Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 290254 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 954 PM EST FRI NOV 28 2014 .SYNOPSIS...
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HIGH PRESSURE ACROSS THE AREA WILL MOVE OFFSHORE SATURDAY. A WARM FRONT LIFTS NORTH THROUGH OUR AREA SATURDAY NIGHT INTO EARLY SUNDAY. A COLD FRONT SAGS SOUTHEAST ACROSS THE MID ATLANTIC STATES MONDAY. STRONG HIGH PRESSURE WILL FOLLOW INTO THE NORTHEAST TUESDAY, FOLLOWED BY ANOTHER FRONTAL SYSTEM AROUND WEDNESDAY. MORE HIGH PRESSURE SHOULD ARRIVE BY THE END OF NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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RADIATIONAL COOLING WAS OCCURRING AND AT THE SAEM TIME CLOUDINESS WAS RAPIDLY INCREASING-STREAMING SEWD THROUGH SOUTHERN AND WESTERN PA. HAVE STILL PERMITTED DECENT RADIATIONAL COOLING PRIOR TO 06Z WITH QUESTIONABLE PERSISTENT SKYCOVER THEREAFTER. COUNTRYSIDE LOWS TONIGHT OVER THE SNOW COVERED NORTHEAST PA AND NORTHWEST NJ WILL BE IN THE 8 TO 13 ABOVE RANGE..A BIT WARMER IN THE URBAN CENTERS. EVEN SOUTHERN AND EASTERN NEW JERSEY JUST A COUPLE OF MILES AWAY FROM THE COAST SHOULD BOTTOM OUT IN THE MID TO UPPER TEENS (DESPITE NO SNOW COVER THERE) BEFORE CLOUD COVER STOPS THE TEMPERATURES FROM FALLING FURTHER. MAINTAINED SMALL CHC FLURRIES OUT WEST TOWARD RDG- ABE- MPO JUST BEFORE SUNRISE IN WAA.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... HIGH PRESSURE WILL BE CENTERED ALONG THE EASTERN SEABOARD SATURDAY MORNING. THE HIGH WILL MOVE OFFSHORE BY THE AFTERNOON AND RETURN FLOW WILL ENSUE. A WAA PATTERN WILL BECOME ESTABLISHED OVER THE MID-ATLANTIC REGION ON SATURDAY AS A RESULT. BASED ON THE 12Z NAM/GFS FORECAST SOUNDINGS, THERE APPEARS TO BE ENOUGH MOISTURE RETURN IN THE MID LEVELS AND ISENTROPIC LIFT TO SEE SOME SNOW SHOWERS OR FLURRIES ACROSS EASTERN PA AND NJ DURING THE DAY. CONFINED CHANCE POPS TO NORTHEAST PA AND NORTHWEST NJ WHERE THE BEST LIFT IS FORECAST AND FLURRIES FARTHER SOUTH AND EAST. FORECAST MAX TEMPS FOR SATURDAY ARE ABOUT 2-5F DEGREES WARMER THAN TODAY, RANGING FROM AROUND FREEZING NORTH OF I-80 TO THE MID 40S IN COASTAL SOUTHERN NJ AND THE DELMARVA. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... BY SATURDAY NIGHT, THE HIGH IS EXPECTED TO HAVE PUSHED WELL OFFSHORE, AND A WARM FRONT IS FORECAST TO LIFT ACROSS THE AREA. THERE IS NOT MUCH VERTICAL MOISTURE ALOFT, ALTHOUGH THERE IS SOME LOW-LEVEL MOISTURE THAT SHOULD SPREAD ACROSS THE AREA. THE QUESTION IS WHETHER THIS JUST INCREASES CLOUD COVER, OR IF THE LOW-LEVEL MOISTURE IS ENOUGH TO PRODUCE SOME PATCHY DRIZZLE ACROSS THE NORTHERN AREAS AS A WEAK SHORT WAVE/VORTICITY IMPULSE APPROACHES OVERNIGHT. IF ANY DRIZZLE DID DEVELOP, TEMPERATURES MAY BE CLOSE ENOUGH TO FREEZING, EVEN BEHIND THE WARM FRONT, THAT IT COULD LEAD TO PATCHY FREEZING DRIZZLE FOR THE FAR NORTHERN ZONES. FOR NOW, WE WILL KEEP THE WEATHER DRY AND LATER SHIFTS DECIDE IF THERE IS GREATER CONFIDENCE TO PUT THIS IN THE FORECAST. ON SUNDAY, THE WARM FRONT SHOULD BE WELL TO OUR NORTH, AND WE WILL BE IN BETWEEN THE HIGH TO OUR EAST AND AN APPROACHING COLD FRONT. ANOTHER WEAK SHORT WAVE/VORTICITY IMPULSE SLIDES ACROSS THE AREA DURING THE DAY, WHILE THERE REMAINS SOME LOW-MID LEVEL MOISTURE ACROSS THE AREA. THERE IS SOME LIGHT QPF FORECAST, MAINLY NORTH AND WEST OF OUR AREA, BUT THERE WILL REMAIN A SLIGHT CHANCE OF SHOWERS SUNDAY. A FRONTAL BOUNDARY IS EXPECTED TO SAG TOWARD THE AREA SUNDAY NIGHT, THEN SLOWLY MOVE THROUGH THE AREA INTO MONDAY INTO MONDAY NIGHT. MOST MODELS INDICATE ANY PRECIPITATION ASSOCIATED WITH THE BOUNDARY WILL BEGIN TO DRY OUT BEFORE REACHING OUR AREA SUNDAY NIGHT INTO EARLY MONDAY, THEN POSSIBLY REDEVELOPING ACROSS OUR SOUTHERN AREAS LATER MONDAY INTO MONDAY NIGHT. WE WILL KEEP CHANCE/SLIGHT CHANCE POPS ACROSS THE AREA DURING THIS PERIOD. THE FRONT SHOULD PUSH TO OUR SOUTH TUESDAY AS HIGH PRESSURE BRIEFLY BUILDS ACROSS THE NORTHEAST. THE ECMWF LINGERS SOME PRECIPITATION ACROSS THE SOUTHERN AREAS DURING THE DAY AS THE FRONT GETS CAUGHT UP TO OUR SOUTH. WE WILL KEEP THE WEATHER DRY FOR MOST OF THE AREA FOR NOW, EXCEPT OUR SOUTHERN ZONES. THERE ARE NOW DIFFERENCES WITH THE FRONTAL SYSTEM THAT IS EXPECTED TO AFFECT THE AREA AROUND NEXT WEDNESDAY. A WARM FRONT MAY LIFT ACROSS THE AREA TUESDAY NIGHT AS THE HIGH RETREATS NORTHEASTWARD. THE GFS KEEPS THE COLD FRONT TO OUR WEST UNTIL LATER IN THE WEEK, WHILE THE ECMWF PULLS THE FRONT THROUGH WEDNESDAY. WE WILL STAY CLOSE TO CONTINUITY AND WPC, WHICH LINES UP BETTER WITH THE ECMWF. THIS KEEPS CHANCE POPS FRO TUESDAY NIGHT INTO WEDNESDAY. STAYING