Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 200738 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 338 AM EDT WED MAY 20 2015 .SYNOPSIS...
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HIGH PRESSURE ACROSS THE MIDWEST WILL EXTEND INTO THE NORTHERN MID ATLANTIC LATER TODAY. A WEAK LOW PRESSURE SYSTEM IS THEN FORECAST TO TRACK TO OUR SOUTH AND EAST THURSDAY AND THURSDAY NIGHT. HIGH PRESSURE BUILDS INTO OUR AREA FOR FRIDAY NIGHT AND MOST OF SATURDAY BEFORE SHIFTING OFFSHORE. A COLD FRONT SHOULD DROP DOWN FROM THE NORTH LATE SUNDAY INTO MONDAY, THEN LIFT BACK NORTH AS A WARM FRONT MONDAY NIGHT. A COLD FRONT WILL BE TO OUR WEST DURING TUESDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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GUSTY NW WINDS TO 20 MPH FOLLOW A COLD FRONTAL PASSAGE EARLY TODAY ADVECTING DRIER COOLER AIR SEWD INTO THE REGION WITH RAPIDLY LOWERING DEW POINTS. REFRESHING AIR COMING. TODAY...BRIGHT SUNSHINE WITH AN FEW SC IN THE AFTN. MAX TEMPS ALMOST 15 DEGREES COOLER THAN THE VALUES OF TUESDAY AND DAYTIME MAX TEMPS ABOUT 3 TO 5 DEGREES BELOW NORMAL, OCCURRING AROUND 4P! (FOR CLIMATE PURPOSES...IT APPEARS DUE TO BOUNDARY LAYER MIXING THAT TODAYS MAX TEMP IN PHL WILL HAVE OCCURRED AT 1AM TODAY-75) GUSTY NORTHWEST WINDS 20 TO 25 MPH. USED THE WARMER 00Z/20 MAVMOS GUIDANCE TEMPS AND OTHERWISE 50 50 BLENDED 00Z/20 NAM/GFS MOS WINDS/DEWS. CONFIDENCE: WELL ABOVE AVERAGE.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... CLEAR TO START WITH RADIATIONAL COOLING HALTED BY RAPIDLY INCREASING AND LOWERING CIRRUS TO AC AFTER 06Z. NO FROST ANTICIPATED UNLESS SKIES REMAIN CLEAR THROUGH 09Z AT WALPACK AND PEQUEST IN NW NJ. THOSE ARE TWO OF THE MOST TYPICALLY COLDER LOW LYING LOCATIONS IN NJ NJ. SO 50 50 BLENDED MOS GUIDANCE LEANING TOWARD THE WARMER GFS MOS TEMPS. && .LONG TERM /THURSDAY THROUGH TUESDAY/...
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THE SYNOPTIC SETUP IS COMPRISED OF A CLOSED LOW ACROSS EASTERN CANADA WHICH AMPLIFIES SOME ACROSS THE NORTHEAST, THEN IT SHIFTS EASTWARD FRIDAY AND OVER THE WEEKEND AS ENERGY STARTS TO EJECT INTO THE CENTRAL AND SOUTHERN PLAINS. THE LATTER WILL TEND TO BUILD A RIDGE FROM NEAR FLORIDA NORTHWESTWARD TOWARD THE MIDWEST SUNDAY INTO MONDAY, THEN IT SHIFTS EASTWARD INTO TUESDAY WITH THE NORTHERN PORTION OF IT FLATTENING SOME. THE MAIN FEATURES OF INTEREST IS WEAK LOW PRESSURE THAT TRACKS TO OUR SOUTH AND EAST THURSDAY AND THURSDAY NIGHT, THEN A WEAK BACKDOOR FRONT LATE SUNDAY INTO MONDAY. WE USED A MODEL BLEND FOR THURSDAY THROUGH SATURDAY, THEN THE 00Z WPC GUIDANCE WITH CONTINUITY THEREAFTER. SOME