FXUS61 KPHI 050920
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
420 AM EST SAT DEC 5 2009

.SYNOPSIS...
LOW PRESSURE WAS DEVELOPING OFF THE SOUTHEAST COAST DURING THE
NIGHT. THE LOW WILL PROGRESS TO THE NORTHEAST AND IT IS EXPECTED
TO PASS ABOUT 250 MILES EAST OF DELAWARE AND NEW JERSEY THIS
EVENING. HIGH PRESSURE IS FORECAST TO BUILD INTO OUR REGION FROM
THE WEST FOR SUNDAY AND MONDAY. A DRY COLD FRONT FROM THE
NORTHWEST IS ANTICIPATED TO ARRIVE ON MONDAY NIGHT. HIGH PRESSURE
SHOULD FOLLOW FOR TUESDAY. STRONG LOW PRESSURE FROM THE SOUTHWEST
IS EXPECTED TO PASS OVER THE NORTHEASTERN STATES ON WEDNESDAY AND
WEDNESDAY NIGHT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AT 4:00 AM, RAIN WAS CONTINUING TO SPREAD UP INTO OUR REGION FROM
THE SOUTH. TEMPERATURES WERE MAINLY IN THE 30S UP NORTH AND IN THE
40S IN THE SOUTH.

THE ADVANCE OF THE PRECIPITATION SHOULD BE GRADUAL. IT MAY NOT
REACH PARTS OF NORTHERN NEW JERSEY AND PARTS OF THE POCONO REGION
UNTIL THE EARLY AFTERNOON HOURS.

FOR READING, QUAKERTOWN, CLINTON, MORRISTOWN AND POINTS TO THE
NORTH, IT APPEARS AS THOUGH THERE WILL BE A MIX OF RAIN AND SNOW,
CHANGING TO ALL SNOW LATE THIS AFTERNOON AND CONTINUING INTO THIS
EVENING. HOWEVER, BASED ON THE EXPECTED TEMPERATURE PROFILES, IT
APPEARS AS THOUGH THE PRECIPITATION WILL BE MAINLY SNOW IN THE
HIGHER ELEVATION THROUGH THE ENTIRE EVENT.

FOR THE FAR UPPER DELMARVA, THE PHILADELPHIA METROPOLITAN AREA
AND CENTRAL NEW JERSEY, THE BOUNDARY LAYER SHOULD REMAIN WARM
ENOUGH TO KEEP THE PRECIPITATION AS RAIN DURING THE DAYLIGHT
HOURS. HOWEVER, AFTER DARK IT APPEARS AS THOUGH THE PRECIPITATION
RATES MAY INCREASE FOR A FEW HOURS AS AN UPPER LEVEL SHORT WAVE
APPROACHES FROM THE SOUTHWEST. THE HEAVIER PRECIPITATION SHOULD
DRAG ENOUGH COLD AIR DOWN TO CAUSE THE RAIN TO CHANGE TO SNOW. IT
LOOKS AS THOUGH MANY LOCATIONS WILL PICK UP AROUND AN INCH OF SNOW
THIS EVENING. WITH THE GROUND REMAINING RELATIVELY WARM, THE SNOW
SHOULD ACCUMULATE MAINLY ON UNPAVED SURFACES.

FOR OUR SOUTHEASTERN COUNTIES, THIS WILL LIKELY BE MAINLY A BRISK
RAIN EVENT, POSSIBLY ENDING AS A VERY BRIEF PERIOD OF SNOW WITH
LITTLE OR NO ACCUMULATION.

BEING THAT THIS WILL BE THE FIRST WINTER WEATHER EVENT OF THE
SEASON FOR MUCH OF OUR AREA, WE HAVE ISSUED WINTER WEATHER
ADVISORIES. OUR SOUTHEASTERN COUNTIES HAVE BEEN EXCLUDED. ALSO, WE
HAVE NOT ISSUED ADVISORIES FOR THE POCONOS OR FOR SUSSEX COUNTY IN
NEW JERSEY. THOSE LOCATIONS HAVE ALREADY RECEIVED SOME SNOW THIS
SEASON, AND THE POSSIBLE INCH OR TWO FROM TODAY INTO TONIGHT
SHOULD NOT CREATE MUCH OF A PROBLEM THERE.

AFTER THE UPPER LEVEL SHORT WAVE PASSES OFF THE MIDDLE ATLANTIC
COAST THIS EVENING, THE PRECIPITATION SHOULD COME TO AN END IN
MUCH OF OUR REGION BEFORE MIDNIGHT.

RAPID CLEARING IS EXPECTED LATE TONIGHT. 

