965
FXUS61 KPHI 182316
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
616 PM EST THU DEC 18 2025
SYNOPSIS
A FRONTAL SYSTEM WILL BRING UNSETTLE WEATHER TONIGHT THROUGH FRIDAY,
FOLLOWED BY VERY WINDY CONDITIONS FRIDAY THROUGH FRIDAY NIGHT AS LOW
PRESSURE STRENGTHENS TO OUR NORTH. HIGH PRESSURE WILL MOVE OFFSHORE
OF THE VIRGINIA AND NORTH CAROLINA COASTS SATURDAY INTO SATURDAY
NIGHT. A COUPLE OF DRY COLD FRONTS ARE EXPECTED TO MOVE ACROSS THE
AREA SUNDAY AND EARLY MONDAY, FOLLOWED BRIEFLY BY HIGH PRESSURE
LATER MONDAY. A WARM FRONT AND SUBSEQUENT COLD FRONT IS THEN
FORECAST TO MOVE ACROSS THE AREA AROUND TUESDAY, FOLLOWED BRIEFLY BY
HIGH PRESSURE WEDNESDAY INTO THURSDAY.
NEAR TERM /THROUGH FRIDAY NIGHT/
OVERALL, THE FORECAST REMAINS LARGELY ON TRACK WITH THE MOST
SIGNIFICANT CHANGE BEING A SLIGHT INCREASE IN THE AMOUNT OF
RAINFALL EXPECTED, AND A SLIGHT SLOW DOWN IN THE TIMING OF THE
SYSTEM. A LOW PRESSURE SYSTEM WILL BRING RAIN AND STRONG WINDS
TO THE AREA BEGINNING TONIGHT AND CONTINUING INTO FRIDAY.
DRY CONDITIONS ARE EXPECTED THROUGH THIS EVENING BUT WITH CLOUD
COVERAGE CONTINUING TO INCREASE WITH THE APPROACHING SYSTEM. A
WARM FRONT THEN LIFTS THROUGH THE AREA TONIGHT WITH A STRONG
COLD FRONT NOT FAR OFF. THIS WILL RESULT IN RAIN OVERSPREADING
THE AREA OVERNIGHT, WITH POCKETS OF HEAVY RAIN AND PERHAPS A FEW
ELEVATED THUNDERSTORMS MIXED IN. IN TERMS OF TIMING, THE
WIDESPREAD RAIN MOVES INTO THE LEHIGH VALLEY AND POCONOS BY
11 PM-12 AM, GRADUALLY MOVING EAST. RAIN WILL CONTINUE THROUGH
THE MORNING COMMUTE, BUT SHOULD MOVE OUT QUICKLY AS WE GET INTO
THE MIDDAY HOURS ON FRIDAY. MOST OF THE AREA WILL END UP WITH
AROUND 0.75 TO 1.25 INCHES OF RAIN, WITH THE HIGHEST AMOUNTS
IN THE POCONOS, WHERE UPWARDS OF 2-2.25" OF RAINFALL ARE
EXPECTED. EVEN WITH A DECENT SNOWPACK IN PLACE, FLOODING IMPACTS
ARE ANTICIPATED TO BE LIMITED AND MAINLY JUST IN URBAN AND POOR
DRAINAGE AREAS. ENSEMBLE RIVER FORECASTS STILL SHOW LESS THAN A
10% CHANCE OF ANY FORECAST POINT REACHING ACTION STAGE. WITH
SUCH A ROBUST WIND FIELD ALOFT AND 50-70 KT LOW LEVEL JET MOVING
THROUGH, A FEW DAMAGING WIND GUSTS CANNOT BE RULED OUT IN
HEAVIER DOWNPOURS. AS SOME OF THE CAMS GET IN RANGE, THERE IS
SOME SIGNAL OF A LOW-TOPPED CONVECTIVE LINE FORMING AND MOVING
THROUGH ALONG THE FRONT. THIS WOULD BE THE FEATURE TO WATCH FOR
ANY DAMAGING WIND GUSTS, WITH THAT LINE LIKELY MOVING THROUGH
BETWEEN 7 AND 10 AM. HOWEVER, INSTABILITY IS VERY LIMITED,
ESPECIALLY SURFACE-BASED INSTABILITY. AS A RESULT, THINKING THE
SEVERE RISK IS LOW ALBEIT NOT ZERO. SPC HAS A GENERAL THUNDER
RISK OVER OUR AREA, WHICH IS ABOUT RIGHT FOR THIS SETUP.
OVERALL, THIS SHOULD BE A BENEFICIAL SOAKING RAIN, THOUGH THERE
LIKELY WILL BE SOME SLOWDOWNS WITH THE MORNING COMMUTE AS THE
HEAVIEST RAIN SHOULD BE MOVING THROUGH THE I-95 CORRIDOR BETWEEN
5 AND 9 AM.
THE MORE NOTICEABLE IMPACT WITH THIS SYSTEM WILL BE THE WINDS.
