FXUS61 KPHI 051438
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
938 AM EST SAT DEC 5 2009
.SYNOPSIS...
LOW PRESSURE THAT WAS DEVELOPING OFF THE SOUTHEAST COAST THIS
MORNING 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/...
THE FORECAST HAS BEEN UPDATED TO REFLECT CURRENT TRENDS. THESE
TRENDS INCLUDE THE RAIN CHANGING TO SNOW INTO THE PHILADELPHIA
AREA EARLIER IN THE AFTERNOON. THIS CHANGE ALSO MEANT WE NEEDED TO
INCREASE SNOW AMOUNTS A BIT AND NOW WE WILL BE FORECASTING 2-4
INCHES IN MOST AREAS FROM PHL NORTHWARD.
THIS QUICKER COOLING IS DUE TO DYNAMIC COOLING FROM LIFT
ASSOCIATED WITH THE UPPER TROUGH AS WELL AS COLD ADVECTION DUE TO
NE WINDS.
THE BEST LIFT IS LATE THIS AFTERNOON AND EARLY THIS EVENING. ALSO,
SINCE THIS WILL OCCUR AS SNOW IS FALLING IN THE ADVISORY AREA,
THIS SHOULD ALLOW SOME ACCUMULATION EVEN ON ROADWAYS.
TO THE SOUTHEAST OF THE ADVISORY AREA, MOSTLY RAIN IS EXPECTED DUE
TO FLOW FROM THE WARMER OCEAN. HOWEVER, EVEN THESE AREAS WILL
PROBABLY GET SOME SNOW MIXED IN, BUT ACCUMULATING SNOW IS NOT
EXPECTED.
BY MIDNIGHT, THE UPPER TROUGH AND ASSOCIATED LOW OFF THE COAST
WILL HEAD OUT TO SEA FAR ENOUGH THAT DRY AIR WILL ARRIVE FROM THE
NW SHUTTING OFF ANY PCPN.
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 /15Z 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 UNTIL 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 UNTIL MIDNIGHT EST TONIGHT FOR NJZ007-
009.
COASTAL FLOOD ADVISORY UNTIL 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 UNTIL 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 UNTIL 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 UNTIL 5 AM EST SUNDAY FOR ANZ430.
&&
$$
SYNOPSIS...IOVINO/STAUBER
NEAR TERM...IOVINO/STAUBER
SHORT TERM...IOVINO
LONG TERM...DELISI
AVIATION...GORSE
MARINE...GORSE
TIDES/COASTAL FLOODING...
