502
FXUS61 KPHI 160607
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
107 AM EST THU JAN 16 2025
SYNOPSIS
COLD AND DRY ARCTIC HIGH PRESSURE WILL REMAIN IN PLACE TO OUR
SOUTHWEST THROUGH THIS MORNING, KEEPING BELOW NORMAL
TEMPERATURES AND DRY CONDITIONS IN PLACE. 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 TODAY/
HIGH PRESSURE REMAINS OVER THE OHIO VALLEY, EXTENDING THROUGH
OUR REGION. MEANWHILE A LOW PRESSURE SYSTEM ACROSS NORTHERN
ONTARIO IS DIVING SOUTH AND EASTWARD. THIS SYSTEM IS THE MAIN
FOCUS OF THE NEAR TERM.
FOR THE REST OF TONIGHT, THE SNOW SHOWERS IN THE POCONOS HAVE
MOSTLY ENDED THANKS TO THE CONTINUED NORTHWESTERLY FLOW, BUT
THESE SHOULD END AS THE GRADIENT WILL FINALLY SLACKENS OFF WHILE
HIGH PRESSURE SLOWLY SLIDES SOUTHEASTWARD AND WEAKENS. THIS
SHOULD ALSO RESULT IN LESS WIND TONIGHT, BUT TEMPERATURES WILL
STILL BE QUITE COLD. MOST LOCALES END UP IN THE TEENS, WITH A
FEW SPOTS IN THE SINGLE DIGITS, WHILE THE WARMEST LOCALES NEAR
THE COAST AND IN THE CITIES STAY NEAR 20 DEGREES.
WE'LL HAVE SOME SUN TO START THURSDAY, BUT CLOUDS WILL SPREAD
IN QUICKLY AS WARM ADVECTION GETS UNDERWAY AHEAD OF THE
AFOREMENTIONED LOW PRESSURE DIVING SOUTHEASTWARD TOWARD US.
EXPECT SOME VERY LIGHT SNOW TO START ENCROACHING ON THE AREA
FROM THE NORTHWEST BY MIDDAY, WITH MUCH OF THE AREA SEEING SOME
LIGHT SNOW BY SUNSET. WE'RE NOT TALKING MUCH HERE, THANKS TO THE
WEAK NATURE OF THE SYSTEM AND THE DRY AIR IN PLACE, GENERALLY
LESS THAN AN INCH, BUT SINCE IT WILL LIKELY BE SNOWING LIGHTLY
NEAR OR DURING RUSH HOUR, ITS NOTABLE FOR POTENTIAL MINOR
IMPACTS, ESPECIALLY WITH RELATIVELY COLD GROUND AND ROAD TEMPS.
THAT SAID, HIGHS LIKELY NUDGE INTO THE LOW 30S FOR MANY BEFORE
THE SNOW BEGINS.
THE SYSTEM PULLS OFF THE COAST THURSDAY NIGHT WITH ANY
LINGERING SNOW SHOWERS ENDING AND SKIES CLEARING TOWARD DAWN.
HOWEVER, THIS SYSTEM IS NOT USHERING IN ANY COLD AIR... IF
ANYTHING, THE AIR MASS MODERATES AS A PACIFIC HIGH STARTS
BUILDING IN BEHIND IT, SO TEMPS LIKELY WON'T BE SIGNIFICANTLY
COLDER THAN TONIGHT... IN FACT, THEY MAY END UP A LITTLE MILDER.
SHORT TERM /TONIGHT THROUGH SATURDAY/
TEMPERATURES WILL REBOUND CLOSER TO NORMAL VALUES FOR FRIDAY,
WITH INCREASING HEIGHTS ALOFT AND AN UPPER RIDGE AXIS PASSING
ACROSS THE REGION INTO THE NIGHT. HIGHS SHOULD BE MAINLY IN THE
UPPER 30S TO LOW 40S UNDER MOSTLY SUNNY SKIES. WHILE NOT THE
WARMEST OF WINTER DAYS, IT WILL DEFINITELY BE THE NICEST DAY FOR
ANY OUTDOOR ACTIVITIES FOR THE FORESEEABLE FUTURE. LOWS IN THE
MID TO UPPER 20S FRIDAY NIGHT WITH INCREASING CLOUDS.
