Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 162223 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 623 PM EDT THU OCT 16 2014 .SYNOPSIS... AN AREA OF LOW PRESSURE WILL MEANDER AROUND TO OUR NORTH DURING THE NEXT COUPLE OF DAYS, THEN THE NEXT COLD FRONT IS SCHEDULED TO MOVE THROUGH EARLY SATURDAY. HIGH PRESSURE THEN BRIEFLY BUILDS INTO OUR AREA LATE SUNDAY INTO MONDAY. ANOTHER COLD FRONT SHOULD ARRIVE LATE MONDAY INTO TUESDAY, THEN SLOWLY EASE OFFSHORE AS LOW PRESSURE DEVELOPS ALONG IT. HIGH PRESSURE WILL THEN START TO BUILD INTO THE OHIO VALLEY WEDNESDAY AND THURSDAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... SECOND EVENING ESTF UPDATE FOR EXPANDING SHOWERS AND ISOLATED TSTMS. THIS ONE AT 608 PM AND THE STANDARD CRON`D 630 PM UPDATE WILL PROBABLY REMAIN IDENTICAL TO THE CURRENTLY POSTED PRODUCTS. KLNS 0.48+ KRDG 0.26+. EXPANDED THE SHOWER RISK A LITTLE EAST AND INCREASED POPS SLIGHTLY. SHARP TROUGH CROSSING PA WITH HEATING OF THE DAY HAS RESULTED IN SHOWERS AND ISOLATED TSTMS CROSSING EASTERN PA WITH SHOWERS ARCED NICELY FROM THE POCONOS SOUTHWARD TO LANCASTER COUNTY AT 618 PM AND SHOWING SIGNS OF DIMINISHING. AM MONITORING FOR FINAL DYING OUT IN THE DELAWARE VALLEY BETWEEN 10 PM AND MIDNIGHT. SKIES WILL GRADUALLY CLEAR VERY LATE TONIGHT AND WITH WINDS DIMINISHING, WE SHOULD BE ABLE TO DROP INTO THE 50S ACROSS THE REGION OVERNIGHT, WITH SOME UPPER 40S ACROSS THE NORTHERN AREAS. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... THE UPPER LOWS TROUGH SHOULD ROTATE THROUGH OUR AREA BY EARLY FRIDAY MORNING. DRIER CONDITIONS LOOK TO BE IN PLACE AND WHILE THERE WILL BE SOME CLOUDS AROUND, PLENTY OF SUNSHINE WILL BE IN STORE FOR OUR AREA. TEMPERATURES WILL RISE INTO THE 70S DURING THE DAY, 60S ACROSS THE NORTHERN TERRAIN. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... THE OVERALL SYNOPTIC PATTERN IS COMPRISED OF AN INITIAL CLOSED LOW WELL TO OUR NORTH, HOWEVER SHORT WAVE ENERGY DIVING SOUTHEASTWARD AMPLIFIES THE WESTERN AND SOUTHERN SIDE ACROSS THE GREAT LAKES FRIDAY NIGHT. THIS FEATURE THEN AMPLIFIES SOME MORE ACROSS THE EAST SATURDAY, WITH THE AXIS PROBABLY SHIFTING TO OUR EAST SUNDAY. WHILE THIS UPPER-LEVEL TROUGH MAY LIFT OUT DURING SUNDAY AND MONDAY, ANOTHER SHARPENING UPPER-LEVEL TROUGH ARRIVES INTO THE NORTHEAST AND MID ATLANTIC MONDAY NIGHT AND TUESDAY. THE UPPER-LEVEL FLOW IS GENERALLY FORECAST TO AMPLIFY QUITE A BIT WITH A RIDGE IN THE PLAINS. THIS SHOULD ALLOW THE TROUGH IN THE EAST TO CLOSE OFF AS WE GO THROUGH TUESDAY AND WEDNESDAY. DEPENDING ON HOW AMPLIFIED IT BECOMES, IT MAY HANG AROUND THROUGH THURSDAY AS WELL ALTHOUGH SOME EASTWARD SHIFT SHOULD OCCUR. THE PASSAGE OF A COUPLE OF COLD FRONTS WILL DELIVER MUCH COOLER AIR ACROSS THE AREA STARING SUNDAY, THEN WE WATCH FOR THE POTENTIAL FOR A WESTERN ATLANTIC STORM TO DEVELOP NEXT WEEK THAT COULD BE CLOSE ENOUGH TO THE COAST. WE USED A MODEL BLEND FOR FRIDAY NIGHT THROUGH SUNDAY, THEN