558
FXUS61 KPHI 170723
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
223 AM EST WED DEC 17 2025
SYNOPSIS
HIGH PRESSURE EXITS TODAY AND IS FOLLOWED BY A WEAK COLD FRONT
THAT PASSES THROUGH THE REGION THIS EVENING. HIGH PRESSURE
BRIEFLY BUILDS IN TONIGHT BEFORE MOVING OUT THROUGH THE DAY
TOMORROW. A STRONG COLD FRONT APPROACHES LATE THURSDAY NIGHT
AND MOVES ACROSS THE REGION ON FRIDAY. HIGH PRESSURE RETURNS ON
SATURDAY, THEN ANOTHER COLD FRONT PASSES THROUGH ON SUNDAY. HIGH
PRESSURE RETURNS FOR THE START OF THE NEW WEEK.
NEAR TERM /THROUGH THURSDAY/
AS THE HIGH PRESSURE SYSTEM FULLY EXITS TODAY, WE SEE SOME UPPER-
LEVEL TROUGHING THAT MOVES INTO THE NORTHEAST. AT THE SURFACE, THERE
IS A LOW PRESSURE SYSTEM IN THE GREAT LAKES REGION WHICH MOVES INTO
QUEBEC THROUGH THE DAY TODAY. A WEAK COLD FRONT ASSOCIATED WITH THIS
LOW PASSES THROUGH THE AREA THIS AFTERNOON INTO THE EVENING. AFTER
THE EARLY MORNING STRATUS ERODES, WE SEE MORE MID AND HIGH CLOUDS
THAT INCREASE AHEAD OF THIS COLD FRONT. OVERALL, THE FRONTAL PASSAGE
LOOKS TO LACK PRECIPITATION. 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 SLIGHTLY COLDER AIR WHICH DOES
NOT LAST FOR LONG. 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.
ANOTHER HIGH PRESSURE SYSTEM MOVES IN TONIGHT AND WILL BE RELATIVELY
FAST MOVING. THIS HIGH WILL BE MOVING OFFSHORE ALREADY BY TOMORROW.
DUE TO THE HIGH PRESSURE SYSTEM BUILDING IN TONIGHT, TRANQUIL
CONDITIONS ARE EXPECTED WITH JUST THE POTENTIAL FOR SOME LOW TO MID
LEVEL CLOUDS FILTERING IN THROUGH THE NIGHT. OUR PRESSURE GRADIENT
WILL LESSEN INTO TONIGHT AND UPPER-LEVEL WINDS ALSO LOWER, SO THE
WINDS WILL BE DECREASING INTO TONIGHT WITH A PERIOD OF NEARLY CALM
WINDS AT TIMES. LOWS TONIGHT WILL BE IN THE 20S.
ONCE THE HIGH PRESSURE SYSTEM DEPARTS TOMORROW, WE SEE WINDS BECOME
MORE OUT OF THE SOUTHEAST TO SOUTH WITH THE RETURN FLOW. THIS ALLOWS
WARMER AIR TO MOVE INTO THE REGION. HIGHS ON THURSDAY WILL REACH
INTO THE MID AND UPPER 40S NORTH AND WEST OF THE FALL LINE AND IN
AND IN THE LOW TO MID 50S ALONG THE I-95 CORRIDOR, THE DELAWARE
VALLEY, AND SOUTHERN NEW JERSEY. HIGHS WILL BE IN THE MID TO UPPER
50S IN SOUTHERN DELMARVA. THESE TEMPERATURES WILL BE UPWARDS OF 10
DEGREES WARMER COMPARED TO WEDNESDAY IN SOME SPOTS. CLOUDS WILL
GRADUALLY INCREASE THROUGHOUT THE DAY WITH SOME SHOWERS STARTING TO
MOVE INTO THE AREA BY THE EVENING HOURS AS OUR NEXT SYSTEM
APPROACHES.
SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/
A SOUTH TO SOUTHWEST PRESSURE GRADIENT WILL TIGHTEN THURSDAY
NIGHT. IN ADDITION, A 60 TO 80 KT LOW LEVEL JET WILL PASS OVER
THE AREA LATE THURSDAY NIGHT THROUGH FRIDAY MORNING. HOWEVER,
GIVEN SOUTHWEST FLOW AS WELL AS WARM AIR AT THE SURFACE AND
ALOFT, MODEL SOUNDINGS ARE NOT INDICATING EFFICIENT ENOUGH
MIXING FOR THE STRONGEST OF THOSE WINDS TO MIX DOWN. GIVEN THE
GRADIENT, THOUGH, WINDS SHOULD INCREASE TO 20 TO 30 MPH WITH 30
TO 40 MPH GUSTS. THERE IS NOT ENOUGH INSTABILITY FOR
THUNDERSTORMS, BUT WILL HAVE TO MONITOR HOW THIS DEVELOPS, AS
THE POTENTIAL FOR A RUMBLE OF THUNDER OR TWO CANNOT BE RULED
OUT, AND IF THAT HAPPENS, SOME LOCALLY STRONGER WIND GUSTS COULD
DEVELOP.
