Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 200140 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 940 PM EDT SUN OCT 19 2014 .SYNOPSIS... HIGH PRESSURE WILL MOVE OFFSHORE TO OUR SOUTH TONIGHT. ON MONDAY A LOW PRESSURE SYSTEM WITH AN ASSOCIATED COLD FRONT WILL DIVE SOUTHEAST FROM THE UPPER GREAT LAKES REACHING OUR REGION DURING THE DAY TUESDAY. ANOTHER LOW PRESSURE WILL FORM OFF THE CAROLINA COASTLINE ON TUESDAY AS WELL. THESE TWO LOW PRESSURE SYSTEMS WILL INTERACT WITH EACH OTHER AND MERGE JUST OFFSHORE WEDNESDAY AND THURSDAY. THE LOW PRESSURE SYSTEM WILL DEPART THE REGION BY FRIDAY WITH HIGH PRESSURE MOVING IN FROM THE WEST BY SATURDAY. THIS WILL BE FOLLOWED BY A COLD FRONTAL PASSAGE SATURDAY NIGHT. ANOTHER AREA OF HIGH PRESSURE MOVES IN FROM THE WEST ON SUNDAY. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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NO CHANGES TO THE FROST/FREEZE HEADLINES THIS EVENING. WE WILL LEAVE THE ADVISORIES/WARNINGS AS THEY ARE AS DEWPOINTS ACROSS MUCH OF THESE AREAS ARE STILL LOW AT THIS POINT THAT THERE IS STILL PLENTY OF ROOM FOR TEMPERATURES TO DROP OVERNIGHT. DEWPOINTS HAVE ACTUALLY RISEN SLIGHTLY WHERE THERE IS NO ADVISORY, AND THERE IS SOME CLOUD COVER MOVING IN FROM THE WEST. SO WE THINK THIS MAY KEEP TEMPERATURES SLIGHTLY WARM ENOUGH TO PREVENT WIDESPREAD FROST AND KEEP IT MORE PATCHY IN THESE AREAS. WIND GUSTS HAVE DROPPED OFF AND WILL BECOME LIGHT AND VARIABLE/CALM ACROSS THE AREA. ANY DIRECTION WILL BE MOSTLY NORTHWEST EARLY, THEN WESTERLY OVERNIGHT. TEMPERATURES TONIGHT WERE A BLEND OF THE MET/MAVMOS WITH A HEAVIER WEIGHTING ON THE SLIGHTLY COOLER MET. THE NAM OVERALL APPEARED TO INITIALIZE BETTER THAN THE GFS UPSTREAM.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... NOT MUCH IN THE WAY OF SENSIBLE WEATHER CHANGE OTHER THAN WE SHOULD BE ABLE TO TACK ON A FEW DEGREES TO DAYTIME HIGHS. WINDS BACK TOWARDS THE SOUTH-SOUTHWEST BY LATE MORNING AS HIGH PRESSURE MOVES OFFSHORE TO OUR SOUTHEAST. DEWPOINTS WILL BEGIN TO CREEP UP THOUGH NOT ENOUGH TO ALLOW FOR COLUMN SATURATION. WE KEEP MONDAY DRY AHEAD OF THE NEXT UPPER LEVEL WAVE RIPPLING ACROSS THE OHIO VALLEY. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... MONDAY NIGHT: CLOUDS AND WAA BEGIN TO INCREASE AHEAD OF THE NEXT COLD FRONTAL SYSTEM. ENOUGH LIFT SHOULD BE PRESENT TO GENERATE SOME SCATTERED SHOWERS ACROSS WESTERN PARTS OF THE CWA BY SUNRISE TUESDAY WITH QPF UNDER 1/10TH OF AN INCH. MAV AND MET GUIDANCE SETS USED FOR MOST WEATHER ELEMENTS IN THIS PERIOD. TUESDAY THROUGH THURSDAY NIGHT: A COASTAL LOW PRESSURE SYSTEM WILL DEVELOP OFFSHORE AND BE SLOW TO MOVE NORTHEAST THROUGHOUT THIS PERIOD. THE END RESULT WILL BE GRAY GLOOMY COOLER DAYS FEATURING RAIN SHOWERS AND SOME BRISK NORTHWESTERLY WINDS WEDNESDAY AND THURSDAY AFTERNOONS. THE FORMATION OF THIS LOW PRESSURE WILL START WITH TWO PIECES, A STRONG UPPER LEVEL LOW AND COLD FRONT DIVING FROM THE GREAT LAKES INTO THE MID-ATLANTIC AND A LOW PRESSURE FORMING OFF THE CAROLINA`S. THE UPPER LOW AND COLD FRONTAL BOUNDARY WILL LEAD TO CONTINUED SCATTERED SHOWERS ON TUESDAY TO THE REGION WITH A MOISTURE