820
FXUS61 KPHI 201156
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
656 AM EST WED NOV 20 2024
SYNOPSIS
A WARM FRONT WILL PROGRESS NORTH ACROSS PARTS OF THE REGION
TODAY. LOW PRESSURE AND AN ASSOCIATED STRONG COLD FRONT MOVES
INTO OUR REGION TONIGHT AND THURSDAY WITH SOME MUCH NEEDED
RAIN AND, IN THE HIGHER TERRAIN, SNOW. LOW PRESSURE THEN
LINGERS ACROSS THE NORTHEAST INTO THE WEEKEND WITH MUCH COLDER
AIR BEFORE MOVING INTO THE CANADIAN MARITIMES BY THE END OF THE
WEEKEND. HIGH PRESSURE THEN ARRIVES FOR LATER SUNDAY AND
ESPECIALLY MONDAY, FOLLOWED BY A COLD FRONT ON TUESDAY.
NEAR TERM /THROUGH THURSDAY/
OVERALL, THE NEAR TERM FORECAST REMAINS ON TRACK. HEADING INTO
THE DAYTIME HOURS, THE WARM FRONT LOOKS REMAIN HUNG UP ACROSS
THE DELMARVA. AS A RESULT, MUCH OF THE DAY IS EXPECTED TO BE
DRY, WITH HIGHS MAINLY IN THE UPPER 50S TO LOW 60S. WEAK LOW
PRESSURE WILL FORM ON THE FRONT ACROSS THE PANHANDLE OF WEST
VIRGINIA, AND AS A RESULT, THE WARM FRONT WILL BEGIN TO BECOME
OCCLUDED AS THE LOW APPROACHES FROM THE WEST. THE SYSTEM WILL
THEN BEGIN TO MAKE MORE SIGNIFICANT PROGRESS TOWARDS OUR REGION
BRINGING MUCH NEEDED, WIDESPREAD, STRATIFORM RAIN TO OUR AREA,
ARRIVING LATE THIS AFTERNOON INTO THE EVENING HOURS.
AS THE INITIAL LOW BEGINS TO LIFT NORTH OF OUR REGION, A NEW
SURFACE LOW LOOKS TO DEVELOP AT THE TRIPLE POINT OF THE
OCCLUDED, WARM, AND TRAILING COLD FRONTS, MORE OR LESS RIGHT
OVER OUR REGION. AS A RESULT, AREAS OF RAINFALL ACROSS DELMARVA
AND SOUTHERN NEW JERSEY MAY BECOME A BIT MORE CONVECTIVE IN
NATURE IN THE DEVELOPING WARM SECTOR AND A RUMBLE OF THUNDER
CAN'T BE COMPLETELY RULED OUT. AREAS FURTHER NORTH LOOK TO
REMAIN WITHIN THE STRATIFORM REGION OF THE SYSTEM ON THE NORTH
AND WEST SIDES OF THE DEVELOPING LOW. THE DEVELOPMENT OF THIS
LOW AND PASSAGE OF THE ASSOCIATED FRONTS AT THE SURFACE WILL
RESULT IN A RAPID WIND SHIFT OCCURING ACROSS THE REGION, FROM
SOUTHEAST OUT AHEAD TO NORTHWEST BEHIND, WITH WINDS BECOMING
GUSTY TO AROUND 20-30 MPH AS THE PRESSURE GRADIENT TIGHTENS AS A
RESULT OF THE DEVELOPING LOW. OVERALL, RAINFALL AMOUNTS REMAIN
LARGELY UNCHANGED WITH 0.5 INCHES TO 1 INCH EXPECTED ACROSS THE
AREA WEDNESDAY NIGHT.
