Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 272326 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 626 PM EST THU NOV 27 2014 .SYNOPSIS... HIGH PRESSURE IS FORECAST TO BUILD ACROSS THE EAST COAST FRIDAY INTO FRIDAY NIGHT, BEFORE MOVING TO THE SOUTH AND EAST SATURDAY INTO SATURDAY NIGHT. A WARM FRONT MAY LIFT NORTH OF THE AREA SATURDAY NIGHT INTO SUNDAY. A COLD FRONT IS EXPECTED TO SAG DOWN ACROSS THE AREA SUNDAY NIGHT, BEFORE SLOWLY MOVING THROUGH THE AREA MONDAY INTO MONDAY NIGHT. HIGH PRESSURE WILL THEN BRIEFLY RETURN TO THE NORTHEAST FOR TUESDAY, FOLLOWED BY ANOTHER FRONTAL SYSTEM AROUND WEDNESDAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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NO BIG CHANGES WILL BE MADE WITH THIS UPDATE, MAINLY ADJUSTMENT TO SKY GRIDS. THE COASTAL LOW THAT BROUGHT WINTRY WEATHER TO THE NORTHWESTERN HALF OF THE FORECAST AREA YESTERDAY IS NOW OVER THE CANADIAN MARITIMES. MEANWHILE, THE UPPER TROUGH ASSOCIATED WITH THIS SYSTEM IS POSITIONED BACK OVER THE EASTERN CONUS. THE SNOW SHOWER ACTIVITY THAT BROUGHT LIGHT SNOWFALL ACCUMULATIONS TO THE HIGHER ELEVATIONS OF THE NORTHEAST PA AND NW NJ THIS MORNING HAS EXITED THE AREA AND IS NOW OVER SOUTHERN NEW ENGLAND. SUBSIDENCE BEHIND THE EXITING SHORTWAVE TROUGH IS MOVING IN, YIELDING SOME BREAKS IN THE CLOUDS. TEMPS HAVE BEEN ABLE TO RISE INTO THE 40S ACROSS THE NORTHERN DELMARVA AND SOUTHERN NJ WHERE CLEARING HAS BEEN MOST PROMINENT. TEMPS WERE STUCK IN THE 30S THIS AFTERNOON. STRATOCU SHOULD ERODE THIS EVENING WITH THE LOSS OF DAYTIME MIXING AND AS DRIER AIR NEAR 925 MB ADVECTS INTO THE AREA. MID AND HI CLOUDS WILL THEN SPREAD IN FROM THE WEST LATE TONIGHT AS THE NEXT UPPER SHORTWAVE TROUGH APPROACHES FROM THE GREAT LAKES. MIN TEMPS TONIGHT RANGE FROM NEAR 20F IN THE POCONOS TO NEAR 30F IN THE DELMARVA, SOUTHERN NJ COAST AND IN CENTER CITY PHILLY.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... THE UPPER TROUGH AXIS IS EXPECTED TO PROGRESS EAST OF THE MID- ATLANTIC REGION BY 12Z FRIDAY. SUBSIDENCE IN ITS WAKE WILL BE ACCOMPANIED BY CLEARING SKIES AND DRY WEATHER FOR BLACK FRIDAY. A CAA REGIME UNDER NORTHWEST FLOW BEHIND THE TROUGH WILL PERSIST AS WELL. SO DESPITE SUNSHINE TOMORROW VS CLOUDY SKIES TODAY, MAX TEMPS FRIDAY WILL BE SEVERAL DEGREES COOLER THAN TODAY. HIGHS RANGE FROM THE UPPER 20S IN THE POCONOS TO NEAR 40F ALONG THE COAST. EXPECT WINDS TO BE BREEZY (GUSTS 20-25 MPH) IN THE MORNING AS HIGH PRESSURE BUILDS IN FROM THE TENNESSEE VALLEY. THE WINDS RELAX A BIT LATE IN THE DAY WHEN THE HIGH SHIFTS OVERHEAD. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... HIGH PRESSURE OVER THE AREA FRIDAY NIGHT WILL BEGIN TO MOVE TO OUR SOUTH AND EAST BY SATURDAY AND SATURDAY NIGHT. SEVERAL WEAK SHORT WAVE/VORTICITY IMPULSES ARE FORECAST TO SLIDE ACROSS THE AREA FRIDAY NIGHT, SATURDAY, AND SATURDAY NIGHT, ALONG WITH AN INCREASE IN MOISTURE ALOFT ACROSS THE NORTHERN AREAS. THERE IS SOME TIMING DIFFERENCES, BUT THERE IS SOME POTENTIAL FOR SOME LIGHT PRECIPITATION TO DEVELOP DURING THIS TIME PERIOD. WE WILL KEEP A SLIGHT CHANCE OF SHOWERS ACROSS OUR NORTHERN ZONES WHERE THEY HAVE A BETTER CHANCE OF SQUEEZING OUT SOME MOISTURE. ANYTHING THAT WOULD FALL IS EXPECTED TO BE LIGHT. ON SUNDAY, WE WILL BE IN BETWEEN THE HIGH TO OUR EAST AND AN APPROACHING COLD FRONT. ANOTHER WEAK SHORT WAVE/VORTICITY IMPULSE AND MOISTURE PLUME ALOFT SPREAD ACROSS THE NORTHERN HALF OF THE AREA SUNDAY, SO THERE REMAINS 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. THERE CONTINUES TO BE SOME SLIGHT DIFFERENCES WITH THIS BOUNDARY WITH THE GFS THE FASTEST, THE CANADIAN THE SLOWEST, AND THE ECMWF IN BETWEEN. ALSO THERE AREA DIFFERENCES