803
FXUS61 KPHI 041811
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
211 PM EDT SAT APR 4 2026
WHAT HAS CHANGED
INCREASED CONFIDENCE IN THE TIMING OF THE FRONT ON SUNDAY.
OTHERWISE, NO MAJOR CHANGES.
KEY MESSAGES
1. A FRONTAL BOUNDARY WILL CONTINUE TO SAG SOUTH THROUGH THE
REGION THIS AFTERNOON AS A BACK DOOR COLD FRONT.
2. SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED ON SUNDAY AS A
COLD FRONT TRACKS THROUGH THE AREA.
3. AN EXTENDED PERIOD OF DRY WEATHER IS EXPECTED FOR THE UPCOMING
WEEK WITH THE RETURN OF WARM TEMPERATURES LATER IN THE WEEK.
DISCUSSION
KEY MESSAGE 1...A FRONTAL BOUNDARY WILL CONTINUE TO SAG SOUTH THROUGH THE
REGION THIS AFTERNOON AS A BACK DOOR COLD FRONT.
A WARM FRONT THAT LIFTED NORTH OF THE REGION FRIDAY EVENING WILL
CONTINUE TO SAG BACK SOUTH AS A BACKDOOR COLD FRONT THROUGH THIS
AFTERNOON. AS OF 1 PM, THE FRONT WAS ALREADY THROUGH ALMOST ALL
OF NJ AND SE PA, AND STARTING TO SLOW ITS PROGRESS AS IT ENTERS
DELMARVA.
DEPENDING ON HOW FAR SOUTH THE FRONT MOVES THROUGH THE
AFTERNOON AND INTO THE LATE NIGHT PERIOD, AREAS ACROSS THE
DELMARVA COULD ALSO SEE NIGHTTIME TEMPERATURES CHALLENGE SOME
RECORD WARMEST LOWS. SEE THE CLIMATE SECTION BELOW FOR
INFORMATION ON RECORD TEMPERATURES FOR APRIL 4TH.
AS THE BACKDOOR FRONT ADVANCES SOUTH AND WEST ACROSS THE REGION,
A SHORT WAVE TROUGH WILL RIDE ALONG THAT BOUNDARY AND MAY
TRIGGER SOME LATE DAY SHOWERS AND POSSIBLE THUNDERSTORMS DUE TO
ELEVATED INSTABILITY. BUT DEPENDING ON HOW FAR SOUTH THAT BACK
DOOR COLD FRONT GETS, THAT MAY INHIBIT INSTABILITY NEEDED FOR
CONVECTION. BEHIND THE FRONT, ENE FLOW WILL SUPPORT A STRONG
LOW-LEVEL INVERSION, CAUSING THE DEVELOPMENT OF SOME STRATUS AND
FOG SATURDAY NIGHT.
KEY MESSAGE 2...SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED ON
SUNDAY AS A COLD FRONT TRACKS THROUGH THE AREA.
A SEQUENCE OF FRONTS WILL CROSS THROUGH THE AREA ON SUNDAY AS LOW
PRESSURE TRACKS THROUGH EASTERN CANADA. FIRST, A WARM FRONT WILL
LIFT BACK NORTH ACROSS THE MID-ATLANTIC DURING THE EARLY MORNING
HOURS ON SUNDAY. A FEW SHOWERS CAN BE ASSOCIATED WITH THIS FRONT. A
LULL IN ACTIVITY IS THEN EXPECTED BEFORE THE COLD FRONT APPROACHES.
THE COLD FRONT IS THEN FORECAST TO ARRIVE AFTER DAYBREAK AND PUSH
OFFSHORE DURING THE AFTERNOON. SHOWERS ARE LIKELY WITH SOME ISOLATED
THUNDERSTORMS POSSIBLE AS A NARROW CORRIDOR OF INSTABILITY MAY CREEP
UP INTO THE DELMARVA AND SOUTHERN NEW JERSEY REGION. AT THIS POINT,
ANY SEVERE POTENTIAL APPEARS TO BE QUITE LIMITED AS MOST OF THE
INSTABILITY LOOKS TO BE ELEVATED IN NATURE. HOWEVER, A FEW RUMBLES
OF THUNDER CANNOT BE RULED OUT. THIS IS IN LINE WITH THE LATEST
OUTLOOK BY SPC, WHICH ONLY CLIPS THE SOUTHEASTERN-MOST PORTIONS OF
SUSSEX COUNTY, DE IN A MARGINAL RISK. ANY SHOWER AND THUNDERSTORM
ACTIVITY WILL END BY MID AFTERNOON.
