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Area Forecast Discussion
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000
FXUS61 KPHI 301959
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
359 PM EDT SUN AUG 30 2015

.SYNOPSIS...
A WEAKENING COLD FRONT WILL ARRIVE TONIGHT, OTHERWISE HIGH PRESSURE
WILL REMAIN CENTERED MAINLY NEAR THE MID ATLANTIC REGION THROUGH
MUCH OF THIS WEEK. A WEAK COLD FRONT SHOULD SLIDE SOUTH THROUGH
OUR REGION THURSDAY NIGHT OR FRIDAY. THEREAFTER, HIGH PRESSURE
WILL RESIDE ALONG THE EASTERN NEW ENGLAND COAST THROUGH SUNDAY,
PROBABLY PROVIDING A LITTLE RELIEF FROM THE HEAT THIS COMING
WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
A SHORT WAVE TROUGH WILL ARRIVE INTO THE NORTHEAST TONIGHT AND AS IT 
DOES IT SHOULD TEND TO WEAKEN. A WEAK COLD FRONT AT THE SURFACE IS 
TIED TO THIS FEATURE, AND WITH SOME INCREASE IN MOISTURE SOME 
SHOWERS AND A THUNDERSTORM ARE ONGOING NEAR OR IN OUR NORTHWESTERN 
ZONES. THE OVERALL LIFT, SHEAR AND INSTABILITY LOOKS WEAK ENOUGH TO 
KEEP ANY CONVECTIVE CORES FROM GETTING TO ROBUST. THE INITIATION 
EARLY ON APPEARED TO BE DRIVEN BY TERRAIN IN NORTHEASTERN 
PENNSYLVANIA, AND VISIBLE SATELLITE IMAGERY THIS AFTERNOON SHOWS THE 
MAIN CUMULUS DEVELOPMENT MAINLY OVER THE HIGHER TERRAIN. THE FLOW 
BELOW ABOUT 10000 FEET IS 15 KNOTS OR LESS, THEREFORE THIS ACTIVITY 
WILL SLOWLY SHIFT EASTWARD THROUGH THIS EVENING ALTHOUGH IT SHOULD 
TEND TO WEAKEN WITH AN EASTERN AND SOUTHERN EXTENT. A FEW LOCALES 
WILL GET SOME NEEDED RAIN IN THE FORM OF DOWNPOURS.

WE THEREFORE KEPT LOW POPS POPS GOING FOR A TIME THROUGH EARLY TO 
MID EVENING, ALTHOUGH INCREASED THEM A BIT ACROSS THE NORTHWEST 
ZONES INTO THIS EVENING GIVEN ADDITIONAL DEVELOPMENT TO OUR WEST. 
SOME GUIDANCE WANTS TO HANG ONTO SOME ISOLATED ACTIVITY OVERNIGHT, 
HOWEVER THAT MAY BE OVERDONE. OTHERWISE, AREAS OF MID TO HIGH LEVEL 
CLOUDINESS WILL MOVE ACROSS THE AREA DUE TO THE INCOMING SHORT WAVE 
TROUGH AND ALSO A NORTHERN JET STREAK PULLING NORTHWARD MOISTURE 
FROM AN THE UPPER-LEVEL LOW ACROSS THE EASTERN GULF COAST.

