080
FXUS61 KPHI 202047
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
347 PM EST FRI DEC 20 2024
SYNOPSIS
LOW PRESSURE IMPACTS THE REGION TONIGHT INTO EARLY SATURDAY. A
STRONG AND COLD HIGH PRESSURE SYSTEM BEGINS TO BUILD IN LATER
SATURDAY, HOLDING INFLUENCE OVER THE REGION THROUGH MONDAY AND
BRINGING FRIGID TEMPERATURES WITH IT. NEXT LOW PRESSURE SYSTEM
COULD IMPACT THE REGION MONDAY NIGHT INTO CHRISTMAS EVE.
NEAR TERM /THROUGH SATURDAY/
315 PM...AS OF MID AFTERNOON, A COMPLEX SYSTEM CONTINUES TO EVOLVE
AS IT'S AFFECTING THE AREA WITH SOME RAIN AND SNOW. AT THE SURFACE,
A PRIMARY LOW HAS WEAKENED OVER OHIO WHILE A SECONDARY LOW
DEVELOPING A COUPLE HUNDRED MILES EAST OF DELMARVA IS STRENGTHENING
AND MOVING NORTH AND EAST. THIS IS OCCURING AS A DEEPENING UPPER
LEVEL TROUGH IS PIVOTING TOWARDS THE COAST PLACING THE AREA IN A
FAVORABLE SPOT FOR LIFT AS DISTURBANCES CONTINUE TO ROTATE AROUND
THE BASE OF THE TROUGH. PRECIPITATION WAS A LITTLE SLOW TO DEVELOP
FOR SOME OF THE AREA BUT HAS BEEN RAMPING UP OVER THE PAST FEW
HOURS. SO FAR, MAINLY RAIN SOUTH OF THE URBAN CORRIDOR BUT MAINLY
SNOW NOT TOO FAR TO THE NORTH OVER PORTIONS OF BERKS, MONTGOMERY AND
BUCKS COUNTIES AND THEN ON INTO CENTRAL AND NORTHERN NJ. THESE AREAS
ARE SEEING TEMPERATURES IN THE LOW TO MID 30S WITH SNOW FALLING
WHILE FROM AROUND PHILLY SOUTH AND EAST IT'S BEEN IN THE UPPER 30S.
MEANWHILE IT'S IN THE 20S ACROSS THE POCONO PLATEAU WHERE WE
MAINTAIN A WINTER WEATHER ADVISORY FOR CARBON AND MONROE COUNTIES.
AS WE HEAD INTO THIS EVENING, THE LOW OVER THE OCEAN WILL CONTINUE
TO DEEPEN WHILE PULLING AWAY BUT THERE WILL STILL BE MULTIPLE
IMPULSES OF UPPER LEVEL ENERGY ROTATING THROUGH THE SLOWING MOVING
UPPER LEVEL TROUGH STILL CENTERED NEAR THE COAST. THIS WILL KEEP
PERIODS OF PRECIPITATION GOING ACROSS THE AREA THAT MAY TEND TO
BECOME A LITTLE MORE FOCUSED NEAR AN INVERTED TROUGH HANGING BACK
FROM THE DEPARTING LOW. THAT SAID, MOST OF THE MODEL GUIDANCE
CONTINUES TO DEPICT THIS FEATURE AS BEING FAIRLY POORLY DEFINED. THE
COMBINATION OF DYNAMIC COOLING, WINDS BACKING MORE TO N/NW AND THE
DIURNAL CYCLE WILL LEAD TO THE RAIN/SNOW LINE COLLAPSING SOUTH/EAST
WITH TIME. IN FACT IT'S LOOKING LIKE THE I-95 CORRIDOR SHOULD
TRANSITION TO MAINLY SNOW THROUGH THIS EVENING WITH A CHANGE OVER
OCCURING NEAR THE COAST OVERNIGHT, EXCEPT EARLIER IN THE EVENING
OVER PORTIONS OF MONMOUTH COUNTY. THIS WILL OCCUR AS LOW
TEMPERATURES BY MORNING DROP INTO THE UPPER 20S TO LOW 30S FOR MOST
AREAS.
IN TERMS OF SNOWFALL AMOUNTS, ONCE AGAIN, NOT TOO MUCH HAS CHANGED.
