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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 070236
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
936 PM EST THU MAR 6 2014

.SYNOPSIS...
HIGH PRESSURE WILL GIVE WAY TO A LOW PRESSURE SYSTEM ORGANIZING OFF
THE SOUTHEASTERN UNITED STATES LATE TONIGHT. THE LOW IS EXPECTED TO
SKIRT BY OUR REGION TOWARDS THE SOUTHEAST AND THEN RAPIDLY MOVE OUT
TO SEA EARLY SATURDAY MORNING. A QUICK MOVING COLD FRONT WILL PUSH
THROUGH THE REGION LATE SATURDAY NIGHT INTO SUNDAY MORNING ALLOWING
FOR A RETURN OF HIGH PRESSURE FOR THE START OF THE NEW WORK WEEK.
THE HIGH WILL DEPART TO OUR SOUTH ON TUESDAY WHILE A CLIPPER LIKE
SYSTEM NEARS FROM THE WEST-NORTHWEST. THIS IS FOLLOWED BY THE
POTENTIAL FOR ANOTHER COASTAL LOW PRESSURE SYSTEM TO CROSS THE
REGION LATE WEDNESDAY AND THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
930 PM UPDATE...HIGH CLOUDS HAVE OVERSPREAD THE REGION, SO THE LOW
TEMPERATURES LOOK ON TRACK AS THE WINDOW OF OPPORTUNITY FOR PRIME
RADIATIONAL COOLING CONDITIONS HAS CLOSED. KEPT THE MENTION OF
FLURRIES AND DRIZZLE THROUGH THE NIGHT AS WELL. HOWEVER...THE LOW
CLOUDS HAVE NOT MADE NEARLY AS MUCH PROGRESS WEST AS PREVIOUSLY
EXPECTED. UNFORTUNATELY THE HIGH CLOUDS ARE MAKING IT DIFFICULT TO
ANALYZE WHY THIS IS, AS IT IS IMPOSSIBLE TO SEE THE EXTENT OF THE
LOW CLOUDS ON SATELLITE. HOWEVER, THE DRY MID LEVEL MAY BE PLAYING
A ROLE, AND IF SO, MAY NOT HAVE AS LONG OF A WINDOW OF TRACE
PRECIPITATION OVERNIGHT.

PREVIOUS NEAR TERM DISCUSSION...THE 12Z MODEL RUN SUITE SHOWED
CLOSER CONSENSUS AND LESS DRIFTING THAN THE PREVIOUS SOUNDING
RUNS. THE INITIALIZATION HAS CAUGHT UP TO THE RIDGING OVER THE WRN
CONUS AND AS SUCH NO FURTHER BACKING OF PCPN OCCURRED VS THE 00Z
RUN OR 12Z RUN FROM YESTERDAY. LOOKS LIKE 06Z GFS RUN CAUGHT UP TO
CONSENSUS. THE MODELS DID LOOK PRETTY GOOD AT 500MB, BUT THE WRF-
NMMB INITIALIZED UP TO 1C TOO COLD AT 850MB AND 925MB. THIS WAS
BETTER THAN THE GFS WHICH INITIALIZED THE CAD WAY TOO MUCH SW OF
US. ALSO THE DP/DT OF THE SFC HIGH SHOWS SLIGHTLY LESS DAMMING VS
THE LAST COUPLE OF SOUNDING RUNS. THE 18Z VERIFICATION OF PCPN
EXTENT SHOWED A SLIGHT BLEEDING OF MSRBL PCPN BEYOND MODEL
PROJECTIONS IN NC, BUT TOO FAST IN PLACES FARTHER TO THE WEST. OUR
CONCLUSION WITH THIS FCST PACKAGE WAS TO GO WITH THE ECMWF`S MASS
FIELDS AND THE WRF-NMM`S THERMAL FIELDS.

THERE IS A CHANCE OF SOME WINTRY PCPN AT THE ONSET, BUT CONFIDENCE
AND THE ABILITY TO MUSTER MORE THAN TRACE AMOUNTS FROM IT ARE TOO
LOW TO ISSUE AN ADVISORY. WE WILL HAVE MENTION IN THE HWO.

