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 211505 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1005 AM EST SAT NOV 21 2009 .SYNOPSIS... HIGH PRESSURE OVER THE OHIO RIVER VALLEY THIS MORNING WILL STRENGTHEN AND BUILD TOWARD NEW ENGLAND THROUGH THE WEEKEND, THEN RECEDE EAST SLOWLY. LOW PRESSURE WILL DEVELOP OFF THE SOUTHEAST COAST ON MONDAY AND MOVE NORTH SLOWLY, PASSING BY TO THE EAST ON TUESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...-- Changed Discussion --HIGH PRESSURE, LOCATED OVER THE OHIO RIVER VALLEY THIS MORNING, WILL CONTINUE TO BUILD SLOWLY TO THE EAST AND NORTHEAST THIS AFTERNOON. AT 10:00 AM, HIGH CLOUDS COVERED OUR FORECAST AREA. THE CIRRUS OVERHEAD IS EXPECTED TO THIN A BIT FOR THIS AFTERNOON AS THE ENTIRE CLOUD SHIELD DRIFTS TO THE EAST. MEANWHILE, SOME STRATOCUMULUS MAY NUDGE DOWN FROM THE NORTHWEST AND OVER SOME OF OUR COUNTIES IN EASTERN PENNSYLVANIA AND NORTHERN NEW JERSEY. ALL IN ALL, A PARTLY SUNNY FORECAST SHOULD COVER THE SITUATION. IT CONTINUES TO APPEAR AS THOUGH AFTERNOON TEMPERATURES IN OUR REGION WILL BE MAINLY IN THE 50S.-- End Changed Discussion --&& .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...-- Changed Discussion --THE WEAK MID LEVEL LOW DRIFTS TOWARDS US TONIGHT, AND AGAIN THE MODEL SOUNDINGS HOLD ONTO SOME LOW LEVEL MOISTURE, ESPECIALLY BUT NOT EXCLUSIVELY NORTHWEST, WHILE SOME HIGH LEVEL MOISTURE APPROACHES AHEAD OF THE NEXT SYSTEM THAT IS ADVANCING IN THE SOUTHERN STREAM. WE GO WITH SOMEWHAT MORE CLOUDINESS NORTHWEST AND SOUTH THAN ELSEWHERE, BUT WE ALLOW FOR THE POSSIBILITY OF SOME DECOUPLING AND RADIATING OVER THE NORMAL RADIATING SPOTS ON THE MIN TEMPERATURES. ELSEWHERE, WE STAY WITH THE CONTINUITY/GUIDANCE COMBINATION. WINDS ARE EXPECTED TO BE LIGHT. ON SUNDAY, THE MID LEVEL LOW OVER US AND A MID LEVEL HIGH TO ITS NORTH VERY MUCH RESEMBLE A REX BLOCK, AND THIS ACTUALLY SEEMS TO ALLOW A LITTLE RIDGING UPSTREAM OF US THAT SLOWS DOWN ADVANCING ENERGY FROM THE SOUTHERN STREAM. WE HAVE BACKED DOWN A BIT ON OUR SUNDAY POPS IN RESPONSE, AND NOW WE ONLY CARRY A SLIGHT CHANCE FAR SOUTH. WE DO INCREASE THE CLOUDS SOME DOWN SOUTH, BUT WE BACK OFF ON THAT TREND NORTH. THE GRADIENT LOOKS TO BEGIN TO TIGHTEN A BIT, ESPECIALLY SOUTH, BETWEEN THE STRENGTHENING SURFACE HIGH TO THE NORTH AND NASCENT SURFACE TROUGHING OFF THE SOUTHEAST COAST. THE COOLER H925 TEMPS OFF THE NAM HAVE GOOD SUPPORT FROM THE 00Z ECMWF, AND SO WE HAVE LEANED TOWARD THE COOLER MET STAT GUIDANCE WITH REGARD TO MAXES. ON SUNDAY NIGHT, THE MODELS START TO DIFFER ON WHETHER THE REX BLOCK CONTINUES TO SLOW THE PROGRESS OF SOUTHERN STREAM ENERGY OR THE ENERGY GETS PULLED TOWARD THE LOW PRESSURE PART OF SAID BLOCK. EVEN THE MODELS THAT FAVOR THE LATTER SOLUTION HAVE SLOWED DOWN THE PROGRESS OF MOISTURE, I295 ISENTROPIC LIFT AND LOWER LEVEL FRONTOGENESIS, SO WE CONTINUED THE TREND OF BACKING OFF SOME ON THE POPS. WE DO BRING IN MORE CLOUDINESS. WE LEANED TOWARD THE COOLER MET STAT GUIDANCE AGAIN ON THE MINS, BASICALLY