THE 12Z WPC GUIDANCE THEREAFTER. SOME ADJUSTMENTS WERE THEN MADE AFTER ADDITIONAL COLLABORATION WITH OUR SURROUNDING OFFICES. FOR FRIDAY NIGHT AND SATURDAY...AN AMPLIFYING UPPER-LEVEL TROUGH IS FORECAST TO SLIDE ACROSS THE GREAT LAKES AND OHIO VALLEY. AN ASSOCIATED SURFACE FRONT SHOULD BE CLEARING OUR AREA SATURDAY MORNING. THERE COULD BE A FEW SHOWERS WITH THIS MAINLY NEAR OUR NORTHWESTERN ZONES SATURDAY, THEN CAA STRENGTHENS ESPECIALLY LATE AS A CYCLONIC FLOW REGIME IS MAINTAINED. IT APPEARS THAT SATURDAY WILL BE THE LAST OF THE MILDER DAYS FOR THE REMAINDER OF THE FORECAST PERIOD AS THE CHILLY AIR DEFINITELY ARRIVES AT NIGHT. AS LOW PRESSURE TRACKS TO OUR NORTH, THE PRESSURE GRADIENT IS FORECAST TO TIGHTEN SATURDAY AND THIS COMBINED WITH THE INCREASING CAA WILL PROMOTE DEEPER MIXING. THEREFORE, BREEZY CONDITIONS ARE ANTICIPATED DURING THE DAY BEFORE SUBSIDING SOME AT NIGHT. FOR SUNDAY AND MONDAY...AN UPPER-LEVEL TROUGH IS FORECAST TO SHIFT ACROSS THE AREA SUNDAY, THEN RELOAD FROM THE WEST MONDAY. A TIGHTENING PRESSURE GRADIENT SUNDAY WITH DECENT MIXING SHOULD RESULT IN BREEZY TO PERHAPS WINDY CONDITIONS, THEN SUBSIDE DURING SUNDAY NIGHT. ANOTHER SURFACE FRONT IS THE FORECAST TO CROSS OUR AREA MONDAY NIGHT WITH LOW PRESSURE STARTING TO DEVELOP ALONG IT. A MUCH COOLER AIRMASS WILL ADVECT INTO OUR AREA DURING THIS TIME AS A RESULT OF THE AMPLIFYING UPPER-LEVEL TROUGH. AS SURFACE HIGH PRESSURE BUILDS INTO THE MID ATLANTIC SUNDAY NIGHT INTO MONDAY, LIGHTER WINDS COMBINED WITH A CHILLY AIRMASS MAY ALLOW FOR SOME FROST DEVELOPMENT EARLY MONDAY ESPECIALLY NORTH AND WEST I-95. THIS WILL DEPEND THOUGH ON ANY CLOUD COVER AS A SYSTEM IS FORECAST TO BE APPROACHING LATE FROM THE NORTHWEST. SOME WEAK WAA AHEAD OF THIS FEATURE MAY TOSS ENOUGH CLOUDS THIS FAR EAST TO KEEP TEMPERATURES UP SOME OR BOTTOM OUT EARLY BEFORE SOME RECOVERY. SOME SLIGHT CHC TO LOW CHC POPS WERE BROUGHT IN FROM WEST TO EAST MONDAY NIGHT WITH THE NEXT SYSTEM. FOR TUESDAY AND WEDNESDAY...THE POSITIONING OF THE STRENGTHENING CLOSED LOW WILL GENERALLY DETERMINE THE TRACK OF A WESTERN ATLANTIC STORM SYSTEM. THIS IS THE INITIAL SURFACE LOW THAT DEVELOPS ON THE EASTBOUND COLD FRONT AS THE THERMAL GRADIENT TIGHTENS. THERE IS SOME MODEL DISAGREEMENT WITH THIS SYSTEM ESPECIALLY WITH THE DETAILS, HOWEVER SOME ENSEMBLE MEMBERS DO HAVE A COASTAL LOW TUCKED IN CLOSER TO THE COAST. WHILE THIS IS OCCURRING, HIGH PRESSURE BUILDS ACROSS THE GREAT LAKES REGION AND TOWARD OUR AREA. THIS ALLOWS FOR A NORTHERLY FLOW OF CHILLY AIR ACROSS THE REGION TO CONTINUE. GIVEN THE UNCERTAINTY ABOUT THE SPECIFICS THIS FAR OUT, WE WENT WITH THE 12Z WPC GUIDANCE WHICH NOW LEANS MORE TOWARD SOME AFFECTS FROM THE CLOSING UPPER-LEVEL LOW, WESTERN ATLANTIC SURFACE LOW AND POSSIBLE WRAPAROUND. THUS WE INCREASED THE POPS INTO THE CHC RANGE. FOR THURSDAY...THE IDEA OF A RATHER ROBUST CLOSED LOW WOULD TEND TO SLOW THE EASTWARD PROGRESSION OF THE SURFACE