578
FXUS61 KPHI 161913
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
213 PM EST TUE DEC 16 2025
SYNOPSIS
HIGH PRESSURE OVER THE MID-ATLANTIC AND SOUTHEAST DRIFTS OUT TO
SEA TONIGHT. A WEAK COLD FRONT PASSES THROUGH THE REGION LATE
WEDNESDAY THROUGH WEDNESDAY NIGHT. HIGH PRESSURE BRIEFLY
DEVELOPS OVER THE AREA THURSDAY BEFORE MOVING OUT TO SEA
THURSDAY NIGHT. 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 WEDNESDAY/
NORTHWESTERLY FLOW ALOFT WILL BECOME MORE ZONAL TONIGHT AS A
SHORTWAVE SHIFTS EAST AWAY FROM THE AREA. A SHORTWAVE WILL SHIFT
EAST OUT OF THE NORTHERN GREAT LAKES REGION WEDNESDAY, PASSING
TO THE NORTH OF THE AREA DURING THE AFTERNOON. AT THE SURFACE,
HIGH PRESSURE CENTERED OVER PORTIONS OF THE SOUTHEAST AND MID-
ATLANTIC WILL SHIFT EASTWARD AWAY FROM THE REGION TONIGHT, WITH
A COLD FRONT MOVING THROUGH WEDNESDAY AFTERNOON.
SKIES SHOULD BE MOSTLY CLEAR ACROSS THE AREA FOR THE MAJORITY
OF THE TONIGHT, AND WINDS WILL BE LIGHT TO START. THEREFORE,
EFFECTIVE RADIATIONAL COOLING IS EXPECTED ONCE AGAIN. SNOWPACK
REMAINS ACROSS MUCH OF THE AREA, WHICH SHOULD AID IN COOLING AS
WELL. TOWARDS DAYBREAK, WINDS WILL BEGIN TO INCREASE OUT OF THE
SOUTHWEST AHEAD OF THE APPROACHING COLD FRONT. TEMPERATURES MAY
BOTTOM OUT DURING THE OVERNIGHT HOURS AS OPPOSED TO NEAR DAWN AS
IS TYPICAL. STILL, MINIMUM TEMPERATURES WILL GENERALLY BE IN
THE UPPER TEENS TO LOW 20S FOR MOST OF THE AREA. NEAR THE COAST,
LOWS CLOSER TO 30 ARE EXPECTED.
WEDNESDAY SHOULD START MOSTLY CLEAR FOR THE AREA, BEFORE MID
AND UPPER-LEVEL CLOUDS BEGIN TO MOVE IN WITH THE APPROACHING
COLD FRONT. WINDS SHOULD INCREASE FURTHER OUT OF THE SOUTHWEST,
WITH GUSTS 20-30 MPH. IT WILL BE A MUCH WARMER DAY THAN THE PAST
SEVERAL, WITH HIGHS IN THE LOW-MID 40S FOR EASTERN PA AND MOST
OF NJ, AND UPPER 40S FOR SOUTHERN PORTIONS OF THE DELMARVA INTO
FAR SOUTHEASTERN NJ. THE COLD FRONT SHOULD PASS THROUGH THE
REGION BY EVENING. PRECIPITATION CHANCES WITH THIS FRONTAL
PASSAGE APPEAR NEGLIGIBLE.
SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/
HIGH PRESSURE WILL MOVE INTO THE AREA WEDNESDAY EVENING BEFORE
PASSING OVERHEAD LATE WEDNESDAY NIGHT. THE HIGH MOVES OFFSHORE
ON THURSDAY AND CONTINUES TO MOVE INTO THE WESTERN ATLANTIC.
QUIET CONDITIONS ON TAP FOR WEDNESDAY NIGHT AND THURSDAY. SKIES
CLEAR OUT WEDNESDAY NIGHT, AND WINDS BECOME NEARLY CALM LATE.