FOR THE SAME REASON THAT WE SITED FOR SUNDAY. ON MONDAY INTO MONDAY NIGHT, THERE IS SOME AGREEMENT THAT ISENTROPIC LIFT MOVES ACROSS THE AREA, FRONTOGENESIS STRENGTHENS /ESPECIALLY OFF THE COAST/ AND Q-VECTOR CONVERGENCE DEVELOPS /AGAIN, ESPECIALLY OFF THE COAST/. THE MID LEVEL BLOCK IS PROGGED TO LIFT NORTHEAST AND OPEN, AND SURFACE LOW PRESSURE IS PROGGED TO DEVELOP AND LIFT FROM THE SOUTHEAST COAST ON MONDAY TO SOMEWHERE OFF THE MID ATLANTIC COAST LATE MONDAY NIGHT. HOW ORGANIZED THAT LOW GETS IS UP IN THE AIR, BUT EVEN THE WEAKER ECMWF HAS A DECENT PRESSURE GRADIENT BETWEEN THE LOW AND THE HIGH TO THE NORTH. WE HAVE GONE WITH POPS THAT RANGE FROM LIKELY SOUTHEAST TO CHANCE ELSEWHERE AS THE INDICATION SEEMS TO BE THAT THE BULK OF THE PRECIPITATION WILL FALL OFF THE COAST. WE DO CARRY A FAIRLY STRONG NORTHEAST FLOW IN THIS REGIME, BUT HOPEFULLY NOTHING LIKE WE DEALT WITH AROUND VETERAN`S DAY. WE GENERALLY CONTINUE TO LEAN TOWARD THE COOLER GUIDANCE.-- End Changed Discussion --&& .LONG TERM /TUESDAY THROUGH FRIDAY/... FOLLOWING TRENDS FROM HPC WHICH GENERALLY WENT WITH THE ECMWF SHOWED LOW PRESSURE MOVING AWAY FROM THE AREA LATE MONDAY NIGHT WITH HIGH PRESSURE IN EASTERN CANADA EXTENDING SOUTH OVER THE REGION. THIS SHOULD MEAN DRYING TRENDS LATE MONDAY NIGHT WITH A DRY DAY ON TUESDAY. TUESDAY NIGHT AND WEDNESDAY WILL SEE ANOTHER FRONT FROM THE WEST MOVE EAST. THIS FRONT SHOULD CROSS THE REGION WEDNESDAY AFTN. WITH THE WARM ADVECTION AHEAD OF THE FRONT LATE TUESDAY NIGHT COULD SEE SOME RAIN AND SHOWERS ARE POSSIBLE DURING THE DAY WEDNESDAY. FOR THANKSGIVING, AN UPPER TROUGH DIGS INTO THE WESTERN GREAT LAKES. WE HAVE WARM ADVECTION OVER THE AREA AND DUE TO THIS COMBINATION THE FORECAST WILL INCLUDE A CHANCE OF SHOWERS. THURSDAY NIGHT, A STRONG COLD FRONT MOVES THROUGH FROM THE NW AND WE GET INTO A COLD ADVECTION PATTERN FOR FRIDAY WITH CYCLONIC FLOW ALOFT AND VERY COOL TEMPERATURES ON FRIDAY. OVER THE FAR NORTHERN ZONES, THERE IS A CHANCE OF RAIN OR SNOW SHOWERS ON FRIDAY. HPC TEMPS ARE GENLY REASONABLE. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...-- Changed Discussion --THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR FLYING CONDITIONS WILL SUPPORT AVIATION INTERESTS TODAY AND TONIGHT, AND PROBABLY SUNDAY MORNING AS WELL. SURFACE HIGH PRESSURE OVER THE EASTERN OHIO VALLEY THIS MORNING WILL STRENGTHEN SLIGHTLY THIS AFTERNOON AND TONIGHT AS IT DRIFTS NORTHEASTWARD. THIS HIGH WILL INITIALLY BE UNDERNEATH AN UPPER TROUGH OVER THE GREAT LAKES AND OHIO VALLEY. THE SOUTHWEST FLOW AHEAD OF THIS TROUGH WAS KICKING SOME JET STREAM CIRRUS NORTHEASTWARD INTO OUR AREA EARLY THIS MORNING. HOWEVER, PROBABLY A GOOD BIT OF THIS WILL BE THIN TODAY. SO, OTHER THAN SOME CIRRUS, A FEW CUMULUS MAY FORM TOWARD MIDDAY AND LINGER INTO THE AFTERNOON. A DRY ATMOSPHERE WILL MEAN NO TENDENCY FOR FOG FORMATION EARLY THIS MORNING. WEST WINDS EARLY THIS MORNING WILL BECOME NORTHWEST LATER THIS MORNING AND CONTINUE THIS AFTERNOON, VEERING TO NORTH BY DARK. SUSTAINED WIND SPEEDS SHOULD BE MOSTLY UNDER 10 KNOTS TODAY. OUTLOOK... DRY WEATHER IS FORECAST TO CONTINUE SUNDAY. A CHANCE OF RAIN IS EXPECTED SUNDAY NIGHT AS LOW PRESSURE WILL MOVE OFF THE SOUTHEAST U.S. COAST SUNDAY NIGHT AND DEVELOP NORTHWARD MONDAY...AND PERHAPS REMAIN JUST OFF THE MID ATLANTIC COAST MONDAY NIGHT AND TUESDAY TO PLAGUE OUR AREA WITH AN OCEANIC FLOW.