688
FXUS61 KPHI 211028
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
628 AM EDT TUE APR 21 2026
WHAT HAS CHANGED
A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR THE DELAWARE BAY AND
A PORTION OF THE ATLANTIC COASTAL WATERS FOR TONIGHT INTO
TOMORROW MORNING.
KEY MESSAGES
1. TRENDING WARMER TODAY AFTER A COLD NIGHT. SOME RAIN SHOWERS
ALSO MOVE IN FOR TONIGHT.
2. A RETURN TO ABOVE AVERAGE TEMPERATURES BRIEFLY LATER THIS
WEEK BEFORE COOLING DOWN AGAIN OVER THE WEEKEND. WIDESPREAD
RAINFALL POSSIBLE OVER THE WEEKEND.
DISCUSSION
KEY MESSAGE 1...TRENDING WARMER TODAY AFTER A COLD NIGHT. SOME
RAIN SHOWERS ALSO MOVE IN FOR TONIGHT INTO WEDNESDAY.
AFTER A COLD NIGHT ACROSS THE AREA, WE START TO WARM UP TODAY.
FREEZE WARNINGS REMAIN UNCHANGED THROUGH MID-MORNING BEFORE WE
SEE TEMPERATURES CLIMB THROUGH THE DAY. THIS WILL BE DUE TO OUR
HIGH PRESSURE SYSTEM MOVING OFFSHORE TODAY AND ALLOWING FOR
RETURN FLOW TO DEVELOP WITH A SOUTH TO SOUTHWEST WIND. WARM AIR
ADVECTION TAKES PLACE TODAY INTO TONIGHT ALLOWING FOR THIS WARM
UP. HIGH TEMPERATURES REACH INTO THE 50S FOR MANY.
IN THE WAKE OF OUR HIGH PRESSURE SYSTEM, A WEAK LOW PRESSURE
SYSTEM APPROACHES THE AREA FROM THE GREAT LAKES REGION TONIGHT
RESULTING IN RAIN SHOWERS DEVELOPING ACROSS THE AREA. THIS
SYSTEM SLOWLY CLEARS THE REGION LATER IN THE DAY WEDNESDAY. LOWS
TONIGHT ARE IN THE MID 30S TO MID 40S WITH HIGHS WEDNESDAY IN
THE UPPER 50S TO UPPER 60S.
KEY MESSAGE 2...A RETURN TO ABOVE AVERAGE TEMPERATURES BRIEFLY
LATER THIS WEEK BEFORE COOLING DOWN AGAIN OVER THE WEEKEND.
WIDESPREAD RAINFALL POSSIBLE OVER THE WEEKEND.
IN THE WAKE OF WEDNESDAY'S SYSTEM, WARM AIR ADVECTION AND
RISING HEIGHTS WILL RESULT IN TEMPERATURES CLIMBING BACK ABOVE
AVERAGE THURSDAY THROUGH FRIDAY. HIGHS FOR MOST OF THE AREA ARE
FORECAST TO BE IN THE 70S FOR THURSDAY. BY FRIDAY, A BACKDOOR
COLD FRONT MAY ARRIVE WHICH PUSHES TEMPS BACK DOWN A FEW
DEGREES, THOUGH UNCERTAINTY HERE IS HIGH AND IF THE FRONT IS
POTENT, IT COULD BE MORE THAN JUST A FEW DEGREES. A LOW PRESSURE
MAY THEN ARRIVE FRIDAY NIGHT INTO SATURDAY WITH SOME SHOWERS,
AND WITH THE AIR MASS BEHIND THE BACKDOOR FRONT BECOMING MORE
FIRMLY ESTABLISHED, SATURDAY NOW LOOKS 10-15 DEGREES COOLER THAN
FRIDAY, POSSIBLY EVEN MORE.
IN TERMS OF RAINFALL, THE NEXT LOW PRESSURE OVER THE WEEKEND
HAS THE POTENTIAL FOR WIDESPREAD SHOWERS OR A PERIOD OF RAIN.
THE STRENGTH AND TIMING OF THE INVOLVED FEATURES FOR THE WEEKEND
HOWEVER IS LOWER CONFIDENCE. THE PATTERN THAT IS CURRENTLY
INDICATED AMONG THE MODEL GUIDANCE HOWEVER WOULD RESULT IN
PERHAPS UP TO A HALF INCH OF VERY BENEFICIAL RAINFALL.
UNCERTAINTY REMAINS HIGH, HOWEVER.
