY
SUNDAY, WHILE THE REST OF THE TAF SITES HAVE PREVAILING MVFR
CONDITIONS FOR MUCH, IF NOT ALL, OF THE 06Z TAF PERIOD.
KEY MESSAGES
1. LOW PRESSURE AND A COLD FRONT MOVE THROUGH THE REGION
TONIGHT INTO SUNDAY WITH RAIN SHOWERS LIKELY.
2. A STATIONARY FRONT SOUTH OF THE REGION COULD KEEP RAIN CHANCES
AROUND, ESPECIALLY FOR DELMARVA THROUGH MID WEEK.
3. A CLOSED MID-LEVEL LOW EJECTING FROM THE OHIO VALLEY COULD HELP
TO SPIN UP SURFACE LOW PRESSURE OFF OUR COAST BY THURSDAY,
POTENTIALLY BRINGING ANOTHER CHANCE FOR RAIN, AND INCREASING THE
RISK FOR COASTAL FLOODING.
DISCUSSION
KEY MESSAGE 1...LOW PRESSURE AND A COLD FRONT MOVE THROUGH THE
REGION TONIGHT INTO SUNDAY WITH RAIN SHOWERS LIKELY.
HIGH PRESSURE SHIFTS AWAY FROM THE REGION LATE TONIGHT AS A LOW
ORGANIZES AND DEVELOPS OVER THE MIDWEST. THE WARM FRONT
ASSOCIATED WITH THIS LOW WILL MOVE NORTHWARD INTO THE REGION
EARLY SUNDAY AFTERNOON, BUT WILL BE QUICKLY FOLLOWED BY A COLD
FRONT SUNDAY EVENING.
REGARDLESS OF THE EXACT EVOLUTION OF THE WARM FRONT, THE LEADING
EDGE OF A LARGE AREA OF RAIN WILL MOVE INTO THE REGION BY LATE
THIS EVENING IN RESPONSE TO MODEST MID AND UPPER LEVEL SYNOPTIC
SCALE LIFT ASSOCIATE WITH THE CYCLOGENSIS. LOCATIONS NORTH OF
PHILADELPHIA WILL HAVE THE GREATEST CHANCE FOR A PROLONGED
PERIOD OF RAINFALL TONIGHT INTO SUNDAY.
AN EASTERLY FLOW WILL BE IN PLACE THIS EVENING THROUGH TONIGHT,
BECOMING SOUTHEASTERLY BY SUNDAY MORNING. AS SUCH, LOW LEVEL
MOISTURE WILL BE ON THE INCREASE, WITH SURFACE DEW POINTS RISING
WELL INTO THE 60S AND PRECIPITABLE WATER VALUES INCREASING TO
NEAR 2 INCHES. PRECIPITABLE WATER VALUES THAT HIGH ARE WELL
ABOVE THE 90TH PERCENTILE.
HOWEVER, WITH LITTLE INSTABILITY, THERE WILL GENERALLY BE A LACK
OF EMBEDDED CONVECTION WITHIN THE AREAS OF RAIN. INSTEAD, THIS
WILL PRIMARILY BE A MORE STEADY, STRATIFORM RAIN EVENT. AS A
RESULT, THE RISK FOR EXCESSIVE RAINFALL LEADING TO FLASH
FLOODING HAS DECREASED. GIVEN THE HIGH PWATS, THERE MAY STILL BE
SOME POCKETS OF MODERATE RAINFALL AT TIMES, PARTICULARLY FOR
AREAS NORTHWEST OF I-95. BUT THE RISK FOR FLOODING IS NOW LOW
(LESS THEN 5 PERCENT) ACROSS THE ENTIRE REGION.
KEY MESSAGE 2...A STATIONARY FRONT SOUTH OF THE REGION COULD KEEP
RAIN CHANCES AROUND, ESPECIALLY FOR DELMARVA THROUGH MID WEEK.
A COLD FRONT WILL TRACK THROUGH THE FORECAST AREA ON SUNDAY NIGHT.
THE FRONT WILL BE SOUTH OF THE REGION ON MONDAY AND REMAIN THERE
THROUGH MID WEEK. CONFIDENCE IS NOT THE HIGHEST PERTAINING TO ALL
ASPECTS OF SENSIBLE WEATHER, NAMELY PRECIPITATION. HOW FAR SOUTH
THAT FRONT SAGS SOUTH WILL BE A BIG FACTOR IN HOW MUCH RAIN WE SEE
THROUGH THE WEEK. THE FURTHER SOUTH IT STALLS, THE LESS LIKELY OUR
REGION WILL SEE CONTINUED RAIN CHANCES THROUGH THE MID WEEK PERIOD.
REGARDLESS, OUR REGION WILL BE ON THE COOL SIDE OF THE FRONT THROUGH
THIS PERIOD KEEPING TEMPERATURES BELOW NORMAL. CONFIDENCE IS HIGHER
HERE.
KEY MESSAGE 3...A CLOSED MID-LEVEL LOW EJECTING FROM THE OHIO VALLEY
COULD HELP TO SPIN UP SURFACE LOW PRESSURE OFF OUR COAST BY
THURSDAY, POTENTIALLY BRINGING ANOTHER CHANCE FOR RAIN, AND
INCREASING THE RISK FOR COASTAL FLOODING.