A WARM FRONT SHOULD LIFT NORTH THROUGH THE AREA ON SATURDAY,
WITH SOUTH TO SOUTHWEST FLOW AND WARM ADVECTION PUSHING
TEMPERATURES INTO THE LOW TO MID 40S ACROSS MUCH OF THE AREA.
SOME PRECIPITATION MOVES IN LATE SATURDAY MORNING, BECOMING MORE
WIDESPREAD INTO THE AFTERNOON AND EVENING AS A COLD FRONT
APPROACHES AND AN AREA OF LOW PRESSURE SLIDES BY TO THE SOUTH.
PRECIPITATION COULD MOVE IN EARLY ENOUGH IN THE LEHIGH VALLEY TO
START AS SNOW, BUT A QUICK CHANGE TO RAIN IS EXPECTED AND RAIN
WILL BE THE DOMINANT PRECIPITATION TYPE FOR SATURDAY. COLD AIR
COULD LINGER A BIT LONGER IN THE POCONOS, WHERE SOME LIGHT SNOW
SHOWERS ANTICIPATED THROUGH THE DAY WITHIN THE POCONO PLATEAU.
SNOWFALL AMOUNTS UP TO AN INCH ARE EXPECTED UP THAT WAY.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
PRECIPITATION, MAINLY IN THE FORM OF RAIN, TAPERS OFF ON
SATURDAY NIGHT, WITH LOW TEMPERATURES DROPPING INTO THE UPPER
20S/LOW 30S. A STRONG ARCTIC FRONT IS EXPECTED TO ARRIVE
SOMETIME SUNDAY, WITH A MUCH COLDER AIRMASS ADVECTING IN BEHIND
IT. SOME GUIDANCE SUGGESTS POTENTIAL FOR A COASTAL SYSTEM
DEVELOPING ALONG THE FRONT LATE SUNDAY INTO EARLY MONDAY,
BRINGING SOME SNOWFALL TO THE REGION. 12Z SUITE OF GUIDANCE HAS
TRENDED A BIT MORE FAVORABLE IN TERMS OF MEASURABLE SNOWFALL.
HOWEVER, GIVEN THAT THE SYSTEM WILL BE RATHER WEAK AND
PROGRESSIVE, SNOWFALL TOTALS AND RESULTING IMPACTS APPEAR MINOR.
NBM PROBABILITIES OF 2+ INCHES OF SNOW (ALSO KNOWN AS ADVISORY
CRITERIA FOR MOST OF THE REGION) IS AROUND 10-20% REGIONWIDE.
HAVE MAINTAINED CHANCE POPS REGION WIDE (25-50%), WITH THE
HIGHER END OF THAT RANGE COMING FOR AREAS SOUTH OF PHILADELPHIA.
TEMPERATURES ON SUNDAY WILL CLIMB INTO THE MID TO UPPER 30S/LOW
40S ON SUNDAY. THIS WILL LIKELY BE THE LAST TIME TEMPERATURES
GET ABOVE FREEZING UNTIL AT LEAST THE END OF NEXT WEEK. THE
ARCTIC AIRMASS ARRIVES BEGINNING SUNDAY NIGHT AS LOWS WILL DROP
INTO THE MID TO UPPER TEENS WITH SOME SPOTS STAYING ABOVE 20.
MONDAY THROUGH WEDNESDAY AND BEYOND 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. 850 MB TEMPERATURES IN
THE -20C TO -25C RANGE WILL LIKELY SPELL TEMPERATURES UPWARDS OF
15 TO 20 DEGREES BELOW NORMAL THROUGH THE MIDDLE OF NEXT WEEK.
THIS WOULD MEAN HIGHS NEAR 20 DEGREES AND LOWS INTO THE SINGLE
DIGITS OR EVEN BELOW ZERO IN SOME SPOTS. WIND CHILLS LIKELY
BELOW ZERO AT NIGHT AND IN THE SINGLE DIGITS DURING THE DAYTIME.