IT WILL BE A WARMER NIGHT ACROSS MUCH OF THE AREA AS THE DEW POINTS 
TEND TO HANG NEAR THE MUGGY LEVEL. SOME FASTER COOLING THIS EVENING 
THOUGH SHOULD OCCUR MAINLY ALONG THE COAST WITH A SEA BREEZE, WHICH 
WILL WEAKEN. AS FOR THE LOW TEMPERATURES, WE USED A MOS BLEND THEN 
MADE SOME LOCAL TWEAKS.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
AN UPPER-LEVEL TROUGH IS FORECAST TO AMPLIFY SOME ACROSS NEW ENGLAND 
ON MONDAY. THE SOUTHWESTERN EXTENT OF THIS FEATURE REACHES INTO THE 
MID ATLANTIC REGION. THIS PROVIDES SOME CYCLONIC FLOW ALOFT, WHILE 
AT THE SURFACE WEAK HIGH PRESSURE GENERALLY REMAINS NEARBY. A WEAK 
SURFACE FRONT OR TROUGH LOOKS TO BE DRAPED ACROSS OUR AREA, AND 
WHILE A SHOWER OR THUNDERSTORM CANNOT BE RULED OUT THIS IS OF LOW 
CONFIDENCE. THE MODEL GUIDANCE OVERALL DOES NOT HAVE A STRONG SIGNAL 
FOR CONVECTIVE DEVELOPMENT, AND SINCE THE CHC LOOKS RATHER LOW WE 
OPTED TO LEAVE OUT ANY MENTION ATTM. IT IS POSSIBLE A FEW ISOLATED 
CELLS ARE AROUND TO START THE DAY AS SOME FORECAST SOUNDINGS DO SHOW 
SOME INCREASE IN MID LEVEL INSTABILITY AROUND DAYBREAK.

OTHERWISE, A DECENT AMOUNT OF MID TO HIGH LEVEL CLOUDS SHOULD BE 
AROUND WHICH WILL COMBINE WITH SOME CUMULUS DEVELOPMENT. A RATHER 
WARM TO HOT AFTERNOON IS EXPECTED GIVEN THE SOUTHWESTERLY FLOW AND 
ANY NOTABLE COOLING ALOFT IS MOSTLY ACROSS NEW ENGLAND. AS A RESULT, 
WE LEANED CLOSER TO THE WARMER GFS MOS FOR MOST PLACES REGARDING 
HIGH TEMPERATURES.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...

500 MB: IN GENERAL, A FAIRLY STRONG SUMMER RIDGE OF HIGH PRESSURE
WILL PREVAIL ALONG THE EAST COAST THROUGH NEXT SUNDAY WITH ONLY A
MINOR WEAKENING OF THIS RIDGE OVER OUR AREA LATE WEDNESDAY INTO
FRIDAY, AS A STRONG SHORT WAVE DIVES SEWD TOWARD THE MARITIMES
(55N/55W). THAT PERMITS A LITTLE MORE NORTHERLY COMPONENT ALOFT
LATE THIS COMING WORKWEEK AND SO AN ASSOCIATED BOUNDARY SLIPS
SOUTHWARD. ITS COOLING EFFECTIVENESS FELT PRIMARILY ALONG THE
COASTAL PLAIN. 

TEMPERATURES: AUGUST THROUGH THE 29TH WAS AVERAGING NEAR OR ABOVE 
NORMAL. KMPO AND KGED WERE THE ONLY TWO OF THE 8 CLIMATE SITES
BELOW NORMAL. KTTN KACY AND KPHL WERE AVERAGING ~1 TO ~2F ABOVE
NORMAL AND WILL WARM THESE LAST TWO DAYS OF THE MONTH.
 
CALENDAR DAY DEPARTURES TUESDAY THROUGH THURSDAY WILL BE 6 TO 12 
DEGREES ABOVE NORMAL WITH THE LARGEST POSITIVE DEPARTURES N AND NW  
OF KPHL OF E PA AND THE NORTHWEST HALF OF NJ. FRIDAY THROUGH SUNDAY
SHOULD STILL AVERAGE 5 DEGREES OR MORE ABOVE NORMAL, POSSIBLY STILL
10 DEGREES ABOVE, ESPECIALLY NW OF I-95. HOW MUCH COOLING OCCURS
FRIDAY AND BEYOND IS DEPENDENT ON THE STRENGTH OF ONSHORE FLOW. IT
APPEARS THE GREATEST IMPACT OF COOLING ONSHORE FLOW WILL BE THE
SOUTHERN NJ AND DE COASTS.
 

