Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 250142 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 942 PM EDT SUN AUG 24 2014 .SYNOPSIS... HIGH PRESSURE WILL REMAIN IN CONTROL OF OUR WEATHER THROUGH TUESDAY. A COLD FRONT WILL SAG SOUTHEAST INTO THE MID ATLANTIC STATES LATE WEDNESDAY OR THURSDAY. THEN THE NATIONAL HURRICANE CENTER TRACKS CRISTOBAL OUT TO SEA WELL TO THE EAST OF THE CAROLINAS LATE THIS WEEK. A MORE SUMMERLIKE WARM HUMID PATTERN APPEARS TO BE UNFOLDING FOR NEXT WEEKEND. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... MINIMAL CHANGES NEEDED TO THE GRIDS THIS EVENING AS THE FORECAST REMAINS ON TRACK. JUST ABOUT ALL THE STRATOCU HAS ERODED WITH JUST SOME POCKETS LEFT ACROSS THE EASTERN SHORE. OTHERWISE, AS THE SURFACE HIGH STARTS TO SETTLE OVERHEAD AND WE LOSE THE MIXING, THE SURFACE WINDS ARE ANTICIPATED TO BECOME RATHER LIGHT FOR MUCH OF THE AREA. THE ONE EXCEPTION MAY BE ALONG THE COAST AND PORTIONS OF THE DELMARVA DUE TO THE ONSHORE FLOW AND A LONGER FETCH INTO THESE AREAS. THIS COULD RESULT IN A BIT MILDER TEMPERATURES OVERNIGHT HERE, AND ELSEWHERE IT WILL BE A COOL NIGHT. SOME PATCHY FOG CANNOT BE RULED OUT LATE, MAINLY ACROSS THE NORTHWEST ZONES WHERE COOL TEMPERATURES WILL PROMOTE NEAR-GROUND SATURATION. ELSEWHERE, NO FOG WAS INCLUDED ATTM. AS FOR LOW TEMPERATURES, WE USED AN EVEN BLEND OF THE NAM/GFS MOS WITH JUST SOME LOCAL TWEAKS. WE UTILIZED THE LAMP/LAV GUIDANCE IN THE HOURLY GRIDS INTO THIS EVENING FOR ASSISTANCE. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... THE SYNOPTIC SETUP IS COMPRISED OF A BUILDING RIDGE INTO THE NORTHEAST AND MID ATLANTIC REGION. WE WILL STILL REMAIN NEAR THE EASTERN EDGE OF THIS RIDGE AT LEAST THROUGH THE EARLY AFTERNOON HOURS, AND SURFACE HIGH PRESSURE WILL CONTINUE TO SETTLE OVER OUR ENTIRE CWA. AS THIS OCCURS WE WILL STILL HAVE AN ONSHORE FLOW CONTINUING, HOWEVER IT WILL WILL BE TURNING LIGHTER /EVEN AT THE COAST/ WITH MORE OF A SEA/BAY BREEZE INFLUENCE TENDING TO TAKE HOLD. THIS WOULD TURN THE WINDS MORE FROM THE SOUTHEAST DURING THE AFTERNOON HOURS. AS THE HEIGHTS RISE ACROSS THE REGION, THE AIRMASS WILL CONTINUE TO MODIFY. THIS WILL RESULT IN A WARMER DAY FOR MUCH OF THE AREA, HOWEVER IT SHOULD BE COOLER CLOSER TO THE COAST AND ALSO THE DELMARVA GIVEN THE LINGERING EFFECTS OF THE ONSHORE FLOW. THE DEW POINTS AWAY FROM THE OCEAN INFLUENCE SHOULD BE MAINLY IN THE 50S WITH THE CONVECTIVE TEMPERATURES HIGHER. THE FORECAST SOUNDINGS DO SHOULD A SHALLOW LAYER OF MOISTURE AT THE TOP OF THE MIXING LAYER, THEREFORE A BIT OF CUMULUS SHOULD DEVELOP. THIS IS ANTICIPATED TO BE LESS THAN WHAT WAS OBSERVED THIS AFTERNOON /SUNDAY/. OVERALL, AFTER SOME PATCHY FOG EARLY AN ABUNDANCE OF SUNSHINE IS ANTICIPATED. AS FOR HIGH TEMPERATURES, WE USED A GENERAL NAM/GFS MOS BLEND. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... 500 MB: A STRONG RIDGE OVER THE OHIO VALLEY WILL PROBABLY SHIFT SLIGHTLY SOUTHEASTWARD INTO THE SOUTHEAST USA NEXT WEEKEND. TEMPERATURES: ABOVE NORMAL TEMPERATURES TUESDAY AND WEDNESDAY MAY COOL TO NEAR OR SLIGHTLY BELOW NORMAL THURSDAY AND FRIDAY BEFORE PROBABLY WARMING UP NEXT WEEKEND. FORECAST BASIS: UNLESS OTHERWISE NOTED THE LONG TERM PERIOD OF THIS FORECAST IS GENERALLY BASED ON A 50 50 BLEND OF THE 12Z/24 NAM/GFS MOS FOR THE PERIOD MONDAY NIGHT - TUESDAY NIGHT...THE 12Z/24 GFS MOS WEDNESDAY AND WEDNESDAY NIGHT...THEN THEREAFTER (THURSDAY ONWARD) THE 1603Z/24 WPC GRIDDED GUIDANCE WHICH AT TIMES IS BLENDED 50 50 WITH THE 12Z/24 MEXMOS. ALL THIS IS EVENTUALLY CHECKED AGAINST THE 12Z/24 ECMWF TO SEE IF WE`RE IN THE BALLPARK WITH ECMWF CYCLICALLY PERSISTENT 18Z 2METER TEMPERATURES. THE PRECIPITATION PROBABILITY GUIDANCE IS CHECKED AGAINST THE 09Z/24 SREF POPS FOR .01 IN 3 HRS THROUGH 00Z THURSDAY AND THEREAFTER THE 12Z/24 GEFS 6HR POPS FOR 0.05 THE DAILIES... MONDAY NIGHT-WEDNESDAY...MOSTLY CLEAR AND INCREASINGLY WARMER WITH A POSSIBLE SPOTTY HEAT WAVE IN PARTS OF THE DELAWARE VALLEY BEGINNING TUESDAY. EARLY MORNING FOG MAY OCCUR BOTH EARLY TUESDAY AND WEDNESDAY FOR THE TYPICAL LOW LYING AREAS BUT NOT A STRONG CHANCE SINCE ITS SO DRY ALOFT. THE FCST MAX TEMPS ARE IN THE UPPER 80S AND MAYBE I SHOULD HAVE PUSHED THEM TO 90 OR 91 FOR WEDNESDAY BUT FOR NOW FCST THE MOST LIKELY MAX TEMPS. NO MATTER...IT WILL BE VERY WARM...ESPECIALLY FOR THIS AUGUST WHICH HAS BEEN RATHER COOL (ONLY 1 90 DEGREE DAY THIS MONTH AT PHL AND SIMILAR TEMPS TO LAST AUGUST 2013 AT PHL) WEDNESDAY NIGHT...THERE MAY BE A BAND OF SCT THUNDERSTORMS...SWI -2, TT NEAR 48C WITH 500MB WIND 30-35 KT AND SMALL CHANCE IT MIGHT RESULT IN AN ISOLATED LATE IN THE SEASON SVR...MAINLY NE PA/NNJ. THURSDAY...TRANSITION TO SLIGHTLY DRIER AND COOLER. STILL WARM. FRIDAY-WEEKEND...WPC GRIDDED POPS BASICALLY ACCEPTED. WPC 1603Z GRIDDED TEMPS WERE RAISED 3-4 DEGREES NEXT WEEKEND TO THE 12Z/24 GFS OPERATIONAL RUN MEX MOS VALUES WHICH IS CONSIDERABLY CLOSER TO THE 12Z/24 OPERATIONAL ECMWF. THE ECMWF IS MODELING THICKNESSES OVER 573DM EACH DAY WITH CREST OF THE RIDGE TSTMS IN OUR AREA OR NEARBY TO THE NORTH. ACTUALLY LOOKS LIKE A CHALLENGING SUMMER PATTERN. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TONIGHT...VFR. THERE COULD BE SOME LOCALIZED FOG DEVELOPMENT LATE, HOWEVER GIVEN THAT SOME DRYING HAS OCCURRED OUR CONFIDENCE IN ANY FOG IMPACTING A TERMINAL IS LOW. THEREFORE NO FOG WAS INCLUDED. WINDS NORTHEAST AT LESS THAN 5 KNOTS, AND EVEN BECOMING LIGHT AND VARIABLE AT SOME TERMINALS. MONDAY...VFR. NORTHEAST WINDS 5-10 KNOTS, BECOMING EAST AND SOUTHEAST IN THE AFTERNOON. OUTLOOK... MONDAY