553
FXUS61 KPHI 120121
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
921 PM EDT TUE MAR 11 2025
SYNOPSIS
A COLD FRONT MOVES ACROSS THE REGION TONIGHT, AND THEN HIGH
PRESSURE SETTLES OVER EASTERN CANADA FROM WEDNESDAY THROUGH
FRIDAY. A WARM FRONT LIFTS NORTH THROUGH THE REGION FRIDAY
NIGHT, AND THEN HIGH PRESSURE ESTABLISHES ITSELF OVER THE MID-
ATLANTIC THIS WEEKEND UNTIL A STRONG COLD FRONT PASSES THROUGH
THE REGION SUNDAY NIGHT. HIGH PRESSURE RETURNS FOR THE START OF
THE NEW WORK WEEK.
NEAR TERM /THROUGH WEDNESDAY/
HEADING INTO TONIGHT, THE WARM WEATHER WILL COME TO AN END. A
BACK DOOR COLD FRONT WILL SINK SOUTH AND PASS THROUGH OVERNIGHT
CAUSING TEMPERATURES TO TAKE A TUMBLE AS WINDS SHIFT FROM
SOUTHERLY TO NORTHERLY. WILL BEGIN TO SEE AN INCREASE IN SOME
HIGH CLOUDS LATE, BUT NO PRECIPITATION IS EXPECTED. LOWS TONIGHT
WILL GENERALLY RANGE FROM THE MID 30S TO MID 40S.
AS A RESULT OF THE BACK DOOR FRONT, A COOLER BUT MORE
SEASONABLE AIRMASS WILL RETURN TO THE REGION ON WEDNESDAY.
SUBTLE HIGH PRESSURE WILL MOVE ACROSS SOUTHERN QUEBEC, CAUSING
SURFACE FLOW TO BECOME MORE EASTERLY, COMMENCING ONSHORE FLOW
OFF THE COOL ATLANTIC WATERS. SKIES WILL BE MOSTLY CLOUDY ACROSS
MUCH OF THE AREA, WITH THE EXCEPTION OF SOUTHERN NJ AND THE
DELMARVA WHICH WILL OBSERVE MORE SUN THAN CLOUDS. SO, WHILE
TEMPERATURES INLAND RECOVER INTO THE LOW TO MID 50S,
TEMPERATURES NEAR THE COAST WILL BE CONSIDERABLY COOLER, ONLY IN
THE 40S. MAY ALSO SEE SOME MARINE FOG ROLL IN LATE IN THE DAY
ESPECIALLY OVER COASTAL SOUTHERN DELAWARE WHERE DEW POINT
DEPRESSIONS ARE LOWER.
SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/
A COLD FRONT WILL PASS THROUGH THE REGION WEDNESDAY NIGHT, AND
WHILE IT SHOULD PASS THROUGH DRY FOR THE MAJORITY OF THE AREA,
THERE MAY BE SOME RAIN AND/OR SNOW SHOWERS IN THE SOUTHERN
POCONOS AND FAR NORTHWEST NEW JERSEY, AND SOME RAIN SHOWERS
ACROSS NEW JERSEY DOWN TO THE I-195 CORRIDOR. ANY QPF OR
SNOWFALL WILL BE MINIMAL, AT BEST.
HIGH PRESSURE THEN SETS UP OVER EASTERN CANADA, AND THE BASE OF
THE HIGH WILL EXTEND DOWN THROUGH THE NORTHEAST. A NORTHEAST
FLOW SETS UP, AND THIS ALLOWS FOR A COOLER, YET STILL A FEW
DEGREES ABOVE NORMAL FOR THIS TIME OF THE YEAR, AIRMASS TO
SPREAD INTO THE LOCAL AREA. HIGHS WILL GENERALLY BE IN THE 50S
ON THURSDAY, THEN A COUPLE OF DEGREES WARMER ON FRIDAY.
SOME PATCHY FOG MAY DEVELOP THURSDAY NIGHT.
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
HIGH PRESSURE OVER EASTERN CANADA LIFTS AWAY FRIDAY NIGHT.
