Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 200814 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 414 AM EDT MON OCT 20 2014 .SYNOPSIS... A HIGH PRESSURE SYSTEM NEAR NORFOLK WILL MOVE OFFSHORE TODAY. A LOW PRESSURE SYSTEM WITH AN ASSOCIATED COLD FRONT OVER LAKE SUPERIOR WILL DIVE SOUTHEAST REACHING OUR REGION DURING THE DAY ON TUESDAY. ANOTHER LOW PRESSURE SYSTEM WILL FORM OFF THE MID ATLANTIC COAST LINE ON TUESDAY AND THEN DRIFT SLOWLY NORTHEAST, REACHING CAPE COD ON THURSDAY AND NOVA SCOTIA ON FRIDAY. HIGH PRESSURE WILL THEN BRIEFLY MOVE IN FROM THE WEST LATE FRIDAY. A COLD FRONT SHOULD PASS THROUGH THE NORTHEAST AROUND SATURDAY NIGHT, WITH ANOTHER HIGH PRESSURE SYSTEM REACHING THE GREAT LAKES ON SUNDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE FROST ADVISORY AND FREEZE WARNING REMAINS IN EFFECT FOR EARLY THIS MORNING, AS MANY AREAS ARE WELL DOWN INTO THE 30S. THE HIGH LEVEL CLOUDS THOUGH MAY HAVE SLOWED THE TEMPERATURE DROP A LITTLE FOR SOME SPOTS. HIGH PRESSURE WILL BE SHIFTING OFFSHORE TODAY ALLOWING A SOUTHWESTERLY FLOW AT THE SURFACE TO DEVELOP. THIS FLOW WILL BE MUCH LESS COMPARED TO THE GUSTINESS THAT WAS OBSERVED YESTERDAY. A ROBUST SHORT WAVE DIVING SOUTHEASTWARD FROM THE MIDWEST WILL HELP CARVE OUT ANOTHER UPPER-LEVEL TROUGH ACROSS THE GREAT LAKES AND OHIO VALLEY DURING THE COURSE OF TODAY. DOWNSTREAM FROM THIS, SOME WEAK WAA IS FORECAST TO OCCUR ACROSS THE MID ATLANTIC. THIS COMBINED WITH THE PRESENCE OF AN UPPER-LEVEL JET WILL SPREAD AREAS OF MID AND HIGH LEVEL CLOUDINESS ACROSS THE REGION. THE MAIN LIFT ASSOCIATED WITH THE AMPLIFYING UPPER-LEVEL TROUGH IS FORECAST TO REMAIN TO OUR WEST, THEREFORE WE MAINTAINED A DRY FORECAST TODAY. WE DID CARRY SOME ADDITIONAL CLOUDINESS THOUGH FOR MANY AREAS. AS FOR HIGH TEMPERATURES, WE USED A MODEL/MOS BLEND WHICH RESULTS IN MILDER TEMPERATURES COMPARED TO YESTERDAY. THIS LINES UP WITH THE WEAK WAA THAT IS ALSO FORECAST THROUGH THE DAY ALONG WITH A SOUTHWESTERLY SURFACE FLOW. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... AN UPPER-LEVEL TROUGH WILL CONTINUE TO AMPLIFY ACROSS THE GREAT LAKES AND NORTHEAST. AS THIS OCCURS, LOW PRESSURE ORGANIZING AT THE SURFACE IS FORECAST TO BE IN THE GENERAL VICINITY OF THE EASTERN GREAT LAKES LATER TONIGHT. THERE IS SOME WAA BEING MAINTAINED AHEAD OF THIS SYSTEM, BUT OVERALL THE BEST FOCUS FOR THIS IS FORECAST TO BE TO OUR SOUTH AND EAST. IN ADDITION, A DECENT SHOT OF LOW-LEVEL THETA-E ADVECTION IS FORECAST TO ARRIVE THROUGH THE NIGHT. AS THE ATMOSPHERE MOISTENS AND THE LARGE SCALE ASCENT BEGINS TO OVERSPREAD THE REGION LATE, SOME SHOWERS COULD DEVELOP. THIS LOOKS TO BE ACROSS OUR WESTERN ZONES WHICH IS WHERE WE HAVE THE HIGHEST /CHC/ POPS LATE. THERE MAY ALSO BE ANOTHER AREA OF FOCUS, WHICH IS OFFSHORE WHERE THE LEADING EDGE OF THE STRONGER THETA-E ADVECTION INTERACTS WITH SOME INSTABILITY PARTIALLY DUE TO THE GULF STREAM. OVERALL, THE CLOUDS ARE FORECAST TO LOWER SOME THROUGH THE NIGHT FROM WEST TO EAST AND THE POPS WERE GRADUALLY INCREASED AS WELL. AS FOR LOW TEMPERATURES, WITH THE THICKENING CLOUDS AND A WEAK SOUTHWESTERLY FLOW IN PLACE IT WILL BE A MILDER