Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 100442 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1242 AM EDT THU JUL 10 2014 .SYNOPSIS... A COLD FRONT WILL MOVE THROUGH THE AREA FROM THE NORTHWEST OVERNIGHT BEFORE STALLING NEAR THE DELMARVA ON THURSDAY. HIGH PRESSURE WILL BRIEFLY BUILD ACROSS THE NORTHEAST FRIDAY INTO SATURDAY, BEFORE IT PUSHES OFFSHORE LATER IN THE DAY SATURDAY. THEN A SERIES OF SURFACE TROUGHS WILL AFFECT THE AREA EARLY NEXT WEEK, FOLLOWED BY A SLOW MOVING COLD FRONT TUESDAY INTO WEDNESDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... A FRONTAL BOUNDARY EXTENDED FROM AROUND RARITAN BAY SOUTHWESTWARD ACROSS LOWER BUCKS COUNTY TO LANCASTER COUNTY AROUND MIDNIGHT. THE BOUNDARY SHOULD CONTINUE TO SINK TO THE SOUTH OVERNIGHT. SHOWERS WERE CONTINUING TO DEVELOP ALONG THE REMNANT OUTFLOW BOUNDARIES FROM EARLIER CONVECTION FROM BERKS COUNTY AND THE LEHIGH VALLEY INTO NORTHERN AND CENTRAL NEW JERSEY. THE ACTIVITY WAS EXPERIENCING A WEAKENING TREND AND BASED ON THE HRRR THAT TREND SHOULD CONTINUE WITH MOST OF THE PRECIPITATION DISSIPATING BY ABOUT 300 AM. WE WILL KEEP A SLIGHT CHANCE OF SHOWERS ACROSS MUCH OF THE SOUTHERN PART OF OUR FORECAST AREA OVERNIGHT DUE TO THE FRONTAL BOUNDARY. HOWEVER, THERE SHOULD BE NO OTHER SIGNIFICANT TRIGGERS FOR PRECIPITATION SO WE WILL NOT MENTION THUNDER THERE. MINIMUM TEMPERATURES ARE EXPECTED TO FALL INTO THE UPPER 50S AND LOWER 60S IN THE ELEVATED TERRAIN UP NORTH IN THE WAKE OF THE FRONTAL PASSAGE. MEANWHILE, LOW TEMPERATURES AHEAD OF THE FRONT SHOULD DROP ONLY INTO THE UPPER 60S AND LOWER 70S. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 AM FRIDAY/... AN AMPLIFIED RIDGE OVER THE ATLANTIC OCEAN WILL BE ASSOCIATED WITH AN OMEGA BLOCK THAT DEVELOPS OVER THE GREENLAND. UPSTREAM RAMIFICATIONS OF THIS BLOCKING PATTERN WILL ALLOW THE UPPER LOW TO REMAIN CUTOFF OVER QUEBEC AND ITS ASSOCIATED LONG WAVE TROUGH OVER THE GREAT LAKES AND MIDWEST. OPERATIONAL MODEL GUIDANCE IN FAIRLY GOOD AGREEMENT WITH THE POSITION OF THE COLD FRONT IN SRN NJ/DELMARVA AT 12Z THURSDAY. THE FRONT WILL BECOME ORIENTED PARALLEL TO THE S-SWLY STEERING FLOW IN BETWEEN THE UPSTREAM TROUGH AND DOWNSTREAM RIDGE, CAUSING THE FRONTAL BOUNDARY TO STALL OVER THE SRN THIRD OF THE CWA ON THURSDAY. THE EXPECTED POSITION OF THE STATIONARY FRONT, POSITION OF THE UPPER-LVL JET STREAK, AND TRACK OF A MID-LVL SHORTWAVE TROUGH ALL CONTRIBUTE TO LARGE-SCALE LIFT FOR SRN NJ, DE, AND THE ERN SHORE OF MD. POPS WERE INCREASED IN THESE SRN ZONES BUT DID NOT QUITE HAVE THE FCST CONFIDENCE TO GO WITH LIKELY POPS DUE TO UNCERTAINTIES IN TIMING OF PRECIP. CLOUDS EXPECTED TO LIMIT CONVECTIVE POTENTIAL AND THUS THE SETUP FOR SEVERE TSTMS NOT NEARLY AS FAVORABLE AS YESTERDAY AND TODAY. CLOUD COVER AND SHOWER CHANCES DECREASE FARTHER NORTH. KEPT FCST DRY NORTH OF INTERSTATES 195 AND 76. MAX TEMP FCST WEIGHTED MORE WITH THE MET GUIDANCE. LIKED THE GRIDDED OUTPUT WITH THE WARMEST TEMPS IN THE PHILA METRO AND CENTRAL NJ, JUST NORTH, WHICH MAY BE JUST NORTH OF THE THICKER CLOUD CLOVER. && .LONG TERM /FRIDAY THROUGH THURSDAY/... AT THE BEGINNING OF THE LONG TERM PERIOD, THE FRONTAL BOUNDARY WILL REMAIN STALLED OUT OFFSHORE OF THE EAST COAST, WHILE PW VALUES LOWER SLIGHTLY ACROSS THE AREA INTO FRIDAY. HOWEVER, THERE COULD REMAIN JUST ENOUGH MOISTURE TO INTERACT WITH ANY SHORT WAVE/VORTICITY IMPULSES THAT SLIDE ACROSS THE AREA WITHIN THE BROAD TROUGH ALOFT THAT WILL REMAIN