PLUME FROM THE CAROLINA LOW WELL OFFSHORE. BY TUESDAY NIGHT WE BEGIN TO SEE MORE INTERACTION BETWEEN THE FEATURES, PHASING. A PHASED LOW FORMS OFF THE SOUTHERN NEW ENGLAND COASTLINE BY WEDNESDAY WITH THE MAJORITY OF ATLANTIC MOISTURE BROUGHT INTO SOUTHERN NEW ENGLAND. TO COMPARE OUR REGION WOULD BE FAVORED FOR JUST SOME WRAP AROUND SHOWERS. OVERALL THE OPERATIONAL MODELS HAVE COME INTO BETTER CONSENSUS TODAY THAT THE ABOVE OUTCOME WILL OCCUR. THIS IS REFLECTED IN BOTH THE 00Z ECMWF ENSEMBLE MEAN COMPARED TO THE OPERATIONAL RUN AND THE 06Z GEFS. WITH THAT BEING SAID, CONFIDENCE CONTINUES TO INCREASE THAT THIS PERIOD WILL BE DOMINATED BY SOME SCATTERED SHOWERS LASTING THROUGH THURSDAY. AREAS FURTHER NORTHEAST CLOSER TO THE LOW STAND THE BEST CHANCE TO SEE THE MOST IN TERMS OF SHOWER ACTIVITY. TIMING DIFFERENCES ON THE SHOWERS ARE STILL PRESENT LEAVING SOME UNCERTAINTY WITH POPS, KEPT AT HIGH CHANCE TO LOW END LIKELY. TOTAL RAINFALL WILL BE UNDER ONE INCH FOR THIS EVENT. THE 12Z ECMWF AND NAM FROM TODAY DO INDICATE THE POTENTIAL FOR SOME HEAVIER SHOWERS ACROSS THE NORTH TUESDAY NIGHT INTO WEDNESDAY AS THE MID-LEVEL ENERGY BEGINS TO TRANSFER TO THE COAST, THIS WILL NEED TO BE WATCHED AS NEW DATA COMES IN. WITH PLENTY OF CLOUDS, LOW TEMPERATURES WILL STAY UP AT NIGHT CLOSE TO 50 FOR MOST OF US WHILE HIGHS STRUGGLE TOWARD 60, COOLER NW. NOT MUCH SPREAD IN THE MODELS AND THERE ENSEMBLES/ STATISTICAL GUIDANCE ON TEMPERATURES, WENT ON THE WARMER END EACH NIGHT AND THE COOLER END DURING EACH DAY. IN TERMS OF TIDES IT LOOKS AS THOUGH THE WIND DIRECTION WILL NOT CREATE DEPARTURES HIGH ENOUGH FOR MINOR COASTAL FLOODING OR CREATE LOW ENOUGH DEPARTURES FOR BLOWOUT TIDES ATTM. FRIDAY: LOW PRESSURE SYSTEM FINALLY DEPARTS WITH HIGH PRESSURE BUILDING BACK IN. THIS ALLOWS FOR CLEARING FROM SOUTH TO NORTH AND THE FIRST DRY DAY IN A WHILE. TEMPERATURES ARE FORECASTED TO BE CLOSER TO MEX GUIDANCE AND THE 12Z ECMWF MODELED TWO METER TEMPERATURES. CONTINUED NORTHWEST WINDS WITH THE BEST CHANCE OF MIXING TO LEAD TO SOME AFTERNOON WIND GUSTS AROUND 20 MPH. FRIDAY NIGHT THROUGH SUNDAY: DURING D+6 AND D+7, THE NEGATIVE NAO/POSITIVE PNA PATTERN OF THE PAST TWO WEEKS IS PROJECTED TO REVERSE. THIS TREND IS UNDERWAY, AND IS EVIDENT IN LESS HIGH- LATITUDE BLOCKING. THE MAIN MID-LEVEL FEATURES IN THIS TIMEFRAME ARE A CLOSED LOW LIFTING INTO THE CANADIAN MARITIMES ON SATURDAY, FOLLOWED BY A SHORT-WAVE MOVING THROUGH A MORE ZONAL FLOW ON SUNDAY. THERE IS MODEL DISAGREEMENT WITH THESE FEATURES, AS THE GFS EJECTS THE CLOSED LOW SLOWER THAN THE ECMWF, RESULTING IN A DELAYED RETURN TO A MORE ZONAL FLOW. THIS FURTHER RESULTS IN THE GFS MOVING THE SHORTWAVE FURTHER NORTHEAST, WHILE THE ECMWF TAKES IT MUCH FURTHER TO THE SOUTH OVER NEW ENGLAND. SOME OF THE GFS ENSEMBLE MEMBERS ALSO SUPPORT THE ECMWF SOLUTION. GIVEN THE GFS INITIALIZED MORE ROBUST WITH THE LEAD SHORT-WAVE /LOCATED OVER NORTHERN SASKATCHEWAN AS OF THIS WRITING/ THAT RESULTS IN THE CUT- OFF LOW, AND PREVIOUS GFS RUNS WERE MORE IN LINE WITH THE ECMWF, FEEL THE GFS SOLUTION IS UNREALISTIC. THE ECMWF SOLUTION IS ALSO MORE REPRESENTATIVE OF THE PROJECTED