FORECAST BASIS: UNLESS OTHERWISE NOTED, 12Z/30 GFS MOS WAS THE
PRIMARY GUIDANCE MONDAY NIGHT-TUESDAY NIGHT, 12Z/30 MEX MOS
WEDNESDAY THROUGH THURSDAY, THEN THE 1521Z/30 WPC GRIDDED
ELEMENTS OF MAX/MIN TEMP, 12 HOUR POP, 6 HOUR DEWPOINT- SKY-WIND
FROM THURSDAY NIGHT ONWARD. THE EXCEPTION HERE...WAS MEX AND WPC
MIN TEMPS WERE BLENDED 50 50 FRI NIGHT AND SAT NIGHT. 

HAZARDS...

A HEAT WAVE WILL BE IN PROGRESS THROUGH THURSDAY FOR THE I-95 
CORRIDOR EASTWARD TO NEAR THE COASTS, ITS DURATION SHOULD BE AT
LEAST 4 DAYS WHETHER OR NOT IT BEGINS THIS AFTERNOON OR MONDAY.
THE QUESTION, DOES IT BREAK ANYTIME FRIDAY-SUNDAY OR JUST GO ON
AND ON THROUGH EARLY NEXT WEEK IN THE INTERIOR NEAR AND NW OF I-95.
IT IS POSSIBLE THE I-95 CORRIDOR COULD SEE AN EXTENDED HEAT WAVE
BEYOND 6 DAYS (TODAY-SUNDAY THROUGH THURSDAY LOOK SOLID FOR 90-95F
AND FRIDAY LOOKS LIKE A BETTER THAN EVEN CHANCE OF 90 PLUS). MAX
HEAT INDEX VALUES IN THIS HEAT WAVE SO FAR ARE FORECAST TO BE IN
THE MID TO UPPER 90S. THERE IS A SLIM CHANCE WE WILL NEED A HEAT
ADVISORY FOR THE URBAN CORRIDOR EITHER OF ANY THREE AFTERNOONS
BETWEEN THIS COMING WEDNESDAY AND FRIDAY.

THUNDERSTORM DRENCHING RAINS? NEAR THE COOL FRONT FRIDAY BUT OVERALL
AS PER WPC, THE DRY SPELL IS GOING TO LAST QUITE AWHILE, POSSIBLY
THROUGH THE START OF LABOR DAY WEEK.
 
THE DAILIES...

MONDAY NIGHT-THURSDAY...FAIR AND HOT AFTERNOONS WITH PATCHY FOG 
POSSIBLE LATE AT NIGHT OVER THE COUNTRYSIDE, MAINLY NW NJ AND E
PA. LIGHT WINDS TEND TO BE W-NW DURING EACH AFTERNOON. SMALL CHC
OF CONVECTION E PA AND NNJ WED AFTN AND THU AFTN PER INSTABILITY
INDICATORS INCLUDING KI. 

THU NIGHT-FRIDAY...A SWD MOVING COLD FRONT MAY SPAWN HEAVY SOUTHWARD 
MOVING CONVECTION BUT ONLY IN A PWAT OF 1.6 INCHES. SLOW MOVERS-
GULLY WASHERS WHERE THEY OCCUR BUT LITTLE PREDICTABILITY ATTM EXCEPT 
MOST OF THE ACTIVITY SHOULD REMAIN JUST INLAND.  POTENTIALLY STILL 
90F VCNTY KPHL SWWD AND WESTWARD ON FRIDAY. DEWPOINTS HIGHER,
AROUND 70F AND 1400J ML CAPE. 0-6KM BULK SHEAR IS POOR FOR ANY
SVR. STRATUS FOG POTENTIAL AT NIGHT AND IN THE MORNING, ESPECIALLY I-80
NORTHWARD.
 
NEXT WEEKEND...FAIR AND VERY WARM. SLIGHT CHANCE FOR AFTN/EVENING
CONVECTION POCONOS TO THE LEHIGH VALLEY AND KRDG PER ECMWF KI AND
A TENDENCY FOR UPSLOPE FLOW-LIFT.
 