HIGH TEMPERATURES ON SUNDAY WILL PUSH INTO THE MID 60S TO LOW 70S
DURING THE MORNING HOURS, BEFORE TEMPERATURES TAKE A TUMBLE IN THE
AFTERNOON IN WAKE OF THE COLD FRONT. WINDS WILL ALSO BE QUITE GUSTY,
ESPECIALLY IN THE MORNING, AS SOUTHERLY FLOW WILL BE ENHANCED AHEAD
OF THE APPROACHING COLD FRONT. GUSTS MAY PUSH UPWARDS OF 30-35 MPH
BEFORE DIMINISHING IN THE AFTERNOON.
KEY MESSAGE 3...AN EXTENDED PERIOD OF DRY WEATHER IS EXPECTED FOR
THE UPCOMING WEEK WITH THE RETURN OF WARM TEMPERATURES LATER IN THE
WEEK.
FOR MONDAY INTO TUESDAY, THE MID-ATLANTIC REGION WILL BE SITUATED
WITHIN THE BASE OF AN UPPER LEVEL TROUGH WHICH WILL DEPART THE
REGION TUESDAY NIGHT. BY WEDNESDAY, A STRENGTHENING MID-LEVEL RIDGE
WILL TAKE SHAPE OVER THE CENTRAL AND EASTERN CONUS THROUGH THE END
OF THE WEEK. AT THE SURFACE, HIGH PRESSURE WILL LARGELY BE IN
CONTROL ASIDE FOR A MEAGER COLD FRONT WHICH WILL PASS THROUGH THE
AREA MONDAY NIGHT INTO TUESDAY. SUPPOSE A STRAY RAIN (OR SNOW)
SHOWER IS POSSIBLE ACROSS FAR NORTHWESTERN AREAS DURING THIS
TIMEFRAME, BUT LARGELY NO PRECIPITATION IS EXPECTED FOR THE UPCOMING
WEEK. AS A RESULT, TEMPERATURES WILL BE SEASONABLY COOL THROUGH
WEDNESDAY, BEFORE BEGINNING TO MODERATE AND TREND BACK TOWARD
SEASONABLY WARM LEVELS BY THURSDAY AND FRIDAY. THIS IS SUPPORTED BY
THE CLIMATE PREDICTION CENTER WHICH OUTLOOKS THE ENTIRE FORECAST
AREA IN A 60-70% CHANCE OF ABOVE-NORMAL TEMPERATURES FOR THE LATE
WEEK PERIOD.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH THE REST OF TODAY...VFR FOR MOST OF THE REMAINDER OF THE
DAY. AFTER 21Z, MARINE LAYER LOW STRATUS COULD START TO MOVE
ONSHORE, RESULTING IN LOWERING CEILINGS. LESS CONFIDENCE NOW ON
THE TIMING OF WHEN THAT STRATUS WILL DEVELOP, BUT LATEST
GUIDANCE TRENDED SLIGHTLY LATER. CURRENT THINKING IS THAT WITH
THE EXCEPTION OF KACY, IFR CEILINGS ARE UNLIKELY BEFORE 00Z.
SOME SHOWERS POSSIBLE THROUGH 00Z, BUT COVERAGE IS EXPECTED TO
BE VERY LIMITED, SO CONFIDENCE THAT ANY ONE TAF SITE WILL SEE
DIRECT IMPACTS IS TOO LOW TO INCLUDE IN THE TAFS. E TO SE WINDS
5 TO 15 KT. LOW CONFIDENCE.
TONIGHT...LOW CLOUDS SHOULD CONTINUE TO SPREAD OVER THE REGION.
BY 03Z, WIDESPREAD IFR WITH POSSIBLE LIFR RESTRICTIONS WILL
DEVELOP FROM THE LOW CEILINGS. SOME VISIBILITY RESTRICTIONS IN
BR OR SHOWERS ARE POSSIBLE, BUT CEILINGS ARE LIKELY TO BE THE
CONTROLLING FACTOR. E WINDS AROUND 10 KTS. THERE IS ALSO A
CONCERN FOR NON-CONVECTIVE LOW LEVEL WIND SHEAR, PARTICULARLY
BETWEEN 06 AND 12Z. LOW CONFIDENCE.