HEADING INTO THURSDAY, THE LOW CONTINUES TO MEANDER NEAR OUR
AREA, THOUGH IS PIVOTING TO THE NORTH AND POTENTIALLY NORTHWEST
AS IT MOVES CYCLONICALLY AROUND A CLOSED UPPER LEVEL LOW. AS A
RESULT, CONTINUED RAINFALL IS FORECAST ACROSS MUCH OF THE
NORTHERN HALF OF THE REGION, PARTICULARLY NORTH OF THE I-78
CORRIDOR. AN ADDITIONAL 0.25-0.75 INCHES OF RAINFALL IS FORECAST
FOR THIS AREA. DRIER AIR WILL BEGIN TO MOVE IN FOR AREAS
FURTHER SOUTH SO THOSE AREAS WILL LIKELY HAVE TO BE CONTENT WITH
WHAT THEY RECEIVE TONIGHT, UNFORTUNATELY. COLD AIR ADVECTION
WILL ALSO BE RAMPING UP ACROSS THE REGION, AS GUSTY WEST-
NORTHWEST WINDS CONTINUE. HIGHS ARE FORECAST TO BE ONLY IN THE
UPPER 40S TO LOW 50S. BY LATER IN THE AFTERNOON, TEMPERATURES AT
THE HIGHEST ELEVATIONS IN THE SOUTHERN POCONOS LOOK TO BECOME
COOL ENOUGH FOR ONGOING TO PRECIPITATION TO CROSSOVER FROM RAIN
TO A RAIN/SNOW MIX, AND EVENTUALLY SNOW.
SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/
STRONG LOW PRESSURE WILL BE LOCATED NEAR NEW YORK CITY THURSDAY
EVENING, WITH STRONG AND GUSTY NORTHWEST WINDS FUNNELING COOLER
AIR SOUTHEASTWARD ACROSS THE REGION. THE UPPER LOW WILL REMAIN
TO OUR WEST IN THE UPPER OHIO VALLEY, AND AS THAT FEATURE HEADS
EAST, THE SURFACE LOW WILL ACTUALLY RETROGRADE SLIGHTLY, WITH IT
BECOMING "CAPTURED" OVER OUR NORTHERN AREAS EARLY FRIDAY.
STRONG FORCING OVER OUR NORTHERN ZONES RELATIVELY CLOSE TO THE
SURFACE LOW AND NORTHEAST OF THE UPPER LOW WILL RESULT IN
CONTINUED PRECIPITATION THROUGH THE NIGHT, WITH PRECIPITATION
TAPERING OFF FURTHER SOUTH AND MOSTLY DRY CONDITIONS IN THE
DELMARVA. WITH THE COLD ADVECTION AT THE SURFACE AND ALOFT, ODDS
FAVOR A TRANSITION TO HEAVY WET SNOW ACROSS THE HIGHER TERRAIN,
ESPECIALLY ABOVE 1500 FEET ON THE POCONO PLATEAU AND POSSIBLY A
FEW HIGHER RIDGES ELSEWHERE IN EASTERN PA AND NORTHERN NJ. WITH
THE BEST ODDS OF HEAVY WET SNOW BEING ACROSS THE POCONOS, HAVE
ISSUED THE FIRST WINTER STORM WATCH OF THE SEASON FOR CARBON AND
MONROE COUNTIES, SPECIFICALLY FOR AT AND ABOVE 1500 FEET. LOWER
ELEVATIONS MAY SEE FAR LESS SNOWFALL, IN FACT THE LOWEST
VALLEYS EVEN UP THERE MAY FAIL TO GET AN ENTIRE INCH OF
ACCUMULATION WITH THIS ELEVATION-DEPENDENT SYSTEM. AS THIS WILL
BE A HEAVY WET SNOW WITH SIGNIFICANT WIND IN THE 20-30 MPH
RANGE, A BIG POTENTIAL IS DOWNED TREES AND POWER LINES. TRAVEL
THURSDAY NIGHT IN PARTICULAR IS DISCOURAGED.
