Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 050916 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 516 AM EDT THU MAY 5 2016 .SYNOPSIS... LOW PRESSURE OFFSHORE WILL MOVE TOWARD THE CANADIAN MARITIMES LATE TODAY AND TONIGHT. MEANWHILE ANOTHER LOW PRESSURE SYSTEM DEVELOPS OFF THE MID ATLANTIC COAST TONIGHT AND FRIDAY, THEN MEANDERS AND WEAKENS AROUND THE REGION INTO SATURDAY. A COLD FRONT IS FORECAST TO MOVE THROUGH SUNDAY MORNING FOLLOWED BY HIGH PRESSURE BUILDING IN FOR MONDAY INTO TUESDAY. A WARM FRONT SHOULD THEN LIFT ACROSS OUR AREA LATE TUESDAY INTO WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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CLOUDY. AREAS OF DRIZZLE EARLY THIS MORNING OTHERWISE A GENERALLY RAINFREE DAY. HRRR IS FIRING UP SOME SHOWERS MIDDAY VCNTY DE BAY AND THEN SE PA AND SNJ THIS AFTN BUT CONFIDENCE IS BELOW AVG ON IF THIS IS GOING TO HAPPEN. TEMPS NEARLY STEADY THROUGH SUNRISE THEN ONLY SMALL RISES DURING THE DAY WITH COLD AIR UNDERRUNNING NORTHEAST WIND ADVECTION FROM THE RESERVOIR OF COOLER WET BULBS OVER NEW ENGLAND. MAX TEMPS MAYBE 15 BELOW NORMAL. GUSTY NORTHEAST WIND 20 TO 25 MPH DURING MIDDAY AND THE AFTERNOON. FCST WAS A 50 50 BLEND OF THE 00Z/5 GFS/NAM MOS. POPS...USED THE HRRR TO KEEP THE MORNING-MIDDAY DRY (EXCEPTING SPOTTY DRIZZLE S PART OF THE FORECAST AREA). CONFIDENCE: ABOVE AVERAGE ON ALL EXCEPT WHETHER ANY SHOWERS WILL DEVELOP MIDDAY-THIS AFTERNOON.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
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APPEARS THAT WARM AIR ADVECTION AND AN INSTABILITY BURST WILL BE DEVELOPING NORTHWESTWARD AS A NEW AREA OF LOW PRESSURE ORGANIZES NEAR DELAWARE. THUNDER POSSIBLE BY DAYBREAK FRIDAY NEAR DELAWARE. SHOWERS MAY BE BRIEFLY HEAVY WHERE THEY DO OCCUR THOUGH PWAT ONLY INCREASES TO NEAR 1 INCH. NORTHEAST WIND...GUSTS GENERALLY UNDER 20 MPH. POPS MAY NEED TO BE RAISED 15 PCT IN LATER FORECAST FOR LATE TONIGHT. 330 AM FORECAST WAS BASED ON A 50 50 BLEND OF THE 00Z/5 GFS/NAM MOS WITH THE POPS MODIFIED BY THE SREF PROBS. WPC QPF 00Z/5 QPF GRIDS USED. AM AWARE WAS MUCH TOO HIGH ON POPS YDY DURING THE DAY KTTN SOUTHWEST THROUGH PHL/ILG/ESN AND MISSED THE THUNDER COASTAL NJ/DE.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/... THE SYNOPTIC SETUP IS COMPRISED OF A CONTINUATION OF AN OMEGA BLOCK FRIDAY, THEN THIS BREAKS DOWN DURING THE COURSE OF THE WEEKEND. THIS CHANGE OCCURS AS A STRONG SHORT WAVE TROUGH DIVES SOUTHEASTWARD FROM CENTRAL CANADA FRIDAY, KICKING OUT THE EASTERN PORTION OF THE OMEGA BLOCK. THIS INCOMING TROUGH AMPLIFIES ACROSS THE NORTHEAST LATER SUNDAY BEFORE GRADUALLY LIFTING OUT MONDAY. A WEAK RIDGE THEN ARRIVES FOR EARLY NEXT WEEK WITH A SURFACE WARM FRONT ALSO MOVING THROUGH. THERE COULD BE SOME TRICKINESS THOUGH NEXT WEEK AS THE NORTHBOUND WARM FRONT MAY STALL