630
FXUS61 KPHI 201526
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1126 AM EDT MON APR 20 2026
WHAT HAS CHANGED
NO SIGNIFICANT CHANGES TO THE FORECAST.
KEY MESSAGES
1. A STRONG COLD FRONT PASSES THROUGH THE REGION INTO THIS MORNING
LEADING TO BELOW NORMAL TEMPERATURES. FROST AND FREEZE HEADLINES
REMAIN IN PLACE DUE TO THESE BELOW NORMAL TEMPERATURES.
2. A RETURN TO ABOVE AVERAGE TEMPERATURES LATER THIS WEEK BEFORE
COOLING DOWN AGAIN OVER THE WEEKEND. WIDESPREAD RAINFALL POSSIBLE
OVER THE WEEKEND.
DISCUSSION
KEY MESSAGE 1...A STRONG COLD FRONT PASSES THROUGH THE REGION INTO
THIS MORNING LEADING TO BELOW NORMAL TEMPERATURES. FROST AND FREEZE
HEADLINES REMAIN IN PLACE DUE TO THESE BELOW NORMAL TEMPERATURES.
AFTER A CHILLIER NIGHT WITH FROST AND FREEZE HEADLINES, WE SEE
TEMPERATURES TODAY REACH INTO THE MID 40S TO MID 50S FOR MANY. SOME
MID-LEVEL ENERGY ROTATES THROUGH THE REGION TODAY ALLOWING FOR THE
POTENTIAL FOR ISOLATED SHOWERS TO DEVELOP MAINLY SOUTHEAST OF THE I-
95 CORRIDOR. GENERALLY, THESE SHOWERS WILL BE IN THE FORM OF LIGHT
RAIN BUT THE COLD AIR ALOFT MAY ALLOW THE POTENTIAL FOR SOME GRAUPEL
TO MIX IN.
BEHIND THE COLD FRONT, A HIGH PRESSURE SYSTEM MOVES EAST
OUT OF THE GREAT LAKES REGION AND OVERHEAD TONIGHT. THIS HIGH
PRESSURE SYSTEM ALLOWS FOR A GOOD OPPORTUNITY FOR RADIATIONAL COOLING
WITH A CLEARING SKY AND LIGHT WINDS. A WIDESPREAD FREEZE LOOKS TO
OCCUR TONIGHT INTO EARLY TOMORROW MORNING AND A FREEZE WARNING IS
NOW IN EFFECT FOR THE WHOLE AREA EXCEPT FOR THE IMMEDIATE COAST. ALL
OF OUR COUNTIES NOW HAVE AN ACTIVE GROWING SEASON DUE TO THE RECENT
EXCESSIVE WARMTH. BLOOMS/VEGETATION HAVE QUICKLY INITIATED AND IN
SOME CASES ARE AHEAD OF SCHEDULE. FRUIT TREES AND OTHER COLD
SENSITIVE PLANTS ALREADY PLANTED ARE OF THE MOST CONCERN. FROST
FORMATION MIGHT BE SOMEWHAT LIMITED GIVEN A MUCH DRIER LOW-LEVEL AIR
MASS IN PLACE TONIGHT. LOWS TONIGHT GENERALLY RANGE FROM THE MID 20S
TO LOW 30S WITH MID TO UPPER 30S NEAR THE COAST.
KEY MESSAGE 2...A RETURN TO ABOVE AVERAGE TEMPERATURES LATER THIS
WEEK BEFORE COOLING DOWN AGAIN OVER THE WEEKEND. SOME SHOWERS
EXPECTED ON WEDNESDAY MORNING WITH MORE WIDESPREAD RAINFALL
POSSIBLE OVER THE WEEKEND.