OCEAN EFFECT SNOW MADE IT BRIEFLY TO LONG BEACH ISLAND DURING THE
MID DAY AND SATELLITE IMAGERY STILL SHOWS STRATOCU LURKING. THE
VEERING OF WINDS MORE TOWARD THE EAST AND COUPLED WITH WEAK WAA
ALOFT SHOULD MORE EFFICIENTLY TRAP THIS STRATOCU MOISTURE TONIGHT.
SO WE EXPECT IT TO SPREAD WESTWARD. THE MESOSCALE MODELS WERE
CORRECT TODAY IN KEEPING MOST OF THE PCPN OFFSHORE. TONIGHT, THEY BE
OVERDOING IT, BUT ARE SHOWING SOME COASTAL CONVERGENCE INDUCED PCPN.
THERE ARE STILL SOME ECHOES OFFSHORE, SO ITS HARD TO TOTALLY
DISCOUNT IT. THE FCST MOISTURE LEVEL IS NOT THAT DEEP AND THERE IS
THE QUESTION AS TO WHETHER OR NOT SOME ICE FROM CLOUDS ABOVE CAN
CONVERT ANY PTYPE CHANCE TO SNOW. SO WE STARTED WITH FLURRIES SOUTH
WHERE THE MOIST LAYER IS DEEPER AND THEN ADDED THE CHANCE OF
FREEZING DRIZZLE (REALLY FREEZING SPRINKLES) LATE. BECAUSE OF THE
ONSHORE FLOW, WE ARE RAISING SFC TEMPERATURES OVERNIGHT NEAR THE
COAST. WE USED THE ECMWF 2M TEMPS AS THE FLOOR AS THEY HAVE SOMEHOW
MANAGED A COLD BIAS AWAY FROM OUR NRN CWA SINCE WE HAVE BEEN SNOW
COVERED. THE PTYPE CHANCES AT THE COAST BECOME LIQUID TOWARD
MORNING.

ON TOP OF THIS MESOSCALE EFFECT, WE HAVE THE SYNOPTIC SCALE SYSTEM
APPROACHING WITH LOW POPS LATE IN DELMARVA. BECAUSE OF THE
APPROACHING AND THICKENING CLOUDS, MIN TEMPS ARE EARLIER THAN USUAL.
WE AGAIN RUN THE RISK OF NOT BEING BULLISH ENOUGH NORTH WHERE THE
CLOUDS ARRIVE LAST. WE WERE MUCH CLOSER TO LOWER GFS MOS NORTH, BUT
CLOSER TO THE WARMER NAM MOS ELSEWHERE.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
WE USED MODELING CONSENSUS OF THE .05 ISOHYET FOR LIKELY POPS AND
HAVE CHANCE POPS TO ABOUT THE INTERSTATE 95 CORRIDOR. MODEL BACKING
HAS STOPPED AND AT LEAST LOOKS GOOD BASED ON THE UPSTREAM 500MB
STRUCTURE. THERE MIGHT BE SOME WINTRY PCPN AT THE ONSET OF THE PCPN
SHIELD NORTHWEST. THE FCST SOUNDINGS SUPPORT SLEET AS THE MOST
LIKELY NON LIQUID PTYPE. MENTION OF WINTRY PTYPES WAS LIMITED TO THE
MORNING AS WARMER AIR ALOFT IS FORECAST TO CONTINUE TO MOVE IN AS
THE DAYTIME HOURS PROGRESS. MAX TEMPS WERE A BIT MORE CONSERVATIVE
AND CLOSER TO STAT GUIDANCE CONSENSUS BECAUSE OF THE CLOUDINESS AND
FLOW OFF THE CHILLY OCEAN. WHILE WINDS OVERALL ARE NOT EXPECTED TO
BE AN ISSUE WITH SYSTEM, GUSTS ALONG COASTAL AREAS SHOULD REACH 20
TO 30 MPH ALONG COASTAL NEW JERSEY AND 30 TO 40 MPH ALONG COASTAL
SUSSEX COUNTY DELAWARE.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
AT THE START OF THE LONGTERM WE WILL BE CONTINUING TO DEAL WITH THE
LINGERING RAIN FROM THE COASTAL LOW WELL TO OUR SOUTHEAST. THE
LATEST GUIDANCE STILL HAS THE SYSTEM PULLING OFF THE COAST EARLY
SATURDAY MORNING BUT THE NORTHWARD DRIFT CONTINUES TO BE THE ISSUE
WITH INCREASES POPS THE PAST COUPLE OF DAYS. RATHER THAN WIPE OUT
ALL THE POPS TOO FAST WE STILL SEE LIKELY POPS ACROSS THE EXTREME
SOUTHERN DELMARVA LATE FRIDAY NIGHT TAPERING TO NOTHING BY
MID-SATURDAY MORNING. WE HAVE INCREASED POPS A BIT FURTHER TO THE
NORTH JUST CLIPPING THE PHILADELPHIA METRO AREA AS PER THE
SREF/GFS/EURO SHOWS. THERE IS MUCH BETTER CONSENSUS WITH THE 12Z
RUNS TODAY AND HOW THEY HANDLE THE OPENING WAVE IN THE MID-LEVELS
ADDING TO HIGHER CONFIDENCE.

