-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 160746
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
346 AM EDT SUN JUN 16 2013

.SYNOPSIS...
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A HIGH PRESSURE SYSTEM CRESTING THE APPALACHIANS WILL MOVE
OFFSHORE TODAY. AN AREA OF LOW PRESSURE WILL TRACK FROM THE GREAT
LAKES INTO SOUTHEASTERN CANADA LATER TODAY INTO MONDAY. ITS FIRST
COLD FRONT IS EXPECTED TO DISSIPATE AS IT MOVES THROUGH THE AREA
LATE TONIGHT. ITS NEXT COLD FRONT IS SCHEDULED TO MOVE THROUGH ON
TUESDAY WITH POSSIBLY A NEW WAVE OF LOW PRESSURE FORMING ALONG IT.
A HIGH PRESSURE SYSTEM WILL THEN BUILD INTO THE FORECAST AREA
WEDNESDAY AND THURSDAY, BEFORE SHIFTING TO OUR EAST FRIDAY INTO
SATURDAY.
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&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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SURFACE HIGH PRESSURE WILL SETTLE TO OUR SOUTHEAST TODAY RESULTING
IN A SOUTHWESTERLY FLOW ACROSS THE AREA. THIS WILL INCREASE THE LOW
LEVEL MOISTURE AND WE WILL SEE CLOUDS MOVE INTO THE REGION THROUGH
THE DAY.

IN THE MID LEVELS, THE FLOW BECOMES MORE ZONAL AND SEVERAL
SHORTWAVES WILL MAKE THEIR WAY THROUGH THE FLOW AND ACROSS OUR AREA.
THE FIRST WAVE WILL MOVE THROUGH THIS MORNING WITH A FEW LIGHT
SHOWERS POSSIBLE. THE SECOND WAVE ARRIVES IN OUR AREA LATER THIS
AFTERNOON/EARLY EVENING. IN ADDITION, A SURFACE TROUGH DEVELOPS TO
OUR WEST AND PUSHES INTO OUR AREA AROUND THE SAME TIME. THIS MAY
HELP TO BE A TRIGGER FOR SHOWER AND THUNDERSTORM DEVELOPMENT THROUGH
THIS EVENING. THE UPPER JET IS LOCATED TO OUR NORTH AND COMBINED
WITH CAPE VALUES LESS THAN 1000J/KG AND EXTENSIVE CLOUD COVER, WE
MAY BE LIMITED IN JUST HOW MUCH CONVECTION CAN GET GOING. WE MAY SEE
A FEW STRONG STORMS DEVELOP BUT OVERALL CONVECTION LOOKS TO BE
LIMITED FOR TODAY.

TEMPERATURES WILL RISE AS WARMER AIR IS ADVECTED INTO THE REGION IN
THE SOUTHWEST FLOW, EVEN THOUGH WE WILL HAVE PLENTY OF CLOUD COVER
AROUND. EXPECT MAXIMUM TEMPERATURES TO BE IN THE 80S ACROSS MOST OF
THE AREA TODAY.
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&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
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THE AFOREMENTIONED SURFACE TROUGH MOVES THROUGH THE AREA TONIGHT
WITH SHOWERS AND THUNDERSTORMS ACCOMPANYING IT. AS THE TROUGH MOVES
TO THE EAST, WE WILL LOSE THE CONVECTIVE FOCUS AND SHOWERS AND
THUNDERSTORMS SHOULD START TO DIMINISH.

IN THE WAKE OF THE TROUGH, WE SHOULD BE ABLE TO LOSE SOME OF OUR
CLOUDINESS AND BECOME PARTLY CLOUDY AS WE HEAD TOWARD MORNING.

TEMPERATURES WILL REMAIN ON THE WARM SIDE AS WE HAVE EXTENSIVE
CLOUDINESS ACROSS THE REGION. EXPECT LOWS TO BE IN THE 60S ACROSS
THE AREA.
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&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
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WHILE THE GFS INITIALIZATION LOOKED BETTER FROM A HEIGHT FIELD
PERSPECTIVE AT 500MB, THE OBSERVED WINDS LOOKED BETTER OFF THE
WRF-NMMB. THE PROBLEM LIES IN THE EVENTUAL EVOLUTION OF THE TROF
THROUGH THE MIDDLE OF THE WEEK WITH THE GFS IN ITS USUAL FAST
TIMING POSN. THERE HAS NOT BEEN CLOSE RUN TO RUN CONTINUITY WITH
THE MODEL ON THIS AND THUS THIS FCST PACKAGE IS GOING TO SHY AWAY
FROM IT, COMING CLOSER TO A SREF AND UKMET SOLN IN THE NEARER LONG
TERM AND A CONTINUITY/LATEST HPC THOUGHTS IN THE FURTHER LONG
TERM. IN GENERAL THE WRF-NMMB LOOKED BETTER AT 925MB AND 850MB,
ALTHOUGH THE THERMAL DIFFERENCES INTO TUESDAY ARE MORE OF TIMING.