IT IS NOT ANTICIPATED TO BE AS COLD TUESDAY NIGHT AS THE AIR
MASS CONTINUES TO MODIFY AND CLOUDS INCREASE WITH HIGH PRESSURE
NOW WELL OFFSHORE. A RETURN, SOUTHERLY, FLOW WILL ALSO BECOME
ESTABLISHED TUESDAY AND CONTINUE WEDNESDAY. THIS ALONG WITH AN
INCREASE IN WARM AIR ADVECTION AND RISING HEIGHTS WILL RESULT IN
TEMPERATURES CLIMBING BACK ABOVE AVERAGE WEDNESDAY THROUGH
FRIDAY. HIGHS FOR MOST OF THE AREA ARE FORECAST TO BE IN THE
MID/UPPER 60S WEDNESDAY, THEN INTO THE 70S FOR THURSDAY AND
FRIDAY. A FRONT MAY ARRIVE FRIDAY NIGHT INTO SATURDAY WITH SOME
SHOWERS, AND WITH THE LOW-LEVEL FLOW MORE ONSHORE IT WILL BRING
IN SOME COOLING STARTING FRIDAY ESPECIALLY CLOSER TO THE COAST.
IF THE MARINE INFLUENCE ENDS UP BEING STRONGER FRIDAY INTO
SATURDAY, THEN MORE LOW CLOUDS MAY COME INTO PLAY ALONG WITH
EVEN COOLER TEMPERATURES.
IN TERMS OF RAINFALL, A WEAK AREA OF LOW PRESSURE SLIDES BY
WEDNESDAY MORNING BRINGING SOME SHOWERS. RAINFALL AMOUNTS
GENERALLY UP TO A TENTH OF AN INCH ARE EXPECTED. ANOTHER AREA
OF LOW PRESSURE MAY ARRIVE DURING THE WEEKEND, ESPECIALLY FOR
SUNDAY, BRINGING 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 TEMPERATURES DROPPING TO AVERAGE OR BELOW AVERAGE OVER
THE WEEKEND, WITH AN INCREASED CHANCE FOR RAINFALL.
AVIATION /15Z MONDAY THROUGH FRIDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TODAY...VFR. A FEW LIGHT/BRIEF SHOWERS OR SPRINKLES POSSIBLE
DURING THE DAY. BKN CEILINGS AROUND 5000-6000 FEET. WEST-
NORTHWEST WIND GUSTING TO AROUND 20 KNOTS DURING THE AFTERNOON.
HIGH CONFIDENCE.
TONIGHT...VFR. A NORTH WIND AROUND 5 KNOTS WITH PERIODS OF LIGHT
AND VARIABLE. HIGH CONFIDENCE.
OUTLOOK...
TUESDAY NIGHT...VFR. NO SIGNIFICANT WEATHER.
WEDNESDAY...MVFR/IFR CONDITIONS EXPECTED ESPECIALLY IN THE
MORNING WITH SHOWERS AND LOW CLOUDS AROUND.
WEDNESDAY NIGHT THROUGH FRIDAY...VFR. NO SIGNIFICANT WEATHER.
FRIDAY NIGHT THROUGH SATURDAY...SUB-VFR CONDITIONS LIKELY AT
TIMES WITH SHOWERS AND LOW CLOUDS MOVING THROUGH.
MARINE
WINDS INCREASE THROUGH THIS MORNING AND INTO THE AFTERNOON OUT OF
THE NORTHWEST. DURING THE AFTERNOON, GUSTS LOOK TO REACH 15-20
KNOTS. TONIGHT WINDS TURN OUT OF THE NORTH WITH GUSTS CONTINUING
AROUND 15-20 KNOTS. SEAS OF 2 TO 4 FEET ARE EXPECTED THROUGH THE
PERIOD.
OUTLOOK...
TUESDAY NIGHT/WEDNESDAY MORNING...SMALL CRAFT ADVISORY
CONDITIONS POSSIBLE (30-40%) WITH WIND GUSTS NEAR 25 KT.
WEDNESDAY AFTERNOON THROUGH SATURDAY...NO MARINE HEADLINES
EXPECTED.
CLIMATE
RECORD LOW TEMPERATURES ARE POSSIBLE AT SOME CLIMATE SITES
TOMORROW, APRIL 21ST. HERE 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 FROM MIDNIGHT TONIGHT TO 9 AM EDT TUESDAY FOR
PAZ054-055-060>062-070-071-101>106.
NJ...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT TUESDAY FOR
NJZ001-007>010-012-013-015>023-027.
DE...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT TUESDAY FOR
DEZ001>003.
MD...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT TUESDAY FOR
MDZ012-015-019-020.
MARINE...NONE.
DISCUSSION...GORSE/GUZZO/HOEFLICH
AVIATION...GUZZO/HOEFLICH
MARINE...GUZZO/HOEFLICH
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