Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 130754 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 354 AM EDT SUN APR 13 2014 .SYNOPSIS... HIGH PRESSURE LOCATED OVER THE WESTERN NORTH ATLANTIC WILL CONTINUE TO INFLUENCE OUR WEATHER FOR TODAY AND MONDAY. A STRONG COLD FRONT IS FORECAST TO APPROACH FROM THE WEST ON MONDAY NIGHT AND TUESDAY AND IT SHOULD PASS THROUGH OUR REGION FROM LATE TUESDAY AFTERNOON INTO EARLY TUESDAY EVENING. HIGH PRESSURE FROM THE WEST IS ANTICIPATED TO BUILD ACROSS THE NORTHEASTERN STATES ON WEDNESDAY AND INTO ATLANTIC CANADA FOR THURSDAY AND FRIDAY. A FRONTAL BOUNDARY APPROACHING FROM THE WEST IS EXPECTED TO PASS THROUGH OUR REGION ON SATURDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A FRONTAL ZONE WILL BE DRAPED FROM NEW ENGLAND TO THE GREAT LAKES THEN DOWN INTO THE MID MISSISSIPPI VALLEY TODAY. LOW PRESSURE IS FORECAST TO TRACK ALONG THIS FRONT IN THE CENTRAL PLAINS TO MID MISSISSIPPI VALLEY REGIONS. MEANWHILE, THE CONTINUATION OF DOWNSTREAM WAA WILL HELP SEND A WARM FRONT NORTHWARD ACROSS OUR AREA THROUGH ABOUT MIDDAY. THIS WILL SIMPLY ENHANCE THE WARMER AIR MASS THAT HAS ALREADY BEEN IN PLACE ACROSS OUR CWA. ALONG WITH THE WAA, MOISTURE ADVECTION WILL ALSO BE UNDERWAY WHICH WILL HELP INCREASE THE SURFACE DEW POINTS GRADUALLY FROM SOUTH TO NORTH THROUGH THE DAY. THIS PROCESS IS ALREADY UNDERWAY EARLY THIS MORNING. THIS COMBINED WITH A NOCTURNAL INVERSION WAS INITIALLY THOUGHT TO HELP FOCUS AREAS OF STRATUS OR FOG EARLY THIS MORNING, HOWEVER THIS PROCESS HAS BEEN RATHER SLOW SO FAR. THEREFORE, WE DID NOT HIT THE LOW CLOUDS AND FOG ALL THAT HARD ATTM. OTHERWISE, BANDS OF MID TO HIGH LEVEL CLOUDS STREAMING BY AT TIMES ESPECIALLY DUE TO SOME DEBRIS CLOUDINESS FROM CONVECTION EARLY THIS MORNING IN THE MIDWEST AND GREAT LAKES. AS THE MOISTURE INCREASES SOME, WE SHOULD BE ABLE TO DEVELOP SOME CUMULUS THIS AFTERNOON. THE MAIN FORCING IS TIED TO A BOUNDARY NEAR THE EASTERN GREAT LAKES, AS THIS IS WHERE A THERMAL GRADIENT ALOFT EXITS. THEREFORE, SHOWERS AND EMBEDDED THUNDER WILL REMAIN TO OUR NORTH ASSOCIATED WITH THIS THERMAL BOUNDARY. AS THE BOUNDARY LAYER WARMS, THE DEPTH OF THE MIXING LAYER WILL GREATLY INCREASE. THE FORECAST SOUNDINGS SHOW AS THIS OCCURS THE LOW-LEVEL LAPSE RATES STEEPEN QUITE A BIT AWAY FROM THE COAST. THIS WILL PROMOTE BREEZY CONDITIONS DEVELOPING ESPECIALLY FROM MIDDAY ON. THIS WILL ALSO HOLD BACK ANY SEA BREEZE DEVELOPMENT, AS THE SYNOPTIC SCALE FLOW IS FROM THE SOUTH AND SOUTHWEST. THEREFORE, LOCALES ESPECIALLY RIGHT ALONG THE NORTHERN COAST OF DELAWARE BAY AND THE JERSEY SHORE WILL BE