ACROSS OUR NORTHERN AREAS AS INCOMING ENERGY SHEARS EASTWARD ALONG IT. AS OF NOW, IT APPEARS OUR AREA GETS INTO THE TRUE WARM SECTOR NEXT WEEK HOWEVER IT MAY BE CLOSE ACROSS THE NORTH STARTING WEDNESDAY. WE USED A MODEL BLEND APPROACH FOR FRIDAY INTO SUNDAY, THEN BLENDED IN THE 00Z WPC GUIDANCE THEREAFTER. SOME ADJUSTMENTS WERE THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH OUR NEIGHBORING OFFICES. FOR FRIDAY AND SATURDAY...A CLOSED LOW CENTERED TO OUR SOUTH TO START FRIDAY IS FORECAST TO MOVE OVER OUR AREA BY LATE IN THE DAY. AS THIS OCCURS, STRONG SHORT WAVE ENERGY PIVOTS NORTH AND THEN NORTHWESTWARD ACROSS OUR AREA FRIDAY. THE MODEL GUIDANCE INDICATES A STRONG 500 MB JET STREAK ROUNDING THE BASE OF THE CLOSED LOW WITH OUR AREA WITHIN THE LEFT EXIT REGION FOR A TIME FRIDAY. THIS FEATURE THEN SHIFTS NORTHEASTWARD DURING THE DAY FRIDAY. AS THIS OCCURS, WAVES OF STRONGER FORCING GENERALLY SHIFT FROM SOUTHEAST TO NORTHWEST. THE PW VALUES ARE FORECAST TO BE BETWEEN 0.75-1.00 INCHES FRIDAY. AS A RESULT, PERIODS OF RAIN ARE EXPECTED TO TRANSLATE FROM SOUTHEAST TO NORTHWEST DURING THE COURSE OF FRIDAY WITH PERHAPS THE MORE WIDESPREAD ACTIVITY OCCURRING IN THE MORNING PRIOR TO THE CENTER OF THE CLOSED LOW ARRIVING. DESPITE FORECAST SOUNDINGS NOT SHOWING MUCH IN THE WAY OF INSTABILITY, THE PRESENCE OF THE 500 MB JET STREAK AND A COLD CORE ALOFT /STEEPENING MID LEVEL LAPSE RATES/ A SLIGHT CHC OF THUNDER WAS ADDED FOR FRIDAY /PERHAPS SMALL HAIL OCCURS WITH ANY EMBEDDED THUNDER/. WE THEN GRADUALLY TAPER OFF THE STEADY RAIN AND TRANSITION TO SOME SHOWERS FRIDAY NIGHT AS THE CLOSED LOW SETTLES RIGHT OVER US AND THE STRONGER FORCING MAY SHIFT WEST AND NORTH. THE CLOSED LOW IS STILL FORECAST TO BE OVER OUR AREA SATURDAY HOWEVER IT LOOKS TO GRADUALLY WEAKEN AND OPEN UP SATURDAY NIGHT. GIVEN THE COLD CORE ALOFT STILL OVER OUR AREA SATURDAY, SOME SHOWERS SHOULD STILL OCCUR. WE LOOK TO FINALLY LOSE THE ONSHORE FLOW COMPONENT SATURDAY, THEREFORE SOME BREAKS IN THE CLOUDS ARE ANTICIPATED WHICH COULD PROVIDE A LITTLE INSTABILITY FOR SOME LOW- TOPPED CONVECTION. THE FORECAST SOUNDINGS DO NOT INDICATE MUCH INSTABILITY AND THEREFORE HELD OFF INTRODUCING A THUNDER MENTION ATTM. A STRONG SHORT WAVE DRIVING SOUTHEASTWARD FROM THE GREAT LAKES REGION SATURDAY NIGHT WILL PUSH A COLD FRONT INTO OUR AREA TOWARD DAYBREAK SUNDAY. THIS TROUGH MAY START TO TAKE ON A NEGATIVE TILT AND WITH A PLUME OF DEEPER MOISTURE THERE IS THE POTENTIAL FOR A BAND OF HEAVIER SHOWERS ACCOMPANYING THE COLD FRONT. AS A RESULT, WE INCREASED THE POPS TOWARD LATER SATURDAY NIGHT. FOR SUNDAY...AN AMPLIFYING UPPER-LEVEL TROUGH THAT MAY TAKE ON A NEGATIVE TILT MOVES ACROSS THE NORTHEAST. THIS DRIVES A COLD FRONT ACROSS OUR AREA SUNDAY MORNING WITH SOME SHOWERS. THE GREATEST CHC FOR SHOWERS LOOKS TO BE ACROSS ABOUT THE NORTHERN HALF OF THE