MODERATE TO LOCALLY HEAVY RAIN DEVELOPS LATE THURSDAY NIGHT AND
CONTINUES THROUGH FRIDAY MORNING BEFORE BEGINNING TO TAPER OFF.
WITH COLD AIR ADVECTION UNDERWAY, SOME SNOW MAY MIX WITH THE
RAIN AS PRECIPITATION ENDS WITH NO SIGNIFICANT IMPACTS.
WITH COLD AIR ADVECTION UNDERWAY, STRONG NORTHWEST WINDS WILL
DEVELOP BEHIND THE DEPARTING COLD FRONT AT 20 TO 30 MPH WITH 30
TO 40 MPH GUSTS FRIDAY EVENING, DIMINISHING AFTER MIDNIGHT.
LOWS THURSDAY NIGHT WILL BE IN THE UPPER 30S TO LOW TO MID 40S
IN THE EVENING, THEN TEMPERATURES WILL RISE THROUGH THE
OVERNIGHT HOURS. HIGHS ON FRIDAY WILL BE IN THE LOW TO MID 50S
NORTH AND WEST OF THE FALL LINE AND IN THE MID TO UPPER 50S
ALONG THE I-95 CORRIDOR, SOUTHERN NEW JERSEY, THE DELAWARE
VALLEY, AND DELMARVA. HIGHS WILL BE IN THE MORNING, AND THEN
TEMPERATURES FALL IN THE AFTERNOON AS THE COLD FRONT PASSES
THROUGH. LOWS FRIDAY NIGHT WILL BE IN THE MID TO UPPER 20S.
THERE IS A 50 TO 70 PERCENT CHANCE FOR OVER 1 INCH OF RAIN FOR
DELMARVA AND SOUTHERN NEW JERSEY AND A 70 TO 80 PERCENT CHANCE
FOR OVER 1 INCH OF RAIN FROM AROUND PHILADELPHIA NORTH. THERE IS
ALSO A 50 TO 60 PERCENT CHANCE FOR OVER 1.5 INCHES OF RAIN
ACROSS THE LEHIGH VALLEY, SOUTHERN POCONOS, AND NORTHERN NEW
JERSEY. WHILE MAINSTEM RIVER FLOODING IS NOT EXPECTED, CANNOT
RULE OUT URBAN AND POOR DRAINAGE FLOODING DUE TO RAINFALL AND
SNOW MELT.
LONG TERM /SATURDAY THROUGH TUESDAY/
HIGH PRESSURE PASSES THROUGH THE SOUTHEAST AND MID-ATLANTIC
SATURDAY THROUGH SUNDAY. QUIET, BUT COLD, CONDITIONS ON TAP FOR
SATURDAY WITH HIGHS IN THE UPPER 30S TO LOW 40S. LOWS SATURDAY
NIGHT WILL BE IN THE UPPER 20S TO LOW 30S. MILDER ON SUNDAY WITH
HIGHS IN THE MID TO UPPER 40S. SOME STRONG SHORTWAVE ENERGY
WILL PASS NORTH OF THE AREA ON SUNDAY AND MAY SPARK OFF SOME
SHOWERS ACROSS THE FAR NORTHERN PORTIONS OF THE FORECAST AREA,
AND THEN SOME SHOWERS ACROSS SOUTHERN PORTIONS OF THE FORECAST
AREA AS A COLD FRONT WORKS ITS WAY THROUGH THE REGION SUNDAY
NIGHT.
HIGHS WILL BE SOME 10 DEGREES COOLER ON MONDAY COMPARED TO
SUNDAY, AND THEN TEMPERATURES REBOUND A BIT ON TUESDAY. ANOTHER
FRONTAL SYSTEM MAY IMPACT THE AREA BY THE MIDDLE OF NEXT WEEK.