SUNDAY...WILL LIKELY START WITH CEILINGS IFR OR MVFR FOR MOST
TAF SITES. A LINE OF SHRA OR TSRA IS EXPECTED TO MOVE THROUGH
THE REGION FROM W TO E, ARRIVING AT KRDG AND KABE BETWEEN 14 AND
18Z, KPHL, KILG, KPNE, KTTN BETWEEN 15 AND 20Z, AND KMIV AND
KACY BETWEEN 17 AND 21Z. ONCE THE LINE OF SHRA AND TSRA MOVES
BY, CONDITIONS SHOULD RETURN TO VFR QUICKLY. WINDS WILL START S
OR SW AROUND 10 TO 15 KT, BUT WITH THE LINE OF SHRA AND TSRA,
EXPECT AN ABRUPT SHIFT TO W OR EVEN NW WINDS AROUND 10G20KT.
MODERATE CONFIDENCE.
OUTLOOK...
SUNDAY NIGHT WEDNESDAY...VFR. ASIDE FOR A STRAY RAIN SHOWER AT
KRDG OR KABE ON MONDAY NIGHT, NO SIGNIFICANT WEATHER EXPECTED.
MARINE
WINDS WILL INCREASE LATER THIS AFTERNOON AND TONIGHT ABOVE SMALL
CRAFT ADVISORY CONDITIONS. SW WINDS AROUND 10-15 KTS EARLY WILL
SHIFT E BEHIND A BACKDOOR FRONT. SCA WINDS POSSIBLE SATURDAY
EVENING ACROSS THE NORTHERN OCEAN ZONES WITH E WINDS GUSTING TO
AROUND 20-25 KTS. OVERNIGHT, THE FRONTAL BOUNDARY IS EXPECTED TO
LIFT NORTHWARD AGAIN WITH WINDS TURNING SW AND RAMPING UP TO
AROUND 20-25 KTS WITH SEAS BUILDING TO 4-6 FEET.
OUTLOOK...
SUNDAY THROUGH SUNDAY NIGHT...SCA CONDITIONS LIKELY. WIND GUSTS UP
TO 25-28 KT WITH SEAS AROUND 5-8 FEET. RAIN SHOWERS LIKELY WITH A
SLIGHT CHANCE OF A THUNDERSTORM.
MONDAY THROUGH WEDNESDAY...LINGERING SCA CONDITIONS POSSIBLE ON
MONDAY MORNING, OTHERWISE, NO MARINE HEADLINES ARE EXPECTED THROUGH
WEDNESDAY. FAIR WEATHER.
CLIMATE
A VERY WARM AIRMASS SATURDAY MAY CHALLENGE RECORD HIGH
TEMPERATURES AS WELL AS RECORD WARMEST LOW TEMPERATURES FOR
APRIL 4TH.
RECORD HIGH TEMPERATURES FOR APRIL 4TH:
SITE...................RECORD...YEAR(S)
AC AIRPORT (ACY).......78.......2017
PHILADELPHIA (PHL).....80.......1892
WILMINGTON (ILG).......80.......1950
ALLENTOWN (ABE)........79.......1928
TRENTON (TTN)..........82.......1892
READING (RDG)..........81.......1921
GEORGETOWN (GED).......81.......2023/2011/1963
MOUNT POCONO (MPO).....78.......1928
AC MARINA (55N)........77.......1999
RECORD WARMEST LOW TEMPERATURES FOR APRIL 4TH:
SITE...................RECORD...YEAR(S)
AC AIRPORT (ACY).......56.......1974
PHILADELPHIA (PHL).....60.......2025
WILMINGTON (ILG).......60.......2025
ALLENTOWN (ABE)........60.......1974
TRENTON (TTN)..........62.......1981
READING (RDG)..........58.......2025
GEORGETOWN (GED).......60.......2025/1950
MOUNT POCONO (MPO).....58.......1981
AC MARINA (55N)........56.......2025
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM TO 2 PM EDT SUNDAY FOR ANZ430-
431.
SMALL CRAFT ADVISORY UNTIL 6 PM EDT SUNDAY FOR ANZ450-451.
SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO 6 PM EDT
SUNDAY FOR ANZ452>455.
DISCUSSION...DESILVA/MJL
AVIATION...DESILVA/JOHNSON
MARINE...DESILVA/JOHNSON
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