MEANWHILE, A WARM FRONT EXTENDING FROM STRONG LOW PRESSURE OVER
NORTHERN AND CENTRAL PLAINS AND UPPER MIDWEST LIFTS NORTH
THROUGH THE MID-ATLANTIC AND NORTHEAST. ONSHORE FLOW PERSISTS,
AND WITH INCREASING LOW LEVEL MOISTURE, PATCHY FOG AND PATCHY
DRIZZLE WILL DEVELOP ACROSS THE REGION INTO SATURDAY MORNING.
COLD FRONT MOVES THROUGH THE GREAT LAKES AND INTO THE OHIO
VALLEY ON SATURDAY. SOME SHORTWAVE ENERGY MAY SPIN OFF AHEAD OF
THE SYSTEM TO SPARK OFF SOME SHOWERS SATURDAY AFTERNOON AND
EVENING. OTHERWISE, WARM AIR ADVECTION DEVELOPS DUE TO STRONG
SOUTHERLY FLOW. HIGHS CLIMB INTO THE 60S FOR MOST OF THE AREA
AND INTO THE LOW 70S FOR DELMARVA. TURNING FAIRLY HUMID FOR MID-
MARCH AS WELL WITH SURFACE DEW POINTS APPROACHING 60 IN MOST
AREAS.
PRESSURE GRADIENT BETWEEN APPROACHING COLD FRONT AND HIGH
PRESSURE OVER THE WESTERN ATLANTIC TIGHTENS FURTHER ON SUNDAY,
COMBINED WITH A STRONG LOW LEVEL JET WILL ALLOW SOUTH WINDS TO
INCREASE TO 15 TO 25 MPH WITH 30 TO 40 MPH GUSTS.
THE TIMING OF THE PASSAGE OF THE FRONT IS STILL IN QUESTION.
12Z/11 GFS SEEMS TO HAVE SPED UP A BIT COMPARED TO THE PREVIOUS
RUN, AND IS NOW MORE SUNDAY AFTERNOON/EARLY EVENING AS OPPOSED
TO SUNDAY NIGHT. THIS WOULD ARRIVE DURING PEAK HEATING OF THE
DAY, AND WITH THE HIGHEST INSTABILITY. INSTABILITY IS FAIRLY
MINIMAL, ALL THINGS CONSIDERED, AS 13Z/11 NBM HAS A 40 TO 50
PERCENT PROBABILITY FOR GREATER THAN 250 J/KG OF SURFACE-BASED
CAPE FOR SOUTHEAST PENNSYLVANIA AND THE EASTERN SHORES OF
MARYLAND AND 20 PERCENT OR LESS FOR NEW JERSEY AND DELAWARE. 12Z
GFS ALSO SHOWING 55 TO 65 KT OF 0-6 KM BULK SHEAR. SUNDAY IS
SHAPING UP TO BE A LOW CAPE/HIGH SHEAR DAY IN WHICH CONVECTION
COULD BE LIMITED, BUT ANY STORMS THAT DEVELOP COULD BE STRONG TO
SEVERE. THIS FRONT DOES LOOK TO BRING MUCH NEEDED AND
BENEFICIAL RAINFALL. WITH PWATS CLOSE TO 1.5 INCHES, HOWEVER,
LOCALIZED HEAVY RAIN AND POOR DRAINAGE FLOODING ARE POSSIBLE.
WILL INCLUDE A CHANCE FOR THUNDERSTORMS IN THE FORECAST SUNDAY
AFTERNOON AND EVENING.
SHOWERS TAPER OFF FROM WEST TO EAST SUNDAY NIGHT. DEPENDING ON
HOW FAR EAST THE FRONT GETS, SOME SHOWERS MAY LINGER ALONG THE
COAST INTO MONDAY MORNING. TURNING COOLER WITH HIGHS IN THE MID
AND UPPER 50S ON MONDAY, WHICH ARE STILL ABOVE NORMAL FOR THIS
TIME OF THE YEAR, WHEN A FEW DEGREES WARMER ON TUESDAY.
AVIATION /01Z WEDNESDAY THROUGH SUNDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TONIGHT...VFR WITH INCREASING HIGH CLOUDS. SOUTHWEST WINDS
EARLY AROUND 5-10 KT WILL SHIFT TO NORTH-NORTHEAST WINDS AROUND
5-10 KT FOLLOWING A COLD FRONTAL PASSAGE. THE FRONT WILL PASS
THROUGH FROM NORTH TO SOUTH BETWEEN 03Z-09Z. MODERATE-HIGH
CONFIDENCE, OVERALL.
