261
FXUS61 KPHI 152315
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
615 PM EST WED JAN 15 2025
SYNOPSIS
COLD AND DRY ARCTIC HIGH PRESSURE WILL REMAIN IN PLACE TO OUR
SOUTHWEST THROUGH TONIGHT, KEEPING BELOW NORMAL TEMPERATURES AND DRY
CONDITIONS IN PLACE. A WEAK AREA OF LOW PRESSURE WILL PASS THROUGH
ON THURSDAY, 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 THURSDAY NIGHT/
615 PM UPDATE...NO MAJOR CHANGES TO THE FORECAST WITH THE EARLY
EVENING UPDATE. LATEST ANALYSIS STILL PLACES HIGH PRESSURE OVER
THE OHIO VALLEY, EXTENDING THROUGH OUR REGION. A WEAK LOW
PRESSURE IS DIVING SOUTHWARD ACROSS ACROSS NORTHWESTERN ONTARIO,
AND THIS SYSTEM IS THE MAIN FOCUS OF THE NEAR TERM.
FOR TONIGHT, A FEW SNOW SHOWERS MAY BE HAD IN THE POCONOS THIS
EVENING 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.
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 /FRIDAY 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 /23Z WEDNESDAY THROUGH MONDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TONIGHT...VFR. WINDS DECREASING TO 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.
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
A SMALL CRAFT ADVISORY REMAINS IN EFFECT INTO THIS EVENING ON
THE COASTAL WATERS. NORTHWEST WINDS WILL GENERALLY BE 15 TO 20
KTS WITH GUSTS UP TO 25 KT AND SEAS OF 4-6 FEET, SLOWLY
DIMINISHING AFTER WITH TIME THIS EVENING.
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 THURSDAY FOR ANZ430-
431-450>455.
SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR
ANZ450>455.
SYNOPSIS...HOEFLICH/RCM/STAARMANN
NEAR TERM...FITZSIMMONS/RCM
SHORT TERM...HOEFLICH/STAARMANN
LONG TERM...HOEFLICH/STAARMANN
AVIATION...FITZSIMMONS/HOEFLICH/RCM
MARINE...HOEFLICH/RCM
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