NIGHT. OVERALL, WE USED A MOS BLEND WITH SOME MINOR ADJUSTMENTS. && .LONG TERM /TUESDAY THROUGH SUNDAY/... THE WRF-NMMB 500MB INITIALIZATION WAS BETTER THAN THE GFS OR THE ECMWF. THE LATTER WAS TOO AMPLIFIED FROM THE MISSISSIPPI VALLEY WESTWARD. THIS PRESENTS THE FCST CONUNDRUM AS THE DP/DT IS SHOWING STRONGER RIDGING IN CENTRAL NOAM VS LAST NIGHT`S SOUNDING RUN. WE SEEM TO BE VACILLATING AROUND A LINE VS TRENDING STEADILY IN ANY SPECIFIC, CONSISTENT DIRECTION. E.G. AT 78 HRS THE CAN GGEM/WRF/GFS/GEFS ENSEMBLE MEAN SFC LOWS ARE STACKED ON TOP OF ONE ANOTHER. THIS FORECAST PACKAGE IS GOING TO GO WITH THIS CONSENSUS AS IT INCLUDES THE BETTER INITIALIZED CLUSTERING PLUS THERE IS NO CLEAR CUT DP/DT. IN THE GRAND SCHEME, IT WILL NOT MAKE THE MIDDLE OF THE WEEK PLEASANT, JUST A SLIGHTLY FASTER IMPROVEMENT THAN THE ECMWF HAS FOR THE LATTER PART. THERE IS FAIRLY GOOD MODELING AGREEMENT ON TUESDAY MORNING OF OUR CWA BEING IN A RELATIVE PCPN LULL BETWEEN IMPULSES. POPS INCREASE DURING THE AFTERNOON AS THE PRIMARY LOW PRESSURE SYSTEM APPROACHES OUR CWA AND IT BECOMES MORE UNSTABLE ALOFT. OTHER THAN THE WRF-NMMB, OTHER MODELS ARE NOT UNSTABLE ENOUGH FOR THUNDER. THE 18Z WRF WAS THE MOST UNSTABLE OF THE 21 SREF MEMBERS IN OUR CWA, SO SHOWERS YES, BUT NO THUNDER. MAX TEMPS CLOSE TO A STAT GUIDANCE BLEND. ON TUESDAY NIGHT THERE IS STILL A CONVECTIVE LOOK TO THE SOUNDINGS AND INSTABILITY IS FORECAST TO BE JUST OFFSHORE. THIS GETS TRICKY WITH THE 2NDRY CYCLOGEN AS TO HOW QUICKLY WILL PCPN GET GENERATED PLUS ANY LEFTOVER CONVECTIVE TRIGGERING. THE CONVECTIVE ELEMENT TO IT HAS BEEN PRODUCING VERY LITTLE CONSISTENCY IN THE QPF FIELDS OTHER THAN TO SUGGEST HEAVIER RAIN BECOMES A POSSIBILITY EAST. THE SECONDARY DEVELOPMENT HAS BEEN IN A STEADY LINE TRENDING A LITTLE BIT SLOWER. SO FOR NOW WHILE WE HAVE LIKELY POPS ACROSS MOST OF OUR CWA, WE DO NOT HAVE MODERATE RAIN MENTIONED. WEDNESDAY LOOKS TO BE THE MOST LIKELY FCST TIME PERIOD FOR RAIN, ESPECIALLY EAST AS OUR CWA WILL BE IN THE MOST DIVERGENT LOCATION OF THE UPPER LEVEL JET AND THE STGST FCST MID LEVEL QVEC CONVERGENCE. WE UPPED POPS AND ARE CARRYING SOME MODERATE INTENSITY RAIN EAST. THE ONGOING 2NDRY CYCLOGENESIS APPEARS TO BE OCCURRING TOO CLOSE TO OUR CWA TO PRODUCE A LONG ENOUGH FETCH OR PERIOD OF ONSHORE WINDS FOR TIDAL FLOODING. IF THE LOW DOES FORM FARTHER TO THE SOUTH, THE CHANCES FOR TIDAL FLOODING WOULD INCREASE. WE ARE ASSISTED ALSO THAT THE MOON`S PERIGEE DOES NOT COINCIDE WITH THE NEW MOON AND THE HIGHEST SPRING TIDES WITH THIS LUNAR PHASE ARE ON THE WEEKEND, TWO DAYS AFTER THE NEW MOON. MODELS START DIVERGING COME WEDNESDAY NIGHT AS TO HOW MUCH PCPN WILL GET WRAPPED INTO OUR CWA. THE CONSENSUS IS A LONGER MORE CIRCUITOUS ROUTE FOR IT TO GET BACK INTO OUR AREA. WE LOSE THE PREDICTED HIGHER LEVEL MOISTURE AND LEANS MORE TOWARD SMALLER RAIN DROPS OR DRIZZLE AS A PREDOMINATE PTYPE. THIS DIVERGENCE IN THE MODELS CONTINUES ON THURSDAY AS TO HOW MUCH PCPN CAN WRAP BACK INTO OUR CWA. THE CONSENSUS CLUSTERING IS THAT MOST OF THIS WILL BE NORTH OF OUR CWA. POPS WERE KEPT AS CHANCE, BUT THE PERSISTENT NE FLOW WILL NOT MAKE FOR TOO NICE A DAY. BY