WEAK SURFACE RIDGING THEN TAKES OVER AND THE LOW-LEVELS BEGIN TO
WARM WITH WESTERLY WINDS ALOFT. SATURDAY WILL BE AN EVEN NICER DAY
THAN FRIDAY WITH TEMPERATURES EXPECTED TO REACH 50F FROM PHILLY
SOUTHWARD, AND UPPER-40S ELSEWHERE. SHOULD HAVE PLENTY OF SUNSHINE
ADDED INTO THE MIX AND WITH A BRISK WEST-NORTHWEST WIND WE COULD ADD
ANOTHER DEGREE OR TWO WITH SOME DOWNSLOPING. NOT QUITE SURE THE SNOW
COVER ACROSS CENTRAL AND EASTERN PENNSYLVANIA WILL HAVE MUCH AN
IMPACT AND THE GUIDANCE AS OF LATE HAS NOT BEEN HANDLING DAYTIME
HIGHS TOO WELL. THAT BEING SAID WE DID EDGE A BIT WARMER THAN STAT
GUIDANCE SUGGESTS THOUGH ADDED CLOUD COVER COULD PROHIBIT SOME.

FRONTAL BOUNDARY WILL SAG THROUGH THE REGION LATE SATURDAY NIGHT
INTO SUNDAY MORNING. CURRENTLY THE FRONT LOOKS MOISTURE STARVED AND
THE ZONAL FLOW OVERHEAD SHOULD LIMIT THE AMOUNT OF MOISTURE THIS
THING COULD TAP INTO, SO BASICALLY IT WOULD HAVE TO BRING ITS OWN
MOISTURE TO THE PARTY. HAVE SLIGHT CHANCE POPS FOR NOW FOR SUNDAY.
TEMPERATURES DROP BEHIND THE FRONT AND SUNDAY LOOKS TO BE THE
COOLEST DAY OVER THE WEEKEND.

ANOTHER WEAK SURFACE RIDGE BUILDS IN BEHIND THE FRONTAL BOUNDARY AND WE
SHOULD SEE ANOTHER UPWARD TICK OR TWO WITH TEMPERATURES. AGAIN
DOWNSLOPING COULD HELP TO BOOST TEMPERATURES BY A COUPLE OF DEGREES
BUT WE SHOULD BE SLIGHTLY ABOVE NORMAL ON MONDAY AND TUESDAY. THE
NEXT NORTHERN STREAM SYSTEM PRESSES IN BY LATE TUESDAY INTO
WEDNESDAY WITH ANOTHER FRONTAL BOUNDARY MOVING THROUGH. AT THIS TIME
THE LONG-RANGE GUIDANCE SHOWS QUITE A BIT OF SPREAD IN TERMS OF
ANOTHER COASTAL OR INTERIOR LOW FORMING JUST TO OUR SOUTH. THERE IS
THE POTENTIAL FOR SYSTEM TO FORM BUT THE RIGHT TIMING NEEDS TO TAKE
SHAPE. WE WILL STILL BE IN SPLIT FLOW LATE IN THE PERIOD BUT SOME OF
THE GUIDANCE IS SUGGESTING NORTHERN AND SOUTHERN STREAM INTERACTION
TO OCCUR. IF THIS WERE TO HAPPEN THAN EAST COAST CYCLOGENESIS COULD
OCCUR. AT THIS JUNCTURE NOTHING THIS IS VERY LOW CONFIDENCE.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