TWEAKS WERE THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH OUR NEIGHBORING OFFICES. FOR THURSDAY...A CLOSED LOW NEAR HUDSON BAY WILL SLOWLY SHIFT EASTWARD. A SHORT WAVE TROUGH EMBEDDED IN THE LARGE SCALE TROUGH IS FORECAST TO SWING ACROSS THE UPPER OHIO VALLEY DURING THE DAY AND THEN NEAR THE NORTHERN MID ATLANTIC IN THE EVENING. THIS FEATURE IS FORECAST TO DRIVE WEAK SURFACE LOW PRESSURE EASTWARD ACROSS VIRGINIA AND NORTH CAROLINA. THERE IS A WINDOW OF OPPORTUNITY FOR INCREASING ISENTROPIC LIFT WITHIN SOME LARGER SCALE LIFT/PVA TO INDUCE AN AREA OF SHOWERS. THERE COULD BE ENOUGH INSTABILITY AT LEAST ALOFT FOR A BIT MORE CONVECTIVE CONTRIBUTION. THE BETTER SETUP IS ACROSS THE DELMARVA AND INTO FAR SOUTHERN NEW JERSEY. THIS MAY ADJUST FARTHER NORTH SOME IF THE SHORT WAVE IS A BIT SHARPER, AS SOME GUIDANCE INDICATES. THEREFORE WE INCREASED THE POPS AND BROUGHT THEM NORTHWARD. THE HIGHEST POPS IN THE LOW LIKELY RANGE ARE ACROSS THE FAR SOUTH AND SOUTHEAST AREAS, AND THEN THEY DECREASE NORTHWARD. THE FEATURE PULLS AWAY AT NIGHT WITH ANY SHOWERS SHIFTING OFFSHORE WITH SOME CLEARING THEREAFTER. WE ARE EXPECTING THICKENING CLOUDS DURING THE DAY WITH MUCH OF THE AREA PROBABLY GOING CLOUDY FOR A TIME, WHICH WILL KEEP HIGH TEMPERATURES ON THE MUCH COOLER SIDE. FOR FRIDAY AND SATURDAY...THE CLOSED LOW TO OUR NORTH IS FORECAST TO BE SHIFTING EASTWARD DURING THIS TIME FRAME AS ENERGY EJECTS INTO THE CENTRAL AND SOUTHERN PLAINS. THIS WILL TAKE SURFACE LOW PRESSURE INTO THE CANADIAN MARITIMES FRIDAY AND A COLD FRONT THROUGH OUR AREA, WITH A TIGHTENED PRESSURE GRADIENT IN PLACE. THIS RELAXES FRIDAY NIGHT AND SATURDAY AS SURFACE HIGH PRESSURE MOVES OVERHEAD. THIS MAY SET THE STAGE FOR A CHILLY LATE FRIDAY NIGHT AND EARLY SATURDAY WITH PERHAPS PATCHY FROST ACROSS THE FAR NORTHERN AREAS. HIGH PRESSURE THEN BEGINS TO SHIFT OFFSHORE LATE SATURDAY AS RIDGING BUILDS TO OUR WEST. FOR SUNDAY AND MONDAY...A RIDGE TO OUR WEST RESULTS FROM A TROUGH ACROSS THE WEST AND ANOTHER TROUGH IN PORTIONS OF EASTERN CANADA. THE LATTER WILL SHARPEN A BIT SUNDAY ACROSS NORTHERN NEW ENGLAND AND THIS SHOULD SET THE STAGE FOR A BACKDOOR FRONT. IT APPEARS THIS BOUNDARY ARRIVES IN OUR AREA SUNDAY NIGHT INTO MONDAY, ALTHOUGH IT MAY BE WEAKER THAN THE RECENT ONE THAT AFFECTED OUR AREA. HOWEVER, WITH THE RIDGE BUILDING AND REPOSITIONING ITSELF OFF THE COAST OF THE SOUTHEASTERN STATES, THE BOUNDARY SHOULD MIGRATE NORTHWARD AS A WARM FRONT. THIS SHOULD BE ASSISTED BY LOW PRESSURE LIFTING ACROSS THE MIDWEST AND WESTERN GREAT LAKES REGION AND DEEPENING SOUTHWESTERLY FLOW ACROSS THE EAST. SOME CONVECTION MAY OCCUR