Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 211424 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1024 AM EDT THU AUG 21 2014 .SYNOPSIS... LOW PRESSURE FROM LAKE ONTARIO TO VIRGINIA PRODUCES OCCASIONALLY UNSETTLED WEATHER HERE THROUGH FRIDAY. QUEBEC HIGH PRESSURE BECOMES OUR PRIMARY WEATHER INFLUENCE LATER THIS WEEKEND THROUGH THE MIDDLE OF NEXT WEEK AS THE HIGH SETTLES SOUTHWARD TO THE MID ATLANTIC STATES. && .NEAR TERM /THROUGH TONIGHT/... 1010AM ESTF HAS REDUCED RAIN CHANCES ALONG THE COAST AND ENHANCED THE WORDING IN NE PA AND NW NJ IN PART DUE TO THE 12Z NAM AND PRIOR ECMWF MASS FIELD PREDICTORS. THE EXTRA CLOUD COVER AND HIGHER THAN MODELED SFC DEWPOINTS IN SE PA N MD ALSO SUGGEST GREATER POTENTIAL INSTABILITY FOR MID AFTN DEVELOPMENT. 12Z SOUNDING FROM IAD/WAL/APG AND OKX REVIEWED. MAX TEMPS 83-86. UNSETTLED WITH POTENTIAL FOR BRIEF POOR DRAINAGE FLOODING AND SMALL HAIL PRODUCING THUNDERSTORMS (G35KT)...PARTICULARLY NE PA AND NW NJ...AND THINKING AKIN TO THE 00Z/21 NSSL WRF AN IN WEAK WAA AHEAD OF THE SFC TROUGH IN CENTRAL PA. THAT DOESN`T RULE OUT THE DELMARVA BUT FOR SOME TIME NOW...IT APPEARS INSTABILITY AND PROXIMITY TO THE COLD TROUGH ALOFT HAS FOCUSED NORTH RATHER THAN SOUTH. PWAT NEAR 1.5 INCHES. MLCAPE 400-600J. MARGINAL 0-6KM BULK SHEAR. OTRW...A NICE DAY WITH TEMPS NEAR OR SLIGHTLY ABOVE NORMAL UNDER MIXED SUN AND CLOUDS. THERE IS STILL MUCH MORE LOW CLOUDINESS OVER SE PA...NE MD AND N DE THIS MORNING THAN ANTICIPATED YDY. THIS SHOULD START THINNING AND LIFTING BY NOON. PLEASE FOLLOW ANY UPDATED SWOMCD`S SWODY1 AND LOCAL PHI PRODUCTS. TONIGHT...A COUPLE OF BANDS OF SHOWERS AND ISOLATED TSTMS IN THE STILL UNSTABLE AIRMASS. SHOWERS SHOULD DIMINISH LATE. NOTING THE 12Z NAM CONTG A THEME OF 2INCH HOURLY TSTMS SOMEWHERE IN E CENTRAL PA INTO CENTRAL NJ THIS EVENING. WHILE THE PLACEMENT IS POSSIBLY WRONG...THE IDEA I THINK IS CORRECT. A PTN OF E CENTRAL OR NE PA IN N OR CENTRAL NJ SHOULD RECEIVE SOME STRONG TSTORMS VERY LATE THIS AFTN OR EVENING. && .SHORT TERM /FRIDAY/... 1000J OF MLCAPE AND SLIGHTLY STRONGER 0-6KM BULK SHEAR CUES INTEREST IN CONVECTION FRI AFTN. SREF HAS DECENT PROBS FOR SHOWERS...ESPECIALLY E PA...S NJ AND THE DELMARVA. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... FRIDAY NIGHT THROUGH SATURDAY...THE REGION REMAINS UNDER NORTHWEST FLOW AS THE STOUT RIDGE REMAINS OVER THE MISSISSIPPI VALLEY, AND THE OTHER HIGH REMAINS OVER EASTERN CANADA. WITH THE NORTHWEST FLOW, EXPECT A FEW EMBEDDED SHORT WAVE TROUGHS TO BRING CHANCES FOR THUNDERSTORMS THROUGH THIS PERIOD. HOWEVER, THE TIMING OF THE INDIVIDUAL SHORT WAVE TROUGHS REMAINS UNCERTAIN. SUNDAY THROUGH THURSDAY...THE HIGH OVER EASTERN CANADA BUILDS SOUTH. WITH THE ASSOCIATED COLD AIR