CWA, THEREFORE RAISED POPS TO HIGH CHC/LOW LIKELY EARLY ON. WHILE A COLD FRONT MOVES THROUGH AND THE FLOW SHIFTS TO THE WEST-NORTHWEST, A WARMER AFTERNOON IS EXPECTED AS MIXING DEEPENS ALONG WITH AN INCREASING BREEZE. FOR MONDAY THROUGH WEDNESDAY...SOME RIDGING SLIDES ACROSS THE AREA MONDAY INTO TUESDAY, HOWEVER LOW PRESSURE MIGRATING FROM THE PLAINS TOWARD THE GREAT LAKES WILL DRIVE DOWNSTREAM WAA. THIS WILL PUSH A WARM FRONT INTO OUR AREA LATE TUESDAY WITH IT LIFTING MOSTLY TO OUR NORTH BY EARLY WEDNESDAY. THE ENERGY WITH THE AFOREMENTIONED SURFACE LOW MAY SHEAR EASTWARD INTO WESTERLY FLOW ALOFT, THEREFORE THE WARM FRONT MAY STALL IN THE VICINITY OF OUR NORTHERN ZONES WEDNESDAY. THE PLACEMENT OF THIS FRONT WILL HAVE AN IMPACT ON OUR TEMPERATURES, HOWEVER PLENTY OF WARMTH SHOULD BE ADVECTING IN FROM THE SOUTH. AS A RESULT, A MUCH WARMER TIME FRAME IS EXPECTED ESPECIALLY WHEN COMPARED TO OUR CURRENT STRETCH OF WEATHER. THE PRECIPITATION CHCS ARE NOT ALL THAT CLEAR ATTM AS IT WILL DEPEND ON POTENTIAL SHEARING ENERGY RUNNING EASTWARD AS THE WARM FRONTS NORTHWARD PROGRESS SLOWS. && .AVIATION /09Z THURSDAY THROUGH MONDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THROUGH 12Z...CIGS VARIABLE BETWEEN 500 AND 1500 FT WITH POCKETS OF 2MI DRIZZLE. IFR CONDS MAINLY VCNTY KPHL/KILG/KMIV/KACY. NORTHEAST GUSTS UNDER 15 KT. AFTER 12Z...CIGS GENERALLY IMPROVE TO BETWEEN 1500 AND 3000 FT BY MIDDAY AND POSSIBLY TO VFR CIGS DURING THE AFTERNOON. ANY LINGERING DRIZZLE EARLY IN THE DAY SHOULD QUIT BY 14Z. NORTHEAST WIND GUSTY 20 TO POSSIBLY 25 KT I95 REGION EASTWARD AND LESS THAN 18 KT VCNTY KRDG AND KABE. TONIGHT...VFR CIGS TO START BUT CONDITIONS SHOULD DEGRADE TO MVFR OR IFR IN SHOWERS/DRIZZLE SOMETIME AFTER 03Z/6. NORTHEAST WIND... GUSTS UNDER 15 KT. OUTLOOK... FRIDAY AND SATURDAY...MVFR/IFR CEILINGS FRIDAY INTO SATURDAY, THEN THIS SHOULD IMPROVE TO VFR SATURDAY ESPECIALLY IN THE AFTERNOON. PERIODS OF RAIN FRIDAY WILL RESULT IN AT LEAST MVFR VISIBILITIES AT TIMES WITH THIS BECOMING MORE SHOWERY AT NIGHT, THEN A FEW SHOWERS ARE STILL POSSIBLE SATURDAY. NORTHEAST WINDS MAINLY AROUND 10 KNOTS FRIDAY AND FRIDAY NIGHT, THEN TURNING SOUTHEAST TO SOUTH SATURDAY. SOME SHOWERS SHOULD ARRIVE LATE SATURDAY NIGHT WITH A COLD FRONT. SUNDAY...SUB-VFR CONDITIONS POSSIBLE IN THE MORNING AS SOME SHOWERS MOVE THROUGH WITH A COLD FRONT, THEN VFR. SOUTHWEST WINDS EARLY, BECOMING WEST-NORTHWEST AND INCREASING TO 10-15 KNOTS WITH GUSTS TO AROUND 20 KNOTS. MONDAY...VFR. WEST TO SOUTHWEST WINDS AROUND 10 KNOTS. && .MARINE... SCA CONTINUES ON THE ATLANTIC WATERS FOR OCCASIONAL GUSTS 25 TO 30 KT AND SEAS OF 6 TO 9 FEET. WILL ADD AN SCA TO LOWER DE BAY IN THE 330 AM FORECAST ISSUANCE WHERE GUSTS TO 25 KT WILL OCCUR. OUTLOOK... LOW PRESSURE MOVES INTO OUR AREA FRIDAY BEFORE MEANDERING AND DISSIPATING THROUGH SATURDAY. AN INCREASE