THROUGH THE EARLY EVENING, WINDS SHOULD BE RATHER LIGHT OUT OF
THE SOUTH, THOUGH A FEW GUSTS AROUND 20 MPH ARE POSSIBLE AT THE
COAST. THINGS BEGIN TO INCREASE AFTER MIDNIGHT AS A BRISK LOW-
LEVEL JET MOVES OVERHEAD. 18Z NAM HAS 50-70 KT AT 925 MB (2000-
2500 FEET) FROM ABOUT 1 AM UNTIL THE FRONTAL PASSAGE AROUND 10
AM-12 PM. NOW, CONSISTENT 50+ KT WINDS WON'T MAKE IT TO THE
SURFACE OVERNIGHT GIVEN A STRONG LOW-LEVEL INVERSION IN THE
WARM- AIR ADVECTION REGIME, BUT WINDS UPWARD OF 30-40 MPH OUT OF
THE SOUTH-SOUTHWEST ARE EXPECTED AHEAD OF THE FRONT, WITH GUSTS
UP TO 45 MPH. THE FRONT COMES THROUGH IN THE LATE MORNING AND
THERE SHOULD BE A LULL IN GUSTY WINDS, BEFORE POST- FRONTAL
WINDS INCREASE. ONCE THE FRONT COMES THROUGH, DEEP LAYER
BOUNDARY MIXING WILL SET UP WITH MODEST COLD-AIR ADVECTION
ALOFT. THIS WILL RESULT IN ANOTHER PERIOD OF GUSTY AND PERHAPS
STRONGER WINDS, WITH GUSTS GENERALLY 35-45 MPH OUT OF THE WEST-
NORTHWEST, BUT UP TO 50 MPH POSSIBLE. WINDS THEN BEGIN TO
DIMINISH LATE FRIDAY EVENING AS DIURNAL MIXING DECREASES THOUGH
GUSTS OF 20-30 MPH WILL REMAIN POSSIBLE THROUGH THE OVERNIGHT
WITH A TIGHT PRESSURE GRADIENT REMAINING IN PLACE. OVERALL,
THERE WERE NO CHANGES FOR THE WIND ADVISORY, WHICH IS STILL IN
EFFECT FOR ALL OF NEW JERSEY, ALL OF EASTERN PA, AND NORTHERN
DELAWARE BEGINNING AT 1 AM FRIDAY.
TEMPERATURES TONIGHT ACTUALLY SHOULD INCREASE AND GET INTO THE
50S REGIONWIDE (WITH LOW 60S IN SPOTS) BEFORE THE FRONT COMES
THROUGH FRIDAY MORNING. ONCE THE FRONT COMES THROUGH,
TEMPERATURES SHOULD DROP PRETTY QUICKLY THROUGH THE DAYTIME
HOURS - DOWN INTO THE UPPER 30S/LOW 40S. TEMPERATURES WILL
CONTINUE TO FALL FRIDAY EVENING INTO FRIDAY NIGHT, INTO THE 30S
EVERYWHERE BEFORE BOTTOMING OUT WITH LOWS IN THE MID 20S FOR
MOST LOCATIONS FRIDAY NIGHT.
SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/
THE PRESSURE GRADIENT WITH LOW PRESSURE TO OUR NORTH AND HIGH
BUILDING TO OUR SOUTH WILL WEAKEN EVEN MORE INTO SATURDAY, SO
WINDS WILL DIMINISH. THIS HIGH WILL BUILD OFFSHORE TO OUR SOUTH
OVERNIGHT SATURDAY AHEAD OF A COUPLE OF APPROACHING COLD FRONT,
SETTING UP RETURN FLOW ACROSS THE AREA THROUGH SATURDAY NIGHT.
LONG TERM /SUNDAY THROUGH THURSDAY/
ON SUNDAY, A COLD FRONT WILL MOVE ACROSS THE AREA, FOLLOWED BY
ANOTHER COLD FRONT EARLY MONDAY, THESE FRONTAL SYSTEMS ARE EXPECTED
TO BE DRY. HOWEVER, TEMPERATURES WILL BELOW NORMAL DROP SUNDAY NIGHT
INTO MONDAY AFTER BEING ABOVE NORMAL SUNDAY.
HIGH PRESSURE BRIEFLY BUILDS INTO THE AREA MONDAY NIGHT, BEFORE
SHIFTING OFFSHORE EARLY TUESDAY AHEAD OF AN APPROACHING WARM FRONT
AND COLD FRONT. THE WARM FRONT WILL MOVE ACROSS THE AREA EARLY
TUESDAY, FOLLOWED BY THE COLD FRONT LATER IN THE DAY TUESDAY. IF THE
PRECIPITATION BEGINS EARLY ENOUGH TUESDAY, IT MAY BEGIN AS SNOW FOR
MOST PLACES, BEFORE CHANGING TO RAIN, OR A RAIN/SNOW MIX LATER IN
THE MORNING INTO THE AFTERNOON. PRECIPITATION AMOUNTS WILL BE LIGHT
DURING THIS PERIOD.
HIGH PRESSURE IS EXPECTED TO BRIEFLY AFFECT THE AREA WEDNESDAY INTO
THURSDAY, BEFORE POSSIBLE UNSETTLED WEATHER LATER IN THE WEEK.