AS A MID LEVEL LOW DIGS IN FROM THE NORTHWEST, MODELS ARE SHOWING
SURFACE CYCLOGENSIS BY WEDNESDAY OFF THE CAROLINAS. AT THIS POINT,
THERE ARE SIGNIFICANT DIFFERENCES IN THE TRACK AND STRENGTH OF THE
LOW. THE CLOSER THE TRACK IS TO THE COAST, THE MORE LIKELY OUR REGION
WILL SEE RAIN AND GUSTY WINDS ON THURSDAY AND FRIDAY. AN EYE WILL
ALSO NEED TO BE KEPT ON TIDES. TRACK, STRENGTH OF THE LOW, DURATION
OF AN ONSHORE WIND COMPONENT, AND FETCH WILL ALL PLAY A ROLE WITH
TIDAL DEPARTURES. IN ADDITION, THE FULL MOON IS ON SATURDAY. LONG
STORY SHORT, SOME SORT OF TIDAL FLOODING MAY EFFECT THE REGION NEXT
WEEK.
AVIATION /06Z SUNDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH TODAY...THE PREVAILING MVFR CEILINGS THAT HAVE ALREADY
DEVELOPED AT MOST TAF SITES ARE EXPECTED TO CONTINUE FOR MOST,
IF NOT ALL OF THE TAF PERIOD. FOR AREAS THAT ARE SEEING MORE
MARINE LAYER STRATUS, ESPECIALLY KACY AND KMIV, COULD SEE THE
PREVAILING VFR CONDITIONS CONTINUE UNTIL VERY LATE IN THE DAY
(AFTER 21Z). BRIEF IFR CONDITIONS POSSIBLE AT KRDG/KABE WITH
MORE MODERATE RAINFALL. SOUTHEAST WINDS AROUND 5-10 KTS
GRADUALLY SHIFTING MORE SSE. MODERATE CONFIDENCE OVERALL, LOW
CONFIDENCE IN TIMING OF IFR CONDITIONS.
TONIGHT...SUB-VFR CONDITIONS LIKELY DUE TO RAIN, STRATUS, AND
FOG. SOUTHWEST WINDS ABRUPTLY SHIFTING TO NORTHWEST WITH A
FRONTAL PASSAGE FROM WEST TO EAST BETWEEN 21 AND 09Z. LOW
CONFIDENCE.
OUTLOOK...
MONDAY...SUB-VFR CONDITIONS POSSIBLE DUE TO PRECIPITATION, LOW
STRATUS, AND FOG.
TUESDAY THROUGH THURSDAY...SUB-VFR CONDITIONS WILL REMAIN POSSIBLE
DUE TO SHOWERS/RAIN. WATCHING A POTENTIAL COASTAL LOW. BREEZY
NORTHEAST WINDS COULD DEVELOP, BUT THEY'LL BE DEPENDENT ON THE
THE TRACK AND STRENGTH OF THE POTENTIAL LOW.
MARINE
CONDITIONS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA THROUGH
SUNDAY NIGHT. WINDS AROUND 10-15 KNOTS GRADUALLY TRANSITION FROM
EAST-SOUTHEAST TONIGHT TO SOUTHERLY SUNDAY AFTERNOON AND
EVENING. A FRONT WILL SHIFT WINDS TO THE NORTHWEST SUNDAY NIGHT. SEAS
MAINLY 3-4 FEET THROUGHOUT THE PERIOD.
OUTLOOK...
MONDAY THROUGH THURSDAY...SCA HEADLINES MAY BE NEEDED STARTING ON
MONDAY FOR EAST TO NORTHEAST WINDS 15 TO 20 KT WITH GUSTS UP TO 25
KT AND 4 TO 6 FT. GALE FORCE WINDS ARE POSSIBLE AS EARLY AS TUESDAY
WITH WIND GUSTS EXCEEDING 35 KTS. SEAS MAY BUILD AS HIGH AS 10 TO 15
FT FROM TUESDAY THROUGH THURSDAY.
LOOKING AHEAD, THERE IS AT LEAST A CHANCE THE GALES WILL PERSIST
THROUGH FRIDAY. HOWEVER, CHANCES WILL BE HIGHLY DEPENDENT ON THE
TRACK OF A POTENTIAL COASTAL LOW.
RIP CURRENTS...
SUNDAY...THE WINDS SHIFT TO SOUTH/SOUTHEAST BUT REMAIN AROUND
15 TO 20 MPH. BREAKING WAVE HEIGHTS IN THE SURF ZONE LOOK TO BE
AROUND 3 TO 4 FEET FOR THE JERSEY SHORE AND 2 TO 4 FEET FOR THE
DELAWARE BEACHES. THERE IS A FORECAST OF A MODERATE RISK OF DANGEROUS
AND LIFE THREATENING RIP CURRENTS ALONG THE NJ AND DE COAST.
MONDAY... WE'LL CONTINUE WITH THE MODERATE RISK FOR DANGEROUS
RIP CURRENTS ON MONDAY AS WINDS WILL SWITCH AROUND TO NORTHEAST
AND INCREASE TO 15 TO 20 MPH DURING THE DAY. BREAKING WAVES IN
THE SURF ZONE WILL BE AROUND 2 TO 3 FEET MOSTLY, BUT COULD END
UP A BIT HIGHER AS WINDS REMAIN MODERATE AND GUSTY.
FOR SPECIFIC BEACH FORECASTS, VISIT WEATHER.GOV/BEACH/PHI
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
DISCUSSION...WFO PHI
AVIATION...WFO PHI
MARINE...WFO PHI
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