SUNDAY NIGHT AND MONDAY ALONG THE BACKDOOR FRONT DUE TO A POSSIBLE INSTABILITY GRADIENT AND LOW-LEVEL CONVERGENCE, HOWEVER MUCH OF THE LIFT SHOULD BE TO OUR WEST CLOSER TO THE WESTERN EDGE OF THE RIDGE. A WARMER AIRMASS SHOULD OVERSPREAD THE AREA ESPECIALLY MONDAY AS THE FRONT LIFTS NORTHWARD, AND SOME INCREASE IN THE DEW POINTS WILL ALSO OCCUR. FOR TUESDAY...WE SHOULD BE IN THE WARM SECTOR DURING THIS TIME FRAME AS A SHORT WAVE ALOFT AND SURFACE LOW PRESSURE TRACK TO OUR NORTH. THIS WILL FLATTEN THE RIDGE SOME AND WHILE THE SURFACE COLD FRONT IS CURRENTLY FORECAST TO STAY TO OUR WEST, SOME CONVECTION CANNOT BE RULED OUT WITH SOUTHWESTERLY FLOW OF WARMER AND MORE HUMID AIR. SOME PLACES MAY MAKE A RUN AT 90 DEGREES IN THE AFTERNOON.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. BEFORE 12Z TODAY...NW GUSTS AROUND 20 KT AND GENERALLY CLEAR SKY. AFTER 12Z TODAY...VFR CLEAR WITH FEW OR SCT SC DURING THE AFTN AOA 5000 FT. NW WIND GUSTS 20-25 KT. TONIGHT...VFR CLEAR TO START THEN CIGS AOA 10000 FT ARRIVING AFTER 06Z. LIGHT NW WIND TURN NNE LATE. OUTLOOK... THURSDAY...CLOUDS THICKEN AND LOWER, HOWEVER AS OF NOW MAINLY VFR. SHOWERS POSSIBLE ESPECIALLY FROM ABOUT KPHL SOUTHWARD, THEN ENDING AT NIGHT. FRIDAY...VFR. NORTHWEST WIND GUSTS TO AROUND 20 KNOTS, DIMINISHING IN THE EVENING. SATURDAY AND SUNDAY...VFR OVERALL, HOWEVER A FRONT SETTLES SOUTHWARD SUNDAY NIGHT WITH A CHANCE OF SOME SHOWERS AND A THUNDERSTORM.
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&& .MARINE...
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OVERNIGHT...THE COLD FRONT PASSES WITH A WSHIFT FROM SW TO NW AND GUSTY AROUND 20 KT. GUSTS COULD REACH 25 KT OVER THE NRN WATERS AFTER 3 AM. SEAS SHOULD BE NO HIGHER THAN 4 FEET. TODAY...NORTHWEST WINDS GUSTY TO NEAR 20 KT. TONIGHT...NORTHWEST WINDS GUSTY 20 KT TURN N-NE AND DIMINISH TO LESS THAN 15 KT BY THURSDAY MORNING. OUTLOOK... THURSDAY AND FRIDAY...WEAK LOW PRESSURE TRACKS TO OUR SOUTH AND EAST THURSDAY AND THURSDAY NIGHT WITH SOME INCREASE IN THE WINDS MAINLY ACROSS THE SOUTH, THEN NORTHWEST WINDS TURN GUSTY ON FRIDAY. DESPITE THE INCREASE IN WINDS AND SOME BUILDING OF THE SEAS, THE CONDITIONS ARE ANTICIPATED TO BE BELOW SMALL CRAFT ADVISORY CRITERIA. SATURDAY AND SUNDAY...HIGH PRESSURE BUILDS OVERHEAD SATURDAY BEFORE SHIFTING OFFSHORE SATURDAY NIGHT INTO SUNDAY. THIS MAY ALLOW FOR SOME SEA/BAY BREEZE ENHANCED WINDS SATURDAY AFTERNOON NEARSHORE. THE WINDS AND SEAS ARE FORECAST TO BE BELOW CRITERIA, ALTHOUGH SOUTHWESTERLY WINDS SUNDAY SHOULD INCREASE WITH GUSTS TO ABOUT 20 KNOTS.
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&& .FIRE WEATHER...
