Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 180830 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 430 AM EDT SAT OCT 18 2014 .SYNOPSIS...
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A COLD FRONT WILL CROSS THE AREA THIS MORNING WITH HIGH PRESSURE BUILDING IN FROM THE PLAINS TONIGHT AND SUNDAY. THE HIGH PRESSURE SYSTEM WILL THEN SLIDE ACROSS THE REGION ON MONDAY. A COLD FRONT WILL CROSS THE AREA AROUND TUESDAY. A SECONDARY LOW PRESSURE SYSTEM WILL FORM ALONG THE FRONTAL BOUNDARY EAST OF THE REGION TUESDAY NIGHT AND WEDNESDAY. THIS LOW PRESSURE SYSTEM WILL MOVE SLOWLY NORTHEAST PASSING CLOSE TO BLOCK ISLAND RHODE ISLAND ON THURSDAY AND THE CAPE COD COASTAL WATERS ON FRIDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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LOW PRESSURE WELL TO THE NORTH AND A PROGRESSIVE H5 SHORT WAVE ACROSS THE GREAT LAKES WILL CAUSE A SFC COLD FRONT TO CROSS THE AREA EARLY TODAY. INCREASING WRLY WINDS AND DRIER AIR WILL BE ACROSS THE REGION WITH THE BETTER CHC FOR CLOUDS AND PCPN BEING FOUND ACROSS THE NRN/WRN AREAS. WE HAVE KEPT THE SLGT CHC POPS FOR THOSE AREAS...WHICH IS CONSISTENT WITH THE OPERATIONAL MODELS AND PREVIOUS FCSTS. TEMPERATURES TODAY WILL BE A FEW DEGREES COOLER THAN YDAY AS THE COLD AIR ADVECTION BEGINS...HIGHS WILL BE IN THE LOW/MID 60S NORTH...UPPER 60S OVER THE DEL VALLEY...AND LOWER 70S OVER SRN DEL. WINDS WILL BE LIGHT SW EARLY...THEN BECOME GUSTY FROM THE W OR NW WITH GUSTS UP TO 25 MPH.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
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CONDITIONS WILL NOT CHANGE TOO MUCH TONIGHT. DRIER/COLDER AIR WILL CONTINUE TO ARRIVE ACROSS THE AREA...AND SLGT CHCS FOR SHOWERS WILL CONTINUE ACROSS THE SRN POCONOS AND NRN NJ. POPS ARE IN THE SLGT CHC RANGE. TEMPERATURES WILL BECOME COLDER WITH LOWS MOSTLY N THE 40S OVER THE REGION...SOME UPPER 30S POSSIBLE ACROSS THE SRN POCONOS. WINDS WILL REMAIN NW AT 5 TO 10 MPH OVERNIGHT.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/...
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THE 500MB INITIALIZATION IN THE MIDWEST PREFERRED THE DEEPER WRF-NMMB OVER THE GFS. ALONG THE CANADIAN COAST HEIGHTS ARE SLIGHTLY HIGHER THAN THE ECMWF AND GFS HAVE. THE WRF-NMMB HAS A BETTER INITIALIZATION THAN THE FORMER. THERMALLY, THERE WERE 1C ERRORS AT 850MB AND 925MB, BUT THEY WENT IN BOTH DIRECTIONS WITH NO DISCERNIBLE TREND. THE LONG TERM CONTINUES TO BE DOMINATED BY A MIDDLE OF THE WORK WEEK MILLER B TYPE SYSTEM WITH THE ONLY CONSISTENCY BEING THE INCONSISTENCY BETWEEN THE MODELS. THE DP/DT ON ALL OF THE MEDIUM RANGE MODELS EXCEPT FOR THE ECMWF WITH THIS SOUNDING RUN WAS A FASTER PROGRESSION OR FARTHER OFFSHORE SECONDARY DEVELOPMENT. DONT LIKE THE ECMWF SOLUTION BECAUSE THERE IS LESS RIDGING AROUND THE CLOSED LOW IN BOTH DIRECTIONS AND THIS RUN CLOSES AND DIGS IT FARTHER SOUTH. IT ALMOST LOOKS LIKE THE CONVECTION HAS TOO MUCH OF AN INFLUENCE ON THE SURFACE/UPPER AIR SYSTEM. AT THE OTHER END OF THE SPECTRUM, THE OP GFS 2NDRY DEVELOPMENT IS SO OFFSHORE IT IGNORES WHERE THE CLOSED LOW IS. THE GEFS ENSEMBLE MEAN LOW POSN LOOKS BETTER VS THE FORCING. THE CAN GGEM AND UKMET AT LEAST ARE MORE CONSISTENT, HAVE TRENDED MORE OFFSHORE. WE STILL SEE THE NEXT SOUNDING RUN AS THE ONE THAT BRINGS THE ENERGY INTO CANADA AS HOPEFULLY A STABILIZING, CONSENSUS BUILDING FACTOR. THE ECMWF ENSEMBLE INFO ARRIVES TOO