-- End Changed Discussion --&& .MARINE...-- Changed Discussion --WIND GUSTS AND SEAS WERE UNDER SMALL CRAFT ADVISORY CRITERIA THIS MORNING AND SHOULD LESSEN SOMEWHAT DURING TODAY AS HIGH PRESSURE CENTERED JUST TO OUR WEST EARLY THIS MORNING IS FORECAST TO BUILD NORTHEASTWARD TONIGHT AND SUNDAY. LOW PRESSURE IS THEN EXPECTED TO MOVE NORTHWARD ALONG OR NEAR THE COAST LATER SUNDAY AND MONDAY AND REMAIN INTO TUESDAY. RIGHT NOW THIS LOW LOOKS LIKE IT WILL NOT BECOME TOO STRONG, BUT AT LEAST STRONG ENOUGH FOR ADVISORY LEVEL WINDS AND SEAS, WITH THE SUNDAY NIGHT INTO TUESDAY TIME FRAME BEING THE PRIME TIME. HOWEVER, THE GRADIENT MAY BE TIGHT ENOUGH OVER OUR SOUTHERN WATERS LATER SUNDAY TO WARRANT A SMALL CRAFT ADVISORY. WAVEWATCH HAS BEEN CONSISTENT IN BUILDING SEAS TO 5 FEET SUNDAY AFTERNOON, SO A SMALL CRAFT ADVISORY WILL BE ISSUED WITH THIS MORNING/S PACKAGE FROM LITTLE EGG INLET SOUTH FOR SUNDAY AFTERNOON (OUR THIRD PERIOD) AND CONTINUED THROUGH SUNDAY NIGHT FOR NOW (OUR FOURTH PERIOD). THIS WILL LIKELY HAVE TO BE EXTENDED IN TIME AS WELL AS GEOGRAPHICALLY. OUR NORTHERN WATERS DON/T LOOK TO START BEFORE SUNDAY NIGHT (WHICH IS OUR FOURTH PERIOD AND TOO FAR IN ADVANCE TO START AN ADVISORY); LOWER (OR MAYBE EVEN ALL OF) DELAWARE BAY COULD NEED AN ADVISORY AS WELL. ONCE IT STARTS, WAVEWATCH HAS ADVISORY LEVEL SEAS THROUGH THIS COMING WEEK. OBVIOUSLY, CONFIDENCE IS PRETTY LOW AFTER MONDAY AND TUESDAY.-- End Changed Discussion --&& .TIDES/COASTAL FLOODING... TIDAL ANOMALIES ARE LIKELY TO INCREASE AGAIN IN RESPONSE TO AN EXPECTED DEVELOPING ONSHORE FLOW SUNDAY AND PARTICULARLY SUNDAY NIGHT THROUGH MONDAY NIGHT. LOW PRESSURE FORECAST TO DEVELOP TO OUR SOUTHEAST WILL CONTRAST WITH HIGH PRESSURE OVER NORTHERN NEW ENGLAND AND THE CANADIAN MARITIMES. AVIATION STORM SURGE GUIDANCE IS PROBABLY UNDERDONE AT THIS EARLY STAGE, AND ANOMALIES MAY RISE TO AROUND 1 FOOT ABOVE NORMAL. THE TIME PERIOD OF CONCERN WILL BE SUNDAY NIGHT INTO TUESDAY; THIS PERIOD IS BETWEEN NEW MOON AND FULL MOON, SO THE ASTRONOMICAL TIDES ARE NOT AS HIGH AS THEY WERE LAST WEEK. UNDER NORMAL CIRCUMSTANCES, THIS WOULDN`T POSE ANY PROBLEMS, BUT WITH THE SEVERE BEACH EROSION THAT OCCURRED WITH LAST WEEK`S STORM, IT MAY BE THAT LOWER TIDAL ANOMALIES WILL HAVE AN EFFECT WHEN THEY ORDINARILY WOULD NOT. IT IS STILL TO BE DETERMINED WHETHER THIS MIGHT CAUSE ANY LEVEL OF TIDAL FLOODING, SO THE SITUATION WILL BE CLOSELY MONITORED DURING THIS WEEKEND. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 PM SUNDAY TO 6 AM EST MONDAY FOR ANZ452>455. && $$ SYNOPSIS...DELISI NEAR TERM...IOVINO SHORT TERM...DELISI LONG TERM...STAUBER