AVIATION /07Z WEDNESDAY THROUGH SUNDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH 12Z...VFR. A PERIOD OF HIGH CLOUDS, THEN SOME CLOUDS
BETWEEN 4000-8000 FEET AGL MAY ARRIVE THROUGH DAYBREAK,
ESPECIALLY FOR KABE/KRDG. WEST- SOUTHWEST OR SOUTHWEST WINDS
AROUND 5 KNOTS, BECOMING LIGHT AND VARIABLE OR CALM. A SOUTHWEST
WIND AROUND 5 KNOTS THEN SHOULD DEVELOP TOWARD DAYBREAK.
MODERATE CONFIDENCE.
WEDNESDAY...VFR WITH AREAS OF MAINLY MID TO HIGH LEVEL CLOUDS.
SOUTHWEST WINDS INCREASING TO 5-10 KNOTS WITH SOME GUSTS TO
AROUND 20 KNOTS MAINLY DURING THE AFTERNOON. LOW-LEVEL WIND
SHEAR NEAR 40 KNOTS MAINLY AT KRDG AND KABE. LOW CONFIDENCE
REGARDING HOW MUCH WIND MIXES DOWN TO THE SURFACE AND RESULTS IN
FREQUENT GUSTS.
WEDNESDAY NIGHT...VFR. LOW TO MID LEVEL CLOUDS LOOK TO FILTER
IN. WEST-NORTHWEST WIND AROUND 5 KNOTS OR LESS MAY GO LIGHT AND
VARIABLE AT TIMES. HIGH CONFIDENCE.
OUTLOOK...
THURSDAY...VFR/NSW.
THURSDAY NIGHT...IFR IN RA AND LOW STRATUS. SW WINDS INCREASE
TO 15 TO 20 KT WITH 25 TO 30 KT GUSTS. A STRONG LOW LEVEL JET
MAY RESULT IN 50 KT OF LLWS.
FRIDAY...IFR IN RA AND LOW STRATUS IN THE MORNING, THEN
IMPROVING CONDITIONS THROUGH THE AFTERNOON. S-SW WINDS ABRUPTLY
SHIFT TO THE W-NW AROUND 18Z AT 15 TO 20 KT WITH 35 TO 35 KT
GUSTS.
FRIDAY NIGHT...VFR. W-NW WINDS 15 TO 20 KT WITH 30 TO 35 KT
GUSTS IN THE EVENING, DIMINISHING AFTER 06Z.
SATURDAY THROUGH SUNDAY...VFR/NSW.
MARINE
A SMALL CRAFT ADVISORY IS IN EFFECT FOR ALL OF THE ATLANTIC
COASTAL WATERS FROM 7 AM TO 7 PM TODAY. THE WINDS SHOULD REMAIN
BELOW ADVISORY CRITERIA ON THE DELAWARE BAY.
SOUTHWEST WINDS INCREASE TO 15-20 KT THIS MORNING WITH GUSTS AS
HIGH AS 25 KT. SEAS WILL INCREASE TO 4-6 FEET. BY THIS EVENING,
WINDS BECOME WESTERLY WHILE DECREASING TO 10-15 KT. SEAS
DECREASE TO 2-4 FEET.
NO MARINE HEADLINES ARE EXPECTED FOR WEDNESDAY NIGHT AND
THURSDAY AS WINDS AND SEAS STAY BELOW SCA CRITERIA.
OUTLOOK...
THURSDAY NIGHT THROUGH FRIDAY...A GALE WATCH HAS BEEN ISSUED FOR
ALL OF THE ATLANTIC COASTAL WATERS AND THE DELAWARE BAY FROM
THURSDAY NIGHT INTO FRIDAY NIGHT. GALE FORCE WINDS DEVELOP
THURSDAY NIGHT IN SW FLOW, THEN ANOTHER PERIOD OF GALES FRIDAY
AFTERNOON IN NW FLOW BEHIND A DEPARTING COLD FRONT. VSBY
RESTRICTIONS IN RAIN. SEAS BUILDING TO 6 TO 10 FEET THURSDAY
NIGHT, THEN 8 TO 12 FEET ON FRIDAY.
FRIDAY NIGHT...GALES WILL DIMINISH AFTER MIDNIGHT, THEN SCA
CONDITIONS.
SATURDAY...SUB-SCA CONDITIONS.
SATURDAY NIGHT THROUGH SUNDAY...SCA CONDITIONS POSSIBLE.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...GALE WATCH FROM THURSDAY EVENING THROUGH FRIDAY EVENING FOR
ANZ430-431.
SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 7 PM EST THIS
EVENING FOR ANZ450>455.
GALE WATCH FROM THURSDAY EVENING THROUGH LATE FRIDAY NIGHT FOR
ANZ450>455.
SYNOPSIS...MPS
NEAR TERM...GUZZO
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...GUZZO/MPS
MARINE...GUZZO/MPS
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