THERE ARE A FEW SIMULATIONS WHICH IMPLY SNOW COULD REACH
SIGNIFICANTLY FURTHER SOUTH ACROSS OUR REGION, EVEN DOWN TO THE
I-95 CORRIDOR AND PHILLY METRO, PARTICULARLY THE CANADIAN
MODELS. FOR THE MOMENT WE'VE MOSTLY DISCOUNTED THAT GUIDANCE AS
BEING OUTLIERS, BUT WILL BE KEEPING IT IN MIND AS WE WATCH
FURTHER PROGRESS WITH THIS SYSTEM. HAVE ALLOWED FOR SOME MIXING
ACROSS AREAS JUST NORTH AND WEST OF THE I-95 CORRIDOR THURSDAY
NIGHT INTO EARLY FRIDAY, BUT LITTLE TO NO ACCUMULATION IS
CURRENTLY EXPECTED OUTSIDE THE POCONOS. EITHER WAY, BRISK AND
COLD WILL BE THE THEM FOR THURSDAY NIGHT, WITH LOWS IN THE 30S
FOR MOST, UPPER 20S PERHAPS IN THE HIGHER TERRAIN OF THE
POCONOS.
FOR THE BULK OF FRIDAY, THE SURFACE LOW WILL REMAIN CAPTURED
UNDER THE UPPER LOW OVER OUR REGION, RESULTING IN CONTINUED
SHOWERS. ENOUGH INSOLATION LIKELY DEVELOPS TO ALLOW A TRANSITION
FROM A RAIN/SNOW MIX TO JUST PLAIN RAIN AT THE LOWER ELEVATIONS,
WITH SIGNIFICANTLY LESS ACCUMULATION IN THE HIGHER TERRAIN AS
WELL, WITH PRECIPITATION STARTING TO TAPER OFF TOWARDS THE END
OF THE DAY AS WE START TO SEE SOME MOVEMENT EASTWARD AND THE
SURFACE LOW BEGINS TO SLOWLY FILL. REGARDLESS, A CHILLY, RAW
DAY WILL BE HAD BY MOST WITH TEMPS GENERALLY NO HIGHER THAN THE
40S REGION-WIDE, WITH TEMPS NOT STRAYING FAR FROM FREEZING IN
THE POCONOS.
PRECIP SHOULD MOSTLY END DURING THE EVENING FRIDAY AS THE
SURFACE AND UPPER LOWS BEGIN MOVING FURTHER EAST, BUT THE BRISK
CONDITIONS CONTINUE. LOWS IN THE 30S FOR MOST, UPPER 20S
POCONOS.
LONG TERM /SATURDAY THROUGH TUESDAY/
THE PATTERN QUIETS DOWN THROUGH THE LONG TERM. AS THE STORM
PULLS FURTHER AWAY TO OUR NORTHEAST ON SATURDAY, A GUSTY
NORTHWEST WIND WILL CONTINUE AND CLOUDS WILL LINGER, WITH SOME
SPOTTY SHOWERS IN THE POCONOS, BUT OVERALL, SIGNIFICANTLY
IMPROVED COMPARED TO FRIDAY. HIGHS MOSTLY IN THE LOWER 50S, A
SIGNIFICANT REBOUND. CLOUDS AND WIND LIKELY CONSPIRE TO KEEP
TEMPS FROM DROPPING TOO MUCH SATURDAY NIGHT, WITH LOWS MOSTLY
30S AGAIN.
WINDS GRADUALLY RELAX A BIT MORE ON SUNDAY WITH MORE SUNSHINE AS
HIGH PRESSURE BUILDS TO OUR SOUTHWEST. THE WARMING TREND WILL
CONTINUE WITH MID 50S BECOMING MORE LIKELY FOR MUCH OF THE AREA.
SOUTHWESTERLY WINDS PICK UP A BIT AHEAD OF AN APPROACHING FRONT
FOR MONDAY, WHICH WILL HELP BRING A BIT MORE WARMER AIR INTO THE
REGION, ELEVATING HIGHS IN SOUTHERN AREAS INTO THE 60S, WITH
MID-UPPER 50S FURTHER NORTH.
THAT FRONT SLIDES INTO THE REGION BY TUESDAY, WHICH WILL START
TO INCREASE THE CHANCE OF SHOWERS WHILE ALSO STARTING TO NUDGE
TEMPS BACK DOWN IN THE NORTH. SOUTH OF THE FRONT, ACROSS
SOUTHERN AREAS, MID 60S STILL LOOK LIKELY.
