Issued by NWS Mt. Holly, NJ
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --000 FXUS61 KPHI 222030 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 330 PM EST SUN NOV 22 2009 .SYNOPSIS...-- Changed Discussion --HIGH PRESSURE, LOCATED OVER THE SAINT LAWRENCE RIVER VALLEY THIS AFTERNOON, WILL DRIFT TO THE EAST AND OFF THE COAST ON MONDAY. MEANWHILE, LOW PRESSURE IS EXPECTED TO DEVELOP OFF THE SOUTHEAST COAST TONIGHT. THE LOW SHOULD PROGRESS TO THE NORTHEAST AND IT IS EXPECTED TO PASS WELL TO THE EAST OF DELAWARE AND NEW JERSEY ON MONDAY NIGHT. A COLD FRONT FROM THE WEST IS ANTICIPATED TO ARRIVE ON THURSDAY. LOW PRESSURE IS FORECAST TO DEVELOP OFF THE SOUTHEAST COAST ON THURSDAY AND IT SHOULD MOVE UP INTO NEW ENGLAND ON FRIDAY. HIGH PRESSURE IS EXPECTED TO BUILD SLOWLY INTO OUR REGION FROM THE WEST DURING THE WEEKEND.-- End Changed Discussion --&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...-- Changed Discussion --AT 3:00 PM, THERE WAS A NORTHEAST WIND AND TEMPERATURES WERE MAINLY IN THE 50S IN OUR REGION. THE POCONOS AND PARTS OF FAR NORTHERN NEW JERSEY WERE IN THE 40S. THE CLOUDS OVER OUR NORTHERN COUNTIES AND OUR SOUTHERN COUNTIES WERE A BIT MORE STUBBORN THAN WE THOUGHT THEY WOULD BE EARLIER IN THE DAY. HOWEVER, AT MID AFTERNOON THE CLOUDS WERE SHOWING SIGNS OF DISSIPATING. THERE WERE ADDITIONAL CLOUDS DRIFTING OFF THE OCEAN AND TOWARD THE NEW JERSEY COAST. ALL IN ALL, WE SHOULD SEE AN INCREASE IN CLOUD COVER TONIGHT AS ADDITIONAL LOW CLOUDS DRIFT OFF THE OCEAN, AND MID AND HIGH LEVEL CLOUDS BUILD UP FROM THE SOUTH. WE WILL BEGIN TO MENTION CHANCE POPS FOR OUR SOUTHERN COUNTIES FOR LATE TONIGHT AS THE PRECIPITATION THAT WAS OVER THE SOUTHEASTERN STATES THIS AFTERNOON CONTINUES TO LIFT TO THE NORTH. TEMPERATURES TONIGHT SHOULD DROP INTO THE 40S IN MUCH OF OUR REGION, WITH SOME 30S POSSIBLE UP NORTH.-- End Changed Discussion --&& .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...-- Changed Discussion --AS HIGH PRESSURE DRIFTS OFF THE COAST OF CANADA`S MARITIME PROVINCES ON MONDAY, A SURFACE RIDGE WILL REMAIN ALONG THE EAST COAST. THE RIDGE AXIS IS FORECAST TO DRIFT FARTHER INLAND ON MONDAY AND TUESDAY BEFORE WORKING ITS WAY BACK TOWARD THE COAST ON WEDNESDAY. IN REGARD TO THE COASTAL LOW, THE 12 UTC GFS AND THE 12 UTC ECMWF ARE SIMILAR IN THEIR HANDLING OF THE FEATURE. THE 12 UTC NAM REMAINS THE OUTLIER. THE LOW SHOULD PASS OFF CAPE HATTERAS ON MONDAY EVENING BEFORE PASSING WELL TO OUR EAST ON MONDAY NIGHT. MEANWHILE, THE REMNANTS OF THE UPPER SYSTEM THAT WAS OVER THE TENNESSEE RIVER VALLEY AND THE LOWER APPALACHIANS THIS AFTERNOON SHOULD LIFT OVER OUR REGION LATE ON MONDAY. SOME OF THE ENERGY ASSOCIATED WITH THE SHORT WAVE OVER THE CENTRAL PLAINS THIS AFTERNOON SHOULD PASS OVERHEAD ON TUESDAY MORNING. WE ARE EXPECTING RAIN TO CONTINUE BUILDING UP FROM THE SOUTH AND INTO OUR REGION ON MONDAY. THE RAIN WILL PERSIST THROUGH MONDAY NIGHT AND INTO EARLY TUESDAY. AFTER THE UPPER LEVEL SHORT WAVE PASSES OVERHEAD ON TUESDAY MORNING, THE CHANCES FOR RAIN SHOULD BEGIN TO DECREASE. IT APPEARS AS THOUGH SOME LOW LEVEL MOISTURE MAY LINGER FOR TUESDAY NIGHT INTO WEDNESDAY, SO WE ARE NOT INDICATING A GREAT DEAL OF CLEARING FOR THE MID WEEK PERIOD, ESPECIALLY WITH OUR NEXT WEATHER SYSTEM APPROACHING FROM THE WEST.