676
FXUS61 KPHI 170553
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1253 AM EST FRI JAN 17 2025
SYNOPSIS
A WEAK DISTURBANCE WILL MOVE OFFSHORE OVERNIGHT. HIGH PRESSURE
BRIEFLY RETURNS ON FRIDAY AHEAD OF A WARM FRONT THAT WILL LIFT
NORTH ON SATURDAY BRINGING THE RETURN OF MILDER WEATHER AND SOME
RAIN TO THE REGION. A STRONG ARCTIC COLD FRONT WILL PASS
THROUGH ON SUNDAY WHILE A SECONDARY LOW DEVELOPS FOR SUNDAY
NIGHT BRINGING THE POTENTIAL FOR SNOW TO THE REGION. COLD
CANADIAN HIGH PRESSURE RETURNS ON MONDAY AND PERSISTS THROUGH
THE MIDDLE OF NEXT WEEK.
NEAR TERM /THROUGH TODAY/
SNOW HAS MOVED OUT OF THE AREA, AND CLOUDS ARE VERY GRADUALLY
CLEARING. EVEN WITH CLEARING SKIES WINDS OF 5 TO 10 KT SHOULD
KEEP CONDITIONS FROM RADIATING TOO LOW. LOWS MOSTLY IN THE
VICINITY OF 20.
SUNSHINE WILL COME TO DOMINATE FRIDAY AS THE PACIFIC HIGH BUILDS
TO OUR SOUTHWEST. HIGHS REACH NEAR 40 IN MUCH OF THE AREA.
DEFINITELY THE NICEST DAY FOR OUTDOOR ACTIVITIES IN THE FORECAST
PERIOD, UNLESS YOU PREFER CLOUDS, RAIN, SNOW, OR BRUTAL COLD,
AT LEAST OF BIT OF EACH APPEAR TO BE IN THE OFFING BEYOND
FRIDAY.
SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/
THE FOCUS OF THE SHORT TERM PERIOD WILL BE ON TWO SYSTEMS, ONE
IMPACTING THE AREA ON SATURDAY IN THE FORM OF LIQUID, WITH THE
SECOND IMPACTING THE AREA ON SUNDAY IN THE FROM OF FROZEN
PRECIPITATION.
FOR FRIDAY NIGHT, EXPECTING RATHER TRANQUIL REGIONS ACROSS THE AREA
AS HIGH PRESSURE SHIFTS OFF THE COAST. WILL SEE MOSTLY CLEAR SKIES
EARLY BECOMING INCREASINGLY MORE CLOUDY BY SATURDAY MORNING. LOW
TEMPERATURES WILL MAINLY BE IN THE 20S TO LOW 30S.
FOR SATURDAY INTO SATURDAY NIGHT, A LOW PRESSURE SYSTEM WILL BE
TRACKING ACROSS INTERIOR CANADA AS A WARM FRONT LIFTS NORTH OF THE
AREA. THIS WARM FRONT WILL BRING A 'BRIEF' RETURN OF SEASONABLE
WEATHER TO THE REGION ALONG WITH A CHANCE OF SOME LIQUID
PRECIPITATION. HIGH TEMPERATURES WILL MAINLY BE IN THE UPPER 30S TO
MID 40S. RAIN SHOULD BEGIN BY LATE MORNING INTO THE EARLY AFTERNOON
FROM SOUTHWEST TO NORTHEAST (WITH A RAIN/SNOW MIX ACROSS THE POCONO
PLATEAU). OVERALL, THE NATURE OF THE SYSTEM APPEARS TO BE QUITE WEAK
SO NOT EXPECTING MORE THAN JUST SPOTTY PERIODS OF LIGHT RAIN (AND
SNOW IN THE POCONOS) ON SATURDAY. RAINFALL AMOUNTS ARE EXPECTED TO
BE LESS THAN A TENTH OF AN INCH WITH A FEW TENTHS OF SNOW POSSIBLE
IN THE POCONOS. THIS SYSTEM WILL QUICKLY EXIT BY SATURDAY EVENING AS
A STRONG COLD FRONT APPROACHES, YIELDING MOSTLY DRY CONDITIONS FOR
SATURDAY NIGHT. LOW TEMPERATURES ON SATURDAY NIGHT WILL MAINLY BE IN
THE 20S TO LOW 30S.