AVIATION /12Z WEDNESDAY THROUGH SUNDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TODAY...MAINLY VFR WITH SOME BRIEF MVFR CIGS POSSIBLE,
PARTICULARLY PRIOR TO 16-18Z. A BRIEF BREAK IN PRECIPITATION
CHANCES IS EXPECTED WITH SMALL CHANCES DEVELOPING ONCE AGAIN
LATE IN THE DAY AFTER 22Z. WINDS OUT OF THE SOUTHEAST AROUND 5
KNOTS. MODERATE CONFIDENCE.
TONIGHT...MAINLY MVFR WITH A PERIOD OF IFR CONDITIONS WITH
RAIN, MOST LIKELY AFTER 03Z. A PERIOD OF WIND GUSTS UP TO 30
KNOTS AND AN ABRUPT WIND SHIFT FROM SOUTHEAST TO NORTHWEST, MOST
LIKELY BETWEEN 05-08Z. DIRECTIONAL LLWS POSSIBLE WITH RAPID WIND
SHIFT. MODERATE CONFIDENCE OVERALL, LOW CONFIDENCE ON TIMING OF
CATEGORY/WIND CHANGES.
THURSDAY...CONDITIONS IMPROVING TO MVFR AND POTENTIALLY VFR,
PARTICULARLY FOR THE MORE SOUTHERN TERMINALS. SOME LINGERING
SHOWERS CONTINUE, PARTICULARLY NEAR AND NORTH OF KTTN AND KABE,
WITH SOME SNOW POSSIBLE NORTHWEST OF KABE, PARTICULARLY LATER IN
THE DAY. GUSTY WEST- NORTHWEST WINDS CONTINUE THURSDAY.
OUTLOOK...
SUB-VFR, WITH POTENTIAL IFR, THURSDAY NIGHT AND FRIDAY WITH
WIDESPREAD SHOWERS, WHICH MAY MIX WITH SNOW AT KRDG AND KABE. NO
ACCUMULATIONS CURRENTLY EXPECTED AT THE TERMINALS. WINDS WILL
ALSO BE GUSTY FROM THE NORTHWEST. IMPROVEMENT TO MOSTLY VFR
SATURDAY BUT STILL WITH A GUSTY NORTHWEST WIND. LIGHTER WINDS
AND SOLIDLY VFR BY SUNDAY.
MARINE
SUB-SCA CONDITIONS EXPECTED THROUGH THIS EVENING. WINDS MAINLY
OUT OF THE SOUTHEAST, INCREASING TO AROUND 10 KNOTS WITH GUSTS
UP TO 20 KNOTS BY LATE THIS AFTERNOON. SEAS OF 1 TO 3 FEET.
TONIGHT, WINDS AND SEAS CONTINUE TO INCREASE. FOR ATLANTIC
COASTAL WATERS SOUTH OF GREAT EGG INLET AND ALONG THE DELAWARE
BAY, WINDS ARE EXPECTED TO BE 20-30 KNOTS WITH GUSTS UP TO 35
KNOTS. A GALE WARNING IS IN EFFECT BEGINNING AT 11 PM FOR THESE
AREAS AS A RESULT. NORTH OF GREAT EGG INLET, WINDS ARE EXPECTED
TO BE 20-25 KNOTS WITH GUSTS UP TO 20 KNOTS, THOUGH A FEW GALE
FORCE GUSTS ARE POSSIBLE. A SMALL CRAFT ADVISORY IS IN EFFECT
FOR THIS AREA AS A RESULT BEGINNING AT 11 PM AS WELL. SEAS OF
4-6 FEET. AN ABRUPT WIND SHIFT IS ALSO EXPECTED LATE IN THE
OVERNIGHT HOURS ACROSS ALL COASTAL WATERS WITH THE PASSAGE OF A
COLD FRONT.
