840
FXUS61 KPHI 160850
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
350 AM EST THU JAN 16 2025
SYNOPSIS
A WEAK AREA OF LOW PRESSURE WILL PASS THROUGH LATER TODAY,
BRINGING A BIT OF LIGHT SNOW. A WARM FRONT WILL LIFT NORTH ON
SATURDAY, BRINGING A SHOT OF WIDESPREAD LIGHT RAINFALL AND
MILDER CONDITIONS. A STRONG ARCTIC COLD FRONT WILL PASS THROUGH
SUNDAY, WITH A WAVE OF LOW PRESSURE RIDING BEHIND IT WHICH MAY
PRODUCE A LITTLE SNOW. A VERY COLD AIR MASS WILL DOMINATE NEXT
WEEK.
NEAR TERM /THROUGH TONIGHT/
A QUICK MOVING CLIPPER SYSTEM WILL IMPACT THE REGION BEGINNING THIS
AFTERNOON INTO THE EVENING, BRINGING POTENTIAL FOR WIDESPREAD LIGHT
SNOWFALL ACCUMULATIONS ALONG WITH CONTINUED BELOW NORMAL
TEMPERATURES.
THE CLIPPER SYSTEM IS CURRENTLY MAKING ITS WAY ACROSS THE GREAT
LAKES EARLY THIS MORNING. MOSTLY CLEAR SKIES WILL QUICKLY GIVE WAY
TO INCREASING CLOUDS AS THE MORNING PROGRESSES WITH THE SYSTEM
APPROACHING FROM UPSTREAM. WESTERLY WINDS IN PLACE EARLY THIS
MORNING WILL SHIFT SOUTHWESTERLY AND INCREASE TO AROUND 10-15 MPH AS
THE SYSTEM'S FRONTAL BOUNDARY APPROACHES BY LATE MORNING AND INTO THE
AFTERNOON. WHILE THIS TECHNICALLY WILL RESULT IN A PERIOD OF WARM
ADVECTION, THE AIRMASS TO OUR SOUTHWEST IS QUITE SIMILAR TO THE ONE
CURRENTLY IN PLACE LOCALLY. SO RESULTING HIGH TEMPERATURES SHOULD BE
FAIRLY SIMILAR TO RECENT DAYS, TOPPING OUT IN THE UPPER 20S TO MID
30S FOR MOST AREAS. CLOUD COVER AND PRECIPITATION SPREADING LATER IN
WILL LIMIT DIURNAL HEATING.
THERE HAS NOT BEEN MUCH CHANGE TO THE FORECAST REGARDING THE
ANTICIPATED LIGHT SNOWFALL INTO THE AFTERNOON AND EVENING. A POTENT,
BUT POSITIVELY TILTED SHORTWAVE TROUGH WILL APPROACH QUICKLY BY
MIDDAY. THE DYNAMICS ALOFT SUPPORT WEAK TO MODEST FORCING FOR ASCENT
RIGHT AROUND THE DGZ LAYER AS THE SHORTWAVE ARRIVES, BEGINNING INTO
THE AFTERNOON ACROSS OUR EAST TO SOUTHEAST PA AREAS. THE FORCING
THEN SPREADS ESE TOWARD THE PHILLY METRO OR SO BY LATE AFTERNOON AND
EARLY EVENING, THEN BEGINNING SHIFTING OFFSHORE BETWEEN THE 7-10 PM
HOURS. THE LIMITING FACTOR WITH THIS SYSTEM IS A LACK OF ANY
NOTABLE MOISTURE ADVECTION AHEAD OF IT, AND A RATHER DRY AIRMASS IN
PLACE AT THE SURFACE. SO WHATEVER SNOW DOES DEVELOP ALOFT WILL TAKE
SOME TIME TO REACH THE GROUND, BUT ONCE IT DOES, TEMPERATURES IN THE
UPPER 20S TO LOW 30S WILL BE COLD ENOUGH TO SUPPORT SOME LIGHT
DUSTING ACCUMULATIONS LESS THAN 1" ACROSS MUCH OF OUR AREA.
POPS CONTINUE TO REFLECT THE LATEST GUIDANCE CONSENSUS OF THE SYSTEM
EVOLUTION. THIS INCLUDES 60-80% FOR MUCH OF OUR PENNSYLVANIA, NEW
JERSEY, AND NORTHERN DELMARVA AREAS, AND IN THE 20-50% RANGE FARTHER
SOUTH INTO DELMARVA WHERE THE SOUTHERN EXTENT OF SNOW IS LESS
CERTAIN. WHILE QPF REMAINS VERY LIGHT (0.05" OR LESS), THE HIGH SNOW
TO LIQUID RATIOS POTENTIALLY AS HIGH AS 20:1 OR MORE SHOULD SUPPORT
A DUSTING LESS THAN 1" FOR AREAS THAT RECEIVE A MORE PERSISTENT,
STEADY LIGHT SNOW. SOME LOCALIZED AMOUNTS AROUND BERKS COUNTY,
LEHIGH VALLEY, OR SOUTHERN POCONOS WHERE SNOW SHOULD PERSIST LONGEST
COULD SEE AROUND 1-2" AT BEST. WHILE THERE IS SOME CONCERN WITH THE
SNOW FALLING AROUND THE EVENING COMMUTE, THE SNOW SHOULD BE LIGHT
AND DRY ENOUGH TO NOT CAUSE ANY SIGNIFICANT TRAVEL ISSUES,
ESPECIALLY IN LIGHT OF THE RESIDUAL SALT ON MANY ROADS. IT SHOULD BE
NOTED THAT NOT EVERYWHERE IS LIKELY TO RECEIVE A MEASURABLE DUSTING
OF SNOW, BUT THE POTENTIAL FOR A DUST EXISTS WITHIN THE AREA
HIGHLIGHTED ON OUR FORECAST SNOWFALL MAP.