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
HIGH PRESSURE AND DRY CONDITIONS ARE FORECAST TO BUILD INTO OUR
REGION FROM THE WEST FOR SUNDAY AND MONDAY. HOWEVER, SOME MID AND
HIGH CLOUDS ARE POSSIBLE FROM SUNDAY NIGHT INTO MONDAY.

A WEAK UPPER LEVEL SHORT WAVE IS FORECAST TO MOVE ACROSS THE
GREAT LAKES REGION ON MONDAY AND IT SHOULD REACH THE NORTHEASTERN
STATES ON MONDAY NIGHT. WHILE THE SYSTEM MAY BRING SOME ADDITIONAL
CLOUDS, WE ARE NOT ANTICIPATING ANY PRECIPITATION WITH IT.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
HIGH PRESSURE WILL MOVE EAST OF THE AREA ON TUESDAY, AND THEN
PRESENT THINKING IS THAT A PRECIPITATION EVENT THAT STARTS WITH
OVERRUNNING AND ISENTROPIC LIFT AND EVENTUALLY INCORPORATES
DYNAMICS AND PERHAPS EVEN SOME INSTABILITY DEVELOPS AS LOW
PRESSURE IS EXPECTED TO MOVE FROM THE OHIO RIVER VALLEY TO LOCALES
JUST TO OUR NORTH. SOME CONVECTION AND SIGNIFICANT WIND MAY BE
ASSOCIATED WITH THIS EVENT, BUT WE'LL KEEP OUR POWDER DRY FOR NOW.
PRECIPITATION TYPE MAINLY LOOKS TO BE RAIN, BUT OVER OUR FAR
NORTHWESTERN AREAS SOME SORT OF MIXED OR SOLID PRECIPITATION COULD
FALL FOR A TIME BOTH BEFORE AND AFTER THE LOW PASSES.

THURSDAY THROUGH FRIDAY LOOK DRY THANKS TO HIGH PRESSURE.

TEMPERATURES THROUGH THE PERIOD OSCILLATE AROUND NORMAL.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

AN AREA OF LOW PRESSURE OFF THE SOUTHEASTERN UNITED STATES COAST
WILL TRACK NORTHEASTWARD TODAY AND TONIGHT. WHILE THE EXACT TRACK
OF THE STORM IS WELL OFF THE COAST, A GOOD AMOUNT OF MOISTURE IS
EXPECTED TO SURGE NORTHWARD AND OVERSPREAD OUR AREA TODAY. AS THE
MOISTURE CONTINUES TO DEEPEN, THE CEILINGS WILL LOWER BELOW VFR
DURING THE COURSE OF THE MORNING AND EARLY AFTERNOON FROM SOUTH TO
NORTH. THERE IS SOME COLDER AND DRIER AIR MOVING INTO THE AREA
FROM THE NORTH AND A NORTH TO NORTHEAST WIND IS EXPECTED TO
INCREASE AND TURN GUSTY AT TIMES /UP TO 25 KNOTS/ ESPECIALLY FROM
THE KPHL METRO AREA ON EASTWARD. THESE WINDS WILL EVENTUALLY SHIFT
AROUND TO THE NORTHWEST LATE TODAY INTO TONIGHT AS THE STORM
SYSTEM MOVES ON BY. THERE ARE PRECIPITATION TYPE CONCERNS GIVEN
THE COLDER AND SOMEWHAT DRIER AIR INVADING THE AREA. OUR
CONFIDENCE ON THE TIMING OF THE PRECIPITATION, ESPECIALLY THE
AREAS THAT START AS RAIN THEN MIX WITH AND CHANGE TO SNOW IS A BIT
BELOW AVERAGE.

FOR KMIV AND KACY...RAIN IS EXPECTED TO OVERSPREAD THE REGION
THROUGH THE MORNING WITH VISIBILITIES AND CEILINGS LOWERING TO
MVFR AND IFR. IT APPEARS THAT THE BULK OF THIS STORM WILL BE RAIN
FOR THESE TERMINALS, ALTHOUGH A MIX WITH SNOW OR PERHAPS EVEN A
CHANGE OVER TO ALL SNOW IS POSSIBLE BEFORE THE PRECIPITATION ENDS
TONIGHT. FOR NOW, WE INTRODUCED A MIX OF RAIN AND SNOW FOR A TIME
THIS EVENING.