-- End Changed Discussion --&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...-- Changed Discussion --A PATTERN CHANGE WILL CONTINUE TO GET UNDERWAY AS WE START THIS PERIOD. THE COMPUTER MODELS ARE IN GOOD AGREEMENT THAT A TROUGH WILL AMPLIFY ACROSS THE NORTHERN PLAINS AND GREAT LAKES REGION AS STRONG ENERGY DIVES SOUTHEASTWARD. THE SHORT WAVE ENERGY, COUPLED WITH THE JET STREAM POSITIONING, WILL TEND TO LEAD TO A CLOSED LOW FROM THE GREAT LAKES REGION DOWN TO THE OHIO VALLEY. WHILE THIS SYNOPTIC EVOLUTION IS AGREED UPON FAIRLY WELL BY THE COMPUTER GUIDANCE, DETAILS ESPECIALLY FROM LATE THURSDAY INTO SATURDAY BECOMES MORE DIFFICULT ALONG WITH LOWER CONFIDENCE AS TO THE LOCATION AND TRACK OF A CLOSED MIDLEVEL CENTER /AS IT MOVES EAST AND NORTHEASTWARD THROUGH THE CENTRAL APPALACHIANS AND NORTHEAST/. GIVEN THE UNCERTAINTY, WE INITIALIZED THE DATABASE WITH HPC GUIDANCE /COMPRISED OF THE ECMWF FOR WEDNESDAY NIGHT THROUGH THURSDAY NIGHT, THEN THE ECMWF/GFS ENSEMBLE MEANS FOR FRIDAY THROUGH SUNDAY/. WE DID MAKE SOME ADJUSTMENTS THOUGH AFTER ADDITIONAL COLLABORATION WITH OUR SURROUNDING OFFICES. BASED ON THE ABOVE, AN INITIAL COLD FRONT WILL BE ARRIVING WEDNESDAY NIGHT AS THE UPPER-LEVEL TROUGH AMPLIFIES TO OUR WEST. AS THE SYSTEM CLOSES OFF AND SLIDES EASTWARD, ENERGY ROTATING AROUND THIS WILL TEND TO KEEP THE CHC OF AT LEAST SOME SHOWERS ON THURSDAY. THERE IS SOME HINTS IN SOME OF THE MODEL GUIDANCE THAT AN INVERTED TROUGH MAY EXTEND ACROSS PORTIONS OF OUR AREA LATE THURSDAY INTO FRIDAY AS A NEW SURFACE LOW FORMS TO OUR EAST. IF THIS IS PRESENT, THEN PRECIPITATION COULD BE ENHANCED SOME ESPECIALLY AS THE MIDLEVEL LOW APPROACHES. FOR FRIDAY, THE SURFACE LOW IS FORECAST TO BE PULLING UP INTO THE VICINITY OF SOUTHERN NEW ENGLAND AND OUR AREA WILL BE UNDER A COLDER CYCLONIC FLOW. GIVEN THE COLDER AIR ARRIVING ALOFT, WE CANNOT RULE OUT SHOWERS /CONVECTIVE?/ WITH EVEN SOME SNOW POSSIBLE ESPECIALLY ACROSS THE NORTHERN AREAS. FOR NOW, WE JUST KEPT THE MENTION OF SNOW ACROSS THE FAR NORTHERN ZONES. IF ENOUGH MOISTURE AND INSTABILITY IS AROUND AS THE CLOSED LOW MOVES BY, WOULD NOT RULE OUT SOME SMALL HAIL/GRAUPEL WITH SOME SHOWERS. A BRISK NORTHWEST FLOW IS FORECAST TO SETUP AS WE GO THROUGH FRIDAY AND SATURDAY. THIS COULD KEEP SOME RAIN/SNOW SHOWERS GOING SATURDAY ESPECIALLY ACROSS THE FAR NORTHERN ZONES AS SOME LAKE ERIE/ONTARIO MOISTURE COULD GET PULLED SOUTHEASTWARD IN THE FORM OF STREAMERS. HIGH PRESSURE THEN BUILDS TO OUR SOUTH SUNDAY WITH THE NORTHWESTERLY FLOW GRADUALLY ON THE DECREASE.-- End Changed Discussion --&& .AVIATION /21Z SUNDAY THROUGH FRIDAY/...