434
FXUS61 KPHI 150741
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
241 AM EST SUN DEC 15 2024
SYNOPSIS
STRONG HIGH PRESSURE ACROSS NEW ENGLAND THIS MORNING WILL MOVE
OFFSHORE BY TONIGHT. A WEAK UPPER AIR SYSTEM MOVES ACROSS OUR
AREA LATER TODAY AND INTO EARLY MONDAY, FOLLOWED BY ANOTHER SYSTEM
LATER MONDAY INTO EARLY TUESDAY. HIGH PRESSURE LOOKS TO BUILD IN
BRIEFLY LATER TUESDAY BEFORE ANOTHER LOW PRESSURE SYSTEM AFFECTS
OUR REGION LATER WEDNESDAY INTO THURSDAY.
NEAR TERM /THROUGH MONDAY/
AS OF EARLY THIS MORNING, SURFACE LOW PRESSURE IS IN WESTERN
ILLINOIS WHILE HIGH PRESSURE IS CENTERED OVER NORTHERN NEW
ENGLAND AND SOUTHERN QUEBEC. IN BETWEEN, OUR REGION REMAINS
FAIRLY TRANQUIL, THOUGH HIGH CLOUDS ARE STARTING TO MOVE
OVERHEAD. WITH THE LIGHT WINDS AND PARTLY CLEAR SKIES, TEMPS
HAVE FALLEN WELL BELOW FREEZING, BUT NOT QUITE AS COLD AS LAST
NIGHT IN MOST LOCALES.
FOR TODAY, THE INCREASING AND LOWERING CLOUD SHIELD MOVING IN
AHEAD OF THE APPROACHING SYSTEM WILL KEEP TEMPERATURE RISES IN
CHECK DESPITE AN EASTERLY FLOW OFF THE RELATIVELY WARM OCEAN.
THUS, HIGHS SHOULD BE MAINLY IN THE 30S NORTH AND WEST OF I-95
BUT IN THE LOWER 40S FURTHER SOUTH AND EAST. 20S WILL
PREDOMINATE AGAIN IN THE POCONOS.
WARM ADVECTION PRECIP BEGINS MOVING IN NEAR SUNSET THIS EVENING
AND OVERSPREADS THE ENTIRE AREA BY MIDNIGHT OR SO. NEAR AND
SOUTHEAST OF I-95, THIS SHOULD JUST BE RAIN, THOUGH AN LITTLE
SNOW OR SLEET RIGHT AT THE ONSET CAN'T BE RULED OUT. FURTHER
NORTHWEST, SNOW MAY OCCUR LONG ENOUGH TO PRODUCE A MODEST
ACCUMULATION ACROSS THE I-78 CORRIDOR, BUT THEN TEMPS SHOULD
WARM AND WE END UP WITH MOSTLY RAIN AFTER MIDNIGHT. THERE MAY BE
A PERIOD OF FREEZING RAIN DURING THE TRANSITION AND THIS MAY
EVENTUALLY NECESSITATE A SOUTHWARD EXPANSION OF THE WINTER
WEATHER ADVISORIES, BUT NOT THAT CONFIDENT JUST YET. DID ADD
WARREN COUNTY NJ AS LATEST GUIDANCE PAINTS AN ICIER OUTCOME
THERE AND POINTS FURTHER NORTH AND WEST, WITH A TENTH TO PERHAPS
.15 INCH OF ICE AS THE SNOW TRANSITIONS TO RAIN TOWARD MORNING.
SNOW SHOULD ALSO LINGER LONG ENOUGH TO DROP AN INCH OR TWO,
ESPECIALLY ACROSS THE POCONO PLATEAU. THE EXISTING TIER OF
ADVISORIES WAS NOT CHANGED.
WARM ADVECTION SHOULD CHANGE PRECIP TO ALL RAIN BY MIDDAY MONDAY
IF NOT SOONER, JUST AS PRECIP IS WINDING DOWN, WITH JUST LINGERING
PATCHY LIGHT RAIN AND DRIZZLE IN THE WAKE OF THE SYSTEM FOR THE
AFTERNOON HOURS. THE SOUTHEASTERLY FLOW SHOULD BRING TEMPS INTO
THE 50S NEAR AND SOUTHEAST OF I-95 BY MONDAY AFTERNOON, WITH
40S FURTHER NORTHWEST, THOUGH THE POCONO PLATEAU MAY REMAIN
STUCK IN THE UPPER 30S.
SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/
ANOTHER SYSTEM ARRIVES ON THE HEELS OF THE SUNDAY NIGHT/MONDAY
SYSTEM AND POPS IN THE NEW FCST CONTINUE TO BE CATEGORICAL FOR
MOST OF THE NORTHERN THREE-QUARTERS OF THE AREA AND LIKELY FOR
DELMARVA AND SOUTH NJ. THE MILDER TEMPERATURE READINGS MONDAY
WILL NOT DROP MUCH INTO THE OVERNIGHT WITH A WARM ADVECTION PATTERN
INITIALLY, SO P-TYPE OF RAIN IS EXPECTED WITH AMOUNTS OF UP TO
1/2 INCH ACROSS THE NORTH AND TAPERING TO A FEW HUNDREDTHS WELL
SOUTH. THE RAINS END TUE MORNING WITH IMPROVING CONDITIONS THRU
THE AFTERNOON. VERY MILD AIR WILL BE IN PLACE, SO HIGHS WILL
RANGE FROM THE MID/UPPER 50S FOR THE NW COUNTIES TO THE LOW 60S
ACROSS THE PHILADELPHIA METRO, DELMARVA AND SOUTH NJ. FAIR
WEATHER WITH SLIGHTLY MILD TEMPS ARE EXPECTED TUE NIGHT.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
THERE SEEMS TO BE SOME AGREEMENT AMONGST THE OPERATIONAL MODELS AT
THE BEGINNING OF THE PERIOD BUT NOT AS MUCH TOWARDS FRIDAY AND NEXT
WEEKEND. WE HAVE JUST POPULATED OUR EXTENDED GRIDS WITH THE NBM AS
WAS DONE PREVIOUSLY.