CLOSE TO WPC AND ECMWF, HIGH PRESSURE IS EXPECTED FOR THURSDAY, WHICH WOULD KEEP THE WEATHER DRY. IF THE GFS HOLDS TRUE WITH THE FRONT LAGGING UNTIL LATER IN THE WEEK, THEN WE`D HAVE A BETTER CHANCE OF PRECIP THURSDAY INTO THURSDAY NIGHT. ALTHOUGH FOR DIFFERENCES REASON, BOTH HAVE A CHANCE OF PRECIPITATION BY FRIDAY. THE GFS REMAINS DUE TO LINGERING PRECIPITATION FROM THE FRONT IT`S INDICATING, WHILE THE ECMWF SHOWS ANOTHER WARM FRONT POSSIBLY LIFTING TOWARD THE AREA AS HIGH PRESSURE LIFTS TO OUR NORTHEAST. SO WE WILL HAVE CHANCE POPS AGAIN DURING THE DAY FRIDAY. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TONIGHT...VFR CLEAR WITH DIMINISHING NW WIND BECOMING CALM OVERNIGHT AS HIGH PRES BUILDS IN THEN VFR CIGS DEVELOPING AOA 7000 FT BETWEEN 03Z AND 08Z. SATURDAY...PREDOMINANTLY VFR. THERE IS A SMALL CHANCE OF A SNOW SHOWER OR FLURRY DURING THE DAYTIME, WHICH MAY BRIEFLY REDUCE VSBYS TO MVFR. THE FORECAST LIKELIHOOD OF THE HAPPENING IS TOO LOW TO INCLUDE IN TAFS, ALTHOUGH ABE/RDG MAY HAVE A SLIGHTLY BETTER CHANCE. A LIGHT SOUTHERLY RETURN FLOW AROUND 5 KT DEVELOPS IN THE MORNING, INCREASING TO AROUND 10 KT DURING THE AFTERNOON. OUTLOOK... SATURDAY NIGHT-SUNDAY NIGHT...MOSTLY VFR. SOUTHWEST WIND GUSTS 15-20 KNOTS. MONDAY-MONDAY NIGHT...CHANCE OF RAIN OR SNOW SHOWERS. GENERALLY VFR UNLESS PRECIPITATION OCCURS. GUSTY NORTHWEST WINDS AROUND 20 KNOTS POSSIBLE. TUESDAY...MOSTLY VFR. TUESDAY NIGHT-WEDNESDAY...MVFR CONDITIONS POSSIBLE WITH A CHANCE OF SHOWERS. GUSTY SOUTHWEST WINDS 15-20 KNOTS.
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&& .MARINE...
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NO HEADLINES ATTM. NEXT SCA LATE SATURDAY FOR REVIEW-ASSESSMENT BY OUR MID SHIFT TO BE SURE AN SCA HEADLINE IS NEEDED. OUTLOOK... SATURDAY NIGHT-SUNDAY NIGHT...SMALL CRAFT ADVISORY CONDITIONS POSSIBLE AS HIGH PRESSURE PUSHES TO OUR SOUTH AND COLD FRONT APPROACHES LATE ON SUNDAY NIGHT. MONDAY-MONDAY NIGHT...SMALL CRAFT ADVISORY CONDITIONS REMAIN POSSIBLE BEHIND THE COLD FRONT THAT MOVES ACROSS THE AREA, ESPECIALLY LATE IN THE DAY AND OVERNIGHT. TUESDAY...CONDITIONS EXPECTED TO DROP BELOW SMALL CRAFT ADVISORY CONDITIONS DURING THE DAY AS HIGH PRESSURE AFFECTS THE WATERS. TUESDAY NIGHT-WEDNESDAY...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED.