-- Changed Discussion --THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS WILL START THE FORECAST LATE THIS AFTERNOON INTO THE EARLY EVENING. HOWEVER, CLOUDS WILL BEGIN TO DEVELOP ACROSS THE AREA AS MOIST NORTHEASTERLY FLOW CONTINUES ACROSS THE AREA. CLOUDS SHOULD BEGIN FORMING AFTER SUNDOWN AND THICKEN THROUGH THE NIGHT. MVFR CEILINGS ARE EXPECTED TO START AROUND OR AFTER MIDNIGHT FOR THE MAJORITY OF THE AREA, AND THEN LOWER TO IFR BY SUNRISE TOMORROW. AS AN AREA OF LOW PRESSURE RIDES UP THE EAST COAST DURING THE DAY TOMORROW, RAIN CHANCES SHOULD INCREASE FROM SOUTH TO NORTH. WINDS WILL REMAIN MOSTLY NORTHEAST THROUGH THE TAF PERIOD, POSSIBLY INCREASING DURING THE DAY TOMORROW. LOW CEILINGS, VISIBILITIES, AND RAINY CONDITIONS WILL CONTINUE THROUGH MONDAY NIGHT. OUTLOOK... THE LOW PRESSURE SYSTEM MOVES OUT OF THE AREA ON TUESDAY, WHICH COULD PROVIDE A BRIEF REPRIEVE LAST TUESDAY INTO EARLY WEDNESDAY. HOWEVER, A FRONTAL BOUNDARY AND ANOTHER COASTAL LOW ARE EXPECTED TO IMPACT THE AREA FOR THE LATTER PART OF THE WEEK.-- End Changed Discussion --&& .MARINE...-- Changed Discussion --A PERSISTENT NORTHEAST FLOW WILL HELP THE SEAS BUILD OVER THE NEXT SEVERAL DAYS, STARTING TONIGHT. AS AN AREA OF LOW PRESSURE MOVES TOWARD THE COASTAL WATERS ON MONDAY, AND HIGH PRESSURE REMAINS TO OUR NORTHEAST, THE PRESSURE GRADIENT WILL TIGHTEN, ALLOWING WINDS TO INCREASE AS WELL. SMALL CRAFT ADVISORIES ARE IN EFFECT NOW FOR THE COASTAL WATERS. THE LOWER BAY MAY GET SOME GUSTA UP TO 25 KT LATER TONIGHT INTO TOMORROW AS WELL, SO WE HAVE A SMALL CRAFT ADVISORY THERE AS WELL. THE LOW PRESSURE SYSTEM WILL CONTINUE MOVING TO OUR NORTHEAST AND OUT OF THE AREA LATE TUESDAY, LEADING TO A BRIEF REPRIEVE FOR LATE TUESDAY INTO EARLY WEDNESDAY. HOWEVER, CONDITIONS WILL LIKELY DIMINISH ONCE AGAIN LATE WEDNESDAY THROUGH THE LATTER PART OF THE WEEK AS A FRONTAL BOUNDARY IS EXPECTED TO APPROACH THE AREA, WITH ANOTHER COASTAL LOW DEVELOPING AND MOVING NEAR OUR AREA. SMALL CRAFT ADVISORIES COULD BE POSSIBLE AGAIN FOR THE END OF THE WORK WEEK.-- End Changed Discussion --&& .TIDES/COASTAL FLOODING...-- Changed Discussion --A PERSISTENT NORTHEAST FLOW WILL REMAIN ACROSS THE AREA FOR THE NEXT SEVERAL DAYS. THIS WILL CAUSE THE TIDES TO BE HIGHER THAN THE CURRENT ASTRONOMICAL FORECASTS. WE WOULD STILL NEED AROUND A 1.5 TO 2 FT TIDAL SURGE ABOVE THE ASTRONOMICAL TIDE, BUT THE FORECAST MODELS ARE ONLY PRODUCING 1 TO 1.5 FT TIDAL SURGES AT THIS TIME. SO THE CURRENT FORECAST IS THAT WE WILL REMAIN ABOUT .5 TO 1.0 FT BELOW MINOR FLOOD STAGE. WE WILL CONTINUE TO MONITOR THE SITUATION IN CASE THINGS CHANCE OVER THE NEXT FEW FORECASTS.-- End Changed Discussion --&& .PHI WATCHES/WARNINGS/ADVISORIES...-- Changed Discussion --PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST TUESDAY FOR ANZ450>455. SMALL CRAFT ADVISORY UNTIL 6 PM EST MONDAY FOR ANZ431.-- End Changed Discussion --&& $$ SYNOPSIS/NEAR TERM/SHORT TERM...IOVINO LONG TERM...GORSE AVIATION/MARINE...ROBERTSON TIDES/COASTAL FLOODING...ROBERTSON