02Z UPDATE...MVFR CEILINGS CONTINUE TO HOLD ALONG OR JUST OFF THE
COAST, ONLY AFFECTING KACY AT THIS HOUR. HAVE PUSHED BACK THE
TIMING OF THE MVFR CEILINGS AT ALL TERMINALS EXCEPT KRDG AND KABE.
HOWEVER, WITH THE HIGH CLOUDS MASKING THE EXTENT OF THE LOW CLOUDS
ON SATELLITE, CONFIDENCE IN THE TIMING IS LOWER THAN USUAL. STILL
EXPECT LOW CLOUDS TO EXTEND ACROSS THE REGION BY 12Z.

ON FRIDAY MORNING, THERE IS A CHANCE THE CEILING MIGHT LOWER TO
IFR ESPECIALLY WITH ANY PRECIPITATION. HIGHEST CHANCES ARE IN NJ
AND DE AIRPORTS. NORTHEAST WINDS SHOULD INCREASE TO ABOUT 10 TO 15
KNOTS ON AVERAGE, WITH POSSIBLE HIGHER GUSTS AT EASTERN AIRPORTS
AND KACY AND KMIV. THE CHANCE FOR PRECIPITATION IS PRIMARILY
CONFINED TO KACY AND KMIV WHERE RA IS LIKELY, AND KPHL AND KILG
WHERE THERE IS A LOW CHANCE OF RA TOMORROW.

DO NOT EXPECT TO SEE ANY IMPROVEMENT IN THE CEILINGS UNTIL THE
WINDS BEGIN TO BACK AFTER 18Z...AT KRDG AND KABE FIRST BY 21Z, AND
THE OTHER AIRPORTS AT OR AFTER 00Z.

OUTLOOK...
FRIDAY NIGHT - SATURDAY...CONDITIONS IMPROVING TO MOSTLY VFR BY
EARLY SATURDAY MORNING. MODERATE CONFIDENCE.

SATURDAY NIGHT - SUNDAY...MOSTLY VFR. LIGHT RAIN/SNOW SHOWERS
POSSIBLE.

MONDAY - TUESDAY...VFR.

&&

.MARINE...
THE SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR LOWER DELAWARE BAY
AND OUR OCEAN WATERS THROUGH FRIDAY DAY. WE UPPED SEAS ABOVE WAVE
WATCH GUIDANCE BASED ON CURRENT VERIFICATION. THERE IS A LOW
CHANCE THAT GALE FORCE WIND GUSTS MIGHT OCCUR FRIDAY DAY ON THE
DELAWARE OCEAN COASTAL WATERS, BUT CHANCES ARE CONSIDERED TOO LOW TO
UPGRADE WITH THIS PACKAGE.

OUTLOOK...
FRIDAY NIGHT - SATURDAY NIGHT...THE SCA CONDITIONS WILL PERSIST
THROUGH SATURDAY MORNING BEFORE TAPERING OFF AS THE COASTAL LOW TO
OUR SOUTHEAST QUICKLY MOVES FURTHER OUT TO SEA.

SUNDAY - TUESDAY...SUB-SCA CONDITIONS ARE EXPECTED AT THIS TIME.
WINDS BECOME MORE NORTHWESTERLY BEHIND A COLD FRONT ON SUNDAY.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST SATURDAY FOR ANZ431-
     450>455.

&&

$$
SYNOPSIS...HEAVENER
NEAR TERM...GIGI/JOHNSON
SHORT TERM...GIGI
LONG TERM...HEAVENER
AVIATION...GIGI/HEAVENER/JOHNSON
MARINE...GIGI/HEAVENER