Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 300751 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 351 AM EDT SAT MAY 30 2015 .SYNOPSIS... HIGH PRESSURE WILL SLOWLY SLIDE EAST OFF THE COAST THROUGH THE DAY TODAY. A COLD FRONT APPROACHES OUR REGION TOMORROW, BEFORE STALLING TOMORROW NIGHT AND EVENTUALLY SLIDING OFF SHORE LATE MONDAY. A HIGH WILL BEGIN BUILDING SOUTHEAST OVER OUR REGION MID WEEK THROUGH THE END OF THE WORK WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... OUR AREA REMAINS ON THE WESTERN EDGE OF THE SURFACE HIGH LOCATED WELL TO OUR EAST ACROSS THE ATLANTIC. RIDGING ALOFT REMAINS TO OUR SOUTHWEST, WITH OUR AREA LOCATED ON THE NORTHWEST EDGE OF THE RIDGE. THIS WILL KEEP A SOUTHERLY/SOUTHWESTERLY FLOW AT THE SURFACE, AND SOUTHWEST FLOW ALOFT. A VERY WARM/WELL ABOVE NORMAL AIRMASS WILL REMAIN IN PLACE ACROSS THE AREA TODAY, WITH MAY AREAS REACHING CLOSE TO 10 DEGREES ABOVE NORMAL ONCE AGAIN. WITH THIS WARM AND MOIST AIRMASS REMAINING IN PLACE, THIS WILL LEAD TO DAYTIME INSTABILITY ACROSS THE AREA. THE GREATEST THREAT FOR SHOWERS/THUNDERSTORMS IS EXPECTED TO BE THE WESTERN THIRD OF THE AREA WHERE THERE IS GREATER LIFT POTENTIAL WITH PASSING SHORT WAVE/VORTICITY IMPULSES. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... THE SURFACE HIGH GETS SQUEEZED FURTHER OFFSHORE TONIGHT, WHILE THE RIDGE ALOFT BEGINS TO BREAK DOWN. ALSO OVERNIGHT, A COLD FRONT BEGINS TO APPROACH THE AREA FROM THE WEST. EVEN THOUGH INSTABILITY WANES OVERNIGHT, THERE REMAINS SOME ENHANCE LIFT ACROSS OUR WESTERN HALF OF THE AREA WITH PASSING SHORT WAVE/VORTICITY IMPULSES. WE KEEP A CHANCE OF SHOWERS AND THUNDERSTORMS FOR THE NORTHERN HALF OF THE AREA OVERNIGHT, WITH THE GREATEST CHANCE ACROSS THE FAR NORTHERN PARTS OF THE AREA. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... ATTENTION REMAINS FOCUSED ON THE EARLY WEEK COLD FRONT AND ASSOCIATE HEAVY RAIN AND FLOODING THREAT. THERE ARE A FEW BIG CHANGES IN MODEL SOLUTIONS AND THE FORECAST THROUGH THIS PERIOD. THE BIGGEST IS THAT BOTH THE GFS AND ECMWF (TO A LESSER EXTENT THE NAM) HAVE TRENDED TOWARDS A SLOWER COLD FRONT AND A FURTHER NORTH TRACK FOR THE SURFACE LOW. IT NOW LOOKS LIKE THE COLD FRONT WILL STALL AND REMAIN OVER OUR REGION UNTIL LATE MONDAY, WHEN IT FINALLY MAKES PROGRESS OFF SHORE. THIS MAKES SENSE GIVEN THE OVER ALL BIG PICTURE WITH A RELATIVELY LOW ROSSBY WAVE NUMBER SUGGESTING LESS PROGRESSIVE LARGE SCALE PATTERN. AS FAR AS WHAT THIS MEANS FOR OUR REGION...THE BIG IMPACT IS THE THREAT FOR HEAVY RAIN IS NOW LATER (NOW IN THE LATE SUNDAY NIGHT TO MONDAY PERIOD). IN ADDITION, WITH THE FURTHER NORTH TRACK OF THE LOW, IT LOOKS LIKE THE SOUTHERN HALF OF OUR REGION, ESPECIALLY DELMARVA, WILL BE IN THE PRIME LOCATION FOR THE DRY SLOT, AT LEAST INITIALLY, AND THE BEST SYNOPTIC SCALE LIFT WILL BE JUST NW OF OUR CWA. THUS, HAVE HIGHEST POPS ACROSS THE POCONOS/NW NJ THROUGH MONDAY, BEFORE SHIFTING THE HIGHEST POPS FURTHER SOUTH AND EAST. IN ADDITION TO RAIN CHANCES, THIS ALSO LOOKS TO HAVE A SIGNIFICANT IMPACT ON OUR TEMPERATURES AS WE SHOULD STAY IN THE WARM SECTOR UNTIL LATE MONDAY. THUS INCREASED MAX T ON MONDAY AS WELL AS THE MIN T ON SUNDAY NIGHT. AS MENTIONED PREVIOUSLY, HEAVY RAIN IS STILL A CONCERN, ALTHOUGH THE EXACT TIMING AND PLACEMENT OF THE HEAVY RAIN THREAT HAS SHIFTED. STORM MOTIONS ARE MODEST, 20 KT OR LESS, AND THE STALLED FRONT COULD SERVE AS A FOCUS FOR TRAINING STORMS. MEAN