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&& .CLIMATE... WITH THANKSGIVING UPON US AND METEOROLOGICAL WINTER KNOCKING ON OUR DOOR, ITS OUR ANNUAL LOOK TO SEE HOW PAST WINTERS HAVE FARED BASED ON PRECEDING FALL PATTERNS AND TRENDS. OUR FORAY LAST FALL ABOUT THE WINTER OF 2013-14 WAS AN UNMITIGATED BUST AS THE NEGATIVE EASTERN PACIFIC OSCILLATION PATTERN (EPO) TOOK HOLD IN NOVEMBER AND NEVER LET GO THE ENTIRE WINTER. WHILE THE COLDER NOVEMBER TRENDED DOWN OUR WINTER TEMPERATURE ANALOGS TO ABOUT NORMAL, IT WAS NOWHERE NEAR ENOUGH. IT WAS ALSO ONLY THE SIXTH TIME (OUT OF FORTY SIX OCCURRENCES) THAT A BOTTOM THIRD WINTER FOLLOWED A WARM OCTOBER. ONCE AGAIN WE ARE HEADING INTO THIS WINTER WITH A RARER COMBINATION OF A WARM OCTOBER AND COLDER NOVEMBER JUST LIKE THE TWO PREVIOUS AUTUMNS. IN TERMS OF ENSO, THE LATEST CONSENSUS OF ALL DYNAMICAL AND STATISTICAL MODELS FOR THE WINTER SEASON IS FOR A WEAK EL NINO TO OCCUR. OF LATE THE EL NINO HAS LOOKED HEALTHIER AS A KELVIN WAVE AND A CURRENTLY ROBUST MJO CYCLE HAVE/WILL HELP BOOST SEA SURFACE TEMPERATURE ANOMALIES (SSTA). AS CPC HAS STATED, THERE IS STILL A SSTA AND ATMOSPHERIC RESPONSE DISCONNECT THAT EXISTS. THE LATEST GLOBAL WIND OSCILLATION READINGS, OUR ATMOSPHERE IS STILL IN AN ENSO NEUTRAL STATE EVEN IF WATER EASTERN TROPICAL PACIFIC TEMPERATURE ANOMALIES HAVE BECOME WARMER. WEAK EL NINOS SINCE 1950 IN PHILADELPHIA HAVE HAD AN AVERAGE TEMPERATURE OF 33.2 DEGREES AND AVERAGE SNOWFALL OF 21.8 INCHES. WEAK EL NINOS, LIKE MOST NON-UBER EL NINOS, FAVOR HAVING MORE MAJOR SNOW STORMS THAN THE CLIMATOLOGICAL AVERAGE. IN THE TEN WEAK EL NINOS SINCE 1950, PHILADELPHIA HAS HAD EIGHT SNOWFALL EVENTS OF SIX INCHES OR MORE, FOUR OF WHICH WERE TEN INCHES OR MORE. THE MOST COMMON MONTH FOR MAJOR SNOWS DURING WEAK EL NINOS IS JANUARY, BUT THEY HAVE OCCURRED IN EVERY MONTH FROM NOVEMBER THROUGH MARCH. LOOKING AT THE MIDDLE AND HIGH LATITUDES, ONCE AGAIN SNOW COVERAGE IN EURASIA WAS OFF TO THE RACES IN SEPTEMBER AND OCTOBER, EVEN FASTER THAN AUTUMN OF 2013. OCTOBER 2014 ONLY TRAILED OCTOBER 1976 FOR TOTAL SNOW COVERAGE. IN THE SATELLITE ERA WHEN BOTH SEPTEMBER AND OCTOBER HAVE HAD ABOVE AVERAGE SNOW COVERAGE, 64 PERCENT OF THE ENSUING PHILADELPHIA WINTERS HAVE BEEN SNOWIER THAN THE CURRENT AVERAGE AND HAD A 50/50 SPLIT WITH TEMPERATURES BEING EITHER ABOVE OR BELOW NORMAL. WHILE 64 PERCENT MAY NOT SOUND DEFINITIVE, SNOWFALL IS NOT A NORMAL DISTRIBUTION BECAUSE SEASONS LIKE 2013-14 SKEW UPWARD THE STATISTICAL AVERAGE. SINCE 1967 (THE START OF THE