OVERALL CONFIDENCE THESE NEXT 6 DAYS: ABOVE AVERAGE.

&&

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

REST OF THIS AFTERNOON...VFR WITH SOME CUMULUS AROUND 5000 FEET, 
ALONG WITH MID TO HIGH LEVEL CLOUDS MOVING THROUGH. SOUTHWESTERLY 
WINDS UP TO 10 KNOTS, WHICH SHOULD TURN MORE SOUTHERLY AT KACY AND 
KILG DUE TO A SEA/BAY BREEZE. A FEW SHOWERS AND A THUNDERSTORM 
WILL BE NEAR THE KABE TO KRDG AREAS BY LATE AFTERNOON.

TONIGHT...VFR OVERALL. A WEAKENING COLD FRONT SHOULD ALLOW A SHOWER 
OR THUNDERSTORM TO ARRIVE MAINLY NEAR THE KABE AND KRDG AREAS THIS 
EVENING, HOWEVER COVERAGE IS EXPECTED TO BE LOW. SOUTHWESTERLY WINDS 
5-10 KNOTS, BECOMING LIGHT AND VARIABLE AT MANY OF THE TERMINALS.
 
MONDAY...LOCALIZED MVFR DUE TO FOG IS POSSIBLE EARLY, OTHERWISE VFR. 
WHILE A SHOWER OR THUNDERSTORM IS POSSIBLE, THE CHANCE APPEARS TO BE 
RATHER LOW AT THIS TIME. LIGHT SOUTHWESTERLY WINDS INCREASING TO
AROUND 10 KNOTS.

OUTLOOK...
MONDAY NIGHT THROUGH WEDNESDAY...VFR CONDITIONS EXPECTED THOUGH
LOCALIZED MVFR/IFR CONDITIONS WITH FOG/ST POSSIBLE EACH MORNING,
MAINLY NEAR KABE-KRDG. LIGHT WIND, TENDS BE NW EACH AFTERNOON.

THURSDAY...MOSTLY VFR CONDITIONS. ISOLATED THUNDERSTORMS POSSIBLE 
LATE.  IFR CIGS/VSBY POSSIBLE N OF I-80 LATE THU NIGHT.  

FRIDAY...VFR WITH BRIEF IFR CONDS POSSIBLE IN TSTMS.  MVFR OR IFR 
CIGS DEVELOPING IN NELY FLOW NEAR AND N OF I-80 WITH POSSIBLE IFR 
VSBY IN FOG AT NIGHT.    

OVERALL LONG TERM AVIATION FCST CONFIDENCE: ABOVE AVERAGE.

&&

.MARINE...
THE CONDITIONS ARE ANTICIPATED TO REMAIN BELOW SMALL CRAFT ADVISORY 
CRITERIA THROUGH MONDAY. HIGH PRESSURE GENERALLY REMAINS NEAR THE 
MID ATLANTIC WHICH WILL KEEP A SOUTHWESTERLY FLOW ACROSS OUR AREA. 
AN INCREASE INTO THIS EVENING IS EXPECTED DUE TO MIXING AND A SEA 
BREEZE CIRCULATION, AND GUSTS TO 20 KNOTS ARE POSSIBLE. THE SEAS 
OVERALL ARE ANTICIPATED TO BE IN THE 1 TO 3 FOOT RANGE ACROSS OUR 
WATERS.

OUTLOOK...
MONDAY NIGHT THROUGH THURSDAY...WINDS AND SEAS SHOULD STAY WELL
BELOW SMALL CRAFT ADVISORY CRITERIA. WATER TEMPERATURES ARE ABOVE
NORMAL.

FRIDAY...ATLC SEAS MAY INCREASE AS AN EASTERLY FLOW DEVELOP BUT
ATTM, BELOW SCA CRITERIA.