FEATURES. THEREFORE WHILE THE CLOSED LOW IS FORECAST TO SHIFT EAST SOME DURING THIS TIME FRAME, THERE MAY BE STILL SOME BACKLASH ON ITS WESTERN FLANK. THIS WILL BE HIGHLY DEPENDENT ON THE LOCATION OF THE LARGE CLOSED LOW AND ITS ASSOCIATED SURFACE LOW AS IT EJECTS NORTHEASTWARD PROBABLY OFF THE SOUTHEASTERN NEW ENGLAND COAST. THEREFORE, WE FAVORED THE 12Z WPC GUIDANCE WITH LOW CHC POPS. && .AVIATION /22Z THURSDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THROUGH TONIGHT...VFR SCT-BKN AOA 4000 FT. SCT IFR SHOWERS AND ISOLATED TSTMS VCNTY KRDG WILL PROBABLY REACH VCNTY KABE THEN WE STILL THINK DISSIPATE BEFORE REACHING KPNE/PHL/KILG TONIGHT. LIGHT SOUTH TO SOUTHWEST WIND SHOULD TURN WEST OVERNIGHT. THERE WAS SOME INDICATION IN THE MODEL GUIDANCE THAT FOG MAY FORM AT A FEW LOCALES, KRDG AND KMIV, OVERNIGHT BUT CONFIDENCE WAS TOO LOW TO INCLUDE IN THE CURRENT TAF. FRIDAY...VFR CONDITIONS EXPECTED ACROSS THE TERMINALS. WINDS WILL INCREASE AROUND LATE MORNING AND BE WEST SOUTHWEST AROUND 10 KNOTS. WINDS GUSTS BELOW 20 KNOTS. OUTLOOK... FRIDAY NIGHT...VFR. SOUTHWEST WINDS DIMINISHING TO 5 KNOTS OR LESS. SATURDAY AND SUNDAY...MAINLY VFR. WEST TO NORTHWEST WINDS AROUND 15 KNOTS WITH GUSTS TO 25 KNOTS BOTH DAYS, HOWEVER DIMINISHING SOME EACH NIGHT. MONDAY AND TUESDAY...VFR OVERALL MONDAY, HOWEVER THEN POSSIBLE SUB-VFR CONDITIONS DEVELOPING TUESDAY WITH SOME RAIN. LIGHT SOUTHWEST WINDS MONDAY, BECOMING NORTHEASTERLY LESS THAN 10 KNOTS TUESDAY. && .MARINE... A SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS REMAINS IN EFFECT ON THE OCEAN WATERS THROUGH SATURDAY. WINDS WILL REMAIN BELOW 25 KNOTS THROUGH FRIDAY. SEAS WILL CONTINUE TO REMAIN ELEVATED AS SWELLS FROM DISTANT MAJOR HURRICANE GONZALO CONTINUE TO MOVE INTO OUR AREA. OUTLOOK... FRIDAY NIGHT...WHILE WINDS SHOULD BE BELOW SMALL CRAFT ADVISORY CRITERIA, SWELLS ON THE OCEAN FROM FAR DISTANT HURRICANE GONZALO SHOULD KEEP SEAS WITHIN SMALL CRAFT ADVISORY CRITERIA. SATURDAY AND SUNDAY...SMALL CRAFT ADVISORY CONDITIONS ARE POSSIBLE ON DELAWARE BAY DUE TO INCREASING WEST AND THEN NORTHWEST WINDS MAINLY STARTING SATURDAY NIGHT. ON THE OCEAN, A COMBINATION OF LEFTOVER SWELLS FROM GONZALO AND A STRONGER WEST THEN NORTHWEST FLOW SHOULD KEEP SMALL CRAFT CONDITIONS GOING. SINCE THE STRONGER WINDS /UP TO 30 KNOTS/ LOOK TO NOT ARRIVE UNTIL SATURDAY NIGHT, THE SMALL CRAFT ADVISORY /EXTENDED TO 22Z SATURDAY/ WAS CHANGED TO CONVEY HAZARDOUS SEAS. A REGULAR ADVISORY SHOULD THEN BE NEEDED FOR SATURDAY NIGHT AND SUNDAY WITH STRONGER CAA AND BETTER MIXING. THE WINDS AND SEAS DECREASE SUNDAY NIGHT. MONDAY AND TUESDAY...THE CONDITIONS ARE ANTICIPATED TO BE BELOW ADVISORY CRITERIA. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 PM EDT SATURDAY FOR ANZ450>455. && $$ SYNOPSIS...GORSE NEAR TERM...DRAG 622 SHORT TERM...MEOLA LONG TERM...GORSE AVIATION...DRAG/GORSE 622 MARINE...GORSE/MEOLA

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