SATELLITE ERA AND OUR LOOK AT THE DR. JUDAH COHEN STUDY) ONLY 1 IN 3 WINTERS HAS HAD ABOVE AVERAGE SNOWFALL. THE STATISTICAL MEDIAN FOR SNOWFALL IN PHILADELPHIA SINCE 1967 IS ABOUT 18 INCHES. BEYOND SIBERIA, THE ARCTIC OSCILLATION AVERAGED NEGATIVE DURING THE MONTH OF OCTOBER. WHEN IT HAS, 70 PERCENT OF ENSUING WINTERS HAS AVERAGED NEGATIVE. THANK-YOU METEOROLOGIST MATT LANZA FOR THIS INFORMATION. ANOTHER PHENOMENON THAT FAVORS A NEGATIVE ARCTIC OSCILLATION FOR THIS UPCOMING WINTER IS THAT WE ARE IN THE EASTERLY PHASE OF THE QUASI-BIANNUAL OSCILLATION STRATOSPHERIC WINDS OVER THE TROPICS. WHEN WE ARE IN THIS PHASE, HISTORICALLY WE HAVE HAD MORE SUDDEN STRATOSPHERIC WARMING EVENTS WHICH OFTEN SPLITS AND DISPLACES EVERYBODY`S FAVORITE POLAR VORTEX FROM NEAR THE NORTH POLE. THERE IS NO GUARANTEE THE WESTERN HEMISPHERE WOULD BE THE SO CALLED BENEFICIARY OF THIS ARCTIC DISPLACEMENT, BUT A HIGHER CHANCE EXISTS THIS WINTER VS NO CHANCE AT ALL. THE ARCTIC OSCILLATION`S COUSIN, THE NORTH ATLANTIC OSCILLATION (NAO), WE HAVE SEEN BEEN THE DRIVER (WINTER OF 2010-11) OR THE CRICKET CHIRPING (LAST WINTER) RECENTLY. UNFORTUNATELY THIS IMPORTANT TELECONNECTION INDEX IS TOUGH TO OUTLOOK MORE THAN WEEKS IN ADVANCE. WHILE THE ARCTIC OSCILLATION AND NORTH ATLANTIC OSCILLATION NORMALLY WORK IN TANDEM, ITS NOT ALWAYS THE CASE. SINCE 1950, 60 PERCENT OF ALL WINTERS HAVE AVERAGED A NEGATIVE ARCTIC OSCILLATION, BUT ONLY 42 PERCENT OF ALL WINTERS HAVE AVERAGED A NEGATIVE NORTH ATLANTIC OSCILLATION. THE LATE JACK ORDILLE POINTED US TO A RESEARCH PAPER USING NEWFOUNDLAND REGION SPRING-SUMMER SEA SURFACE TEMPERATURE ANOMALIES AS A PREDICTOR OF THE NAO FOR THE ENSUING WINTER. IT HAS WORKED WELL THE LAST COUPLE OF WINTERS (HERE COMES THE JINX) AND IT FAVORS A NEGATIVE NAO FOR THIS UPCOMING WINTER. THIS BRINGS US TO OUR LAST (BUT NOT LEAST) OSCILLATION INDEX, THE PACIFIC DECADAL OSCILLATION (PDO). CURRENTLY THE OSCILLATION IS IN TEXTBOOK POSITIVE POSITION. SO MUCH SO, THAT WHEN ITS BEEN THIS POSITIVE DURING THE MONTH OF OCTOBER, IT HAS NEVER AVERAGED NEGATIVE (HERE COMES ANOTHER ANNOUNCER`S JINX: 15 OF 15 TIMES SINCE 1900) DURING THE UPCOMING WINTER. ELEVEN OF THOSE WINTERS HAVE AVERAGED COLDER THAN THE CURRENT AVERAGE (AND AVERAGED AROUND 20 INCHES OF SNOW) IN PHILADELPHIA. HISTORICALLY ABOUT 2/3RDS OF ALL WINTERS SINCE 1900 HAVE AVERAGED COLDER THAN NORMAL IN PHILADELPHIA WHEN THE PDO HAS AVERAGED POSITIVE. IN FACT, THE GREATEST POINT OF FAILURE WHEN WARM OCTOBERS HAVE NOT BEEN FOLLOWED BY WARMER WINTERS HAS BEEN WHEN