&&

.RIP CURRENTS...
A LONG PERIOD EAST TO SOUTHEAST SWELL, 10-11 SECONDS, CONTINUES TO 
ROLL IN ALONG THE COAST. THIS COMBINED WITH INCREASED SOUTHERLY 
WINDS WILL RESULT IN TRICKY CONDITIONS AT TIMES WITHIN THE SURF ZONE 
ESPECIALLY DURING TIDE CHANGES. AS A RESULT THERE IS A MODERATE RISK 
FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS THROUGH THIS EVENING 
ALONG THE NEW JERSEY SHORE AND THE DELAWARE BEACHES.

THE OUTLOOK IS FOR GENERALLY LOW ENHANCED CONDITIONS THIS WEEK WITH 
A SLIGHTLY SUBSIDING 1-2 FOOT 10 SECOND SE SWELL. ITS POSSIBLE WE
WILL STILL NEED TO CARRY A MDT RISK ON MONDAY BASED ON THE VERY SLOW
TO SUBSIDE SWELL OF TODAY-SUNDAY.

NEXT FRIDAY ONWARD MAY SEE THE RISK INCREASE, WITH A CHANCE OF MODERATE
NEXT WEEKEND OR MONDAY DEPENDING ON THE EVENTUAL DEVELOPMENT OF
OFFSHORE LOW PRESSURE AND ITS WESTWARD SWEEPING SWELLS. LOTS OF
UNCERTAINTY NEXT WEEKEND.

IN THE MEANTIME, SWIM SAFELY WITHIN THE WATCHFUL SAFETY VIEW OF
OUR BEACH PATROLS.

&&

.CLIMATE...
THIS SECTION MAY BE DISCARDED TONIGHT. 

AUGUST: KPHL (POR 1872) AND KACY (POR 1874), BARRING ANY MORE RAIN 
THIS MONTH, WILL BE 10TH DRIEST ON RECORD WITH 0.98 AND 1.25" 
RESPECTIVELY. THE KILG 1.54 INCHES IS 13TH DRIEST ON RECORD
PROVIDED NO MORE RAIN FALLS BEFORE 1 AM TUESDAY.
 
LISTING THE SEASONS 90F OR WARMER DAYS AS INFO FOR YOU TO ADD ONTO 
AS THE WEEK PROGRESSES.

THESE TOTALS AS OF THE 29TH AND DO NOT INCLUDE TODAYS 90 PLUS.  


KPHL 28, MEAN 21. IF WE ADD 5 MORE DAYS 90F BETWEEN NOW AND SEPT
9 (TOTAL PROJECTED AT LEAST 33) AND KPHL WILL HAVE THE 18TH
HIGHEST SEASONAL TOTAL OF 90 OR HIGHER. POR TO 1872 

KABE 12  POR MEAN 17
KACY 16  POR MEAN 10
KILG 11  POR MEAN 20

SAMPLING OF OTHER LOCATION TOTALS FOR 2015 ARE BELOW. 
KPNE 30
KVAY 15
KRDG 17
KTTN 20
KGED 18
KFWN 6

RECORDS: NONE POSTED THROUGH THURSDAY. THE RECORDS ARE MORE
VULNERABLE FRIDAY-SUNDAY BUT AT THIS TIME NOT WORTH POSTING. 

THE CLOSEST POSSIBLE NEAR RECORD POTENTIAL APPEARS TO KACY ON
WED/THU OF THIS WEEK WITH A 94 IN 1980 ON THE 2ND AND 95 IN 1994
ON THE 3RD. AGAIN, COASTAL SEA BREEZES WILL PROBABLY PRECLUDE.

OTHERWISE MANY RECORDS NEAR 100F WERE ESTABLISHED IN 1953 BETWEEN
AUGUST 31 AND SEPTEMBER 3RD. 

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...DRAG/GORSE 4P
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...DRAG 4P
AVIATION...DRAG/GORSE 4P
MARINE...DRAG/GORSE 4P
RIP CURRENTS...4P
CLIMATE...4P



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