THE MILD WEATHER FROM THE SHORT TERM CONTINUES INTO WEDNESDAY WITH
SUBTLE RIDGING ALOFT AND A SURFACE RIDGE OFF THE COAST. HIGHS FOR
DELMARVA AND SOUTH NJ WILL TOP OUT IN THE UPPER 50S/LOW 60S WHILE
AREAS FURTHER NW WILL STILL BE ABOVE NORMAL, BUT HIGHS THERE
WILL BE IN THE LOW/MID 50S. EARLY WEDNESDAY WILL BE DRY BUT
RAINS WILL MOVE IN RATHER QUICKLY FROM W TO E BY AFTERNOON AND
REMAIN INTO THE OVERNIGHT. LIKELY TO CATEGORICAL POPS ARE IN THE
FCST ATTM. RAIN WITH PERHAPS A FEW SNOWFLAKES ACROSS THE
SOUTHERN POCONOS WED NIGHT.
LOW PRESSURE WILL SPIN-UP ACROSS THE UPPER OHIO VALLEY AND THEN PASS
NORTH OF THE AREA WHILE DEEPENING WED NIGHT AND THU. ONCE THE
ASSOCIATED COLD FRONT CROSSES THE AREA TEMPS WILL DROP BACK TO
NORMAL LEVELS THU. THEN BACK BELOW NORMAL FOR FRI AND THE
WEEKEND. IT APPEARS THAT THE UPPER TROUGH WILL KEEP
OPPORTUNITIES FOR SCATTERED RAINS/SNOWS THU/FRI
AFTERNOON/EVENING. AGAIN, WITH LIMITED CONFIDENCE IN THE LATER
PART OF THE PERIOD, WE'LL JUST HAVE THE NBMS SLIGHT CHANCE TO
LOW CHANCE POPS FOR NOW.
AVIATION /07Z SUNDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
THROUGH 12Z THIS MORNING...VFR. E-NE WINDS 5 KT OR LESS. HIGH
CONFIDENCE.
TODAY...VFR. E-NE WINDS 5 KTS OR SO. MODERATE CONFIDENCE.
TONIGHT...DETERIORATING TO IFR CIGS AND VSBY AFTER MIDNIGHT AS
RAIN OVERSPREADS THE REGION. FREEZING RAIN AND SNOW POSSIBLE AT
THE ONSET FOR KRDG AND ESPECIALLY KABE. E-NE WINDS 5 KTS OR SO.
LOW CONFIDENCE.
MONDAY...IFR CIGS MOST OF THE DAY WITH SOME CHANCE OF IFR VSBY
TOO DUE TO LINGERING MIST/DRIZZLE. WINDS BECOMING E-SE 5-10 KTS.
LOW CONFIDENCE.
OUTLOOK...
TUESDAY... THERE MAY BE SOME LOWER CIGS DURING THE MORNING, BUT
IMPROVING CONDITIONS BY AFTERNOON.
WEDNESDAY... WIDESPREAD LOWER CIGS/VSBYS PROBABLE WITH RAINS
ACROSS THE AREA.
THURSDAY... THERE MAY BE SOME LOWER CIGS DURING THE MORNING, BUT
IMPROVING CONDITIONS BY AFTERNOON.
MARINE
SUB-SCA CONDITIONS TODAY. HOWEVER, BUILDING SEAS NECESSITATED
ISSUANCES OF A SMALL CRAFT ADVISORY FOR OUR SOUTHERN AND CENTRAL
OCEAN ZONES STARTING THIS EVENING, SPREADING A LITTLE FURTHER
NORTH MONDAY MORNING. WINDS EASTERLY 5-10 KTS BUT WAVES WILL
REACH AROUND 5 FT STARTING THIS EVENING.
OUTLOOK...
MONDAY NIGHT THROUGH TUESDAY...A SYSTEM WILL BRING SOME RAIN
OVER THE WATERS AS WELL AS A PERIOD OF SMALL CRAFT ADVISORY
CONDITIONS LIKELY MONDAY NIGHT INTO TUESDAY.
TUESDAY NIGHT...SCA CONDITIONS DIMINISH. FAIR WEATHER.
WEDNESDAY...NO MARINE HEADLINES EXPECTED. RAIN EXPECTED.
THURSDAY...LOW-END SCA WINDS/SEAS POSSIBLE. CHANCE OR RAIN.
PHI WATCHES/WARNINGS/ADVISORIES
PA...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 9 AM EST
MONDAY FOR PAZ054-055.
NJ...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 9 AM EST
MONDAY FOR NJZ001.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 6 AM EST
MONDAY FOR NJZ007.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EST MONDAY FOR ANZ451.
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 PM EST MONDAY
FOR ANZ452>455.
SYNOPSIS...OHARA
NEAR TERM...RCM
SHORT TERM...OHARA
LONG TERM...OHARA
AVIATION...OHARA/RCM
MARINE...OHARA/RCM
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