GREATEST SNOWFALL TOTALS AROUND 2-3" (LOCALLY 4") ARE EXPECTED
ACROSS THE POCONO PLATEAU OF CARBON AND MONROE COUNTIES AND EXTREME
NORTHERN NEW JERSEY. FOR MOST PORTIONS OF EASTERN PA INTO
CENTRAL/NORTHERN NJ JUST SOUTH OF HERE GENERALLY EXPECT 1-2 WITH
LOCALLY UP TO 3 INCHES. MEANWHILE THE I-95 CORRIDOR, INCLUDING
PHILLY, SHOULD SEE A LIGHT COATING UP TO AN INCH OR SO WITH A LOT OF
THE ACCUMULATION BEING ON GRASSY SURFACES AS OPPOSED TO ROADS WHICH
COULD REMAIN MAINLY WET.
PRECIPITATION WILL COME TO AN END WEST TO EAST LATE TONIGHT INTO
SATURDAY MORNING AS THE LOW CONTINUES TO PULL AWAY TO THE NORTH AND
EAST WHILE CONTINUING TO RAPIDLY DEEPEN. BEHIND THE DEPARTING LOW, A
VERY TIGHT PRESSURE GRADIENT WILL FORM AS STRONG CANADIAN HIGH
PRESSURE WILL BUILD IN FROM THE NORTH AND WEST, LEADING TO WINDY
CONDITIONS DURING THE DAY SATURDAY WITH NW WINDS 15-20 MPH AND GUSTS
UP TO 30 MPH. COMBINED WITH AFTERNOON TEMPERATURES IN THE UPPER 20S
TO MID 30S, WE WILL BE LOOKING AT WIND CHILLS IN THE TEENS AND 20S
FOR MUCH OF THE DAY. WIND CHILLS IN THE POCONOS LOOK TO LINGER IN
THE SINGLE DIGITS ALL DAY.
SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/
AS OUR LOW PRESSURE SYSTEM EXITS, WE SEE A PRESSURE GRADIENT TIGHTEN
WITH CANADIAN HIGH PRESSURE BUILDING INTO THE REGION FROM THE NORTH
AND WEST. THIS WILL LEAD TO WINDY CONDITIONS WITH A NW WIND OF 10-15
MPH AND GUSTS UPWARDS OF 30 MPH. THE REAL STORY AT THIS POINT
BECOMES THE COLD CONDITIONS WE WILL EXPERIENCE. SINGLE DIGITS FOR
THE POCONOS AND WIDESPREAD TEENS ELSEWHERE AS THIS ARCTIC AIR
FILTERS IN. WHEN YOU FACTOR IN THE WIND THAT WAS MENTIONED ABOVE,
WIND CHILLS WILL BE IN THE SINGLE DIGITS FOR MOST, EVEN FEELING
SEVERAL DEGREES BELOW ZERO FOR THE POCONO PLATEAU! ZOOMING IN ON THE
POCONOS AND GIVEN THE FORECAST, A COLD WEATHER ADVISORY HAS BEEN
ISSUED FOR CARBON AND MONROE COUNTY. THE CRITERIA FOR THE ADVISORY
IS -10 WHICH IS EXPECTED TO BE MET WITH WIND CHILLS REACHING AS LOW
AS -10 TO -12 SATURDAY NIGHT.
DAYTIME HIGHS ON SUNDAY WILL BE VERY COLD! HIGHS WILL BE IN THE
TEENS FOR THE POCONOS AND PLENTY OF 20S ELSEWHERE. ONE POSITIVE IS
THAT THE WIND DECREASES THROUGHOUT THE DAY SUNDAY AS HIGH PRESSURE
MOVES OVERHEAD. WIND CHILLS WILL BE IN THE TEENS (POCONOS WILL SEE
WIND CHILLS DOWN TO THE SINGLE DIGITS). COME SUNDAY NIGHT INTO EARLY
MONDAY MORNING, WINDS WILL BECOME MOSTLY CALM, BUT STRONG
RADIATIONAL COOLING IS EXPECTED WITH A CLEAR SKY. AS A RESULT, WE
WILL RADIATE VERY EFFICIENTLY AND TEMPERATURES ARE EXPECTED TO
CRATER INTO THE SINGLE DIGITS FOR MUCH OF THE REGION WITH THE PHILLY
METRO, COASTAL AREAS, AND THE DELMARVA IN THE LOW-TEENS. GIVEN THE
CALMER WINDS, HOWEVER, WIND CHILLS WILL NOT BE TOO DIFFERENT, BUT
STILL BE IN THE SINGLE DIGITS FOR MOST OF THE REGION.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
BEGINNING ON MONDAY EVENING,ENHANCED MID AND UPPER-LEVEL FLOW FROM
AN APPROACHING TROUGH WILL BEGIN TO OVERSPREAD THE REGION. IN
RESPONSE, A WEAK SURFACE LOW WILL TRAVERSE THE NORTHERN PARTS OF OUR
REGION, LEADING TO INCREASED CHANCES FOR PRECIPITATION ACROSS THE
AREA, PARTICULARLY FROM LATE MONDAY NIGHT AND INTO THE DAY ON
TUESDAY. RIGHT NOW, PRECIPITATION AMOUNTS APPEAR LIGHT, AND
TEMPERATURES LOOK TO WARM INTO THE MID/UPPER 30S ACROSS MUCH OF THE
AREA DURING THE DAY ON TUESDAY. WITH THAT SAID, IT IS POSSIBLE THAT
A LITTLE WINTRY PRECIPITATION COULD OCCUR WITH THE PASSAGE OF THIS
SYSTEM. AS OF RIGHT NOW, IT APPEARS THAT THIS WOULD BE MOST LIKELY
ACROSS CENTRAL AND NORTHERN PORTIONS OF THE FORECAST AREA.