FOR SUNDAY INTO SUNDAY NIGHT, THE STRONG ARCTIC COLD FRONT WILL
CROSS THROUGH THE REGION EARLY SUNDAY MORNING ADVECTING A MUCH
COLDER AIRMASS INTO THE REGION DURING THE DAY. AS IT DOES SO, AN
AREA OF LOW PRESSURE WILL ALSO BE DEVELOPING OVER THE DEEP SOUTH
NEAR THE TAIL-END OF THE ARCTIC FRONT. THIS AREA OF LOW PRESSURE
WILL RIDE ALONG THE FRONTAL BOUNDARY AND STRENGTHEN AS IT MOVES OFF
OF THE CAROLINA COASTLINE BY SUNDAY AFTERNOON.
FROM HERE, FORECAST GUIDANCE VARIES GREATLY AND ULTIMATELY WILL
DETERMINE WHAT WILL OCCUR SUNDAY AFTERNOON INTO SUNDAY NIGHT. IF THE
TRACK OF THE LOW IS CLOSE ENOUGH TO THE COAST, A LARGE PORTION OF
THE REGION IS LIKELY TO OBSERVE ACCUMULATING SNOWFALL (SIMILAR TO
WHAT THE 12Z/GFS DEPICTS). IF THE TRACK OF THE LOW IS SUPPRESSED
FURTHER SOUTH AND EAST (SIMILAR TO THE 12Z/ECMWF), THEN ACCUMULATING
SNOW MAY ONLY BE CONFINED TO COASTAL AREAS. WHEREAS IF THE TRACK OF
THE LOW, HUGS THE IMMEDIATE COASTLINE, THEN THE MOST SIGNIFICANT
SNOWS WILL BE FOCUSED NORTH AND WEST (DEPICTED BY THE 12Z/CANADIAN).
REGARDLESS OF THE VARIANCE IN GLOBAL GUIDANCE, HAVE SEEN AN INCREASE
IN OVERALL QPF VALUES AND IN SNOW PROBS. THUS, THERE IS AN INCREASE
IN FORECASTER CONFIDENCE THAT ACCUMULATING SNOW IS ON THE TABLE
SUNDAY AFTERNOON/EVENING ESPECIALLY SINCE COLD AIR WILL BE
ADVECTING IN FROM THE NORTHWEST. SO WITH THIS BEING SAID, THE
GREATEST POTENTIAL FOR HIGHER ACCUMULATIONS ARE FOR AREAS ALONG
THE I-95 CORRIDOR AND POINTS NORTH AND WEST WHERE THE INITIAL
FORECAST CALLS FOR 2-4" OF SNOW THROUGH 00Z MONDAY. LESSER
AMOUNTS UPWARDS OF 1-2" ARE FORECAST NEAR COASTAL AREAS THROUGH
THE SAME TIMEFRAME. OBVIOUSLY, A LOT CAN CHANGE OVER THE NEXT
60-72 HOURS AS WE OBTAIN MORE HI-RES/SHORT RANGE FORECAST
GUIDANCE AND STORM TOTAL SNOWFALL COVERS THE 'FULL DURATION' OF
THE EVENT, SO STAY TUNED FOR THE LATEST DETAILS TO THE FORECAST
OVER THE COMING DAYS!
LONG TERM /MONDAY THROUGH THURSDAY/
IN THE WAKE OF THE DEPARTING SYSTEM AND ARCTIC COLD FRONT, THE EARLY
TO MIDDLE PORTION OF THE WEEK WILL FEATURE BY FAR THE COLDEST
AIRMASS OF THE SEASON. STRONG, EXPANSIVE AND COLD, CANADIAN HIGH
PRESSURE WILL SINK SOUTHWARD OUT OF THE HIGH PLAINS ON MONDAY BEFORE
GRADUALLY SHIFTING SOUTHEAST TOWARD THE MID-ATLANTIC REGION BY
WEDNESDAY AND THURSDAY. WITH SUCH A COLD/DRY AIRMASS IN PLACE, THERE
DOES NOT APPEAR TO BE ANY REAL CHANCE FOR SOME PRECIPITATION DURING
THIS PERIOD, HOWEVER THERE IS A SLIGHT CHANCE FOR SOME LIGHT SNOW ON
TUESDAY NIGHT AS A SYSTEM OFFSHORE SKIRTS ON BY.