IN THE ONSHORE FLOW FRIDAY ESPECIALLY ACROSS OUR NORTHERN ATLANTIC COASTAL WATERS WILL ALLOW FOR GUSTS TO AROUND 25 KNOTS BEFORE DIMINISHING BY LATER IN THE DAY. THE FLOW THEN DECREASES FRIDAY NIGHT BEFORE TURNING SOUTHERLY SATURDAY AHEAD OF A COLD FRONT THAT THEN MOVES THROUGH SUNDAY MORNING. BEHIND THE FRONT, A WEST-NORTHWEST WIND SHOULD GUST TO AROUND 20 KNOTS BEFORE DIMINISHING SOME SUNDAY NIGHT INTO MONDAY. SEAS ON OUR ATLANTIC COASTAL WATERS SHOULD BE AT OR ABOVE 5 FEET INTO SATURDAY, THEREFORE THE SMALL CRAFT ADVISORY HAS BEEN EXTENDED THROUGH FRIDAY NIGHT. THEREAFTER SOME UNCERTAINTY EXISTS AS THE WINDS LESSEN FOR A TIME AND TURN SOUTHERLY SATURDAY. THE SEAS SHOULD THEN BE BELOW 5 FEET SUNDAY AND MONDAY. && .TIDES/COASTAL FLOODING...
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MAXIMUM WEDNESDAY EVENING TIDES ALONG THE NJ AND DE COASTS WERE WITHIN 1 INCH OF THE MINOR TIDAL INUNDATION FLOOD THRESHOLD WITH SURGE VALUES OF 1 TO 1.2 FEET. THE PERSISTENT NORTHEAST FLOW WILL CAUSE THE TIDAL SURGE TO BE AT LEAST 1.0 TO 1.5 FEET FOR BOTH OF TODAYS HIGH TIDE CYCLES. AND ANOTHER ADVISORY WAS ISSUED THIS MORNING AT 330 AM. THOSE VALUES ALONG WITH THE INCREASING ASTRONOMICAL TIDES AS WE APPROACH FRIDAY`S NEW MOON WILL RESULT IN MINOR TIDAL FLOODING ALONG THE NEW JERSEY AND DELAWARE COASTS AT HIGH TIDE, ESPECIALLY THIS THURSDAY EVENING. THIS MORNINGS ADVISORY ALONG THE DE COAST WILL BE MARGINAL, SIMILAR TO LAST EVENING. ALONG THE OCEANFRONT THE INCOMING WAVES WILL BE A FOOT OR 2 HIGHER THAN THOSE OF LAST EVENING. ADDITIONALLY, THE DAY SHIFT MAY BE EXTENDING THE CF ADVISORY TO THE TIDAL DE RIVER DOWNSTREAM FROM THE COMMODORE BARRY BRIDGE INTO THE EXTREME UPPER PART OF DE BAY (REEDY POINT LINK) FOR THE LATE THURSDAY EVENING HIGH TIDE CYCLE. THE NEW MOON ON FRIDAY WILL CONTINUE TO ADD TO THE ASTRONOMICAL COMPONENT OF THE TIDES. AS A RESULT, WE WILL NOT NEED MUCH OF A POSITIVE SURGE DEPARTURE ESPECIALLY WITH A CONTINUED ONSHORE FLOW LEADING UP TO THE HIGH TIDE CYCLE. AS A RESULT, MINOR TIDAL FLOODING LOOKS TO OCCUR WITH THE FRIDAY NIGHT HIGH TIDE ALONG THE COAST AND UP DELAWARE BAY.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE. NJ...COASTAL FLOOD ADVISORY FROM 6 PM THIS EVENING TO MIDNIGHT EDT TONIGHT FOR NJZ012>014-020>027. DE...COASTAL FLOOD ADVISORY FROM 6 PM THIS EVENING TO MIDNIGHT EDT TONIGHT FOR DEZ002>004. COASTAL FLOOD ADVISORY UNTIL 11 AM EDT THIS MORNING FOR DEZ002>004. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SATURDAY FOR ANZ450>455. SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ431.
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&& $$ SYNOPSIS...GORSE NEAR TERM...DRAG 516A SHORT TERM...DRAG 516A LONG TERM...GORSE AVIATION...DRAG/GORSE 516A MARINE...DRAG/GORSE 516A TIDES/COASTAL FLOODING...516A

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