Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 091500 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1100 AM EDT WED JUL 9 2014 .SYNOPSIS... LOW PRESSURE WILL CONTINUE TO MOVE ACROSS EASTERN CANADA THROUGH THURSDAY, WHICH WILL PULL ANOTHER COOL FRONT ACROSS OUR AREA LATER TODAY. THIS FRONT WILL THEN SETTLE TO OUR SOUTH THURSDAY. HIGH PRESSURE WILL THEN BRIEFLY BUILD ACROSS THE NORTHEAST FRIDAY INTO SATURDAY, BEFORE IT SLIDES OFFSHORE DURING SATURDAY. THE NEXT COLD FRONT IS SCHEDULED TO ARRIVE LATER MONDAY INTO TUESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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14Z SFC ANALYSIS SHOWS A 990 MB SFC LOW OF CENTRAL QUEBEC WITH A COLD FRONT EXTENDING S-SWWD INTO LAKE ONTARIO AND LAKE ERIE. DIFFICULT TO DISCERN PRE-FRONTAL SFC TROUGH BASED ON THE WIND/ PRESSURE FIELDS BUT THERE IS A SUBTLE THERMAL/MOISTURE BOUNDARY FROM ABOUT THE CHSPK BAY TO CENTRAL NJ WHERE TEMPS (DEWPOINTS) ARE IN THE 80S (LOWER 70S) SOUTH AND EAST OF THE BOUNDARY AND UPPER 70S (MID TO UPPER 60S) FARTHER NORTH AND WEST. THE MID-ATLANTIC REGION REMAINS SITUATED WITHIN PRE-FRONTAL WARM SECTOR OF THIS SYSTEM THOUGH THE AIRMASS IS NOT QUITE AS HOT TODAY AS YESTERDAY IN WAKE OF LAST NIGHT`S COLD FROPA. MAX TEMPS IN THE MID/UPPER 80S IN THE LEHIGH VALLEY, POCONOS AND ALONG THE COAST AND LOWER 90S IN THE URBAN I-95 CORRIDOR AND DELMARVA. DID NOT HAVE MUCH SUPPORT FOR INCREASING MAX TEMPS FROM PREVIOUS FCST BASED ON CURRENT CLOUD COVER HAMPERING FULL SUNSHINE ACROSS MUCH OF THE AREA. HEAT INDICES IN THE LOW TO MID 90S ARE EXPECTED IN THE URBAN AREAS AND DELMARVA. A BAND OF SHOWERS ASSOCIATED WITH THE PRE-FRONTAL SHORTWAVE TROUGH WILL MOVE E-NE FROM THE CHSPK BAY INTO THE DELMARVA AND SRN NJ LATE THIS MRNG AND EARLY THIS AFTN. MAY SEE AN ISO TSTM DEVELOP WITH THIS ACTIVITY BUT OVERALL COVERAGE AND STRENGTH OF CONVECTION WILL BE LIMITED WITHOUT MUCH OF AN OPPORTUNITY FOR THE BOUNDARY LAYER TO DESTABILIZE BEFOREHAND. EXPECT ADDITIONAL CONVECTION TO DEVELOP IN CENTRAL PA JUST AHEAD OF THE COLD FRONT DURING THE EARLY AFTN. THESE SHOWERS AND STORMS ARE THEN EXPECTED TO PROGRESS EWD INTO ERN PA LATER IN THE AFTN. LIMITED POPS TO CHANCE WITH SYNOPTIC LIFT BEING RATHER WEAK. DESPITE FCST SOUNDINGS FOR ERN PA ONLY SHOWING MLCAPE OF AROUND 1000 J/KG, A SIGNIFICANT INTRUSION OF MID-LVL DRY AIR BENEATH AN INVERTED V WILL BE SUPPORTIVE OF A FEW STRONG TO PERHAPS SEVERE DOWNBURSTS. ASSUMING AMPLE TIME FOR THE AIRMASS TO RECOVER FROM THE MIDDAY SHOWERS, A FEW OF THESE STORMS COULD REACH THE DELMARVA/NJ BY EARLY THIS EVE AND ALSO BE STRONG TO SEVERE AS CONVECTION MOVES INTO AN ENVIRONMENT WITH GREATER INSTABILITY.