-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 161956
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
356 PM EDT THU MAY 16 2013

.SYNOPSIS...
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A COLD FRONT WILL PUSH TO OUR SOUTH TONIGHT AND STALL TO OUR SOUTH
THROUGH THE UPCOMING WEEKEND. THE FRONTAL BOUNDARY IS EXPECTED TO
RETURN NORTHWARD AS A WARM FRONT LATE MONDAY INTO TUESDAY. ANOTHER
FRONTAL SYSTEM IS EXPECTED TO APPROACH THE AREA FROM THE WEST AND
MOVE THROUGH THE AREA DURING THE MIDDLE TO LATE PART OF NEXT WEEK.
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&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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DURING THE AFTERNOON, INSTABILITY AND MOISTURE WERE TRYING TO MOVE
IN FROM THE SOUTHWEST ACROSS THE AREA NEAR AND SOUTH OF THE I-78
CORRIDOR TO TAP SOME LINGERING MID LEVEL FORCING. AS ONE MOVED
FURTHER EAST ACROSS THAT AREA, THERE STILL WAS A CONSIDERABLE AMOUNT
OF CIN TO OVERCOME AS OF 18Z. OUR TAKE ON THIS IS THAT THE BEST
CHANCES FOR ACTIVITY EARLY IN THE NEAR TERM ARE OVER THE
SOUTHWESTERN PART OF THE FORECAST AREA, ALTHOUGH THE LATEST HRRR RUN
BROUGHT SOME SCATTERED ACTIVITY FURTHER NORTH. SINCE IT WAS FAIRLY
ACCURATE WITH THE MORNING ACTIVITY, WE KEPT A SLIGHT CHANCE WHERE
THE RAPID REFRESH INDICATED, BUT WE HAVE THE BEST CHANCE SOUTH OF
THE MASON-DIXON LINE. WE EXPECT TO LOSE ANY CONVECTION BY MIDNIGHT
AS A SECONDARY COLD FRONT WILL DROP ACROSS THE AREA AND PUSH DRIER
AIR SOUTH.

TEMPERATURES ARE A GUIDANCE/CONTINUITY BLEND. UP NORTH, THERE MAY BE
SOME RADIATING WITH LOWER DEW POINTS ALREADY IN PLACE AND WINDS
EXPECTED TO GO LIGHT AT LEAST INTO THE EVENING HOURS. THE SECONDARY
FRONT MAY MIX THINGS A BIT AND TURN THE REST OF THE NIGHT INTO A
MILDLY ADVECTIVE ONE.
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&&

.SHORT TERM /6 AM FRIDAY THROUGH 6 AM FRIDAY/...
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OUR FORECAST IS THAT THE SURFACE HIGH RIDGING DOWN FROM CENTRAL
CANADA AND SOME LOCAL MID LEVEL RIDGING TO OUR WEST (AHEAD OF A SLOW
MOVING SYSTEM THAT WAS THE CLOSED LOW RESPONSIBLE FOR THE SPLIT FLOW
EARLIER IN THE WEEK) WILL CARVE OUT A DRY DAY FOR THE ENTIRE
FORECAST AREA. THERE SHOULD BE A DECENT AMOUNT OF SUNSHINE, ALTHOUGH
SOME HIGH CLOUDINESS MAY BEGIN TO INVADE FROM THE SOUTH AND WEST
DURING THE COURSE OF THE DAY. WINDS SHOULD BE RATHER LIGHT AS HIGH
PRESSURE MOVES OVER US. TEMPERATURES ARE A GUIDANCE/CONTINUITY BLEND
IN LINE WITH H925 TEMPERATURES, AND ARE FORECAST TO BE A BIT ABOVE
NORMAL. THE CAVEAT IS THAT WE EXPECT A SEA BREEZE TO DEVELOP DURING
THE COURSE OF THE DAY.
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&&