FOR KPHL, KPNE, KPHL AND KTTN...RAIN IS EXPECTED TO START FROM
SOUTH TO NORTH LATER THIS MORNING, ALTHOUGH KTTN MAY START TO MIX
WITH SOME SNOW. AS COLDER AIR INFILTRATES THE AREA DURING THE
COURSE OF THE AFTERNOON, THE RAIN WILL MIX WITH AND GRADUALLY
CHANGE OVER TO ALL SNOW BEFORE TAPERING OFF TONIGHT. THERE IS THE
POTENTIAL FOR THE PRECIPITATION TO FALL AT AN INCREASED RATE FOR A
TIME, MOSTLY LATE THIS AFTERNOON AND EARLY THIS EVENING. IF THIS
OCCURS, THE RAIN OR RAIN/SNOW MIX COULD CHANGE OVER TO ALL SNOW
FASTER. FOR NOW, WE MAINTAINED THE TRANSITION FROM RAIN TO A
RAIN/SNOW MIX THEN TO SNOW. THE CEILINGS AND VISIBILITIES WILL
LOWER TO MVFR AND IFR ON AVERAGE.

FOR KABE AND KRDG...THESE TERMINALS ARE EXPECTED TO BE IN THE
COLDER AIR THEREFORE LEANED TOWARD SNOW AS THE DOMINANT
PRECIPITATION TYPE. IT IS POSSIBLE THAT RAIN OCCURS OR AT LEAST
MIXES IN FOR A TIME ESPECIALLY IF THE PRECIPITATION INTENSITY IS
RATHER LIGHT, THEREFORE A REVISION MAY BE NEEDED. WE BROUGHT THE
PRECIPITATION NORTHWARD BY MID TO LATE MORNING. THE CEILINGS AND
VISIBILITIES WILL LOWER TO MVFR AND IFR WITH A PERIOD OF LIFR
VISIBILITIES OCCURRING DURING ANY HEAVIER SNOW.

OBSERVATIONS AND RADAR TRENDS WILL BE MONITORED AND AMENDMENTS
WILL BE ISSUED TO MAKE ANY NECESSARY ADJUSTMENTS. CONDITIONS AT
ALL THE TERMINALS ARE EXPECTED TO RAPIDLY IMPROVE LATE TONIGHT AS
THE STORM SYSTEM PULLS AWAY. THE NORTHWEST WINDS ARE EXPECTED TO
HOLD UP DURING THE NIGHT, ALTHOUGH A DOWNWARD TREND IS EXPECTED.

OUTLOOK...
HIGH PRESSURE BUILDS IN FOR SUNDAY WITH LITTLE IN THE WAY OF
CLOUDS AND A NORTHWEST WIND AT ABOUT 10 KNOTS OR LESS. THIS HIGH
PRESSURE SYSTEM THEN SLIDES TO OUR EAST MONDAY AS A WEAK FRONT MAY
SLIDE THROUGH MONDAY NIGHT INTO TUESDAY. A POTENTIALLY SIGNIFICANT
STORM MAY THEN ARRIVE WEDNESDAY INTO THURSDAY.

&&

.MARINE...
A LOW PRESSURE SYSTEM ORGANIZING OFF THE SOUTHEASTERN UNITED
STATES COAST THIS MORNING WILL TRACK NORTHEASTWARD TODAY AND
TONIGHT. THE NORTH TO NORTHEASTERLY WINDS WILL INCREASE AS A
RESULT OF A TIGHTENING PRESSURE GRADIENT. THE FORECAST SOUNDINGS
INDICATE THAT GALE FORCE GUSTS WILL OCCUR FROM SOUTH TO NORTH
TODAY INTO TONIGHT. IT APPEARS THAT GALES MAY NOT OCCUR IN THE
SOUTHERN AREAS UNTIL LATER THIS AFTERNOON AND PERHAPS STARTING AS
LATE AS TONIGHT IN THE LOWER DELAWARE BAY. THERE IS A CHANCE THAT
THE WINDS DO RAMP UP QUICK ENOUGH TO ALLOW SOME GALE FORCE GUSTS
TO OCCUR AT SOME POINT THIS AFTERNOON. FOR NOW, WE DECIDED TO KEEP
THE TIMING OF THE PREVIOUSLY ISSUED GALE WARNING. THE GALE WATCH
FOR THE NORTHERN TWO ZONES WILL BE UPGRADED TO A WARNING AS
NORTHERLY WINDS RAMP UP TONIGHT /A SMALL CRAFT ADVISORY BEGINS
HERE AT 15Z AND GOES TO 23Z/. THESE HEADLINES WILL RUN UNTIL 10Z
SUNDAY. GIVEN THE WINDS THAT WE ARE COMING UP WITH AND THAT IT
LOOKS MORE MARGINAL, WE ELECTED TO CHANGE THE GALE WATCH FOR THE
UPPER DELAWARE BAY TO A SMALL CRAFT ADVISORY. THIS WILL RUN FROM
15Z TODAY TO 10Z SUNDAY.