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... MUCH OF THE REGION WILL FINALLY SEE A SHIFT TO NORTHWESTERLY WINDS TONIGHT HERALDING DRY AND COLD AIR ADVECTION. THUS, SHOULD SEE MOST CONVECTION WIND DOWN BY MIDNIGHT, WITH THE EXCEPTION OF CLOSER TO THE SHORE WHICH WILL SEE A LATER ARRIVAL OF THE COOLER AND DRIER AIR. WITHIN THE WARM SECTOR, THERE WILL REMAIN AT LEAST ELEVATED INSTABILITY FOR MUCH OF THE NIGHT. && .LONG TERM /THURSDAY THROUGH TUESDAY/... THE OVERALL SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH FROM SOUTHEASTERN CANADA TO THE MID ATLANTIC REGION. THIS FEATURE IS FORECAST TO GRADUALLY LIFT OUT THROUGH LATE FRIDAY, HOWEVER ANOTHER TROUGH THEN AMPLIFIES ACROSS THE MIDWEST AND GREAT LAKES REGION. THIS WILL GENERALLY KEEP OUR AREA UNDER A CYCLONIC FLOW REGIME WITH A COLD FRONT OR TWO SETTLING SOUTHEASTWARD WITH TIME. WE USED A MODEL BLEND THURSDAY INTO SATURDAY, THEN BLENDED THE 00Z WPC GUIDANCE INTO CONTINUITY. FOR THURSDAY AND FRIDAY...A COOL FRONT LOOKS TO BE DRAPED NEAR OUR SOUTHEASTERN ZONES THURSDAY BEFORE TENDING TO DISSIPATE FRIDAY. THERE IS THE PRESENCE OF THE UPPER-LEVEL TROUGH, THEREFORE A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE ESPECIALLY THURSDAY. THE BETTER CHC APPEARS TO BE ACROSS THE SOUTHERN ZONES GIVEN THE PROXIMITY OF THE LINGERING FRONT AND SOME DEEPER MOISTURE. HIGH PRESSURE STARTS TO BUILD IN FRIDAY, HOWEVER IT SHOULD THEN BE SHIFTING TO NEAR THE SOUTHERN NEW ENGLAND COAST AT NIGHT. THIS WILL DEVELOP AN ONSHORE FLOW, HOWEVER IT IS NOT ALL THAT CERTAIN HOW MUCH DEEPER MOISTURE REMAINS AS THIS OCCURS. FOR SATURDAY AND SUNDAY...AS HIGH PRESSURE SLIPS OFF THE SOUTHEASTERN NEW ENGLAND COAST SATURDAY MORNING, THE FLOW SHOULD TURN FROM EAST-SOUTHEAST TO MORE SOUTHERLY. AS THIS OCCURS, SOME WAA MAY ALLOW A LINGERING BOUNDARY TO OUR SOUTH TO LIFT BACK NORTH AS A WARM FRONT. OVERALL WHILE SATURDAY LOOKS TO BE DRY, AN ISOLATED SHOWER OR THUNDERSTORM CANNOT BE RULED OUT DURING PEAK HEATING ESPECIALLY INLAND NORTH OF A POSSIBLE WARM FRONTAL FEATURE. AS THE UPPER-LEVEL FLOW STARTS TO TURN MORE CYCLONIC SUNDAY, SOME SHOWERS AND THUNDERSTORMS MAY DEVELOP ESPECIALLY INLAND IN THE AFTERNOON PROBABLY TIED TO A LEE SIDE TROUGH. OVERALL, WE USED A 50/50 BLEND OF CONTINUITY AND WPC GUIDANCE. FOR MONDAY AND TUESDAY...A SIGNIFICANT UPPER-LEVEL TROUGH MAY SLIDE ACROSS THE GREAT LAKES REGION. THIS WILL DRIVE LOW PRESSURE WELL TO OUR NORTH, HOWEVER THE ASSOCIATED COLD FRONT WILL ARRIVE INTO OUR AREA AROUND THE LATE MONDAY INTO TUESDAY TIME FRAME. THERE SHOULD BE DECENT INSTABILITY AHEAD OF THIS FEATURE AS DEEPER MOISTURE ADVECTS NORTHEASTWARD IN ADVANCE OF THE SURFACE FRONT, AND ALSO INCREASING CYCLONIC FLOW. THIS COULD RESULT IN SOME STRONGER CONVECTIVE CELLS, HOWEVER THE SEVERE WEATHER THREAT WILL DEPEND ON THE TIMING OF THE LARGE SCALE FORCING AND ORGANIZATION AS WELL AS THE ACTUAL INSTABILITY. AS OF NOW, MONDAY MAY HAVE A HIGHER CHC OF CONVECTION ESPECIALLY ACROSS OUR WESTERN ZONES. WE KEPT CHC POPS AS A RESULT. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR THIS MRNG. LGT SHRA AT MIV/ACY BETWEEN 15-18Z AND IN VC OF ILG. AN ISO SHRA OR TSRA WILL START TO DEVELOP PRIMARILY WEST OF THE TERMINALS DURING THE ERY AFTN. THE HIGHEST CHANCES FOR TSRA LOOK TO BE AT ABE/RDG THIS AFTN AND PHL/MIV IN THE EVE...THOUGH EVEN AT THESE LOCATIONS, CHANCE FOR DEVELOPMENT IS TOO LOW AND COVERAGE IS EXPECTED TO BE TOO LIMITED TO INCLUDE ANYTHING MORE THAN A PROB30 IN THE TAFS AT THIS TIME. EXPECT A WIND SHIFT TO NORTHWESTERLY WINDS AFTER 00Z TONIGHT, BRINGING IN DRIER AIR AND DECREASING THE CHANCES FOR ANY MORE BR DEVELOPMENT. OUTLOOK... THURSDAY AND FRIDAY...A FEW SHOWERS AND THUNDERSTORMS SHOULD BE AROUND MAINLY THURSDAY WITH LOCALLY SUB-VFR CONDITIONS. OTHERWISE, MAINLY VFR. SATURDAY AND SUNDAY...SOME SHOWERS AND THUNDERSTORMS POSSIBLE ESPECIALLY SUNDAY AFTERNOON AND EVENING, RESULTING IN BRIEF SUB-VFR CONDITIONS.
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&& .MARINE...
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SCA WAS CANCELLED FOR THIS MRNG AS WINDS ARE LIGHT AND THE SEAS HAVE SUBSIDED TO 3-4 FT. EXPECT SLY WINDS TO INCREASE THIS AFTN AND EVE WITH GUSTS OF 20-25 KT POSSIBLE. SEAS ALSO INCREASE TO 3-5 FT. HAVE HOISTED A SCA FOR THIS PERIOD FOR ALL COASTAL MARINE ZONES. ADDITIONALLY, SOME THUNDERSTORMS THIS AFTERNOON AND EVENING WILL BE CAPABLE OF LOCALLY STRONG GUSTY WINDS. SMW`S MAY BE NEEDED. OUTLOOK... THURSDAY...A FRONTAL BOUNDARY LOOKS TO LINGER NEAR THE SOUTHERN WATERS, HOWEVER SUB-ADVISORY CONDITIONS ARE ANTICIPATED. FRIDAY AND SATURDAY...HIGH PRESSURE ARRIVES FRIDAY THEN SHIFTS OFF THE SOUTHEASTERN NEW ENGLAND COAST FRIDAY NIGHT AND SATURDAY. THIS MAY RESULT IN AN ONSHORE FLOW THAT STRENGTHENS SOME FOR A TIME BEFORE TURNING MORE SOUTHERLY. IT APPEARS THOUGH THAT THE CONDITIONS WILL REMAIN BELOW ADVISORY CRITERIA. SUNDAY...A WARM FRONT MAY NEAR OUR SOUTHERN WATERS, HOWEVER THE FLOW LOOKS WEAK ENOUGH TO KEEP CONDITIONS BELOW ADVISORY CRITERIA.
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&& .RIP CURRENTS... THE THREAT FOR RIP CURRENTS ALONG THE NEW JERSEY SHORE IS MODERATE TODAY. && .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 MIDNIGHT EDT TONIGHT FOR ANZ450>455.
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&& $$ SYNOPSIS...GORSE NEAR TERM...KLEIN SHORT TERM...JOHNSON LONG TERM...GORSE AVIATION...GORSE/KLEIN MARINE...GORSE/KLEIN RIP CURRENTS...STAFF

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