167
FXUS61 KPHI 211719
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
119 PM 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 /18Z TUESDAY THROUGH SUNDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TODAY...VFR WITH MOSTLY CLEAR SKIES. LINGERING NORTHERLY WINDS
WILL TRANSITION TO SOUTH-SOUTHWEST AROUND 5-10 KT THIS
AFTERNOON. HIGH CONFIDENCE.
TONIGHT...PREVAILING VFR. INCREASING CLOUDS IN THE EVENING WILL
GIVE WAY TO BKN/OVC SKIES OVERNIGHT. A SLIGHT CHANCE OF RAIN
SHOWERS EARLY IN THE EVENING (BETWEEN 00-03Z), BEFORE INCREASING
AGAIN AFTER 06-10Z. A SLIGHT CHANCE OF MVFR CEILINGS WITH
SHOWERS, BUT EXPECT VFR CONDITIONS TO REMAIN. SOUTH-SOUTHEAST
WINDS AROUND 10 KT, LOCALLY HIGHER NEAR KMIV/KACY. MODERATE
CONFIDENCE OVERALL.
WEDNESDAY...PREVAILING VFR FOR MOST TERMINALS, WITH MVFR
CEILINGS LIKELY AT KABE AND POSSIBLY KRDG/KTTN. RAIN SHOWERS
CONTINUE THROUGH THE MORNING AND END FROM NORTHWEST TO SOUTHEAST
BETWEEN 15-18Z. SKIES SHOULD BEGIN TO SCATTER OUT AFTER 18Z.
SOUTH-SOUTHEAST WINDS WILL GRADUALLY BECOME NORTH-NORTHWEST IN
THE AFTERNOON AROUND 5-10 KT. LOW-MODERATE CONFIDENCE.
OUTLOOK...
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...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
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...DESILVA/GUZZO/RCM
MARINE...GUZZO/RCM
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