THE INCREASING NORTH TO NORTHEAST WIND WILL BUILD THE SEAS AND WE
WENT FAIRLY CLOSE TO WAVEWATCH WHICH IS ALSO NEAR CONTINUITY. HIGH
PRESSURE THEN BUILDS INTO THE AREA SUNDAY, HOWEVER A NORTHWESTERLY
WIND LOOKS TO HOLD UP FOR A TIME. THEREFORE, A SMALL CRAFT
ADVISORY MAY BE NEEDED FOLLOWING THE GALE WARNING EARLY SUNDAY
MORNING. THE SURFACE HIGH SLIDES TO OUR EAST MONDAY WITH LIGHTER
WINDS EXPECTED INTO TUESDAY. ON WEDNESDAY, A POTENTIALLY
SIGNIFICANT STORM LOOKS TO MOVE IN WITH THE POSSIBILITY OF GALE
FORCE WINDS. THIS MAY PERSIST ON THURSDAY AS THE STORM WRAPS UP TO
OUR NORTH.

&&

.TIDES/COASTAL FLOODING...
DESPITE THE RELATIVELY LIGHT FLOW EARLY THIS MORNING, TIDAL
DEPARTURES HAVE INCREASED TO AROUND A HALF OF A FOOT. WE ONLY NEED
BETWEEN 0.5 AND 0.8 OF A FOOT OF A POSITIVE DEPARTURE TO GIVE
MINOR TIDAL FLOODING DURING THIS MORNINGS HIGH TIDE ALONG THE
COAST AND ADJACENT BACK BAYS FROM OCEAN COUNTY, NEW JERSEY
SOUTHWARD. WE THEREFORE MAINTAINED THE ADVISORY ALONG THE COAST
AND ADJACENT BACK BAYS FROM OCEAN COUNTY SOUTH. THIS LOOKS TO BE A
QUICK EVENT, AND FOR NOW NO ADVISORY WILL BE ISSUED FOR MONMOUTH
COUNTY, NEW JERSEY, DELAWARE BAY, THE TIDAL DELAWARE AND
CHESAPEAKE BAY. THIS EVENINGS HIGH TIDE IS MUCH LOWER THAN THE
HIGHER HIGH TIDE. WE WOULD NEED DEPARTURES OF OVER 2 FEET FOR
MINOR FLOODING THIS EVENING AND THIS APPEARS UNLIKELY. BY EARLY
SUNDAY MORNINGS HIGH TIDE, WINDS SHOULD BE OFFSHORE AND TIDES
SHOULD BE CLOSER TO NORMAL.

SEAS WILL BE GETTING ROUGH THROUGH THIS EVENING AS GALE FORCE
NORTHEASTERLY WINDS ARE EXPECTED. THIS MAY CAUSE SOME BEACH
EROSION DUE TO THE INCREASED SURF.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO MIDNIGHT 
     EST TONIGHT FOR PAZ070-071.
     WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO MIDNIGHT 
     EST TONIGHT FOR PAZ060>062-067>069.
NJ...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO MIDNIGHT 
     EST TONIGHT FOR NJZ008-010-012-013-015>019.
     WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO MIDNIGHT 
     EST TONIGHT FOR NJZ007-009.
     COASTAL FLOOD ADVISORY FROM 8 AM THIS MORNING TO 1 PM EST THIS 
     AFTERNOON FOR NJZ020-022>027.
DE...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO MIDNIGHT 
     EST TONIGHT FOR DEZ001.
     COASTAL FLOOD ADVISORY FROM 8 AM THIS MORNING TO 1 PM EST THIS 
     AFTERNOON FOR DEZ003-004.
MD...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO MIDNIGHT 
     EST TONIGHT FOR MDZ008-012.
MARINE...GALE WARNING UNTIL 5 AM EST SUNDAY FOR ANZ431-452>455.
     SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 6 PM EST THIS 
     EVENING FOR ANZ450-451.
     GALE WARNING FROM 6 PM THIS EVENING TO 5 AM EST SUNDAY FOR 
     ANZ450-451.
     SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 5 AM EST 
     SUNDAY FOR ANZ430.

&&

$$

SYNOPSIS...IOVINO
NEAR TERM...IOVINO
SHORT TERM...IOVINO
LONG TERM...DELISI
AVIATION...GORSE
MARINE...GORSE
TIDES/COASTAL FLOODING...GORSE