544
FXUS61 KPHI 160721
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
221 AM EST TUE DEC 16 2025
SYNOPSIS
OUR ARCTIC HIGH PRESSURE SYSTEM HAS SETTLED OVER THE SOUTHEAST
US THIS MORNING BEFORE MOVING OUT TO SEA INTO TONIGHT. A WEAK
FRONT PASSES THROUGH WEDNESDAY, THEN A STRONG COLD FRONT MOVES
THROUGH OUR REGION THURSDAY NIGHT AND FRIDAY. HIGH PRESSURE
RETURNS INTO THE WEEKEND. HOWEVER, A WEAK COLD FRONT PASSES
THROUGH SUNDAY NIGHT. HIGH PRESSURE ONCE AGAIN BUILDS IN FOR
MONDAY.
NEAR TERM /THROUGH WEDNESDAY/
THE HIGH PRESSURE SYSTEM THAT HAS BEEN IN CONTROL IS NOW
SETTLING OVER THE SOUTHEAST US BEFORE SLIDING OFFSHORE TODAY
INTO TONIGHT. DUE TO THE HIGH PRESSURE SYSTEM MOVING OFFSHORE,
WE SEE THE WINDS THROUGH THE DAY CHANGE FROM OUT OF THE WEST TO
EVENTUALLY SOUTHWEST LATE IN THE DAY. ALTHOUGH WE SEE THAT
SOUTHWESTERLY WIND, IT IS LATE IN THE DAY AND WE STILL HAVE A
SOLID SNOWPACK, SO TEMPERATURES ONLY MODERATE SLIGHTLY. HIGHS
TODAY WILL BE MAINLY IN THE MID 20S TO MID 30S. THE INFLUENCE OF
THE HIGH PRESSURE SYSTEM WILL ALLOW FOR MINIMAL CLOUD COVER THIS
MORNING. SOME MID AND HIGH CLOUDS LOOK TO INCREASE THIS
AFTERNOON AND EVENING WITH A SIGNAL FOR A PIECE OF UPPER-LEVEL
ENERGY TO ROTATE THROUGH THE REGION. PRECIPITATION IS NOT
EXPECTED AS THIS DISTURBANCE MOVES THROUGH.
AS THE HIGH PRESSURE SYSTEM CONTINUES TO EXIT TONIGHT, IT ALLOWS FOR
A CLEAR SKY WITH WINDS RELATIVELY LIGHT. WHEN COMBINED WITH THE
LINGERING SNOWPACK, THIS WILL ALLOW TEMPERATURES TO RADIATE DOWN
INTO THE TEENS AND LOW 20S.
ONCE THE HIGH FULLY EXITS, WE SEE SOME UPPER-LEVEL TROUGHING THAT
MOVES INTO THE NORTHEAST WEDNESDAY. AT THE SURFACE, THERE IS A LOW
PRESSURE SYSTEM IN THE GREAT LAKES REGION WHICH MOVES INTO THE
NORTHEAST. A WEAK COLD FRONT ASSOCIATED WITH THIS LOW PASSES
THROUGH THE AREA WEDNESDAY. CLOUDS DO INCREASE AHEAD OF THIS
COLD FRONT WEDNESDAY BUT THE FRONTAL PASSAGE LOOKS OVERALL
PRETTY DRY. A SOUTHWEST WIND AHEAD OF THE COLD FRONT WILL ALLOW
TEMPERATURES TO RISE INTO THE 40S FOR MANY. AS THE COLD FRONT
PASSES THROUGH, WE SEE THE WINDS SHIFT TO BE MORE OUT OF THE
WEST WHICH WILL START TO USHER IN COLDER AIR. THERE WILL BE A
TIGHTENING PRESSURE GRADIENT BETWEEN THE DEPARTING HIGH AND THE
LOW MOVING INTO THE NORTHEAST. ALSO, THERE ARE STRONGER WINDS
ALOFT BUT THE POTENTIAL FOR THESE WINDS TO MIX DOWN MAY BE
LIMITED DUE TO THE MILDER AIR FILTERING IN. OVERALL, WIND GUSTS
LOOK TO BE 20-25 MPH ON WEDNESDAY WITH OCCASIONAL GUSTS TO 30
MPH IN THE HIGHER ELEVATIONS.
SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/
HIGH PRESSURE THEN BUILDS BACK OVER THE AREA FOR WEDNESDAY
NIGHT AND THURSDAY. STILL COLD WEDNESDAY NIGHT WITH LOWS IN THE
20S, BUT THEN HIGHS REBOUND ON THURSDAY TO ABOVE NORMAL LEVELS
IN THE UPPER 40S TO LOW 50S NORTH AND WEST OF THE FALL LINE AND
IN THE LOW TO MID 50S ACROSS THE DELAWARE VALLEY, DELMARVA, AND
SOUTHERN NEW JERSEY.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
HIGH PRESSURE MOVES OUT TO SEA THURSDAY NIGHT, AND LOW PRESSURE
PASSING THROUGH THE GREAT LAKES WILL DRAG A COLD FRONT INTO THE
REGION LATE THURSDAY NIGHT AND FRIDAY. TEMPERATURES WILL BE
WARM ENOUGH FOR THIS TO BE A MOSTLY RAIN EVENT, THOUGH WITH COLD
AIR ADVECTION ON THE BACK SIDE OF THE SYSTEM, THERE MAY BE SOME
RAIN/SNOW MIX IN THE SOUTHERN POCONOS AND PORTIONS OF THE
LEHIGH VALLEY. THERE ARE SOME SIGNALS FOR SOME MODERATE TO
POSSIBLY EVEN HEAVY RAINFALL OVER THE AREA WITH THIS SYSTEM. THE
BULK OF THE RAIN, AT LEAST AT THIS TIME, LOOKS TO FALL BETWEEN
MIDNIGHT OR SO THURSDAY NIGHT THROUGH FRIDAY AFTERNOON. 13Z NBM
PROBABILITY OF 24 HOUR PRECIPITATION ENDING 7 PM FRIDAY IS 70 TO
80 PERCENT FOR GREATER THAN 0.5 INCHES AND 40 TO 60 PERCENT FOR
GREATER THAN 1 INCH. LOWS THURSDAY NIGHT WILL BE IN THE UPPER
30S TO LOW 40S, AND THEN HIGHS ON FRIDAY WILL BE IN THE UPPER
40S TO LOW 50S. THIS RAINFALL SHOULD TAKE CARE OF THE BULK OF
THE SNOWPACK OVER THE AREA.
COLD FRONT PASSES THROUGH BY FRIDAY NIGHT AND THEN ARCTIC HIGH
PRESSURE BUILDS BACK INTO THE REGION WITH LOWS IN THE 20S FRIDAY
NIGHT AND THEN HIGHS IN THE UPPER 30S TO LOW 40S ON SATURDAY.
SOME STRONG SHORTWAVES WILL PASS THROUGH THE REGION WITH MINIMAL
IMPACTS.
HIGH PRESSURE SLIDES OFFSHORE SATURDAY NIGHT AND TEMPERATURES
REBOUND ON SUNDAY WITH HIGHS IN THE MID TO UPPER 40S. A WEAK
FRONT MAY PASS THROUGH THE REGION SUNDAY NIGHT AND THEN HIGH
PRESSURE RETURNS ON MONDAY WITH NEAR TO SLIGHTLY BELOW NORMAL
LEVELS.
AVIATION /07Z TUESDAY THROUGH SATURDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH 12Z...VFR. CEILINGS WILL GRADUALLY CLEAR OUT OVERNIGHT.
WEST TO SOUTHWEST WINDS AROUND 5 KNOTS, BECOMING LIGHT AND
VARIABLE AT TIMES. MODERATE CONFIDENCE.
TUESDAY...VFR. LIGHT AND VARIABLE WINDS BECOMING WEST-NORTHWEST
AROUND 5 KNOTS IN THE MORNING, THEN BECOMING WEST TO SOUTHWEST
IN THE AFTERNOON. HIGH CONFIDENCE.
TUESDAY NIGHT...VFR. A SOUTHWEST WIND AROUND 5 KNOTS WITH SOME
MID AND HIGH CLOUDS AROUND. HIGH CONFIDENCE.
OUTLOOK...
WEDNESDAY THROUGH THURSDAY...VFR/NSW.
THURSDAY NIGHT THROUGH FRIDAY...SUB-VFR CONDS IN RA THROUGH
FRIDAY AFTERNOON. SW WINDS GUSTING 25 TO 30 KT THURSDAY NIGHT,
TURNING W-NW ON FRIDAY.
FRIDAY NIGHT THROUGH SATURDAY...VFR/NSW.
MARINE
NO MARINE HEADLINES ARE EXPECTED THROUGH TUESDAY NIGHT.
FOR TODAY, A WEST-NORTHWEST WIND AROUND 10-15 KT EARLY WILL LESSEN
TO 5-10 KT THROUGH THE DAY WITH SEAS OF 1-3 FEET EXPECTED. FAIR
WEATHER.
OVERNIGHT TUESDAY, WINDS WILL INCREASE OUT OF THE SOUTHWEST AT 15-20
KT AND SEAS INCREASE TO 2-4 FEET.
ON WEDNESDAY, MARGINAL SCA CONDITIONS ARE POSSIBLE WITH GUSTS NEAR
25 KT AND SEAS BUILDING TO 4-5 FEET.
OUTLOOK...
WEDNESDAY NIGHT THROUGH THURSDAY...SUB-SCA CONDITIONS.
THURSDAY NIGHT THROUGH FRIDAY...STRONG SCA CONDITIONS
DEVELOPING WITH GALES POSSIBLE ON FRIDAY. VSBY RESTRICTIONS IN
RAIN AND FOG.
FRIDAY NIGHT...SCA CONDITIONS.
SATURDAY...SUB-SCA CONDITIONS.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
SYNOPSIS...MPS
NEAR TERM...GUZZO
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...GUZZO/MPS
MARINE...GUZZO/MPS
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