Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 021943 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 343 PM EDT WED SEP 2 2015 .SYNOPSIS...
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A WEAK SURFACE TROUGH WILL PUSH SOUTH OF THE AREA THROUGH THURSDAY, AHEAD OF A BACKDOOR COLD FRONT THAT WILL PUSH ACROSS THE AREA THURSDAY NIGHT INTO FRIDAY. HIGH PRESSURE WILL BUILD ACROSS THE REGION FROM THE NORTH SATURDAY AND REMAIN ACROSS THE AREA THROUGH EARLY NEXT WEEK. A COLD FRONT WILL BEGIN TO APPROACH THE AREA FROM THE WEST ON TUESDAY.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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HIGH PRESSURE WILL REMAIN OVER THE GULF COAST AND MIDWEST STATES THRU TONIGHT WHILE A WEAK LOW PRESSURE TROUGH BECOMES STATIONARY OVER THE MID-ATLANTIC REGION. TRIMMED BACK ON POPS FOR THE REST OF THE AFTERNOON BUT AN ISOLATED POP-UP SHOWER OR STORM IS POSSIBLE IN THE LOWER DELMARVA. UNDER A FAVORABLE RADIATIONAL COOLING SETUP THIS EVENING, EXPECT ANOTHER ROUND OF FOG TO DEVELOP OVERNIGHT INTO EARLY THURSDAY MORNING. SIMILAR TO THIS MORNING, FOG WILL LIKELY BE MOST WIDESPREAD AND DENSE FROM THE DELAWARE VALLEY TO THE COAST SINCE THE ATMOSPHERE WILL BE PRIMED WITH HIGHER DEWPOINTS WHERE TODAY`S SEA-BREEZE FRONT MAKES IT THRU. WILL HIGHLIGHT THE POTENTIAL FOR ANOTHER DENSE FOG EVENT IN THE HWO. THERE IS UNCERTAINTY IN THE EXTENT OF THE DENSE FOG TONIGHT AS THE MID-LEVEL SUBSIDENCE INVERSION THAT IS PARTIALLY RESPONSIBLE FOR TRAPPING MOISTURE NEAR THE SURFACE WILL BE WEAKER TONIGHT THAN IT WAS LAST NIGHT.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
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THE UPPER RIDGE WILL REMAIN ANCHORED OVER THE SOUTHERN PLAINS ON THURSDAY. A COUPLE OF THE SHORTWAVE TROUGHS TRACKING AROUND THE PERIPHERY OF THE RIDGE WILL MOVE SOUTHEASTWARD INTO THE GREAT LAKES AND NORTHEAST STATES. AT THE SURFACE, A PRESSURE TROUGH ASSOCIATED WITH A SUBTLE BACKDOOR COLD FRONT WILL SHARPEN OVER SOUTHERN NEW ENGLAND AND THE NORTHERN MID ATLANTIC. THE FRONT WILL BE SLOW TO PROGRESS SOUTHWARD THRU OUR AREA WITH WEAK NORTHERLY STEERING FLOW UNDER 10 KT IN THE BOUNDARY LAYER. FORECAST SOUNDINGS INDICATE A WEAKENING OF THE CAP OVER THE NEXT 24 HOURS WITH MODEST CAA OCCURRING NEAR 700 MB. THERMODYNAMIC PROFILES WILL BE MORE SUPPORTIVE OF CONVECTION THURSDAY THAN TODAY AS A RESULT. HOWEVER, EXPECT ANY COVERAGE OF SHOWERS AND STORMS TO BE PREDOMINATELY ISOLATED OWING TO A LACK OF ORGANIZED LIFT (EXCEPT FOR LOW-LEVEL CONVERGENCE NEAR THE BACKDOOR FRONT AND ALSO ALONG THE SEA- BREEZE BOUNDARY). FORECAST MAX TEMPS FOR THURSDAY VERY SIMILAR TO TODAY AND YESTERDAY`S...80S IN THE HIGHLANDS AND ALONG THE COAST, MID 90S IN THE URBAN AREA, AND LOW 90S ELSEWHERE.