FOLLOWING THE SYSTEM'S DEPARTURE TONIGHT, TEMPERATURES WILL FALL TO
THE UPPER 10S TO MID 20S AS SKIES CLEAR OUT OVERNIGHT. A PACIFIC
HIGH BUILDING TO OUR SOUTHWEST OVERNIGHT, LACK OF ANY COLD
ADVECTION, AND A PERSIST WNW BREEZE SHOULD PREVENT TEMPERATURES FROM
BOTTOMING OUT MUCH, BUT IT'LL STILL BE COLD WITH SLIGHTLY BELOW
NORMAL LOW TEMPERATURES. WIND CHILLS MAINLY IN THE 10S.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
THE STORY OF THIS PERIOD WILL BE THE RELATIVE WARMTH (ESPECIALLY AS
COMPARED TO WHAT WILL BE COMING IN THE LONG TERM). THANKS TO
DEVELOPING LOW LEVEL SOUTHERLY FLOW, TEMPERATURES ON FRIDAY WILL BE
NEAR NORMAL, WITH HIGHS IN THE LOWER 30S TO LOWER 40S. BY SATURDAY,
TEMPERATURES WILL BE SLIGHTLY ABOVE NORMAL WITH HIGHS FROM THE MID
30S TO UPPER 40S.
AS THE NEXT COLD FRONT APPROACHES FROM THE WEST, PRECIPITATION COULD
MOVE IN, PRIMARILY IN THE AFTERNOON AND EVENING. THE PRECIPITATION
MAY START AS LIGHT SNOW IN THE POCONOS AND LEHIGH VALLEY, BUT A
QUICK CHANGE TO RAIN IS EXPECTED AND RAIN WILL BE THE DOMINANT
PRECIPITATION TYPE FOR SATURDAY. TOTAL PRECIPITATION AMOUNTS WILL BE
LIGHT, GENERALLY ONE TENTH OF AN INCH OR LESS, AND AREAS WHERE
PRECIPITATION COULD START AS SNOW, SNOW ACCUMULATION IS EXPECTED TO
BE VERY LIGHT - GENERALLY ONLY A FEW TENTHS OF AN INCH.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
A STRONG ARCTIC COLD FRONT IS EXPECTED TO ARRIVE SOMETIME SUNDAY,
WITH A MUCH COLDER AIRMASS ADVECTING IN BEHIND IT. STILL WATCHING
THE POTENTIAL FOR A LOW TO DEVELOP ON THE FRONT ONCE IT IS SOUTH AND
EAST OF OUR REGION, WHICH COULD BRING SOME SNOWFALL TO THE REGION.
THE 00Z SUITE OF GUIDANCE BACKED OFF AGAIN ON THIS POTENTIAL
(SIMILAR TO THE TREND FROM 24 HOURS AGO). GIVEN THAT THERE HAS BEEN
POOR RUN TO RUN CONSISTENCY ON THIS SYSTEM, STAYED CLOSE TO A BLEND
OF GUIDANCE AND PREVIOUS FORECAST. EVEN IF IT DEVELOPS, THE SYSTEM
WILL BE RATHER WEAK AND PROGRESSIVE, SO SNOWFALL TOTALS AND
RESULTING IMPACTS APPEAR MINOR.
MONDAY THROUGH WEDNESDAY WILL FEATURE THE COLDEST AIRMASS SO FAR
THIS SEASON AS ARCTIC AIR IS EXPECTED TO BE IN PLACE ACROSS A LARGE
PORTION OF THE CONUS FROM THE MIDWEST EASTWARD ACROSS MUCH OF THE
NORTHEAST. THE COLDEST DAY APPEARS TO BE TUESDAY, BEFORE THE AIR
MASS MODERATES SOME. HIGHS ON TUESDAY ARE CURRENTLY FORECAST TO
RANGE FROM THE MID SINGLE DIGITS ABOVE ZERO IN THE SOUTHERN POCONOS
TO NEAR 20 AT COASTAL AREAS. ON BOTH MONDAY NIGHT AND TUESDAY NIGHT,
LOWS ARE EXPECTED TO BE IN THE SINGLE DIGITS (SINGLE DIGITS BELOW
ZERO FOR THE HIGHER TERRAIN, AND SINGLE DIGITS ABOVE ZERO FOR AREAS
NEAR AND SOUTHEAST OF THE FALL LINE.