LATE TO BE UTILIZED. IT HAS BEEN FAVORING A PROGRESSIVE OR FARTHER NORTH SOLUTION THAN THE OP RUNS. IN AN EFFORT TO NOT WINDSHIELD WIPE THE FORECAST, WE HAVE MAINTAINED A NEAR STATUS QUO IN THE LONG TERM. WHILE WE LIKE THE IDEA OF A CLOSING LOW STALLING FARTHER TO THE EAST, THE IDEA THAT THE CCB PCPN WILL JUST DO AN END RUN THAT BYPASSES OUR CWA IS NOT THE MOST LIKELY SOLUTION. THE LONG TERM STARTS SIMPLER ON SUNDAY WITH THE TROF EXITING OUR CWA AND RIDGING RETURNING. ONE LAST VORT MAX HAS TO COME THRU EARLY. IT WILL BE A BRISK FALL DAY WITH PEAK WIND GUSTS REACHING AT LEAST 20 TO 25 MPH IN MOST PLACES. THE CONVECTIVE TEMP NORTH IS STILL WITHIN REACH DURING THE MORNING, SO WE HEDGED MORE CLOUDINESS THERE. NOT INCLUDED AT THIS MOMENT, BUT THERE MIGHT BE A RESIDUAL SPRINKLE OR FLURRY IN THE POCONOS. FARTHER TO THE SOUTH, THE AMOUNT OF MOISTURE IS LESS AND THE CONVECTIVE TEMP OBTAINABILITY GOES SOONER, MOSTLY SUNNY SKIES EXPECTED. THE KATABATIC FLOW IS QUITE GOOD, BUT MODELING THERMAL FIELDS INDICATE THAT THE LOWER NAM MOS MAX TEMPS STILL LOOK MORE REASONABLE. NO BIG CHANGE TO SUNDAY NIGHT AS WINDS WILL SHUT OFF QUICKLY AND TEMPERATURES PLUNGE. THE UNCERTAINTY REMAINS WITH HOW MUCH HIGH LEVEL MOISTURE (CLOUDS) THAT MAY STOP THE FORMATION OF FROST OR HALT THE DROP IN TEMPERATURES LATE. WHILE WE SIDED WITH THE LOWER STAT GUIDANCE BECAUSE OF THE INHERENT POTENTIAL, CONFIDENCE COULD BE HIGHER. WE ADDED PATCHY FROST TO THE GRIDS (MENTION IN THE HWO ALSO CONTINUES). WITH THE RIDGE AXIS EAST OF OUR CWA AND SHORT WAVES MOVING THROUGH, THERE SHOULD BE MORE CLOUDINESS ON MONDAY. IN SPITE OF THE WAA, HEIGHTS ARE STILL PREDICTED TO RISE AND THIS IN TURN RAISES THE QUESTION ABOUT AVAILABLE MOISTURE. THUS, A DRY FORECAST IS CONTINUED. REMAINED FAIRLY CONSERVATIVE WITH THE MAX TEMPS BECAUSE OF MORE CLOUDS. GFS AND WRF-NMMB ON SAME PAGE WITH BETTER OMEGA WRN HALF OF OUR CWA OVERNIGHT ON MONDAY. THE FORCING IS NOT BAD OVERALL AS MID LEVEL QVEC CONVERGENCE, JET STREAK AND TROWAL PASS ACROSS OUR CWA. MOISTURE MIGHT STILL BE A LIMITER. GIVEN THOSE FORCING MECHANISMS WE DID GO WITH HIGHER POPS THAN STAT GUIDANCE. ON TUESDAY THE INITIAL LOW AND FRONT ARE PREDICTED TO APPROACH. THE INSTABILITY ALOFT BETWEEN 850MB AND 500MB IS NEARLY SUPPORTIVE OF THUNDER. NO SFC BASED INSTABILITY IS PREDICTED. BUT GIVEN THE NEAR INSTABILITY ALOFT, WE CHANGED THE PTYPE TO CONVECTIVE AND KEPT CHC POPS. THAT ENDS WHAT WE BELIEVE IS THE EASIER PART OF THE LONG TERM. THE REMAINING PART IN AN EFFORT TO DO NO HARM OR SEVERE WHIPSAWING WE MAINTAINED CONTINUITY FOR THE MOST PART. MILLER B(S) NORMALLY CAUSE HEADACHES (IF THIS WAS JANUARY MORE TRIPS TO THE FIRST AID KIT WOULD BE MADE) IN OUR CWA AS WE ARE OFTEN NEAR THE CUT OFF POINT FOR PCPN. WE ARE BANKING ON A CLOSER TO THE COAST DEVELOPMENT TO KEEP PCPN CHANCES IN FOR TUE NGT AND WED. THEN IT BECOMES UNCERTAIN AS TO HOW LONG WILL THE CCB CHANCES CONTINUE. THE GREATER CHANCES REMAIN EAST WHERE POPS WERE KEPT HIGHEST. STAT GUIDANCE APPEARS STRANGELY HIGH WITH TEMPS. BUT WATER TEMPS ARE STILL IN THE 60S AND THE SURFACE HIGH IS QUITE DISPLACED. WE COMPROMISED BETWEEN CONTINUITY AND LATEST WPC/STAT GUIDANCE. THIS NUDGE UP MADE US REMOVE THE BRIEF MENTION OF SNOW IN THE POCONOS. EVEN THE LATEST ECMWF WOULD NOT CAUSE ANY QPF RELATED ISSUES. BUT WITH THE ONSHORE FLOW AND THE APPROACHING NEW MOON, WE WILL HAVE TO KEEP AN EYE ON TIDAL DEPARTURES. WE KEPT FRIDAY DRY.