RADIATIONAL COOLING CONDITIONS DEVELOP, AND LOWS WEDNESDAY NIGHT
WILL DROP INTO THE TEENS AND 20S. RETURN FLOW SETS UP BEHIND
THE DEPARTING HIGH AND AHEAD OF AN APPROACHING COLD FRONT ON
THURSDAY. WARM AIR ADVECTION WILL BE UNDERWAY, AND HIGHS ON
THURSDAY CLIMB 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 SOME 10 DEGREES WARMER COMPARED TO
WEDNESDAY. CLOUDS WILL INCREASE THROUGHOUT THE DAY, BUT THERE
SHOULD BE ENOUGH SUNSHINE AND TEMPERATURES WILL BE WARM ENOUGH
TO ALLOW FOR THE SNOWPACK TO AT LEAST BEGIN TO MELT OFF.
A DEVELOPING STORM SYSTEM WILL THEN IMPACT THE AREA STARTING
THURSDAY NIGHT. LOW PRESSURE OVER THE NORTHERN PLAINS THURSDAY
MORNING WILL MOVE INTO THE GREAT LAKES DURING THE DAY, THEN
LIFTS INTO THE PROVINCES OF ONTARIO AND QUEBEC THURSDAY NIGHT
THROUGH FRIDAY MORNING. AS IS DOES, A STRONG COLD FRONT WILL
DEVELOP AS ARCTIC HIGH PRESSURE BUILDS INTO THE CENTRAL UNITED
STATES. MEANWHILE, A DEEPENING H5 TROUGH WITH STRONG SHORTWAVE
ENERGY WILL BUILD DOWN THROUGH THE GREAT LAKES AND OHIO VALLEY
AND INTO THE GULF COAST STATES AND SOUTHEAST. THE COLD FRONT
WILL PASS THROUGH THE REGION FRIDAY AFTERNOON, AND THEN COLD AIR
ADVECTION WILL BE UNDERWAY AS ARCTIC HIGH PRESSURE BUILDS IN
FROM THE WEST.
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 /19Z TUESDAY THROUGH SUNDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH 00Z...VFR. WEST-SOUTHWEST WIND AROUND 5 KT. HIGH
CONFIDENCE.
TONIGHT...VFR. WIND BECOMING LGT/VRB WITH CALM PERIOD POSSIBLE.
WIND WILL BEGIN TO INCREASE AGAIN OUT OF THE SOUTHWEST TO
AROUND 5 KT PRIOR TO 12Z. HIGH CONFIDENCE.
WEDNESDAY...VFR. SCT MID-LEVEL CLOUDS AFTER 15-17Z. SOUTHWEST
WIND AROUND 5 KT INCREASING TO AROUND 10 KT WITH GUSTS 20-25 KT
DURING THE AFTERNOON. LLWS POSSIBLE BETWEEN 13Z AND 17Z FOR KRDG
AND KABE. LOWER CONFIDENCE IN LLWS FOR THE I-95 TERMINALS.
MODERATE CONFIDENCE.
OUTLOOK...
WEDNESDAY NIGHT THROUGH 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 HAS BEEN ISSUED FOR ALL COASTAL WATERS
FROM 7 AM WEDNESDAY THROUGH 7 PM.
SOUTHWEST WINDS AROUND 10 KT TONIGHT WILL INCREASE TO 15-25 KT
WEDNESDAY MORNING, WITH GUSTS AS HIGH AS 30 KT POSSIBLE. WINDS
WILL BECOME WESTERLY BY LATE WEDNESDAY AFTERNOON, AND DECREASE
TO 10-15 KT BY EVENING. SEAS 1-2 FEET TONIGHT, INCREASING TO 3-5
FEET WEDNESDAY.
OUTLOOK...
WEDNESDAY NIGHT THROUGH THURSDAY...SUB-SCA CONDITIONS.
THURSDAY NIGHT THROUGH FRIDAY...GALE FORCE WINDS DEVELOPING
THURSDAY NIGHT IN SW FLOW, THEN WILL CONTINUE FRIDAY AFTERNOON
IN NW FLOW BEHIND A DEPARTING COLD FRONT. VSBY RESTRICTIONS IN
RAIN. SEAS BUILDING TO 6 TO 8 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...SMALL CRAFT ADVISORY FROM 7 AM TO 7 PM EST WEDNESDAY FOR
ANZ450>455.
SYNOPSIS...MPS
NEAR TERM...COOPER
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...COOPER/MPS
MARINE...COOPER/MPS
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