WEDNESDAY...VFR WITH SCT/BKN MID-HIGH LEVEL CLOUDS. NORTH-
NORTHEAST WINDS AROUND 5-10 KT IN THE MORNING WILL BECOME EAST-
SOUTHEAST WINDS AROUND 7-12 KT IN THE AFTERNOON. HIGH
WEDNESDAY NIGHT...MOSTLY VFR, BUT THERE IS THE POTENTIAL FOR
SUB-VFR CONDITIONS TOWARDS KRDG/KABE IN BRIEF SHRA AND/OR SHSN.
CONFIDENCE.
OUTLOOK...
THURSDAY THROUGH FRIDAY NIGHT...VFR DURING THE DAY, BUT SUB-VFR
CONDITIONS POSSIBLE AT NIGHT AND IN THE EARLY MORNING IN FOG
AND/OR LOW STRATUS, MOST LIKELY AT COASTAL TERMINALS.
SATURDAY...VFR. SCATTERED SHRA POSSIBLE IN THE AFTERNOON.
SUNDAY...VFR INITIALLY, THEN BRIEF SUB-VFR CONDITIONS IN
AFTERNOON AND EVENING SHRA WITH SCATTERED TSRA. SOUTH WINDS 15
TO 20 KT WITH 25 TO 35 KT GUSTS.
MARINE
LIGHT SOUTH-SOUTHWEST WINDS WILL INCREASE TO AROUND 10-15 KT
THROUGH EARLY THIS EVENING. SEAS OF 1-3 FEET. FAIR WEATHER.
AFTER MIDNIGHT, WINDS WILL SHIFT FROM SOUTHWEST TO NORTH-
NORTHEAST AROUND 10-15 KT WITH GUSTS UP TO 20 KT.
NORTHEAST WINDS WILL CONTINUE INTO WEDNESDAY AROUND 12-17 KT
WITH GUSTS UP TO 23-25 KT POSSIBLE WITH SEAS NEARING 5 FEET. AS
A RESULT, OPTED TO ISSUE A SMALL CRAFT ADVISORY FOR COASTAL
WATERS NORTH OF CAPE HENLOPEN UP TO MANASQUAN INLET. WINDS AND
SEAS WILL BE LESSER OFF THE COAST OF MONMOUTH COUNTY, NJ AND OFF
THE COAST OF DELAWARE. MARINE FOG POSSIBLE SOUTH OF CAPE MAY
LATE IN THE AFTERNOON.
OUTLOOK...
WEDNESDAY NIGHT THROUGH FRIDAY...SEAS WILL BUILD TO AROUND 5
FEET ON THE OCEAN WATERS, SUBSIDING ON FRIDAY AFTERNOON. A SCA
MAY BE NEEDED. VSBY RESTRICTIONS IN FOG POSSIBLE AT NIGHT AND IN
THE MORNING, ESPECIALLY ALONG THE COASTS.
SATURDAY...SCA CONDITIONS LIKELY.
SUNDAY...GALE FORCE WINDS LIKELY. VSBY RESTRICTIONS IN
AFTERNOON SHOWERS. SCATTERED THUNDERSTORMS POSSIBLE.
FIRE WEATHER
FOR WEDNESDAY, WINDS WILL BE CONSIDERABLY LIGHTER AND HAVE MORE
OF AN ONSHORE COMPONENT. EAST WINDS AROUND 10-15 MPH WITH MINRH
VALUES IN THE 30-40% RANGE. CONSIDERING IMPROVING RHS AND
LIGHTER WINDS, METEOROLOGICAL CONDITIONS DO NOT POSE A RISK FOR
FIRE SPREAD.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 9 AM TO 6 PM EDT WEDNESDAY FOR
ANZ451>454.
SYNOPSIS...MPS
NEAR TERM...DESILVA/HOEFLICH
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...DESILVA/HOEFLICH/MPS
MARINE...DESILVA/HOEFLICH/MPS
FIRE WEATHER...
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