FOR NOW, THE PEAK OF THE COLD LOOKS TO OCCUR DURING THE MONDAY NIGHT
THROUGH WEDNESDAY NIGHT TIMEFRAME, AS 850 MB TEMPERATURES ARE
FORECAST TO BE BETWEEN -20C TO -24C DURING THIS TIME! SO IN TERMS
HIGH TEMPS, EXPECTING MOSTLY MID TEENS/LOW 20S WITH LOW TEMPS IN THE
SINGLE DIGITS (NEGATIVES IN THE HIGHER TERRAIN AREAS). FEEL-LIKE
TEMPERATURES WILL MOSTLY BE IN THE SINGLE DIGITS DURING THE DAY AND
IN THE NEGATIVES AT NIGHT, SO COLD WEATHER ADVISORIES/WARNINGS MAY
BE WARRANTED IN THE COMING DAYS.
THERE IS QUITE HIGH CONFIDENCE THAT THIS RELATIVELY PROLONGED PERIOD
OF DANGEROUSLY COLD TEMPERATURES WILL OCCUR, 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 /06Z FRIDAY THROUGH TUESDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH TODAY...PREVAILING VFR. BRIEF REDUCTIONS IN VISIBILITY
TO MVFR ARE POSSIBLE THROUGH SUNRISE, BUT OTHERWISE, VFR SHOULD
PREVAIL. WINDS BECOMING WEST- NORTHWEST 5-10 KTS. HIGH
CONFIDENCE.
TONIGHT...VFR. WINDS SHIFTING TO SW AND EVENTUALLY S THROUGH THE
NIGHT, BUT SHOULD BE LIGHT (GENERALLY LESS THAN 10 KT.
OUTLOOK...
SATURDAY THROUGH SATURDAY NIGHT...SUB-VFR CONDITIONS POSSIBLE,
ESPECIALLY FOR SATURDAY AFTERNOON. RAIN EXPECTED.
SUNDAY THROUGH SUNDAY NIGHT...SUB-VFR CONDITIONS PROBABLE,
ESPECIALLY SUNDAY AFTERNOON AND EVENING. LIGHT TO MODERATE SNOW
EXPECTED.
MONDAY THROUGH TUESDAY...VFR. NO SIGNIFICANT WEATHER EXPECTED.
MARINE
SNOW WILL END DURING THE EARLY OVERNIGHT PERIOD AS A DISTURBANCE
MOVES OFFSHORE. FOLLOWING IT, WINDS BECOME NORTHWESTERLY AS THE LOW
PRESSURE REDEVELOPS OFF THE COAST AND MOVES OUT TO SEA OVERNIGHT.
A SCA CONTINUES FOR THE LOWER AND MIDDLE OCEAN ZONES FOR LATE TONIGHT
INTO EARLY FRIDAY MORNING. FREEZING SPRAY MAY BE AN ISSUE DURING
THIS PERIOD AS WELL. THEREAFTER, WINDS SHOULD DECLINE BELOW ADVISORY
LEVELS. SEAS THRU THE PERIOD 2-4 FT.
OUTLOOK...
FRIDAY NIGHT THROUGH SATURDAY...MARGINAL SCA CONDITIONS
POSSIBLE AS WIND GUSTS WILL BRIEFLY APPROACH 25 KT ON SATURDAY
MORNING.
SATURDAY NIGHT THROUGH SUNDAY...NO MARINE HEADLINES EXPECTED.
SUNDAY NIGHT THROUGH TUESDAY...SCA CONDITIONS LIKELY AS WIND GUSTS
WILL RANGE BETWEEN 25-30 KT WITH SEAS AROUND 5 FEET. DUE TO THE
COMBINATION OF COLD AIR/WATER TEMPERATURES, GUSTY WINDS, AND
ENHANCED SEAS, FREEZING SPRAY ACCRETION IS LIKELY.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 9 AM EST THIS MORNING FOR
ANZ451>455.
SYNOPSIS...DESILVA/RCM
NEAR TERM...JOHNSON/RCM
SHORT TERM...DESILVA
LONG TERM...DESILVA/JOHNSON
AVIATION...DESILVA/JOHNSON
MARINE...DESILVA/RCM
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