AN INITIAL COLD FRONT IS EXPECTED TO DISSIPATE AS IT MOVES THROUGH
OUR CWA EARLY MONDAY. IN ITS WAKE WESTERLY FLOW IS PREDICTED TO OCCUR
AS IS MID LEVEL CAPPING TO DEVELOP. WE HAVE EXPANDED ON THE IDEA
OF THE POTENTIAL FOR A DRY MONDAY LIMITING POPS TO THE SE CWA IN
THE MORNING WHERE CAPPING MAY NOT BE IN PLACE IN TIME AND THE FAR
NORTHWEST WHERE ITS EROSION FROM A PREDICTED APPROACHING SHORT
WAVE MIGHT ARRIVE BY THE END OF THE DAY. OUR CWA IS ALSO PREDICTED
TO BE ON THE CONVERGENT SIDE OF THE APPROACHING 250MB JET WITH NO
FCST MID LEVEL QVEC CONVERGENCE. ALL POINT TO RELATIVELY LOW POPS
IF ANY. NOT MANY CHANGES TO MAX TEMPS. REMAINED RELATIVELY
CONSERVATIVE WITH THEM GIVEN THE RECENT WETNESS. ACTUAL MAX TEMPS
EVEN WEST OF US VS TRADITIONAL 1000-850MB THICKNESS VALUES HAVE
NOT BEEN THAT ROBUST.

A SECOND COLD FRONT IS PREDICTED TO APPROACH OUR CWA ON MONDAY NIGHT
OR IF ONE WOULD FOLLOW THE GFS CLEAR MOST OF THE AREA BY MORNING.
REGARDLESS OF THE GFS TIMING, ANY ONGOING CONVECTION THAT DEVELOPS
IN MORE FAVORABLE REGIONS WOULD STAND THE CHANCE OF SURVIVING. PLUS
WE ARE FORECAST TO GET INTO A MORE FAVORABLE QUADRANT OF THE JET
ALOFT. MIN TEMPS NOT FAR FROM STAT GUIDANCE.

THEN TUESDAY IN PARTICULAR, (NOT AS CONFIDENT ABOUT TUESDAY
NIGHT) WE MAINTAINED POPS AND CHOSE A CLOSER TO SREF SOLUTION FOR
THE POSITIONING OF THE COLD FRONT AND THE WAVE ON IT. ONLY BOWING
TO THE GFS IS TO PLACE HIGHER POPS SE BOTH PERIODS. EVEN THE
PRESENT GFS SOLN KEEPS OUR CWA IN THE FAVORABLE ENTRANCE REGION OF
THE 250MB JET TUESDAY WITH FCST MID LEVEL QVEC CONVERGENCE PRETTY
MUCH THRUT OUR AREA. AS FAR AS STRONG/SEVERE THREAT IS CONCERNED, THE
FCST CAPES ARE NOT THAT ROBUST, ALTHOUGH THE BULK SHEAR WILL BE
INCREASING. A BIT CONCERNED ABOUT CLOUDINESS PUTTING A LID PER SE
ON TSRA STRENGTH. LATEST GUIDANCE SUGGEST IF THERE WOULD BE A SPOT
FOR STRONGER STORMS, IT WOULD BE IN THE SERN PART OF OUR CWA. NOT
PARTICULARLY CONFIDENT ABOUT MAX TEMPS BECAUSE OF THE COMPLICATION
FROM SKY COVER AND DIFFERENCES IN FRONTAL POSNS. SINCE ANDREA MOST
OF OUR PCPN CHANCES HAVE BEEN OUTPERFORMING AND WHILE SOME OF THE
MEDIUM RANGE MODEL OUTPUT HAS SOME GRIDSCALE FEEDBACK LOOK TO
THEM, THE FCST PWAT ARE EXPECTED TO GET TO AROUND 1.5". AT THE
LEAST SOME TYPICALLY OR LOCALLY HEAVY DOWNPOURS WOULD BE POSSIBLE.

NO BIG CHANGES THEN WERE MADE FOR THE REST OF THE LONG TERM. DONT
KNOW HOW MANY MORE OF THESE WE WILL HAVE THIS MET SUMMER, BUT ANOTHER
REFRESHING CANADIAN AIR MASS IS FORECAST TO ARRIVE FOR WEDNESDAY
AND THURSDAY BEFORE THE ATTENDING HIGH PRESSURE SYSTEM MOVES
OFFSHORE. THE RETURN FLOW WILL NOT ONLY BRING IN HIGHER TEMPS, BUT
ALSO A CHANCE FOR MORE THUNDERSTORMS AS A WEAK WARM FRONT MOVES
THROUGH THE AREA.
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&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
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HE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

MAINLY VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD.