.LONG TERM /FRIDAY THROUGH THURSDAY/...
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THE COLD FRONT WILL REMAIN STALLED TO OUR SOUTH FOR THE UPCOMING
WEEKEND. FRIDAY NIGHT INTO SATURDAY, HIGH PRESSURE WILL NOSE DOWN
ACROSS OUR AREA FROM THE NORTH, KEEPING THE FRONT TO OUR SOUTH AND
KEEPING OUR AREA IN MORE OF AN EASTERLY/SOUTHEASTERLY FLOW. SOME
GUIDANCE IS TRYING TO BRING SOME LIGHT QPF ACROSS THE AREA AS EARLY
AS FRIDAY NIGHT, BUT WE WILL KEEP FRIDAY NIGHT DRY. AS WE MOVE INTO
THE WEEKEND, A SLOW MOVING SHORT WAVE WILL BE SLIDING ACROSS THE
OHIO RIVER VALLEY AND TOWARD THE EAST COAST. THIS WILL PUSH SEVERAL
WEAK DISTURBANCES ACROSS THE AREA THROUGH THE WEEKEND, WHICH MAY
HELP CREATE SOME SHOWER ACTIVITY. THE AIRMASS SHOULD BE FAIRLY
STABLE, SO WE ARE NOT EXPECTING THUNDERSTORMS AT THIS TIME. WITH THE
EASTERLY/SOUTHEASTERLY FLOW, TEMPERATURES ARE NOT EXPECTED TO WARM
SIGNIFICANTLY EITHER.

AS THE HIGH PRESSURE REMAINS TO OUR NORTHEAST AND SLOWLY BUILDS OUT
TO SEA MONDAY INTO TUESDAY, MOISTURE WILL CONTINUE TO PUSH ACROSS
THE AREA THROUGH EARLY NEXT WEEK. THE FRONTAL BOUNDARY TO OUR SOUTH
IS EXPECTED TO BEGIN PUSHING BACK NORTHWARD AS A WARM FRONT AS WELL,
AND MAY MOVE THROUGH THE AREA BY MONDAY NIGHT INTO TUESDAY. WE COULD
CONTINUE TO SEE SOME PRECIPITATION ACROSS THE AREA AHEAD OF THE WARM
FRONTAL BOUNDARY AS SEVERAL WEAK DISTURBANCES MOVE ACROSS THE AREA
IN THE WESTERLY FLOW ALOFT.

AFTER THE WARM FRONT MOVES THROUGH, TUESDAY AND WEDNESDAY OF NEXT
WEEK LOOK TO BE THE WARMEST DAYS. WE DID NOT GO AS HIGH AS WHAT THE
850 MB ECMWF/GFS TEMPS WOULD FORECAST FOR SURFACE MAXES, BUT WE
SHOULD BE ABLE TO REACH AT LEAST THE LOW 80S FOR MUCH OF THE AREA.
WE WILL KEEP A CHANCE OF SHOWERS/THUNDERSTORMS IN THE FORECAST
TUESDAY/WEDNESDAY AS WE SHOULD BE IN THE WARM SECTOR AHEAD OF THE
NEXT APPROACHING FRONTAL SYSTEM. ANY SHORT WAVES/VORT MAXES COULD
HELP CREATE SHOWERS/THUNDERSTORMS WITH THE AVAILABLE INSTABILITY.

THE LATEST GFS/ECMWF VARY ON THEIR TIMING OF THE NEXT FRONTAL
SYSTEM. THE GFS BRINGS THE FRONT THROUGH WEDNESDAY NIGHT INTO
THURSDAY, WHILE THE ECMWF BRINGS IT THROUGH THURSDAY NIGHT INTO
FRIDAY. BEING SO FAR OUT, WE WILL KEEP A CHANCE OF SHOWERS IN THE
FORECAST THROUGH THURSDAY NIGHT FOR NOW.
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&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

SHOWER ACTIVITY HAD SLIPPED INTO THE MARYLAND EASTERN SHORE,
CENTRAL AND SOUTHERN DELAWARE AND FAR SOUTHERN NJ EARLY THIS
AFTERNOON. RADAR TRENDS SUGGESTED THAT ONLY SOME LIGHT SHOWERS
THREATENED THE SOUTHEASTERN TAF SITES EARLY. FURTHER NORTH, THERE IS
ONLY A SLIGHT CHANCE OF ANY ACTIVITY. ALL THE TAFS ARE VFR WITH SOME
CUMULUS EARLY AND THEN MID AND HIGH CLOUDS RECEDING SOUTHWARD TONIGHT.
MAINLY HIGH CLOUDS WITH PERHAPS A FEW CUMULUS ARE EXPECTED ON
FRIDAY. DRIER AIR IS EXPECTED TO MOVE DOWN FROM THE NORTH TONIGHT,
SO WE DON`T FORECAST ANY OVERNIGHT VISIBILITY RESTRICTIONS.

