689
FXUS61 KPHI 171917
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
217 PM EST WED DEC 17 2025
SYNOPSIS
A WEAK FRONT MOVES THROUGH THE REGION THIS EVENING, THEN HIGH
PRESSURE BUILDS OVER THE AREA TONIGHT BEFORE MOVING OFFSHORE ON
THURSDAY. A WARM FRONT LIFTS NORTH THROUGH THE REGION THURSDAY
NIGHT, FOLLOWED BY A STRONG COLD FRONT ON FRIDAY. HIGH PRESSURE
MOVES THROUGH THE MID-ATLANTIC ON SATURDAY, FOLLOWED BY A COLD
FRONT SUNDAY. HIGH PRESSURE BRIEFLY RETURNS ON MONDAY, AND THEN
ANOTHER FRONTAL BOUNDARY IMPACTS THE AREA TUESDAY. HIGH PRESSURE
RETURNS ON WEDNESDAY.
NEAR TERM /THROUGH THURSDAY/
A MILDER AFTERNOON IS UNDERWAY (COMPARED TO RECENT DAYS) AS THE
AREA IS IN A SW FLOW AHEAD OF A COLD FRONT. THIS HAS RESULTED
IN TEMPERATURES RISING MAINLY INTO THE 40S WITH EVEN SOME 50S
OVER DELMARVA. IT WILL REMAIN RELATIVELY MILD THROUGH THE REST
OF THE DAYLIGHT HOURS UNDER A MIX OF SUN AND CLOUDS WITH SW
WINDS AROUND 10 MPH.
AS WE HEAD INTO THIS EVENING, THE AREA WILL BE NEAR THE TAIL
END OF A COLD FRONT AS LOW PRESSURE MOVING THROUGH EASTERN
CANADA PASSES BY FAR TO OUR NORTH. THIS WILL RESULT IN WINDS
GOING W/NW FOR A TIME BEFORE BECOMING VERY LIGHT TO EVEN CALM IN
SPOTS OVERNIGHT AS HIGH PRESSURE BUILDS IN RIGHT OVER THE AREA.
THIS WILL CREATE SOME CHALLENGES IN THE FORECAST. RADIATIONAL
COOLING CONDITIONS WILL BE GOOD WITH THIS SET UP AND SO
TEMPERATURES HAVE THE POTENTIAL TO FALL CLOSE TO DEW POINTS
RESULTING IN SOME FOG OR LOW STRATUS POTENTIALLY DEVELOPING.
THERE WILL ALSO BE ADDED LOW LEVEL MOISTURE FROM THE SNOW PACK.
MITIGATING FACTORS THOUGH ARE THAT SLIGHTLY DRIER AIR WILL BE
TRYING TO WORK IN FOR A TIME THIS EVENING BEHIND THE COLD FRONT
AND ALSO THAT THE WINDS NOT TOO FAR OFF THE GROUND SHOULD REMAIN
ELEVATED OVERNIGHT WHICH COULD CAUSE ENOUGH MIXING TO KEEP
WIDESPREAD FOG AT BAY. FOR THE TIME BEING, ADDED IN PATCHY FOG
FOR MOST OF THE AREA. EXPECT LOWS TONIGHT GENERALLY IN THE 20S
EXCEPT LOW 30S NEAR THE COAST.
FOR THURSDAY, HIGH PRESSURE MOVES EASTWARD OFF THE COAST AS A
LARGE AREA OF LOW PRESSURE ADVANCES EASTWARD INTO THE WESTERN
GREAT LAKES REGION. THIS WILL RESULT IN THE FLOW TURNING MORE
S/SE. IT WILL ONCE AGAIN BE A TRICKY FORECAST AS THERE'S THE
POTENTIAL FOR INCREASING LOW LEVEL MOISTURE TO REMAIN TRAPPED
BELOW AN INVERSION WHICH COULD KEEP THE AREA UNDER A DECK OF LOW
STRATUS. BEST CHANCE OF SEEING ANY SUN WILL BE IN THE MORNING
TO EARLY AFTERNOON BEFORE CLOUDS ASSOCIATED WITH THE SYSTEM TO
OUR WEST MOVE IN BY LATER IN THE DAY. IN TERMS OF TEMPERATURES,
THERE WILL BE A WARM FRONT BEGINNING TO MOVE BACK INTO THE AREA
FROM THE SOUTH SO THE WARMEST TEMPERATURES AND AREAS MOST
FAVORED TO SEE ANY SUN WILL BE OUR SOUTHERN MOST ZONES OVER
DELMARVA INTO ADJACENT FAR SOUTHERN NJ. THESE AREAS LOOK TO GET
INTO THE 50S. FARTHER NORTH, GENERALLY EXPECT DAYTIME HIGHS IN
THE 40S EXCEPT UPPER 30S OVER THE SOUTHERN POCONOS. ONE THING TO
NOTE THOUGH IS THAT THESE TEMPERATURES WILL CONTINUE TO WARM AT
NIGHT DUE TO STRENGTHENING WARM AIR ADVECTION. THE DAYTIME
SHOULD BE MAINLY FREE OF ANY PRECIPITATION EXCEPT BY LATE DAY
THERE COULD BE SOME SHOWERS DEVELOPING OVER PORTIONS OF NORTHERN
DELMARVA INTO EASTERN PA AND NEARBY LOCATIONS IN NJ NEAR THE PA
BORDER. POPS THOUGH ARE ONLY AROUND 20-30 PERCENT.
SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/
LOW PRESSURE MOVING THROUGH THE GREAT LAKES THURSDAY NIGHT WILL
LIFT INTO EASTERN CANADA ON FRIDAY. A DEEP H5 TROUGH WILL DIG
DOWN INTO THE TENNESSEE VALLEY AND THE MID-ATLANTIC, AND A
STRONG COLD FRONT WILL CROSS THE AREA ON FRIDAY. STRONG WARM AIR
ADVECTION DEVELOPS AHEAD OF THE COLD FRONT THURSDAY NIGHT
THROUGH FRIDAY MORNING, THEN STRONG COLD AIR ADVECTION DEVELOPS
BEHIND THE DEPARTING COLD FRONT. THIS RESULTS IN A NON-DIURNAL
TEMPERATURE CURVE IN WHICH TEMPERATURES WILL RISE THURSDAY
NIGHT, AND THEN TEMPERATURES FALL DURING THE DAY FRIDAY AS THE
COLD FRONT WORKS ITS WAY THROUGH THE REGION.
IN TERMS OF SENSIBLE WEATHER, THE TWO MAIN IMPACTS FROM THIS
SYSTEM ARE MODERATE TO HEAVY RAIN AND GUSTY TO POTENTIALLY
DAMAGING WINDS. THE SOUTHERLY PRESSURE GRADIENT TIGHTENS OVER
THE AREA BETWEEN HIGH PRESSURE OFFSHORE, LOW PRESSURE PASSING
NORTH OF THE AREA, AND HIGH PRESSURE BUILDING INTO THE CENTRAL
UNITED STATES. IN ADDITION, A 60 TO 70 KT LOW LEVEL JET WILL
MOVE ACROSS THE REGION LATE THURSDAY NIGHT THROUGH FRIDAY
MORNING. FOR THE MOST PART, CAN EXPECT SOUTH WINDS 15 TO 25 MPH
WITH 30 TO 40 MPH GUSTS LATE THURSDAY NIGHT THROUGH FRIDAY
MORNING, THOUGH GUSTS UP TO 50 MPH ARE LIKELY FOR THE SOUTHERN
POCONOS, THE LEHIGH VALLEY, THE DELAWARE VALLEY, MOST OF NEW
JERSEY AND COASTAL DELAWARE. THERE SHOULD BE A LULL IN THE WINDS
LATE FRIDAY MORNING, THEN WEST TO NORTHWEST WINDS RAMP UP
FRIDAY AFTERNOON AND EVENING ONCE AGAIN WITH 30 TO 40 MPH GUSTS
FOR MOST OF THE AREA, AND GUSTS UP TO 50 MPH FOR THOSE SAME
AREAS. WINDS THEN DIMINISH LATE FRIDAY NIGHT. A WIND ADVISORY IS
NOW IN EFFECT FOR THURSDAY NIGHT THROUGH FRIDAY NIGHT FOR MOST
OF THE AREA, THOUGH WILL NOTE A LULL IN THE STRONGEST WINDS. THE
OVERALL TREND IS SHOWING STRONGER WIND GUSTS, SO WILL FOLLOW
SUIT ACCORDINGLY.
RAIN DEVELOPS THURSDAY EVENING, AND THEN THE HEAVIEST RAIN
DEVELOPS LATE THURSDAY NIGHT THROUGH FRIDAY MORNING IN
ASSOCIATION WITH THE AFOREMENTIONED LOW LEVEL JET. THERE SHOULD
BE A LULL IN THE RAIN FRIDAY MORNING, BUT THEN THE COLD FRONT
PASSES THROUGH THE REGION LATE FRIDAY MORNING THROUGH FRIDAY
AFTERNOON. WHILE SURFACE BASED INSTABILITY WILL BE MINIMAL,
THERE WILL BE SOME 200 TO 300 J/KG OF ML MUCAPE AHEAD OF THE
FRONT AND 65 TO 75 KT 0-6 KM BULK SHEAR WITH THE PASSAGE OF THE
FRONT. THIS SHOULD BE ENOUGH TO PRODUCE A FEW ELEVATED
THUNDERSTORMS ACROSS THE REGION. WILL GO AHEAD AND ADD SLIGHT
CHANCE FOR THUNDERSTORMS TO THE FORECAST FRIDAY MORNING. A FEW
STRONGER STORMS COULD PRODUCE LOCALLY DAMAGING WIND GUSTS, BUT
CHANCES IN THIS HAPPENING ARE QUITE LOW, BUT NOT ZERO. A LINE OF
HEAVY RAIN SHOWERS WILL DEVELOP WITH THE PASSAGE OF THE COLD
FRONT. TEMPERATURES THEN CRASH AS STRONG COLD AIR ADVECTION
DEVELOPS.