LACK OF HIGH-LATITUDE BLOCKING. OR SATURDAY, SHORT-WAVE RIDGING ALOFT WILL ALLOW HIGH PRESSURE TO BUILD IN FROM THE WEST, WITH TEMPS AT 850 HPA SUPPORTING HIGH TEMPERATURES AT SEASONABLE LEVELS. A COLD FRONT IS PROJECTED TO MOVE THROUGH THE REGION SOMETIME IN THE LATE SATURDAY INTO EARLY SUNDAY TIMEFRAME. AT THIS TIME, THE ECMWF INDICATES THE BEST DYNAMICS SITUATED TO THE NORTH AND LIMITED MOISTURE, BUT IT IS TOO FAR OUT TO SPECULATE ON PRECIP CHANCES. IF THE TIMING OF THE FRONT HOLDS, PROJECTED 850 HPA TEMPS WOULD SUPPORT BELOW NORMAL HIGHS ON SUNDAY. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TONIGHT...VFR WITH ONLY CIRRUS CLOUDS EXPECTED OVERNIGHT. WIND GUSTS HAVE DROPPED OFF AND WINDS WILL BECOME LIGHT AND VARIABLE/CALM MOST PLACES OVERNIGHT. ANY DIRECTION WILL SWITCH FROM MOSTLY NORTHWEST TO WEST OVERNIGHT. MONDAY...VFR. WINDS BACK TOWARDS THE SOUTH-SOUTHWEST AND INCREASE TO AROUND 10 KNOTS. INCREASING CIRRUS BECOMING ALTOCU BY EARLY AFTERNOON. THINK ANY RAIN CHANCES HOLDS OFF UNTIL LATE MONDAY NIGHT. OUTLOOK... MONDAY NIGHT AND TUESDAY...SOME RESTRICTIONS TO MVFR WITH SCATTERED SHOWERS. TUESDAY NIGHT THROUGH THURSDAY... SOME MVFR RESTRICTIONS WITH SCATTERED SHOWERS. NORTH TO NORTHWEST WINDS WEDNESDAY AFTERNOON THROUGH THURSDAY FROM 10-15 KNOTS WITH HIGHER GUSTS. THURSDAY NIGHT AND FRIDAY: VFR, NORTHWEST WIND GUSTS FRIDAY AFTERNOON FROM 15-20 KNOTS.
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&& .MARINE...
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TONIGHT...THE SMALL CRAFT ADVISORY ON THE DELAWARE BAY WAS ALLOWED TO EXPIRE AT 8PM AS GUSTS HAVE DROPPED OFF THERE. THE OCEAN FRONT REMAINS UNCHANGED FROM THE MIDNIGHT END TIME. HIGH PRESSURE MOVING IN WILL ALLOW THE WIND AND SEAS TO RELAX LATE TONIGHT. MONDAY...SUB-SCA CONDITIONS. WINDS BACK TOWARDS THE SOUTH-SOUTHWEST TOMORROW AFTERNOON AROUND 10 TO 15 KNOTS. SEAS REMAIN 2 TO 3 FEET. OUTLOOK... MONDAY NIGHT THROUGH WEDNESDAY: SEAS AND WINDS BELOW SCA CRITERIA BUT INCREASING WEDNESDAY WITH THE DEVELOPMENT OF A LOW PRESSURE TO OUR NORTHEAST. WEDNESDAY NIGHT THROUGH FRIDAY: OVERALL THINKING IS THAT WAVEWATCH IS UNDERDONE BY ABOUT A FOOT ON THE SEAS. SEAS WILL LIKELY BE AT OR OVER FIVE FEET THROUGH MOST OF THIS PERIOD WITH SOME DECREASE IN THE SEAS FRIDAY. NORTHWEST WIND GUSTS OVER 25 KNOTS ARE ALSO POSSIBLE EACH AFTERNOON. SCA POSSIBLE FOR MOST OF THIS TIMEFRAME.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...FREEZE WARNING FROM 3 AM TO 8 AM EDT MONDAY FOR PAZ054-055-061- 062. FROST ADVISORY FROM 2 AM TO 8 AM EDT MONDAY FOR PAZ060-101>106. NJ...FREEZE WARNING FROM 3 AM TO 8 AM EDT MONDAY FOR NJZ001-007>010. FREEZE WARNING FROM 4 AM TO 8 AM EDT MONDAY FOR NJZ020>022-027. FROST ADVISORY FROM 2 AM TO 8 AM EDT MONDAY FOR NJZ012-013- 015>019-023. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ430-431- 450>455.
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&& $$ SYNOPSIS...FRANCK/GAINES NEAR TERM...HEAVENER/ROBERTSON SHORT TERM...HEAVENER LONG TERM...FRANCK/GAINES AVIATION...GAINES/HEAVENER/ROBERTSON MARINE...GAINES/HEAVENER/ROBERTSON

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