THE PDO HAS BEEN STRONGLY POSITIVE IN THE AUTUMN. LOCALLY, OF THE 46 WARMEST WINTERS IN PHILADELPHIA ON RECORD, HALF OF THEM HAVE OCCURRED AFTER A WARM OCTOBER. GIVEN THE STATE OF THE PDO, WE DON`T HAVE A WARM FEELING ABOUT THAT THIS WINTER. THIS NOVEMBER WILL END AGAIN CLOSE TO THE CUSP BETWEEN THE UNSEASONABLY COLD AND NORMAL TERCILES. REGARDLESS THIS IS A RARER OCCURRENCE AND A CONTRADICTION IN THE STUDY FIRST DONE IN WHICH THE STRONGEST CORRELATOR FOR A WARM WINTER IS A WARM OCTOBER WHILE THE STRONGEST CORRELATOR FOR A COLD WINTER IS A COLD NOVEMBER. IN 2012 OCTOBER WON, LAST YEAR NOVEMBER WON. UNLIKE THE LAST TWO WINTERS, WE ARE EXPECTING A WEAK EL NINO AND NOT ENSO NEUTRAL NEGATIVE. WHILE THE PACIFIC FAVORS COLD AGAIN, THE TYPE OF COLD LOOKS DIFFERENT AS POSITIVE SEA SURFACE TEMPERATURE ANOMALIES ARE FARTHER EAST THAN THEY WERE LAST AUTUMN. SO HERE ARE OUR ANALOGS FOR THE UPCOMING WINTER. THEY ARE BASED ON WARMER THAN CURRENT NORMAL OCTOBERS AND COLDER THAN CURRENT NORMAL NOVEMBERS. THE ANALOGS ARE A COMBINATION OF MODERATE, WEAK AND ENSO POSITIVE WINTERS. SEVEN OF THESE ALSO HAD POSITIVE PDO(S) DURING THE WINTER, THE ONE EXCEPTION (1953-4) WE KEPT BECAUSE IT WAS A WEAK EL NINO AND IT ALSO WAS A SNOWY NOVEMBER. AS ALWAYS PAST PERFORMANCE MAY NOT BE AN INDICATOR OF FUTURE TRENDS....AND NOW TO THE GREAT EIGHT: SEASON DEC JAN FEB WINTER SEASONAL WINTER AVG AVG AVG AVG SNOWFALL PCPN 1905-06 39.2 39.4 33.6 37.4 20.5 8.61 1914-15 33.3 36.6 38.6 36.2 32.5 19.64 1939-40 38.1 25.3 34.8 32.7 22.3 7.77 1941-42 38.3 30.5 30.8 33.2 10.3 9.24 1951-52 38.7 37.3 38.2 38.1 16.2 12.21 1953-54 39.4 31.7 41.7 37.6 22.6 7.58 1986-87 37.9 31.9 32.5 34.1 25.7 11.64 2002-03 35.4 28.6 29.9 31.3 46.3 11.02 AVG 37.5 32.7 35.0 35.1 24.6 11.59 1981-2010 NML 37.5 33.0 35.7 35.4 22.4 9.24 THE OFFICIAL CPC OUTLOOK FOR THE WINTER IS FOR EQUAL CHANCES OF IT BEING EITHER WARMER OR COLDER THAN NORMAL AND A GREATER CHANCE OF IT BEING WETTER THAN NORMAL. WE HOPE EVERYONE HAD A GREAT THANKSGIVING AND WE HOPE YOU WILL HAVE A HAPPY UPCOMING HOLIDAY SEASON. MAY THIS WINTER BE BEYOND YOUR WILDEST EXPECTATIONS. && .EQUIPMENT... THE DIX RADAR OUTAGE IS EXPECTED TO CONTINUE UNTIL THE TECHNICIANS ARE ABLE TO REPLACE THE BAD HARDWARE ON SATURDAY. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...ROBERTSON/DRAG 955 NEAR TERM...DRAG 955 SHORT TERM...KLEIN LONG TERM...ROBERTSON AVIATION...DRAG/KLEIN/ROBERTSON 955 MARINE...DRAG/KLEIN/ROBERTSON 955 CLIMATE... EQUIPMENT...

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