REGARDING WINDS, THE LATEST MODELS SHOW THEM PICKING UP FROM OUT OF
THE WEST EARLY IN THE TAF PERIOD WITH SOME GUSTS ABOVE 20 KT
POSSIBLE, THEN THEY SHOULD RELAX THIS EVENING BEFORE SHIFTING TO THE
NORTH OVERNIGHT THANKS TO A SECONDARY COLD FRONT. GENERALLY, WINDS
SHOULD BE RATHER GENTLE ON FRIDAY.

A SEA BREEZE HAD DEVELOPED AT ACY EARLIER TODAY, BUT WE THINK THE
STRENGTHENING WEST WIND WILL OVERWHELM IT EARLY IN THE TAF PERIOD. A
SEA BREEZE LIKELY WILL AFFECT ACY ON FRIDAY.

OUTLOOK...
FRIDAY NIGHT...MOSTLY VFR.

SATURDAY-SATURDAY NIGHT...MAINLY VFR WITH LOWERING CLOUDS. A
SLIGHT CHANCE OF SHOWERS AND SOUTH TO SOUTHEAST WINDS AROUND 5
KNOTS.

SUNDAY-SUNDAY NIGHT...GENERALLY VFR EXPECTED, POSSIBLE MVFR CIGS,
ESPECIALLY WITH ANY SHOWERS.

MONDAY-TUESDAY...GENERALLY VFR, POSSIBLE MVFR CIGS/VSBYS,
ESPECIALLY WITH ANY SHOWERS/THUNDERSTORMS.
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&&

.MARINE...
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ALTHOUGH WINDS WERE QUITE LIGHT OVER THE WATERS THIS AFTERNOON, A
RESURGENT SWELL ALONG THE FAR NORTHERN WATERS REQUIRED A SHORT-FUSED
ADVISORY FOR HAZARDOUS SEAS NORTH OF MANASQUAN INLET. MODELS SHOW
THE SWELL RETREATING BY THIS EVENING, AND THEN SEAS SHOULD BE
SUB-ADVISORY AND MORE OF A MIX OF DIMINISHING SWELLS AND MODEST TO
MODERATE WIND WAVES. THAT WILL BRING WINDS AND SEAS OVER ALL WATERS
BELOW ADVISORY CRITERIA THROUGH FRIDAY.

LIGHT WINDS THROUGH THIS EVENING ARE EXPECTED TO BECOME NORTHERLY
AND PICK UP SOME AS A SECONDARY COLD FRONT DROPS ACROSS THE COASTAL
WATERS OF NEW JERSEY AND DELAWARE. FORECAST PRESSURE RISES SUPPORT A
MODERATE BUT NOT ADVISORY LEVEL WIND. WINDS SHOULD DIMINISH AGAIN ON
FRIDAY. THE WINDS MAY BECOME ONSHORE NEAR LAND.

OUTLOOK...
CONDITIONS SHOULD REMAIN BELOW ADVISORY LEVELS THROUGH SATURDAY.
HOWEVER, WINDS MAY RETURN CLOSE TO ADVISORY LEVELS STARTING
SATURDAY NIGHT INTO SUNDAY AS THE PRESSURE GRADIENT TIGHTENS
ACROSS THE WATERS AS HIGH PRESSURE PUSHES OFF THE NORTHEAST COAST.
WITH THE EASTERLY/SOUTHEASTERLY FLOW, SEAS MAY RETURN TO SMALL
CRAFT ADVISORY LEVELS DUE TO THE LONG FETCH STARTING SUNDAY AND
CONTINUING INTO TUESDAY.
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&&

.FIRE WEATHER...
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WE WILL MENTION IN THE FIRE WEATHER FORECAST THAN MINIMUM RELATIVE
HUMIDITY LEVELS WILL DROP TO OR BELOW 30 PERCENT ON FRIDAY AFTERNOON
FOR MUCH OF THE FORECAST AREA. WINDS AND FINE FUELS ARE NOT A
CONCERN.
-- End Changed Discussion --

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 PM EDT THIS
     AFTERNOON FOR ANZ450.

&&

$$
SYNOPSIS...ROBERTSON
NEAR TERM...DELISI
SHORT TERM...DELISI
LONG TERM...ROBERTSON/YOUNG
AVIATION...DELISI/ROBERTSON
MARINE...DELISI/ROBERTSON
FIRE WEATHER...DELISI