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&& .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
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A CHANCE FOR UNSETTLED WEATHER FOR THE END OF THE WORK WEEK, FOLLOWED BY A QUIET WEEKEND AND BEGINNING OF NEXT WEEK. THE BACKDOOR COLD FRONT PUSHES INTO THE AREA THURSDAY NIGHT, THEN SLOWLY SLIDES THROUGH THE AREA DURING THE DAY FRIDAY. SHOWER ACTIVITY MAY DIMINISH SOME OVERNIGHT THURSDAY, BUT WE EXPECT SHOWERS AND THUNDERSTORMS TO REDEVELOP DURING THE DAY FRIDAY, ESPECIALLY FOR THE SOUTHERN HALF OF THE AREA AS THE FRONT SLOWLY SAGS SOUTHWARD ACROSS THE AREA. PRECIPITATION AMOUNTS ARE FORECAST TO BE FAIRLY LIGHT, GENERALLY 0.25 INCHES OR LESS. HOWEVER, THERE COULD BE SOME HEAVIER RAINFALL AMOUNTS AS PW VALUES INCREASE TO 1.5-1.75 INCHES, ESPECIALLY WHERE THUNDERSTORMS OCCUR. ONCE THE FRONT PUSHES SOUTH OF THE AREA FRIDAY NIGHT, HIGH PRESSURE WILL BUILD BACK ACROSS THE EAST COAST FROM THE NORTH FROM SATURDAY THROUGH TUESDAY, WHICH WILL PROVIDE DRY WEATHER ACROSS THE AREA. A COLD FRONT WILL BEGIN TO APPROACH THE AREA LATE TUESDAY, AND THERE IS A SLIGHT CHANCE A FEW SHOWERS MAY AFFECT THE NORTHWESTERN PORTION OF THE AREA. TEMPERATURES COOL OFF SLIGHTLY FRIDAY INTO SATURDAY, FOLLOWED BY A WARMING TREND SUNDAY INTO TUESDAY.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR THRU THIS EVENING. AT 1930Z, A SEA-BREEZE FRONT WAS MOVING THRU THE NJ PINE BARRENS AND NEAR MIV. THIS SEA BREEZE WILL CONTINUE TO PROGRESS INLAND ALL THE WAY INTO THE I-95 TERMINALS BY AROUND 00Z. WINDS WILL SHIFT FROM OUT OF THE W-NW TO THE S-SE BUT WILL BE LIGHT (UNDER 10 KT). THE MAIN FOCUS FOR THIS TAF PERIOD IS THE POTENTIAL FOR ANOTHER ROUND OF FOG OVERNIGHT AND EARLY THURSDAY MORNING. WENT WITH A PERSISTENCE FORECAST FOR TONIGHT, WHICH YIELDS A MUCH MORE PESSISMISTIC FORECAST IN TERMS OF VISIBILITIES THAN ALL AVAILABLE NWP AND STAT GUIDANCE HAD INDICATED THUS FAR. CONFIDENCE IN FOG IS HIGHEST CLOSER TO THE COAST, SO WENT WITH LIFR AT MIV AND FOG EARLY THURSDAY MORNING. CIGS AND LOW CLOUDS LIFTS BY 14-15Z THURSDAY. VFR FOR MOST OF THE DAY. ISOLATED SHOWERS AND STORMS FORECAST TO DEVELOPS DURING THE AFTERNOON. FOCUS OF THIS POTENTIAL CONVECTION IS IN THE HIGHLANDS (CLOSEST TO RDG AND ABE) AHEAD OF A COLD FRONT. ANTICIPATED COVERAGE IS TOO LOW TO INCLUDE IN THE TAFS THIS FAR OUT. OUTLOOK... THURSDAY NIGHT-FRIDAY...MAINLY VFR. SCATTERED SHOWERS OR THUNDERSTORMS POSSIBLE, WHICH MAY LOWER CIGS AND/OR VSBYS, ESPECIALLY FRIDAY. GUSTY EAST-NORTHEAST WINDS 15-20 KNOTS FRIDAY AFTERNOON. FRIDAY NIGHT-MONDAY NIGHT...MOSTLY VFR. GUSTY E-NE WINDS AROUND 15- 20 KNOTS SATURDAY AFTERNOON. PATCHY FOG/STRATUS POSSIBLE AROUND DAYBREAK EACH DAY.
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&& .MARINE...
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WINDS AND SEAS BELOW SCA LEVELS TONIGHT AND THURSDAY. WINDS COULD BE AS STRONG AS 15 KT THRU THIS EVE AND AGAIN THURSDAY AFTERNOON ONCE THE SEA-BREEZE FRONT MOVES INLAND. OUTLOOK... THURSDAY NIGHT...SUB-ADVISORY CONDITIONS EXPECTED AS A BACKDOOR COLD FRONT MOVES ACROSS THE WATERS. FRIDAY-SATURDAY NIGHT...SEAS BEGIN TO BUILD TO SMALL CRAFT ADVISORY LEVELS WITH THE EASTERLY FETCH BEHIND THE BACKDOOR COLD FRONT DURING THE DAY FRIDAY AND CONTINUE INTO SATURDAY. WINDS MAY APPROACH OR EXCEED SMALL CRAFT ADVISORY LEVELS BEHIND THE BACKDOOR COLD FRONT FRIDAY-FRIDAY NIGHT. SUNDAY-MONDAY NIGHT...SEAS EXPECTED TO SUBSIDE BACK BELOW SMALL CRAFT ADVISORY CONDITIONS.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...ROBERTSON NEAR TERM...KLEIN SHORT TERM...KLEIN LONG TERM...ROBERTSON AVIATION...KLEIN/ROBERTSON MARINE...KLEIN/ROBERTSON

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