HIGH AND MID LEVEL CLOUDINESS WILL INCREASE THROUGH THIS MORNING,
MOVING IN FROM THE WEST. AS HIGH PRESSURE SETTLES TO OUR SOUTHEAST,
THE RETURN FLOW AROUND THE HIGH WILL CAUSE AN INCREASE IN LOW LEVEL
MOISTURE. A SURFACE TROUGH DEVELOPS ACROSS OUR AREA TODAY AND MAY
HELP TO BE A FOCUS FOR SHOWERS AND THUNDERSTORMS THIS AFTERNOON. WE
ADDED SOME VFR SHOWERS TO THE TAFS FOR LATER THIS AFTERNOON/EVENING.
TIMING STILL REMAINS AN ISSUE AND WITH LOW CONFIDENCE, NO THUNDER
WAS INCLUDED AT THIS TIME.

A SOUTHWESTERLY FLOW DEVELOPS AS HIGH PRESSURE SETTLES TO OUR
SOUTHEAST. GOOD VERTICAL MIXING WILL OCCUR OVER LAND AND THE WINDS
WILL BECOME GUSTY BY LATE MORNING AND CONTINUE THROUGH THE EARLY
EVENING WITH GUSTS UP TO 25 KNOTS EXPECTED. WINDS WILL BEGIN SUBSIDE
TONIGHT, GOING LIGHT AND VARIABLE IN SOME LOCATIONS.

OUTLOOK...
MONDAY...MOSTLY VFR. ISOLATED MVFR CAUSING SHOWERS AND THUNDERSTORMS.

MONDAY NIGHT AND TUESDAY...AVERAGING VFR, HOWEVER MVFR OR LOWER AT
TIMES IN SHOWERS AND THUNDERSTORMS.

TUESDAY NIGHT...VFR WITH SOME POCKETS OF MVFR OR IFR AT OUTLYING
AIRPORTS AND TERMINALS IN FOG AND ANY RESIDUAL PRECIPITATION EARLY.

WEDNESDAY AND THURSDAY...VFR.
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&&

.MARINE...
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A SMALL CRAFT ADVISORY WILL BE IN EFFECT FROM THIS AFTERNOON THROUGH
LATE TONIGHT ON THE OCEAN WATERS.

CONDITIONS ON THE AREA WATERS WILL START OFF FAIRLY BENIGN TODAY AS
HIGH PRESSURE SETTLES TO OUR SOUTHEAST. SEAS WILL GRADUALLY START TO
BUILD IN THE SOUTH TO SOUTHWEST FLOW AND WILL START TO APPROACH 5
FEET THIS AFTERNOON AND WILL THEN REMAIN NEAR 5 FEET THROUGH MUCH OF
TONIGHT. WINDS WILL GUST AROUND 20 KNOTS ON THE WATERS TODAY. WHILE
THE WINDS JUST ABOVE THE SURFACE LOOK TO BE IN THE 25 TO 30 KNOT
RANGE, AN INVERSION OVER THE WATER AS WARMER AIR MOVES IN, WILL
PREVENT THEM FROM MIXING EFFICIENTLY DOWN TO THE SURFACE. A FEW
GUSTS UP TO 25 KNOTS MAY OCCUR, ESPECIALLY LATER THIS AFTERNOON.

OUTLOOK...
UNCERTAINTY HIGHER THAN AVERAGE BECAUSE OF MODELING DIFFERENCES WITH
RESPECT TO THE DEVELOPMENT OF A WAVE OF LOW PRESSURE ON THE FRONT
ABOUT TUESDAY. FOR MONDAY SMALL CRAFT ADVISORY CONDITIONS (MAINLY
SEAS ON THE OCEAN) MIGHT LINGER INTO THE MORNING BEFORE THE
WEAKENING FIRST FRONT LOOSENS THE PRESSURE GRADIENT. AFTER THAT, THE
NEXT WAVE OF LOW PRESSURE MIGHT BE STRONG ENOUGH TO BRING SMALL
CRAFT ADVISORY CONDITIONS (5 FOOT SEAS) BACK TO THE OCEAN ZONES ON
TUESDAY. THEN THE CIRCULATION BETWEEN THAT WAVE OF LOW PRESSURE AND
APPROACHING HIGH PRESSURE SYSTEM MIGHT CAUSE WIND GUSTS TO BE CLOSE
OR REACH SMALL CRAFT ADVISORY CRITERIA LATER TUESDAY INTO WEDNESDAY
ACROSS OUR ENTIRE MARINE AREA. AS THE HIGH PRESSURE SYSTEM IS
FORECAST TO COME CLOSER LATER WEDNESDAY INTO THURSDAY, WE ARE MORE
CONFIDENT ABOUT SUB SMALL CRAFT ADVISORY CONDITIONS OCCURRING ON
ALL OF THE AREA WATERS.
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&&

.PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 6 AM EDT
     MONDAY FOR ANZ450>455.
-- End Changed Discussion --

&&

$$
SYNOPSIS...GIGI/GORSE
NEAR TERM...MEOLA
SHORT TERM...MEOLA
LONG TERM...GIGI
AVIATION...GIGI/GORSE/MEOLA
MARINE...GIGI/MEOLA