A PERIOD OF A FEW DAYS OF WELL BELOW FREEZING TEMPERATURES
COULD LEAD TO SOME COLD WEATHER IMPACTS TO INFRASTRUCTURE,
INCLUDING FREEZING WATER PIPES AND HIGH DEMAND FOR HEATING
ENERGY. CONFIDENCE IS RATHER HIGH IN A SIGNIFICANT COLD AIR
OUTBREAK OCCURRING AND COLD WEATHER HEADLINES WILL LIKELY BE
NEEDED NEXT WEEK.
AVIATION /06Z THURSDAY THROUGH MONDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TONIGHT...VFR. WESTERLY WINDS AROUND 5-10 KT. HIGH CONFIDENCE.
THURSDAY...VFR BEFORE 17Z, THEN A PERIOD OF LIGHT SNOW POSSIBLE
AT ALL TERMINALS BETWEEN 17Z TO 03Z, WITH POTENTIAL FOR MVFR
CONDITIONS. BEST CHANCES FOR RESTRICTIONS AT RDG AND ABE.
SOUTHWEST WINDS 5-10 KTS. MODERATE CONFIDENCE OVERALL.
OUTLOOK...
FRIDAY THROUGH FRIDAY NIGHT...VFR. NO SIGNIFICANT WEATHER.
SATURDAY THROUGH SATURDAY NIGHT...MVFR CONDITIONS EXPECTED
(80-90%) WITH PERIODS OF IFR POSSIBLE (20-30%) AS RAIN MOVES IN
BY MIDDAY.
SUNDAY THROUGH SUNDAY NIGHT...SUB-VFR CONDITIONS POSSIBLE
(30-50%) WITH CHANCE OF RAIN/SNOW SHOWERS DURING THE DAY, AND
SNOW AT NIGHT.
MONDAY...VFR. WIND GUSTS OUT OF THE WEST/NORTHWEST 20-25 KT
EXPECTED.
MARINE
THE SMALL CRAFT ADVISORY WAS ALLOWED TO EXPIRE AS SCHEDULED AT
MIDNIGHT. NORTHWEST WINDS WILL GENERALLY BE 15 TO 20 KTS AND
SEAS OF 2-4 FEET, SLOWLY DIMINISHING THROUGH THE NIGHT.
DUE TO THE COMBINATION OF COLD AIR/WATER TEMPERATURES, GUSTY
WINDS, AND ENHANCED SEAS, MODERATE FREEZING SPRAY ACCRETION IS
LIKELY BEGINNING AGAIN TONIGHT THROUGH EARLY THURSDAY AS WATER
TEMPS SHOULD BE SUFFICIENTLY COLDER THUS ALLOWING FOR MORE
EFFICIENT ICE ACCRETION. FOR THIS REASON, ANOTHER FREEZING SPRAY
ADVISORY HAS BEEN ISSUED TONIGHT INTO EARLY THURSDAY. NO MARINE
HEADLINES EXPECTED THURSDAY AFTERNOON AND NIGHT, THOUGH SOME
LIGHT SNOW IS POSSIBLE.
OUTLOOK...
FRIDAY THROUGH FRIDAY NIGHT...NO MARINE HEADLINES EXPECTED.
SATURDAY...SCA CONDITIONS POSSIBLE (30-40%) ESPECIALLY ON THE
NORTHERN WATERS. SEAS ALSO COULD APPROACH 5 FEET FOR A BRIEF
PERIOD.
SATURDAY NIGHT...NO MARINE HEADLINES EXPECTED.
SUNDAY THROUGH MONDAY...SCA CONDITIONS LIKELY (60-70%) WITH
SEAS BUILDING TO NEAR 5 FEET AND WIND GUSTS INCREASING BEHIND A
COLD FRONT.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...FREEZING SPRAY ADVISORY UNTIL 11 AM EST THIS MORNING FOR
ANZ430-431-450>455.
SYNOPSIS...HOEFLICH/RCM/STAARMANN
NEAR TERM...FITZSIMMONS/RCM/STAARMANN
SHORT TERM...HOEFLICH/STAARMANN
LONG TERM...HOEFLICH/STAARMANN
AVIATION...FITZSIMMONS/HOEFLICH/RCM/STAARMANN
MARINE...FITZSIMMONS/HOEFLICH/RCM/STAARMANN
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