WEDNESDAY AND ESPECIALLY THURSDAY WE ARE GOING BELOW STAT GUIDANCE FOR TEMPERATURES. SLOW IMPROVEMENT THE REST OF THE WORK WEEK WITH AT LEAST A WELL TIMED BREAK COME THE WEEKEND. AN APPROACHING COLD FRONT IS NOT EXPECTED TO HAVE ANY MOISTURE TO GENERATE SHOWERS. AS PREVIOUSLY MENTIONED A PREDICTED TELECONNECTION SWITCH TO A POSITIVE AO/NAO AND NEGATIVE PNA WILL BRING A MILDER REGIME BACK INTO THE CONUS. NOT SURPRISING WE ARE HAVING A PCPN EVENT DURING THIS SWITCH EITHER. SO BY THE WEEKEND FAIR WEATHER RETURNS ALONG WITH ABOVE NORMAL TEMPERATURES. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAY...VFR, WITH A CEILING AT TIMES MAINLY AT OR ABOVE 15000 FEET. LIGHT AND VARIABLE WINDS, BECOMING SOUTHWESTERLY AND INCREASING TO AROUND 10 KNOTS. TONIGHT...VFR, WITH A CEILING LOWERING TO BETWEEN 5000-8000 FEET. SOME SHOWERS MAY APPROACH KABE AND KRDG TOWARD DAYBREAK. SOUTH-SOUTHWEST WINDS DIMINISHING TO 5 KNOTS, AND EVEN BECOMING LIGHT AND VARIABLE AT SOME TERMINALS. OUTLOOK... TUESDAY...SOME MVFR CONDITIONS MAINLY DUE TO CIGS ARE POSSIBLE DURING THE AFTERNOON. TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...PREVAILING MVFR CONDITIONS (MAINLY CIGS) WITH SOME IFR CONDITIONS (MAINLY DUE TO CIGS AGAIN) SHOULD OCCUR. HIGHEST POSSIBILITIES EASTERN TERMINALS AND AIRPORTS. GUSTIER NORTHEAST TO NORTH WINDS EXPECTED WEDNESDAY AND WEDNESDAY NIGHT. THURSDAY...PREVAILING MVFR CONDITIONS. GREATEST DURATION NORTHERN AIRPORTS AND TERMINALS. GUSTY NORTHWEST WINDS. THURSDAY NIGHT AND FRIDAY...BECOMING VFR THURSDAY NIGHT AND VFR FRIDAY. GUSTY NORTHWEST WINDS POSSIBLE. && .MARINE... TODAY AND TONIGHT...THE CONDITIONS ARE EXPECTED TO BE BELOW SMALL CRAFT ADVISORY CRITERIA. HIGH PRESSURE SHIFTS TO THE EAST ALLOWING A SOUTH-SOUTHWEST FLOW TO DEVELOP. THIS WILL BE ON THE LIGHTER SIDE FOR MUCH OF TODAY, HOWEVER IS IS FORECAST TO INCREASE SOME LATER TODAY AND TONIGHT FOR A TIME. THE OVERALL BOUNDARY LAYER FLOW SHOULD BE LIGHT ENOUGH THOUGH TO KEEP THE WINDS BELOW 25 KNOTS. THE SEAS ARE ANTICIPATED TO BE AT OR BELOW 4 FEET. OUTLOOK... TUESDAY AND TUESDAY NIGHT...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED. WEDNESDAY THROUGH FRIDAY...A PROTRACTED PERIOD OF SMALL CRAFT ADVISORY CONDITIONS IS POSSIBLE THROUGH THE PERIOD. A SECONDARY LOW PRESSURE SYSTEM DEVELOPMENT SHOULD INCREASE THE GRADIENT ON WEDNESDAY AND MORE CONFIDENTLY WEDNESDAY NIGHT. WINDS AND SEAS SHOULD LIKELY PEAK ON WEDNESDAY NIGHT AND THURSDAY WITH SLOW IMPROVEMENT THEREAFTER WITH DELAWARE BAY FIRST TO LOOSE SMALL CRAFT ADVISORY CONDITIONS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...FREEZE WARNING UNTIL 8 AM EDT THIS MORNING FOR PAZ054-055-061- 062. FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR PAZ060-101>106. NJ...FREEZE WARNING UNTIL 8 AM EDT THIS MORNING FOR NJZ001-007>010- 020>022-027. FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR NJZ012-013- 015>019-023. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...FRANCK/GAINES/GIGI NEAR TERM...GORSE SHORT TERM...GORSE LONG TERM...GIGI AVIATION...GAINES/GIGI/GORSE MARINE...GAINES/GIGI/GORSE

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