CLOUD RH IS QUITE HIGH, AND THE PWAT VALUES ARE WELL ABOVE NORMAL FOR JUNE. THE ONLY RISK FACTOR THAT IS MARGINAL IS THE DEPTH OF THE WARM CLOUD LAYER, AROUND 11K FT, ISN/T VERY DEEP CONSIDERING THE TIME OF YEAR. BOTTOM LINE, IT LOOKS LIKE THE HIGHEST HEAVY RAIN THREAT WILL BE ACROSS THE NORTHERN HALF OF THE REGION SUNDAY NIGHT INTO MONDAY, ALTHOUGH THERE IS STILL A RISK OF HEAVY RAIN ACROSS THE SOUTHERN HALF OF THE REGION, PRIMARILY MONDAY INTO MONDAY NIGHT. WEDNESDAY THROUGH SATURDAY...HIGH BUILDS IN FOR MUCH OF THE WORK WEEK, BEFORE SHIFTING OFF SHORE BY THE WEEKEND. ANOTHER LOW COULD CROSS THE FAR NORTHERN GREAT LAKES REGION, BUT THERE ARE SOME BIG DIFFERENCES IN THE TRACK AMONG LONG RANGE MODELS, SO HAVE STAYED CLOSE TO THE PREVIOUS FORECAST TO START THE WEEKEND. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. A PERIOD OF MVFR OR IFR CIGS/VSBYS ARE EXPECTED FOR A PORTION OF THE AREA THIS MORNING. THESE LOWER CIGS/VSBYS WILL BURN OFF AND LIFT WITHING A COUPLE HOURS AFTER SUNRISE. VFR CONDITIONS SHOULD THEN REMAIN ACROSS THE TAF SITES THROUGH MUCH OF TONIGHT. WE COULD GET MORE MVFR OR IFR CIGS/VSBYS AGAIN TONIGHT INTO SUNDAY MORNING. SCATTERED SHOWERS OR THUNDERSTORMS ARE POSSIBLE TODAY INTO TONIGHT, MAINLY FOR ABE/RDG. WE`VE INCLUDED A SHRA GROUP, BUT HAVE NOT INCLUDED TSRA SINCE CONFIDENCE IS LOW IN THEIR OCCURRENCE AT THIS TIME. WINDS ARE FORECAST TO INCREASE OUT OF THE SOUTH-SOUTHWEST TODAY, AND GUST 15-20 KNOTS DURING THE LATE MORNING AND AFTERNOON ARE EXPECTED. THE WIND GUSTS SHOULD DROP OFF AFTER SUNSET. OUTLOOK... SUNDAY THROUGH MONDAY...WIDESPREAD MVFR AND IFR CONDITIONS POSSIBLE WITH WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS. MONDAY NIGHT INTO TUESDAY...COLD FRONT PUSHES THROUGH BRINGING A WIND SHIFT...LINGERING SHOWERS COULD REDUCE CEILINGS AND VISIBILITIES TO MVFR WEDNESDAY...GENERALLY VFR CONDITIONS EXPECTED. && .MARINE... SUB-SMALL CRAFT ADVISORY CONDITIONS CONTINUE TO BE FORECAST FOR THE WATERS TODAY INTO TONIGHT AS SOUTHERLY WINDS CONTINUE. HOWEVER, WINDS WILL GUST AROUND 20 KNOTS AT TIMES THIS AFTERNOON INTO TONIGHT. SOUNDINGS DO SHOW SOME STRONGER WINDS ABOVE THE SURFACE, BUT THEY ARE NOT EXPECTED TO MIX DOWN TO THE SURFACE AT THIS TIME. SEAS ARE FORECAST TO BUILD TO 4 FEET TODAY INTO TONIGHT AS WELL. OUTLOOK... SUNDAY THROUGH MONDAY...WINDS AND SEAS MAY BE CLOSE TO SMALL CRAFT ADVISORY CRITERIA THROUGH OUT THIS PERIOD. LOWER VISIBILITIES POSSIBLE IN HEAVY RAIN. MONDAY NIGHT THROUGH TUESDAY...WINDS SHIFT AROUND OUT OF THE NORTHWEST AS A COLD FRONT MOVES THROUGH. HOWEVER WINDS AND SEAS SHOULD REMAIN BELOW SCA CRITERIA. WEDNESDAY...WINDS AND SEAS ARE EXPECTED TO BE BELOW SCA CRITERIA. && .RIP CURRENTS... NEW WEBLINK, WORKS BEST ON FIREFOX. DISPLAYS THE FCST GRAPHIC ETC. WWW.WEATHER.GOV/PHI/SURFRIP4 THE INITIAL RIP CURRENT RISK FOR THE NEW JERSEY COAST TODAY IS MODERATE WHILE FOR THE DELAWARE COAST THE INITIAL RIP CURRENT RISK IS LOW. THIS FOLLOWS OUR LONG TIME IN HOUSE PROCEDURE. THE GRIDDED PROCEDURE SPLITS NEW JERSEY IN HALF WITH THE MODERATE RISK IN OCEAN AND MONMOUTH COUNTIES. IN GENERAL LOOKS LIKE PREDICTED WINDS ARE STRONGER PROGRESSIVELY FARTHER NORTH ALONG ON THE WATERS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...JOHNSON NEAR TERM...ROBERTSON SHORT TERM...ROBERTSON LONG TERM...JOHNSON AVIATION...JOHNSON/ROBERTSON MARINE...JOHNSON/ROBERTSON RIP CURRENTS...

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