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TODAY...WE`LL SEE WINDS GUSTING TO 25 MPH AND DRY FINE FUELS ACROSS PORTIONS OF THE REGION, BUT MINIMUM RH`S ARE FORECAST TO BE IN THE 28-35% RANGE. FOR FRIDAY AFTERNOON, A NORTHWESTERLY WIND WITH GUSTS TO 20-25 MPH. THIS WILL COMBINE WITH RELATIVE HUMIDITY VALUES NEARING 30 PERCENT IN SOME AREAS ALONG WITH DRY FINE FUELS.
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&& .RIP CURRENTS... SST`S ABOVE NORMAL AND JUST OFF THE COAST SSTS WELL ABOVE NORMAL BY ALMOST 3C. THIS IS NOT GOOD ONCE IT TURNS HOT AND BEACHES ARE UNGUARDED. BE SMART ABOUT ANY SWIMMING EARLY THIS SEASON. ATLANTIC COASTAL WATER TEMPS ARE WARMING --UPPER 50S TO MID 60S. RIP CURRENT AWARENESS WEEK FOR MT HOLLY IS JUNE 7-13 WITH PSAS VIA PUBLIC INFORMATION STATEMENTS, SOCIAL MEDIA, NOAA WEATHER RADIO AND ANY MEDIA INTERVIEWS DESIRED (CONTACT OFFICE). FOR RIP CURRENTS: DESPITE ANTICIPATED PROJECTIONS OF LOW OR MODERATE RISK THROUGH THE MEMORIAL DAY WEEKEND, EARLY SEASON FATALITIES OCCUR WHEN SWIMMING AT UNGUARDED TIMES/LOCATIONS. WEAKER SWIMMERS OR SWIMMING IN AREAS WHERE RIP CURRENTS ARE STRONGER (JETTIES) CAN QUICKLY BECOME LIFE THREATENING. WHEN TRAINED LIFEGUARDS ARE NOT NEARBY, TIMELY RESCUE IS MUCH LESS LIKELY. LETS GET THROUGH THE MONTH OF MAY WITH ALL SWIMMERS SAFE! SWIM IN THE PRESENCE OF LIFE GUARDS! THANK YOU. && .CLIMATE... **TOP 10 WARMEST MAY APPEARS LIKELY IN PTNS OF THE FORECAST AREA** THE FIRST 19 DAYS OF MAY IN OUR FORECAST AREA ARE AVERAGING WITHIN ABOUT 1/2 DEGREE OF 7 DEGREES ABOVE NORMAL. BASED ON THE ENSEMBLE AND FORECAST DETERMINISTICALLY CONSERVATIVE INCLUDING OUR 330 PM MAY 19 PROJECTIONS THROUGH THE 26TH AND THEN THE CONSERVATIVE FTPRHA THEREAFTER THROUGH THE 29TH AND NORMAL TEMPS THE 30TH AND 31ST...OUTLOOKS A TOP 10 WARMEST MAY ON RECORD. IN ACTUALITY, WE THINK TEMPS WILL BE ABOVE NORMAL THOSE LAST TWO DAYS OF THE MONTH. FOR PHILADELPHIA...PERIOD OF RECORD BACK TO 1874. PROJECTING AN AVG TEMP OF 68.7 OR NEARLY 5 DEGREES ABOVE NORMAL (4.8) AND 3RD WARMEST ON RECORD. WARMEST WAS 70.8 IN 1991. THEN 69.2 2004. FOR ALLENTOWN...POR TO 1922. PROJECTING 65.0 OR 5.1 DEGREES ABOVE NORMAL AND 8TH WARMEST ON RECORD. WARMEST WAS 67.2 IN 1991. NORMAL FIRST DATE OF 90 OR HIGHER. PHILADELPHIA MAY 29 ALLENTOWN MAY 30 WILMINGTON JUNE 4 ATLANTIC CITY JUNE 11. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GORSE NEAR TERM...DRAG SHORT TERM...DRAG LONG TERM...GORSE AVIATION...DRAG/GORSE MARINE...DRAG/GORSE FIRE WEATHER... RIP CURRENTS... CLIMATE...

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