IT IS INCREASINGLY LIKELY THAT THIS RELATIVELY PROLONGED PERIOD OF
DANGEROUSLY COLD TEMPERATURES WILL HAPPEN, RESULTING IN IMPACTS TO
PEOPLE, ANIMALS, AND INFRASTRUCTURE. DANGEROUSLY COLD CONDITIONS FOR
PEOPLE AND ANIMALS ARE POSSIBLE RESULTING IN AN INCREASED RISK OF
HYPOTHERMIA AND FROST BITE. FOR INFRASTRUCTURE, IMPACTS COULD
INCLUDE FREEZING WATER PIPES AND HIGH DEMAND FOR HEATING ENERGY.
STAY TUNED TO THE LATEST FORECAST FOR ADDITIONAL INFORMATION AS WE
GET CLOSER.
AVIATION /09Z THURSDAY THROUGH MONDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE,
KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH 12Z...VFR. WESTERLY WINDS 5-10 KTS. HIGH CONFIDENCE.
TODAY...INITIALLY VFR THROUGH 18Z, THEN CEILINGS LOWERING TO NEAR
MVFR. PERIODS OF LIGHT SNOW DEVELOPING AT RDG/ABE AFTER 18Z, AND
AFTER 21Z FOR THE I-95 TERMINALS, WITH MVFR CEILINGS AND VISIBILITY
RESTRICTIONS POSSIBLE AT TIMES. SOME LIGHT SNOW OR FLURRIES AROUND
MIV/ACY AS WELL, THOUGH POTENTIAL FOR RESTRICTIONS THERE IS LOWER.
THE EVOLUTION OF THE SNOW LIKELY WON'T BE AS CLEAN AS THE TAFS MAY
MAKE IT SEEM, BUT WE'VE ADDED TEMPO GROUPS FOR THE LOWER CONDITIONS
DURING THE MOST PROBABLE TIME FRAMES FOR MVFR RESTRICTIONS. WSW
WINDS 5-10 KTS EARLY, SHIFTING SOUTHWEST AND INCREASING TO NEAR 10-
15 KTS BY 18Z. MODERATE CONFIDENCE OVERALL, BUT LOWER CONFIDENCE IN
THE EXACT TIMING OF ANY RESTRICTIONS.
TONIGHT...ANY LINGERING RESTRICTIONS FROM SNOW AND LOWER CEILINGS
ENDING BY AROUND 03Z, THEN VFR THE REST OF THE NIGHT. SOUTHWEST
WINDS 5-10 KTS EARLY, SHIFTING WNW BY 03Z. HIGH CONFIDENCE.
OUTLOOK...
FRIDAY...VFR.
SATURDAY AND SUNDAY...PERIODS OF MVFR CONDITIONS POSSIBLE WITH RAIN
(SAT) AND SNOW (SUN).
MONDAY...VFR. GUSTY NW WINDS UP TO 25 KT.
MARINE
THE FREEZING SPRAY ADVISORY WAS CANCELED. SEAS AND WINDS HAVE
DIMINISHED SUCH THAT FREEZING SPRAY SHOULD NO LONGER BE A
SIGNIFICANT THREAT, ALTHOUGH WE HAVE CARRIED A MENTION OF A CHANCE
OF IT IN THE FORECAST THROUGH THE MORNING. WINDS GENERALLY REMAINING
AROUND 10-20 KTS THROUGH TONIGHT WITH SOME BRIEF GUSTS UP TO 25 KTS
POSSIBLE OFFSHORE OF DELAWARE BAY LATE TONIGHT. SEAS 1-3 FEET.
OUTLOOK...
FRIDAY AND SATURDAY...WINDS AND SEAS SHOULD STAY BELOW SCA CRITERIA.
HOWEVER, THERE IS A SMALL CHANCE (20 - 30%) FOR A PERIOD OF SCA
CONDITIONS ON THE NORTHERN NJ COASTAL WATERS ON SATURDAY.
SUNDAY...SEAS ON THE COASTAL WATERS ARE LIKELY TO BUILD NEAR OR
ABOVE 5 FEET DURING THE DAY ON SUNDAY.
SUNDAY NIGHT THROUGH MONDAY (AND BEYOND)...INCREASING CONCERN FOR A
PROLONGED PERIOD OF FREEZING SPRAY STARTING SUNDAY NIGHT AND
CONTINUING INTO MID WEEK. SCA CONDITIONS LIKELY (60-70%) ON THE
COASTAL WATERS, PRIMARILY DUE TO ELEVATED SEAS, THOUGH A PERIOD OF
WIND GUSTS OF 25 TO 30 KT IS POSSIBLE ESPECIALLY MONDAY, WHICH COULD
ALSO RESULT IN SCA CONDITIONS ON THE DELAWARE BAY.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
SYNOPSIS...JOHNSON/STAARMANN
NEAR TERM...STAARMANN
SHORT TERM...HOEFLICH/JOHNSON
LONG TERM...HOEFLICH/JOHNSON
AVIATION...JOHNSON/STAARMANN
MARINE...JOHNSON/STAARMANN
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