NIGHT-WEDNESDAY EARLY AFTERNOON...MOSTLY VFR. ONLY EXCEPTION WOULD BE POSSIBLE SPOTTY COUNTRYSIDE MVFR FOG EARLY TUESDAY AND WEDNESDAY MORNINGS. LIGHT WIND. LATE WEDNESDAY AFTERNOON-WEDNESDAY NIGHT...MOSTLY VFR WITH A SMALL CHANCE OF MVFR CONDITION TSTMS OVER PA AND NJ...ESPECIALLY I78 NORTH. SW WIND GUSTS MOSTLY UNDER 18 KT. THURSDAY... MOSTLY VFR. WIND TURNING NORTH. FRIDAY...PROBABLY VFR. EASTERLY OR SOUTHEAST FLOW WITH VFR CIRRUS OR AC DEVELOPING. && .MARINE... HIGH PRESSURE BUILDS DOWN FROM THE NORTH THROUGH MONDAY. THIS WILL MAINTAIN AN ONSHORE FLOW ALSO THROUGH MONDAY, HOWEVER THE PRESSURE GRADIENT WILL CONTINUE TO RELAX SOUTHWARD. THIS IS EXPECTED TO RESULT IN LESS GUSTINESS THROUGH TIME, HOWEVER THE PERSISTENT ONSHORE FLOW WILL KEEP THE SEAS ELEVATED. THIS IS MAINLY ACROSS OUR SOUTHERN OCEAN ZONES GIVEN A BETTER FETCH AND INITIALLY STRONGER WINDS. THIS LOOKS TO CONTINUE RIGHT THROUGH MONDAY, THEREFORE THE SMALL CRAFT ADVISORY FROM LITTLE EGG INLET SOUTHWARD WILL BE EXTENDED THROUGH AT LEAST THE DAY MONDAY. FARTHER NORTH, THERE IS RATHER LIMITED BUOY DATA /SEAS AT BUOY 44017 CONTINUE TO BE BELOW 5 FEET/ AND THEREFORE WE ARE ASSUMING SEAS WILL REMAIN UNDER ADVISORY CRITERIA HERE. THE WINDS ARE ANTICIPATED TO BE BELOW 25 KNOTS FOR THE NORTHERN ZONES AND DELAWARE BAY. OUTLOOK... MONDAY NIGHT...MAY STILL HAVE LINGERING SCA HAZARDOUS 5FT SEAS ON THE DE WATERS DUE TO THE PERSISTENT NE FETCH CONTG LONGER THAN PREVIOUSLY ANTICIPATED BUT FOR NOW NO SCA HEADLINE. TUESDAY-WEDNESDAY MORNING...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED WITH HIGH PRESSURE ACROSS THE WATERS. WEDNESDAY AFTERNOON-FRIDAY...LONG PERIOD (AROUND 12 SECOND) SOUTHEAST SWELLS POSSIBLE AND ARE ASSOCIATED WITH CRISTOBAL... WHICH SHOULD MAKE A RIGHT HAND TURN SEAWARD OUT TO THE EAST OF THE CAROLINAS SOMETIME MID OR LATE WEEK. SEE NHC FOR THE TRACK. && .RIP CURRENTS... THE THREAT OF RIP CURRENTS FOR MONDAY IS HIGH. AN INCREASING WATER LEVEL, WITH THE NEW MOON OCCURRING AT 1013AM, COMBINED WITH THE LONG FETCHED ONSHORE FLOW WILL ADD TO THE THREAT OF DANGEROUS RIP CURRENTS TOMORROW. WITH THE TROPICAL SYSTEM EXPECTED TO LIFT NORTHEASTWARD /STAYING WELL OFFSHORE/, LONGER PERIOD SWELLS SHOULD LEAD TO AN ENHANCED RIP CURRENT RISK LATER THIS WEEK. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...HIGH RIP CURRENT RISK FROM 6 AM EDT MONDAY THROUGH MONDAY EVENING FOR NJZ014-024>026. DE...HIGH RIP CURRENT RISK FROM 6 AM EDT MONDAY THROUGH MONDAY EVENING FOR DEZ004. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT MONDAY FOR ANZ452>455. && $$ SYNOPSIS...DRAG NEAR TERM...GORSE/HEAVENER SHORT TERM...GORSE LONG TERM...DRAG AVIATION...DRAG/GORSE MARINE...DRAG/GORSE RIP CURRENTS...HEAVENER/DRAG

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