566
FXUS61 KPHI 191958
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
358 PM EDT SAT SEP 19 2026
WHAT HAS CHANGED
UPDATED KEY MESSAGE 1 SECTIONS WITH LATEST GUIDANCE. THE RISK
FOR EXCESSIVE RAINFALL ON SUNDAY HAS DECREASED.
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 /19Z SATURDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 00Z. AFTER 00Z,
MVFR CEILINGS ARE LIKELY TO START BUILDING IN FROM THE WEST AS
AREAS OF RAIN APPROACH. ANOTHER AREA OF LOW CLOUDS MAY BUILD IN
FROM THE EAST DUE TO ONSHORE FLOW/MARINE STRATUS MOVING IN.
WINDS ARE EXPECTED TO GRADUALLY VEER FROM E TO SE TO S THROUGH
THE TAF PERIOD. WIND SPEEDS WILL BE 10 TO 15 KNOTS THIS
AFTERNOON, AND AT OR BELOW 10KT THEREAFTER.
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
EASTERLY WINDS WILL DIMINISH TO 10 TO 15 KNOTS BY LATE THIS
AFTERNOON, WITH SEAS LESS THAN 5 FEET.
ONCE WINDS AND SEAS SUBSIDE, CONDITIONS ARE EXPECTED TO REMAIN
BELOW SCA CRITERIA THROUGH SUNDAY NIGHT.
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.
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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