WITH QPF AMOUNTS, SO WE WILL KEEP CHANCE/SLIGHT CHANCE POPS ACROSS THE AREA DURING THIS PERIOD. THE FRONT SHOULD PUSH TO OUR SOUTH AS HIGH PRESSURE BRIEFLY BUILDS ACROSS THE NORTHEAST TUESDAY. THE GFS AND ECMWF INDICATE DRIER AIR BUILDING ACROSS THE AREA DURING THE DAY, SO WE MAKE THE FORECAST DRY FOR TUESDAY DAY. ANOTHER FRONTAL SYSTEM IS EXPECTED TO AFFECT THE AREA AROUND NEXT WEDNESDAY. A WARM FRONT MAY LIFT ACROSS THE AREA TUESDAY NIGHT AS THE HIGH RETREATS NORTHEASTWARD, BEFORE A COLD FRONT MOVES ACROSS THE AREA ON WEDNESDAY. PRECIPITATION CHANCES INCREASE TUESDAY INT WEDNESDAY, THEN LOWER BEHIND THE FRONT WEDNESDAY NIGHT INTO THURSDAY AS HIGH PRESSURE BUILDS BACK ACROSS THE NORTHEAST AGAIN. && .AVIATION /23Z THURSDAY THROUGH TUESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. 00Z TAFS ARE VFR. FOR TONIGHT SOME PATCHY VFR CLOUDS NEAR THE BORDER OF LOW AND MID CLOUD LEVEL PREDICTED AS TWO DISTURBANCES TO OUR WEST PASS THROUGH. HIGHEST CONFIDENCE OF A CIG ARE AT WESTERN AIRPORTS AND TERMINALS. NORTHWEST WINDS WILL AVERAGE 5 TO 10 KNOTS. NO VSBY RESTRICTIONS. ON FRIDAY, NO CIGS ARE PREDICTED, POSSIBLY A SCATTERED DECK OF SOME RATHER FLAT LOOKING STRATOCU CLOUDS. NORTHWEST WINDS WILL FRESHEN WITH SUSTAINED SPEEDS AVERAGING 10 TO 15 KNOTS AND PEAK GUSTS AROUND 20 KNOTS. THE HIGHEST GUSTS ARE EXPECTED TO OCCUR FROM MID MORNING INTO EARLY AFTERNOON WITH A SLOW DECREASE IN SPEEDS AND GUSTS THEREAFTER. START OF FRIDAY EVENING, A MUCH LIGHTER NORTHWEST WIND WITH AN ADVANCING MID LEVEL VFR CIG PREDICTED. OUTLOOK... FRIDAY NIGHT-MONDAY...MOSTLY VFR. WIND GUSTS 15-20 KNOTS EACH DAY; SOUTHWEST SATURDAY & SUNDAY, AND NORTHWEST ON MONDAY. MONDAY NIGHT...CHANCE OF RAIN OR SNOW SHOWERS. GENERALLY VFR UNLESS PRECIPITATION OCCURS. GUSTY NORTHWEST WINDS AROUND 20 KNOTS POSSIBLE. TUESDAY...MOSTLY VFR.
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&& .MARINE...
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THE SCA FOR HAZARDOUS SEAS THAT WAS IN EFFECT FOR THIS AFTN HAS BEEN CANCELLED. HOWEVER, A NEW SCA WAS ISSUED FOR TONIGHT AND FRIDAY FOR THE DE BAY AND MOST OF THE OCEAN ZONES TO COVER THE EXPECTED NORTHWEST PRESSURE SURGE. MIXING WILL BE EFFECTIVE WITH EVEN COLDER AIR MOVING ABOVE THE RELATIVELY WARMER WATERS. THE ONE EXCEPTION TO THE SCA IS THE COASTAL WATERS FROM SANDY HOOK TO MANASQUAN INLET. THE SCA FOR THIS NORTHERN MOST ZONE IS ONLY IN EFFECT FRIDAY SINCE THE PRESSURE GRADIENT WILL BE A BIT WEAKER TONIGHT AND THE GUST POTENTIAL SHOULD BE CAPPED AROUND 20 KT. OUTLOOK... FRIDAY NIGHT-SATURDAY...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED AS HIGH PRESSURE BUILDS OVER THE WATERS. SATURDAY-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. TUESDAY...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED AS HIGH PRESSURE AFFECTS THE WATERS.
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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 DONT 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 IS HAVING A GREAT THANKSGIVING AND WE HOPE YOU WILL HAVE A HAPPY UPCOMING HOLIDAY SEASON. MAY THIS WINTER BE BEYOND YOUR WILDEST EXPECTATIONS. && .EQUIPMENT... KDIX WSR-88D RADAR IS INOPERATIVE. TECHNICIANS HAVE BEEN NOTIFIED AND WILL TROUBLESHOOT THE ISSUE. TPHL TDWR SHOULD PROVIDE SUFFICIENT BACKUP RADAR COVERAGE. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST FRIDAY FOR ANZ430-431- 451>455. SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EST FRIDAY FOR ANZ450. && $$ SYNOPSIS...ROBERTSON NEAR TERM...GIGI/KLEIN SHORT TERM...KLEIN LONG TERM...ROBERTSON AVIATION...KLEIN/ROBERTSON MARINE...KLEIN/ROBERTSON CLIMATE...GIGI EQUIPMENT...

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