ADVECTION, COULD SEE HIGHS ESPECIALLY EARLY IN THE WEEKEND 5 TO 10 DEGREES BELOW NORMAL. BY TUESDAY HOWEVER, THE HIGH STARTS TO SHIFT OFF SHORE, LEAVING THE REGION UNDER SOUTHERLY FLOW AND LEADING TO A MODEST WARMING TREND. HOWEVER, ALSO TOWARDS THE END OF THIS FORECAST PERIOD THE GFS AND ECMWF SOLUTIONS DIFFER GREATLY ON THE TIMING OF AN UPPER LEVEL TROUGH AND ASSOCIATED SURFACE COLD FRONT THAT WILL BE PROPAGATING EAST ON THE HEALS OF THE HIGH. STILL, BOTH SOLUTIONS SHOW THESE FEATURES JUST BEYOND THE SEVEN DAY FORECAST. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAY...PERIOD OF MVFR CIGS IN E PA NE MD AND N DE THROUGH 16Z OTRW VFR SCT-BKN AOA 4000 FT THIS AFTERNOON BUT LOCAL IFR CONDS IN SCT SHOWERS AND TSTMS THIS AFTN. LIGHT SOUTH WIND. BUT A NW WIND GUST TO 35 KT POSSIBLE ASSOCIATED WITH AN AFTN TSTM NEAR AND N OF KABE. TONIGHT...VFR CIGS MAY DEGRADE TO MVFR CONDS IN FOG LATE. IFR CONDS IN LEFTOVER EARLY NIGHT SHOWERS AND TSTMS. FRIDAY...CIGS 2500-4000 FT WITH LOWER IFR CONDS IN SCT SHOWERS AND TSTMS AND A WIND TURNING LIGHT EASTERLY. OUTLOOK... FRIDAY AND SATURDAY...MOSTLY VFR. ISOLATED TO SCATTERED TSRA ARE POSSIBLE ACROSS THE REGION. UNDER ANY TSRA MVFR CEILINGS AND BRIEF IFR VISIBILITIES WILL BE POSSIBLE. SUNDAY THROUGH MONDAY...GENERALLY VFR. && .MARINE... SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED THROUGH FRIDAY WITH SEAS 3 FEET OR LESS AND SOUTH TO SOUTHEAST WINDS 5 TO 10 KNOTS BECOMING EASTERLY FRIDAY. WE`VE NOT SEEN ANY NEW MAREPS THIS WEEK FROM MARINERS IN OUR EASY USE (INTERNET AND/OR SMART PHONE) LINK WWW.WEATHER.GOV/PHI/MAROBSFORM THIS HAS BEEN DERIVED FOR THE MARINER TO EASILY POST INFO INSTANTLY TO THE NWS FOR USE IN OUR MARINE PRODUCTS. OUTLOOK... FRIDAY NIGHT...SCA NE WIND GUSTS MAY DEVELOP LATE AT NIGHT ON THE ATLC WATERS. SATURDAY...OCCASIONAL GUSTS NEAR 25 KT AND WAVE HEIGHTS APPROACHING 5 FT ARE POSSIBLE ESPECIALLY SATURDAY AFTERNOON THROUGH SATURDAY NIGHT. SUNDAY AND MONDAY...WAVE HEIGHTS AND WINDS SLOWLY FALLING BELOW SMALL CRAFT ADVISORY CRITERIA SUNDAY MORNING AND SHOULD REMAIN BELOW CRITERIA THROUGH MONDAY. && .CLIMATE... WE RCD INQUIRY ON HOW THE CLIMATE PROGRAM SELECTS FOR OUR 530 PM CLI. OUR PROGRAM SEARCHES MAX/MIN TEMP DATA FOR THE DAY ENDING 5PM SHARP. THAT DATA IS INGESTED INTO THE 530 PM POSTED CLI. IF A MAX TEMP OCCURS THEREAFTER...IT IS REFLECTED IN THE END OF DAY SUMMARY POSTS AROUND 230 AM EDT THE NEXT DAY AND ALSO YOU CAN CHECK THE 8 PM RTPPHI WHICH POSTS AROUND 815 PM EDT. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...DRAG/JOHNSON NEAR TERM...DRAG 1023 SHORT TERM...DRAG 1023 LONG TERM...JOHNSON AVIATION...DRAG/JOHNSON 1023 MARINE...DRAG/JOHNSON CLIMATE...

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