LOW TEMPERATURES THURSDAY NIGHT WILL OCCUR THURSDAY EVENING,
AND WILL RANGE FROM THE LOW TO MID 40S, THOUGH PERHAPS A FEW
DEGREES COOLER IN THE SOUTHERN POCONOS AND A FEW DEGREES WARMER
IN SOUTHERN DELMARVA. HIGHS ON FRIDAY WILL OCCUR IN THE MORNING,
AND WILL GENERALLY BE IN THE LOW TO MID 50S NORTH AND WEST OF
THE FALL LINE AND IN THE UPPER 50S ACROSS SOUTHERN NEW JERSEY,
THE DELAWARE VALLEY, AND DELMARVA. TEMPERATURES WILL FALL INTO
THE UPPER 30S AND LOW 40S BY FRIDAY AFTERNOON. LOWS FRIDAY NIGHT
WILL BE IN THE 20S.
STORM TOTAL RAINFALL IS TRENDING UP FOR THE NORTHERN HALF OF
THE FORECAST AREA AND TRENDING DOWN FOR THE SOUTHERN HALF, AND
GENERALLY 1 TO AS MUCH AS 2 INCHES ACROSS THE SOUTHERN POCONOS,
NORTHERN NEW JERSEY, AND THE LEHIGH VALLEY AND 1/2 INCH TO 1
INCH ACROSS SOUTHERN NEW JERSEY, THE DELAWARE VALLEY, AND
DELMARVA. WIDESPREAD MAINSTEM FLOODING IS NOT A CONCERN, BUT
MINOR FLOODING AND URBAN AND POOR DRAINAGE FLOODING IS POSSIBLE
DUE TO THE HEAVY RAINFALL AND MELTING SNOW.
DRY AND COLDER ON SATURDAY WITH HIGHS IN THE UPPER 30S TO LOW
40S.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
ALTHOUGH SEVERAL FRONTAL BOUNDARIES WILL IMPACT THE AREA DURING
THE LONG TERM PERIOD, MOST OF THESE FRONTS WILL BE FAIRLY
BENIGN. HIGH PRESSURE MOVES OFFSHORE SATURDAY NIGHT AND THEN A
COLD FRONT PASSES THROUGH ON SUNDAY. NO SIGNIFICANT WEATHER WITH
ITS PASSAGE. WARMER AHEAD OF THE FRONT WITH HIGHS IN THE 40S,
THEN COLDER ON MONDAY WITH HIGHS IN THE 30S.
ANOTHER COLD FRONT PASSES THROUGH ON TUESDAY WITH A MIX OF RAIN
AND SNOW, WITH RAIN TO THE SOUTH AND SNOW TO THE NORTH AND A
MIX IN BETWEEN.
CONDITIONS DRY OUT ON WEDNESDAY. NEAR NORMAL TEMPERATURES
TUESDAY AND WEDNESDAY.
AVIATION /19Z WEDNESDAY THROUGH MONDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THIS AFTERNOON...VFR WITH AREAS OF MAINLY MID TO HIGH LEVEL
CLOUDS. SOUTHWEST WINDS AROUND 5-10 KNOTS WITH SOME GUSTS TO
AROUND 20 KNOTS POSSIBLE AT TIMES. FORECAST CONFIDENCE IS
OVERALL HIGH EXCEPT MODERATE REGARDING WIND GUSTS.
TONIGHT...VFR TO START THIS EVENING BUT THERE IS THE POTENTIAL
FOR SUB VFR CONDITIONS DEVELOPING BY LATER IN THE EVENING INTO
THE OVERNIGHT (AFTER 3Z) AS SOME PATCHY FOG AND/OR LOW STRATUS
MAY DEVELOP. FOR NOW, HAVE INDICATED TEMPO GROUPS FOR 3SM VSBY
AT THE MORE CLIMO FAVORED FOG SITES...RDG, ABE, TTN, MIV. WINDS
LIGHT (UNDER 5 KNOTS) AND VARIABLE BUT GENERALLY FAVORING A NW
DIRECTION UNTIL LATE AT NIGHT WHEN THEY SHOULD VEER TO NE. LOW
CONFIDENCE REGARDING CIGS/VISBYS WITH MODERATE CONFIDENCE IN THE
WIND FORECAST.