AVIATION /10Z TUESDAY THROUGH SATURDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TODAY...VFR WITH INCREASING CLOUDS, PARTICULARLY FOR THE
AFTERNOON. A NORTH WIND IN THE MORNING, TRANSITIONS TO SOUTHWEST
AROUND 5-10 KT IN THE AFTERNOON. TOWARD EVENING, WINDS TURN
MORE SOUTHERLY AT 5-10 KT. HIGH CONFIDENCE.
TONIGHT...MAINLY VFR. CEILINGS CONTINUE TO LOWER OVERNIGHT, BUT
WERE KEPT ABOVE MVFR. RAIN SHOWERS MAINLY LOOK TO MOVE IN AFTER
AROUND 06Z AND MVFR CONDITIONS ARE POSSIBLE IF ANY SHOWERS GO
OVER A TERMINAL. THIS WAS TOO LOW CONFIDENCE TO INCLUDE IN THE
CURRENT TAFS FOR TONIGHT. WINDS REMAIN OUT OF THE SOUTH AT 5-10
KT. KACY/KMIV SEE WINDS PICK UP OUT OF THE SOUTH AFTER AROUND
06Z WITH GUSTS UPWARDS OF 20 KT.
OUTLOOK...
SUB-VFR CONDITIONS POSSIBLE WEDNESDAY WITH SHOWERS. VFR LIKELY
RETURNS BY WEDNESDAY NIGHT AND CONTINUES THROUGH FRIDAY. SUB-VFR
THEN LIKELY RETURNS FRIDAY NIGHT AND ESPECIALLY SATURDAY.
MARINE
A NORTH WIND IN THE MORNING GRADUALLY SHIFTS TO BE OUT OF THE
SOUTH- SOUTHEAST THIS AFTERNOON AT AROUND 10 KNOTS WITH GUSTS UP
TO 15 KNOTS. WINDS INCREASE OUT OF THE SOUTH TONIGHT AT 15-20
KNOTS WITH GUSTS TO 25 KNOTS. A SMALL CRAFT ADVISORY HAS BEEN
ISSUED FOR THE DELAWARE BAY FROM 2AM TO 8AM WEDNESDAY. FOR A
PORTION OF THE ATLANTIC COASTAL WATERS, A SMALL CRAFT ADVISORY
HAS BEEN ISSUED FROM 2AM TO 11AM WEDNESDAY. SEAS THROUGH THE
PERIOD ARE 2-4 FEET.
OUTLOOK...
SUB-SCA EXPECTED WEDNESDAY NIGHT THROUGH FRIDAY NIGHT. MARGINAL
SCA CONDITIONS POSSIBLE SATURDAY WITH GUSTS UP TO 25 KTS AND
SEAS UP TO 5 FEET.
CLIMATE
RECORD LOW TEMPERATURES ARE POSSIBLE AT SOME CLIMATE SITES FOR
THIS MORNING, APRIL 21ST. BELOW ARE THE DAILY LOW TEMPERATURE
RECORDS FOR 4/21:
DAILY RECORD LOW TEMPERATURES
APRIL 21
SITE RECORD/YEAR
ALLENTOWN (ABE) 28/1925 & 1956 & 2018
AC AIRPORT (ACY) 25/1981
AC MARINA (55N) 26/1875
GEORGETOWN (GED) 27/1961
MOUNT POCONO (MPO) 11/1908
PHILADELPHIA (PHL) 27/1875
READING (RDG) 26/1982
TRENTON (TTN) 30/1907 & 1925
WILMINGTON (ILG) 28/1925
PHI WATCHES/WARNINGS/ADVISORIES
PA...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR PAZ060>062-070-
071-101>106.
FREEZE WARNING UNTIL 10 AM EDT THIS MORNING FOR PAZ054-055.
NJ...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR NJZ007>010-
012>023-027.
FREEZE WARNING UNTIL 10 AM EDT THIS MORNING FOR NJZ001.
DE...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR DEZ001>003.
MD...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR MDZ012-015-019-
020.
MARINE...SMALL CRAFT ADVISORY FROM 2 AM TO 8 AM EDT WEDNESDAY FOR
ANZ430-431.
SMALL CRAFT ADVISORY FROM 2 AM TO 11 AM EDT WEDNESDAY FOR
ANZ450>455.
DISCUSSION...GUZZO/RCM
AVIATION...GUZZO/RCM
MARINE...GUZZO/RCM
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