362
FXUS61 KPHI 151800
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
100 PM 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/
920 AM UPDATE...AS OF MID MORNING, CLOUDS ARE INCREASING AHEAD
OF THE SYSTEM STILL ON TAP FOR LATER TODAY / TONIGHT BUT IT'S
TAKING SLIGHTLY LONGER COMPARED TO PREVIOUS FORECAST AND AS A
RESULT PARTS OF THE REGION HAVE SEEN SOME SUNSHINE TO START THE
DAY. SO THERE WERE SOME MINOR ADJUSTMENTS MADE TO THE SKY COVER
FORECAST FOR TODAY. ALSO MADE SOME MINOR ADJUSTMENTS TO
TEMPERATURE AND DEWPOINT GRIDS BASED ON LATEST OBS. OTHERWISE NO
FURTHER CHANGES WITH THE MID MORNING UPDATE. PREVIOUS DISCUSSED
ON FOLLOWS BELOW.
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 NBM'S SLIGHT CHANCE TO
LOW CHANCE POPS FOR NOW.
AVIATION /18Z SUNDAY THROUGH FRIDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
TODAY...VFR. E-NE WINDS 5 KTS OR SO. MODERATE CONFIDENCE.
TONIGHT...DETERIORATING TO MVFR AND THEN IFR CIGS AND VSBY AS
RAIN OVERSPREADS THE REGION. CONDITIONS LOOK TO DROP TO MVFR
BETWEEN 00Z AND 03Z FOR MOST SITES (CLOSER TO 03Z-05Z FOR SOUTH
JERSEY TERMINALS). FREEZING RAIN AND SNOW POSSIBLE AT THE ONSET
FOR KRDG AND ESPECIALLY KABE, CHANGING TO ALL RAIN BY AROUND
03-05Z AND IFR CONDITIONS BEGIN DEVELOPING AROUND THIS TIME. IFR
CONDITIONS PROGRESS EASTWARD REACHING I-95 TERMINALS AROUND
07-09Z AND SOUTH JERSEY TERMINALS CLOSER TO DAWN. E-NE WINDS 5
KTS OR SO. LLWS POSSIBLE AS SOUTHEASTERLY WINDS AROUND 30-35
KTS DEVELOP AROUND 2000 FT, MOST LIKELY AFTER 05Z. 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...FITZSIMMONS/RCM
SHORT TERM...OHARA
LONG TERM...OHARA
AVIATION...AKL/OHARA/RCM
MARINE...OHARA/RCM
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