FOR THURSDAY, WINDS ARE EXPECTED TO DECREASE SLIGHTLY AND
MAINLY BE BELOW GALE FORCE. HOWEVER, SMALL CRAFT ADVISORY
CONDITIONS ARE EXPECTED TO CONTINUE ACROSS ALL COASTAL WATERS AS
WINDS AND SEAS REMAIN ELEVATED.
OUTLOOK...
POTENT LOW PRESSURE WILL CERTAINLY RESULT IN HIGH END SMALL
CRAFT ADVISORY CONDITIONS AND IN FACT MAY RESULT IN LOW-END
GALES THURSDAY NIGHT THROUGH FRIDAY NIGHT. FOR THE TIME BEING
HAVE HELD OFF ON ANY GALE WATCHES/WARNINGS AS THE FIRST PUSH OF
GALE WINDS IS EXPECTED TONIGHT AND EARLY THURSDAY, BUT THIS MAY
BE REVISED IN FUTURE UPDATES. CONDITIONS SHOULD SUBSIDE TO SCA
LEVELS FOR SATURDAY AND START DROPPING BELOW SCA LEVELS ON
SUNDAY.
HYDROLOGY
SIGNIFICANT RAINFALL IS FORECAST ACROSS THE REGION FOR THE FIRST
TIME IN MONTHS, WITH WIDESPREAD TOTALS IN EXCESS OF 2 INCHES
EXPECTED ACROSS NORTHERN PARTS OF THE FORECAST AREA. WITH THE
GROUND RELATIVELY DRY AND HARD, WE COULD END UP WITH SOME MINOR
FLOODING ISSUES DUE TO EXCESSIVE RUNOFF, DESPITE HOW LOW WATER
LEVELS ARE PRESENTLY. THESE WOULD MAINLY BE FOR THE FLASHIER
SMALL STREAMS. IN ADDITION, ACCUMULATION OF LEAVES AROUND STORM
DRAINS MAY RESULT IN LOCALIZED ROADWAY ISSUES. THAT ALL HAVING
BEEN SAID, GIVEN THE EXCESSIVE DRYNESS ACROSS THE REGION
PRESENTLY, THERE ARE NO PLANS FOR A FLOOD WATCH AT THIS TIME.
CLIMATE
DRIEST AUTUMN (SEP-NOV) ON RECORD, AND ANY 3-CALENDAR MONTH
PERIOD ON RECORD, PLUS CURRENT STATUS:
9/1-11/19 DRIEST DRIEST 3 YEAR/
SITE 2024 PRECIP AUTUMN YEAR CALENDAR MONTHS MONTHS
ALLENTOWN (ABE) 1.61 3.81 1922 3.58 OCT-DEC 1928
A.C. AIRPORT (ACY) 0.99 3.34 2001 2.35 OCT-DEC 1946
A.C. MARINA (55N) 0.79 2.89 1941 2.52 AUG-OCT 1895
GEORGETOWN (GED) 0.85 2.67 2001 2.20 AUG-OCT 2024
MOUNT POCONO (MPO) 3.17 4.21 1931 3.36 OCT-DEC 1928
PHILADELPHIA (PHL) 1.09 2.37 1922 2.37 SEP-NOV 1922
READING (RDG) 1.42 2.89 1922 2.89 SEP-NOV 1922
TRENTON (TTN) 0.71 3.18 1922 2.66 JUN-AUG 1966
WILMINGTON (ILG) 0.86 3.17 1922 3.17 SEP-NOV 1922
PHI WATCHES/WARNINGS/ADVISORIES
PA...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY
AFTERNOON FOR PAZ054-055.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...GALE WARNING FROM 11 PM THIS EVENING TO 7 AM EST THURSDAY FOR
ANZ430-431-453>455.
SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO 6 AM EST
FRIDAY FOR ANZ450>452.
SYNOPSIS...GORSE/RCM
NEAR TERM...AKL
SHORT TERM...RCM
LONG TERM...RCM
AVIATION...AKL/RCM
MARINE...AKL/RCM
HYDROLOGY...WFO PHI
CLIMATE...WFO PHI
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