AVIATION /00Z FRIDAY THROUGH TUESDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
TONIGHT...CONDITIONS DROPPING TO MVFR AND THEN IFR AS THE NIGHT
GOES ON AS RAIN, SOME OF WHICH COULD BE HEAVY AT TIMES,
OVERSPREADS THE AREA. SOUTHERLY WINDS INCREASING TO AROUND 10-20
KT WITH GUSTS GETTING NEAR 30 KT BY DAYBREAK. HAVE ADDED
PERIODS OF LOW-LEVEL WIND SHEAR AS A BRISK LOW-LEVEL JET MOVES
OVERHEAD, POTENTIALLY UPWARDS OF 50-60 KT AT FL020. LOW
CONFIDENCE IN TIMING OF RESTRICTIONS, MODERATE CONFIDENCE IN
EXTENT RESTRICTIONS, AND HIGH CONFIDENCE IN A PERIOD OF LLWS
OVERNIGHT.
FRIDAY...IFR TO START, POTENTIALLY EVEN AS LOW AS LIFR, THOUGH
CONFIDENCE WAS NOT HIGH ENOUGH TO GO THAT LOW IN THE TAFS. A
FRONT PASSES THROUGH BETWEEN 11Z-14Z, WITH WINDS QUICKLY
CHANGING DIRECTION FROM SOUTH-SOUTHWEST TO WEST-NORTHWEST. A
SQUALL LINE MOVING ALONG THE FRONT COULD BRING A BRIEF PERIOD OF
TSRA. WINDS START OUT SSW AROUND 15-20 KT WITH GUSTS 30-35 KT,
BECOMING WNW. BRIEF LULL IN WINDS AS FRONT PASSES, BUT BEHIND
THE FRONT, WINDS OUT OF THE WNW WILL BE AROUND 15-25 KT WITH
GUSTS 30-40 KT. ONCE FRONT PASSES, CONDITIONS SHOULD LIFT
QUICKLY BACK TO VFR AROUND 15Z-17Z. MODERATE CONFIDENCE IN
TIMING OF WIND SHIFTS, LOW CONFIDENCE IN EXTENT AND TIMING OF
RESTRICTIONS AND WHEN CONDITIONS IMPROVE.
OUTLOOK...
FRIDAY NIGHT...VFR CONDITIONS EXPECTED. GUSTY WEST WINDS
25-30 KNOTS EARLY.
SATURDAY-SATURDAY NIGHT...VFR CONDITIONS. SOUTHWEST WINDS 5-10
KNOTS.
SUNDAY-SUNDAY NIGHT...VFR CONDITIONS. WEST WINDS 5-15 KNOTS WITH
GUSTS 20-25 KNOTS.
MONDAY-MONDAY NIGHT...VFR CONDITIONS. NORTHWEST WINDS 5-10 KNOTS
DURING THE DAY, BECOMING LIGHT OVERNIGHT.
TUESDAY...SUB-VFR CONDITIONS POSSIBLE, WITH RAIN OR SNOW ALSO
POSSIBLE.
MARINE
NO MARINE HEADLINES IN PLACE THROUGH THIS EVENING. WINDS OUT OF
THE SOUTHEAST AROUND 10-15 KT AND SEAS 2 TO 4 FEET.
FOR TONIGHT, A GALE WARNING IS IN PLACE FOR ALL MARINE ZONES. WINDS
OVERNIGHT WILL BE OUT OF THE SOUTH/SOUTHEAST WITH GUSTS 30-40
KT AND SEAS 6 TO 10 FEET.
FOR FRIDAY, THE GALE WARNING REMAINS IN PLACE FOR ALL MARINE ZONES.
A COLD FRONT WILL COME THROUGH, RESULTING IN A PERIOD OF SUB-GALE
WINDS, BUT WINDS WILL PICK OUT OF THE WEST-NORTHWEST IN THE
WAKE OF THE COLD FRONT, WITH ANOTHER PERIOD OF 30-40 KT GUSTS
EXPECTED. SEAS 8 TO 13 FEET.
OUTLOOK...
FRIDAY NIGHT...GALE WARNING REMAINS IN EFFECT INTO EARLY FRIDAY
NIGHT, THEN CONDITIONS LOWER TO SMALL CRAFT ADVISORY LEVELS.
SATURDAY-MONDAY...SMALL CRAFT ADVISORY CONDITIONS REMAIN IN EFFECT.
MONDAY NIGHT..CONDITIONS LOWER BELOW ADVISORY LEVELS.
TUESDAY...CONDITIONS EXPECTED TO RETURN TO SMALL CRAFT ADVISORY
LEVELS.
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 UNTIL 1 AM EST SATURDAY FOR ANZ430-431-450>455.
SYNOPSIS...ROBERTSON
NEAR TERM...AKL/HOEFLICH
SHORT TERM...ROBERTSON
LONG TERM...ROBERTSON
AVIATION...AKL/MJL/ROBERTSON
MARINE...AKL/ROBERTSON
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