THERE IS SOME INDICATION THAT AN ADDITIONAL WEAK IMPULSE COULD BRING
A SLIGHT CHANCE FOR LIGHT RAIN AND SNOW ACROSS PORTIONS OF THE AREA
PRIMARILY ON THURSDAY. OTHERWISE, IT APPEARS THAT MID-LEVEL RIDGING
WILL BEGIN TO SET IN TOWARDS THE END OF THE WEEK WITH DRY CONDITIONS
AND TEMPERATURES NEAR SEASONAL NORMALS.
AVIATION /21Z FRIDAY THROUGH WEDNESDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
REST OF THIS AFTERNOON...CONDITIONS CONTINUING TO DETERIORATE WITH
ANY AREAS THAT ARE STILL MVFR LIKELY TO BECOME IFR BY LATE THIS
AFTERNOON. PERIODS OF SNOW CONTINUING AT ABE AND RDG WITH EVEN SOME
SNOW POSSIBLY MIXING IN WITH THE RAIN AT PHL AND PNE. N-NE WINDS
AROUND 5-10 KT. LOW CONFIDENCE, ESPECIALLY WITH RESPECT TO TIMING OF
RESTRICTIONS.
TONIGHT...MAINLY IFR CONDITIONS EXPECTED WITH PERIODS OF LIGHT SNOW
AND/OR A RAIN/SNOW MIX BECOMING MAINLY SNOW BY THE OVERNIGHT.
CEILINGS MAY GRADUALLY RISE TO MVFR AFTER 06Z. NW-N WINDS AROUND 5-
10 KT. LOW CONFIDENCE OVERALL.
SATURDAY...IMPROVING CONDITIONS TO VFR BY MID/LATE MORNING WITH
WINDS INCREASING OUT OF THE NW TO AROUND 15 GUSTING UP TO 25-30
KNOTS. MODERATE CONFIDENCE.
OUTLOOK...
SATURDAY NIGHT THROUGH MONDAY...VFR CONDITIONS ARE EXPECTED
THROUGH AT LEAST MONDAY NIGHT. NO SIGNIFICANT WEATHER IS
EXPECTED.
TUESDAY...MVFR CONDITIONS POSSIBLE WITH A SYSTEM MOVING IN FROM THE
GREAT LAKES.
WEDNESDAY...CONDITIONS SHOULD IMPROVE TO VFR.
MARINE
SCA REMAINS IN EFFECT THROUGH SATURDAY. NE WINDS SHIFTING TO NW AND
MAY DIMINISH FOR A TIME THIS EVENING BEFORE RAMPING UP BY LATER
TONIGHT THROUGH SATURDAY WITH GUSTS UP TO 30 KNOTS SATURDAY. SEAS
GENERALLY 4-7 FEET.
OUTLOOK...
SUNDAY THROUGH WEDNESDAY...SCA CONDITIONS MAY LINGER INTO EARLY SUNDAY
MORNING. OTHERWISE, MARINE CONDITIONS WILL REMAIN BELOW
ADVISORY CRITERIA THROUGH WEDNESDAY.
PHI WATCHES/WARNINGS/ADVISORIES
PA...WINTER WEATHER ADVISORY UNTIL 7 AM EST SATURDAY FOR PAZ054-055.
COLD WEATHER ADVISORY FROM 8 PM SATURDAY TO 9 AM EST SUNDAY
FOR PAZ054-055.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 5 AM SATURDAY TO MIDNIGHT EST
SATURDAY NIGHT FOR ANZ430-431.
SMALL CRAFT ADVISORY UNTIL 6 AM EST SUNDAY FOR ANZ450>455.
SYNOPSIS...FITZSIMMONS/MJL
NEAR TERM...FITZSIMMONS
SHORT TERM...GUZZO
LONG TERM...COOPER
AVIATION...COOPER/FITZSIMMONS/GUZZO
MARINE...COOPER/FITZSIMMONS/GUZZO
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