ACROSS THE EAST COAST. THE GREATEST LIKELIHOOD IS ACROSS OUR FAR SOUTHERN NEW JERSEY AND SOUTHERN DELMARVA ZONES, WHICH WILL BE CLOSER TO ANY INFLUENCE OF THE FRONT TO OUR SOUTH AND WHERE ANY MOISTURE REMAINS POOLED. HIGH PRESSURE WILL CONTINUE TO SLIDE ACROSS THE NORTHEAST FRIDAY INTO FRIDAY NIGHT WHICH SHOULD HELP REINFORCE THE DRYING POTENTIAL. THE HIGH BUILDS OFF THE NORTHEAST COAST SATURDAY, WHICH WILL ALLOW A RETURN FLOW TO DEVELOP ACROSS THE AREA. WITH THIS RETURN FLOW, MOISTURE RETURNS, AND WITH A VORTICITY IMPULSE APPROACHING THE AREA SATURDAY, A FEW SCATTERED SHOWERS/THUNDERSTORMS COULD DEVELOP. THESE WILL LIKELY BE MAINLY AFTERNOON/DIURNALLY DRIVEN AND DIMINISH AFTER SUNSET. AS WE MOVE INTO SUNDAY AND EARLY NEXT WEEK, WE ALMOST COPY AND PAST THE FORECAST FROM THE LAST SEVERAL DAYS, AND PASTE IT INTO THE FORECAST SUNDAY THROUGH WEDNESDAY PERIOD NEXT WEEK. AN AREA OF LOW PRESSURE IS EXPECTED TO MOVE INTO SOUTHEASTERN CANADA, WHILE A SERIES OF FRONTAL BOUNDARY CIRCLE AROUND THE LOW ACROSS THE GREAT LAKES AND NORTHEAST. AHEAD OF THESE BOUNDARIES, A PRE-FRONTAL/LEE- SIDE TROUGH IS POSSIBLE EACH DAY. SEVERAL SHORT WAVE/VORTICITY IMPULSES ARE EXPECTED TO MOVE ACROSS OUR AREA EACH DAY, WHICH WILL MAKE SHOWERS AND THUNDERSTORMS POSSIBLE EACH DAY UNTIL THE MAIN COLD FRONT MOVES ACROSS THE AREA. THIS IS NOT EXPECTED UNTIL AT LEAST TUESDAY NIGHT INTO WEDNESDAY. SO WE WILL HAVE AT LEAST A CHANCE OF SHOWERS/THUNDERSTORMS EACH DAY FROM SUNDAY THROUGH TUESDAY. EVEN THOUGH THERE IS A CHANCE EACH DAY, IT IS NOT EXPECTED TO BE A COMPLETE WASHOUT EVERYWHERE EACH DAY. STILL, INSTABILITY WILL BE INCREASING, AND PW VALUES WILL AS WELL. SO WE IT REMAINS POSSIBLE FOR PERIOD OF HEAVY RAINFALL AND STRONG STORMS AS WELL. ANY SEVERE POTENTIAL WILL DEPEND ON EACH DAY`S INSTABILITY AND WIND/SHEAR PROFILES WHICH WILL BECOME MORE EVIDENT IN THE DAYS TO COME. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. MAINLY VFR TONIGHT. THE EXCEPTION WILL BE IN LIGHT FOG WITH SOME MVFR CONDITIONS. THE COLD FRONT WILL PROGRESS SWD THRU THE TERMINALS TNGT AND WILL BE ASSOCIATED WITH A WIND SHIFT FROM S TO NW AND EVENTUALLY N-NE BY THU. ADDITIONAL SHRA EXPECTED IN VC OF ILG/MIV/ACY ON THU. TSRA CHANCES WILL BE LOW. OUTLOOK... THURSDAY NIGHT-FRIDAY...MOSTLY VFR. A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS, MAINLY ACROSS OUR SOUTHERN TAF SITES. FRIDAY NIGHT-SATURDAY NIGHT...MVFR CIGS POSSIBLE WITH EASTERLY FLOW. SUNDAY-MONDAY...SHOWERS AND THUNDERSTORMS POSSIBLE, WHICH COULD LOWER CIGS/VSBYS. && .MARINE... EXPECTING WIND SPEEDS TO DECREASE OVERNIGHT WITH 3 TO 4 FOOT SEAS ON THE OCEAN. WINDS SHOULD BE LIGHT ON THURSDAY WITH THE FRONTAL BOUNDARY STALLING OVER THE WATERS. POTENTIAL FOR A FEW TSTMS ON THURSDAY NEAR THE DELAWARE WATERS. OUTLOOK... THURSDAY NIGHT-FRIDAY...SUB-ADVISORY CONDITIONS EXPECTED. CHANCE OF SHOWERS/THUNDERSTORMS, MAINLY SOUTHERN WATERS. HIGHER WINDS/SEAS NEAR THUNDERSTORMS. FRIDAY NIGHT-SATURDAY NIGHT...SUB-ADVISORY CONDITIONS EXPECTED. SUNDAY-MONDAY...SUB-ADVISORY CONDITIONS EXPECTED, BUT WINDS WILL BE INCREASING IN THE SOUTHWESTERLY FLOW AHEAD OF AN APPROACHING FRONTAL BOUNDARY. CHANCE OF SHOWERS/THUNDERSTORMS. HIGHER WINDS/SEAS NEAR THUNDERSTORMS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...ROBERTSON NEAR TERM...IOVINO SHORT TERM...KLEIN LONG TERM...ROBERTSON AVIATION...KLEIN/ROBERTSON MARINE...KLEIN/KRUZDLO/ROBERTSON

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