THURSDAY...POTENTIAL FOR SUB VFR CONDITIONS TO LINGER INTO THE
MORNING AND THEN IF THEY DO IMPROVE, CONDITIONS GO BACK DOWNHILL
LATER IN THE DAY AS LOW STRATUS ASSOCIATED WITH THE NEXT SYSTEM
MOVES INTO THE AREA. SE/S WINDS AROUND 5-10 KNOTS.
OUTLOOK...
THURSDAY NIGHT...IFR IN RA AND LOW CLOUDS. S WINDS 15 TO 25 KT
WITH 35 TO 45 KT. POTENTIAL FOR LLWS DESPITE THE STRONG SURFACE
WINDS DUE TO A 60+ KT LOW LEVEL JET.
FRIDAY...IFR IN THE MORNING IN RA. AN ISOLATED TSRA POSSIBLE
AROUND MIDDAY. VFR IN THE AFTERNOON. S-SW WINDS 15 TO 25 KT WITH
35 TO 45 KT GUSTS, TURNING W-NW IN THE AFTERNOON.
FRIDAY NIGHT...VFR. W-NW WINDS 15 TO 20 KT WITH GUSTS UP TO 30
KT, DIMINISHING TO 5 TO 10 KT LATE.
SATURDAY THROUGH SUNDAY...VFR. NSW.
MONDAY...VFR. NSW.
MARINE
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR ALL WATERS UNTIL 7
PM THIS EVENING. AFTER THIS TIME, THE WINDS AND SEAS LOOK TO
REMAIN AT SUB SCA LEVELS THROUGH THURSDAY. SEAS 4 TO 5 FEET THIS
AFTERNOON DIMINISHING TO 2-3 FEET THIS EVENING AND THEN
INCREASING TO 3-4 FEET THURSDAY.
OUTLOOK...
THURSDAY NIGHT...GALE WARNING NOW IN EFFECT. S-SW WINDS 20 TO
30 KT WITH 35 TO 45 KT GUSTS. SEAS BUILDING TO 6 TO 9 FEET. VSBY
RESTRICTIONS IN RAIN AND FOG.
FRIDAY...GALE WARNING NOW IN EFFECT. S-SW WINDS 20 TO 30 KT
WITH 35 TO 45 KT GUSTS IN THE MORNING, THEN WINDS DIMINISH A BIT
AROUND MIDDAY, THEN TURN W-NW AND INCREASE TO 20 TO 30 KT WITH
35 TO 40 KT GUSTS IN THE AFTERNOON BEHIND A DEPARTING COLD
FRONT. VSBY RESTRICTIONS IN RAIN AND FOG IN THE MORNING. A
ISOLATED THUNDERSTORM IS POSSIBLE IN THE LATE MORNING/EARLY
AFTERNOON WITH THE PASSAGE OF THE COLD FRONT.
FRIDAY NIGHT...GALE FORCE WINDS IN THE EVENING, DIMINISHING
AFTER MIDNIGHT. SCA CONDITIONS FOR THE REST OF THE NIGHT.
SATURDAY...SUB-SCA CONDITIONS.
SATURDAY NIGHT THROUGH SUNDAY NIGHT...SCA CONDITIONS EXPECTED
WITH WIND GUSTS TO 30 KT AND SEAS 4 TO 7 FEET.
MONDAY...LINGERING SCA CONDITIONS POSSIBLE.
PHI WATCHES/WARNINGS/ADVISORIES
PA...WIND ADVISORY FROM 1 AM FRIDAY TO 1 AM EST SATURDAY FOR PAZ054-
055-060>062-070-071-101>106.
NJ...WIND ADVISORY FROM 1 AM FRIDAY TO 1 AM EST SATURDAY FOR NJZ001-
007>010-012>027.
DE...WIND ADVISORY FROM 1 AM FRIDAY TO 1 AM EST SATURDAY FOR DEZ001-
004.
MD...NONE.
MARINE...GALE WARNING FROM 6 PM THURSDAY TO 10 PM EST FRIDAY FOR ANZ430-
431.
SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR
ANZ450>455.
GALE WARNING FROM 6 PM THURSDAY TO 1 AM EST SATURDAY FOR
ANZ450>455.
SYNOPSIS...MPS
NEAR TERM...FITZSIMMONS
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...FITZSIMMONS/MPS
MARINE...FITZSIMMONS/MPS
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