COOLER. AS FOR HIGH TEMPERATURES, WE USED A BLEND OF THE NAM/GFS 2 METER TEMPERATURES THEN ADJUSTED UP A LITTLE BIT GIVEN THE EXPECTED MIXING. THE COASTAL LOCALES WERE KEPT COOLER GIVEN THE SOUTHERLY FLOW. FOR THE HOURLY GRIDS EARLY THIS MORNING, WE USED A BLEND OF THE LAMP/LAV GUIDANCE TO HELP ASSIST WITH TRENDS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... OUR REGION WILL REMAIN WITHIN THE WARM SECTOR THROUGH TONIGHT AS WE ARE BETWEEN A RIDGE TO THE SOUTHEAST AND A SHARPENING UPPER- LEVEL TROUGH FROM THE MIDWEST TO THE CENTRAL PLAINS. THIS WILL RESULT IN THE SOUTHERLY FLOW BEING MAINTAINED UNDER A DECENT FLOW REGIME. THIS WILL MAINTAIN SOME MOISTURE ADVECTION FROM THE SOUTH, AND THEREFORE HIGHER SURFACE DEW POINTS. AS THE SOUTHWESTERLY FLOW CONTINUES ALONG WITH THE SHARPENING TROUGH WELL TO OUR WEST, AT LEAST SOME MID TO HIGH CLOUDS WILL CONTINUE TO STREAM ACROSS THE AREA. HOWEVER, AS THE MOISTURE DEEPENS SOME IN THE LOWER LEVELS IT MAY BECOME TRAPPED ENOUGH UNDER THE NOCTURNAL INVERSION. THIS COULD RESULT IN SOME STRATUS OR FOG. THE BOUNDARY LAYER WHILE IT WILL COOL, IT SHOULD REMAIN MILD ENOUGH TO PROMOTE AT LEAST SOME WIND FOR MUCH OF THE AREA. THIS MAY HELP KEEP THE LOWEST LEVELS MIXED ENOUGH TO KEEP STRATUS OR FOG MAINLY AT BAY. ONE ITEM OF NOTE THOUGH IS THE FORECAST DEW POINTS TO GRADUALLY INCREASE THROUGH THE 50S, AND THIS ADVECTS OVER THE COOLER WATERS IT COULD INDUCE SOME FOG. THEREFORE, WE ADDED PATCHY FOG FOR NOW LATE OVER THE COASTAL WATERS AND THE ADJACENT COASTAL LOCALES. AS FOR LOW TEMPERATURES, WE USED MOSTLY A BLEND OF THE NAM/GFS MOS. && .LONG TERM /MONDAY THROUGH SATURDAY/... THE RIDGE OVER THE WESTERN NORTH ATLANTIC SHOULD CONTINUE TO INFLUENCE OUR REGION FOR MONDAY, BRINGING FAIR WEATHER AND AFTERNOON TEMPERATURES IN THE 70S AT MOST LOCATIONS. THE MAIN WEATHER EVENT FOR THE WEEK IS STILL EXPECTED DURING THE LATE MONDAY NIGHT THROUGH EARLY TUESDAY NIGHT TIME FRAME. THE AXIS OF A DEEP MID LEVEL TROUGH IS EXPECTED TO EXTEND FROM THE WESTERN GREAT LAKES TO THE TEXAS GULF COAST ON TUESDAY MORNING. THE FEATURE SHOULD LIFT NORTHEASTWARD TAKING ON A NEGATIVE TILT LATE ON TUESDAY. THE AXIS OF THE TROUGH IS ANTICIPATED TO PASS OVER OUR REGION LATE ON TUESDAY NIGHT. THE GUIDANCE SEEMS TO BE FOCUSING ON THE LATE TUESDAY AFTERNOON INTO EARLY TUESDAY EVENING TIME FRAME FOR THE PASSAGE OF THE STRONG SURFACE COLD FRONT ASSOCIATED WITH THE MID LEVEL TROUGH. SHOWERS ARE EXPECTED TO BEGIN MOVING INTO OUR REGION FROM THE WEST ON MONDAY NIGHT AND THEY SHOULD CONTINUE INTO TUESDAY. IT APPEARS AS THOUGH THE BEST CHANCE FOR MODERATE TO HEAVY