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&& .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. A FRONT WILL CROSS THE REGION TODAY FOLLOWED BY AND UPPER AIR DISTURBANCE LATER TODAY. THERE WILL BE CLOUDINESS ASSOCIATED WITH THESE FEATURES...BUT MOST OF THE PERSISTENT CLOUDS WILL BE ACROSS KRDG/KABE WHERE WE HAVE CIGS (VFR) MUCH OF THE DAY. FURTHER S/E...A MORE VARIABLE SKY COVER WITH MOSTLY SCT AND OCNL BKN CLOUDS EARLY THIS AFTERNOON. NO PCPN IS MENTIONED IN THE TAFS...A FEW SHOWERS FAR N/W ARE POSSIBLE HOWEVER. WINDS WILL BECOME SW EARLY AND THE INCREASE FROM THE W WITH G20-25 BY MID MORNING. WINDS WILL TREND MORE NW BY DUSK. TONIGHT...VFR WITH SOME MID LEVEL CLOUDS S. GENTLE WEST/NW WINDS. OUTLOOK... SUNDAY AND SUNDAY NIGHT...VFR CONDITIONS EXPECTED. GUSTY WEST TO NORTHWEST WINDS EXPECTED WITH GUSTS TO 25 KNOTS, MAINLY DURING THE DAY ON SUNDAY. MONDAY...VFR CONDITIONS EXPECTED. MONDAY NIGHT AND TUESDAY...PERIODS OF SUB-VFR CONDITIONS AS SHOWERS MOVE INTO THE REGION. TUESDAY NIGHT AND WEDNESDAY...MORE WIDESPREAD MVFR CONDITIONS POSSIBLE, ESPECIALLY EASTERN AIRPORTS AND TERMINALS. SOME GUSTY NORTH WINDS POSSIBLE WEDNESDAY.
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&& .MARINE...
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WE WILL ONLY MAKE ONE CHANGE TO THE PRESENT SCA FLAGS WITH THE EARLY SAT MORNING CWF. WE WILL MAKE THE START TIME OF THE SCA FLAG ON DEL BAY AT 1100 AM INSTEAD OF THE PRESENT 200 PM. IT APPEARS THE ENOUGH CAA AND MIXING WILL OCCUR BY THEN FOR SOME G25. ON THE OCEAN...5 TO 6 FT SWELLS ARE ALREADY BEING OBSERVED...AND THE ADDED WINDS LATER THIS MORNING WILL CONTRIBUTE TO CHOPPY SEAS. SCA FLAGS WILL CONTINUE TONIGHT. FAIR WEATHER EXPECTED TODAY AND TONIGHT. OUTLOOK... SUNDAY AND SUNDAY NIGHT...SMALL CRAFT CONDITIONS PREDICTED THROUGHOUT THE AREA WATERS SUNDAY DAY. THEY SHOULD LINGER ON THE OCEAN INTO SUNDAY EVENING AND THE SMALL CRAFT ADVISORY WAS EXTENDED. MONDAY THROUGH TUESDAY NIGHT...SUB-ADVISORY CONDITIONS ARE EXPECTED ACROSS THE AREA WATERS. WEDNESDAY...BOTH WINDS AND WAVES WILL RESPOND TO THE DEVELOPING SECONDARY LOW. A SMALL CRAFT ADVISORY MAY BE NEEDED.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT SUNDAY NIGHT FOR ANZ450>455. SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 6 PM EDT SUNDAY FOR ANZ430-431.
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&& $$ SYNOPSIS...GIGI/MEOLA NEAR TERM...O`HARA SHORT TERM...O`HARA LONG TERM...GIGI/MEOLA AVIATION...GIGI/MEOLA/O`HARA MARINE...GIGI/MEOLA/O`HARA

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