RAINFALL WILL BE IN THE VICINITY OF THE FRONTAL BOUNDARY. THE MODELS ARE INDICATING GOOD LIFT WITH THE FEATURE WHICH SEEMS REASONABLE DUE THE PROGRESSIVE NATURE OF THE BOUNDARY AND THE SHARP TEMPERATURE CONTRAST. ALSO, A 60 PLUS KNOT LOW LEVEL SOUTH SOUTHWESTERLY JET IS FORECAST TO DEVELOP OVER OUR REGION IN ADVANCE OF THE FRONT ON TUESDAY. THE LOW LEVEL JET WILL DRAW ADDITIONAL MOISTURE INTO THE SYSTEM. PRECIPITABLE WATER VALUES ARE EXPECTED TO RISE NEAR OR ABOVE 1.5 INCHES. THE GUIDANCE CONTINUES TO FOCUS MAINLY ON THE 0.75 TO 1.25 INCH RANGE FOR RAINFALL AMOUNTS WITH THE FRONT, SO WE WILL KEEP MENTIONING THE POTENTIAL FOR MODERATE TO HEAVY RAIN. THE GUIDANCE HAS BEEN A BIT HIGH ON PRECIPITATION AMOUNTS RECENTLY SO WE ARE HOPEFUL THAT THOSE NUMBERS WILL BE AT THE HIGH END OF THE RANGE FOR OUR AREA WHICH WOULD LIMIT THE THREAT OF FLOODING. THE STORM PREDICTION CENTER HAS PLACED THE CENTRAL AND SOUTHERN PARTS OF OUR REGION IN ITS GENERAL THUNDERSTORM AREA FOR TUESDAY. THE STRONG LIFT MAY VERY WELL RESULT IN SCATTERED THUNDER, ESPECIALLY NEAR THE FRONT. THE CONSENSUS OF THE LATEST GUIDANCE SUGGESTS THAT THE PRECIPITATION WILL BE OFF THE COAST BEFORE MIDNIGHT, IN ADVANCE OF THE MID LEVEL TROUGH AXIS. THE EXPECTED TIMING WOULD NOT ALLOW ENOUGH COLD AIR TO ARRIVE BEFORE THE PRECIPITATION ENDS TO CAUSE THE RAIN TO CHANGE TO SNOW ANYWHERE IN OUR COUNTY WARNING AREA. COOL HIGH PRESSURE FROM THE WEST IS FORECAST TO BUILD ACROSS THE NORTHEASTERN STATES ON WEDNESDAY AND INTO ATLANTIC CANADA LATE IN THE WEEK. A SURFACE RIDGE AXIS IS ANTICIPATED TO DEVELOP DOWN THE LEE OF THE APPALACHIANS. THE PATTERN WILL KEEP OUR REGION IN A COOL NORTH TO NORTHEAST SURFACE FLOW. TEMPERATURES WILL BE BELOW NORMAL. A PARTLY CLOUDY TO MOSTLY CLEAR SKY IS ANTICIPATED FOR BOTH WEDNESDAY NIGHT AND THURSDAY NIGHT. THE WIND MAY BECOME LIGHT ENOUGH ALONG THE INTERSTATE 95 CORRIDOR AND INTO SOUTHEASTERN PENNSYLVANIA TO RESULT IN THE DEVELOPMENT OF SOME PATCHY FROST THERE DURING THE EARLY MORNING HOURS ON BOTH THURSDAY AND FRIDAY. AS THE HIGH PULLS TO THE NORTHEAST AND FARTHER AWAY FROM OUR REGION A MID LEVEL TROUGH AND ITS ASSOCIATED SURFACE FRONT ARE EXPECTED TO APPROACH FROM THE WEST AND AFFECT OUR REGION FROM FRIDAY NIGHT INTO SATURDAY. WE HAVE MENTIONED A CHANCE OF RAIN SHOWERS. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAY...VFR OVERALL. HOWEVER, SOME STRATUS OR FOG IS POSSIBLE EARLY THIS MORNING. LIGHT SOUTHERLY WINDS OR LIGHT AND VARIABLE, BECOMING SOUTH-SOUTHWEST AND INCREASING TO 10 TO 15 KNOTS WITH GUSTS UP TO 25 KNOTS. THE MAJORITY OF THE GUSTS SHOULD OCCUR FROM MIDDAY ON. TONIGHT...VFR OVERALL. HOWEVER, THERE IS A CHANCE SOME STRATUS OR FOG DEVELOPS TOWARD DAYBREAK MONDAY. OUR CONFIDENCE IS LOW AS OF NOW AS JUST ENOUGH WIND MAY KEEP SOME MIXING OCCURRING. SOUTHERLY WINDS NEAR 10 KNOTS, BUT A BIT GUSTY EARLY. OUTLOOK... MONDAY...MAINLY VFR. PATCHY EARLY MORNING LOW CLOUDS AND FOG MAY LOWER CONDITIONS INTO THE MVFR AND IFR RANGES. MONDAY NIGHT...LOWERING CONDITIONS LATE AT NIGHT AS RAIN SHOWERS BEGIN TO MOVE INTO OUR REGION FROM THE WEST. TUESDAY...MVFR AND IFR CONDITIONS IN RAIN SHOWERS. THE RAIN MAY BECOME HEAVY AT TIMES, ESPECIALLY IN THE AFTERNOON. TUESDAY NIGHT...MVFR AND IFR CONDITIONS IN RAIN SHOWERS, IMPROVING TO VFR LATE AT NIGHT. WEDNESDAY THROUGH THURSDAY...MAINLY VFR. && .MARINE... A WARM FRONT WILL LIFT NORTH ACROSS OUR AREA TODAY, MAINTAINING AN ALREADY WARM AIR MASS ACROSS THE MID ATLANTIC. THE SOUTHERLY FLOW WILL INCREASE THROUGH TONIGHT, HOWEVER AS IS THE CASE THIS TIME OF THE YEAR, A MUCH WARMER AIR MASS ABOVE THE COOLER WATERS WILL RESULT IN A SHARP LOW-LEVEL INVERSION. THE FORECAST SOUNDINGS INDICATE THAT WINDS TO ABOUT 25 KNOTS ARE JUST ABOVE THE SURFACE, HOWEVER THE MIXING SHOULD BE LIMITED ESPECIALLY AWAY FROM THE COAST. WE ARE MORE CONFIDENT ABOUT NEAR SHORE GUSTS TO ABOUT 25 KNOTS DURING THE COURSE OF THIS AFTERNOON AND TONIGHT, BUT THIS DECREASES FARTHER OFFSHORE. WE WILL MAINTAIN THE SMALL CRAFT ADVISORY AS THE SUSTAINED SOUTHERLY FLOW IS EXPECTED TO BUILD THE SEAS TO ABOUT 5 FEET THROUGH TONIGHT. WE DID SLOW THIS DOWN A BIT AS THE MODELS MAY BE MIXING THE WINDS DOWN A BIT TO MUCH. SINCE NEAR SHORE GUSTS SHOULD REACH UP TO 25 KNOTS, WE OPTED TO ADD A SMALL CRAFT ADVISORY FOR DELAWARE BAY THIS AFTERNOON AND THIS EVENING. OUTLOOK... MONDAY...A SMALL CRAFT ADVISORY IS IN EFFECT FOR OUR OCEAN WATERS. WE ARE EXPECTING GUSTY SOUTHERLY WINDS AND WAVE HEIGHTS AROUND 5 FEET. MONDAY NIGHT AND TUESDAY...SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED. THE WIND WILL BE FROM THE SOUTH. TUESDAY NIGHT AND WEDNESDAY...SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED. THE WIND WILL VEER FROM THE NORTHWEST TO THE NORTH. WEDNESDAY NIGHT AND THURSDAY...SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED. THE WIND WILL BE FROM THE NORTHEAST. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 PM EDT MONDAY FOR ANZ450>455. SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO MIDNIGHT EDT TONIGHT FOR ANZ430-431. && $$ SYNOPSIS...IOVINO NEAR TERM...GORSE SHORT TERM...GORSE LONG TERM...IOVINO AVIATION...GORSE/IOVINO MARINE...GORSE/IOVINO

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