Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 111952 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 252 PM EST THU FEB 11 2016 .SYNOPSIS...
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HIGH PRESSURE WILL SETTLE ACROSS THE AREA TONIGHT AND THEN MOVE TO THE EAST FRIDAY. A LOW PRESSURE AREA WILL MOVE ACROSS SOUTHERN CANADA AND CAUSE AN ARCTIC FRONT TO CROSS OUR AREA FRIDAY NIGHT. HIGH PRESSURE WILL BUILD IN OVER THE WEEKEND AND CREST OVER THE REGION SUNDAY NIGHT. LOW PRESSURE WILL AFFECT THE ARE EARLY NEXT WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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THROUGH 8 PM...CONTINUING SNOW SHOWER FORECAST, POSSIBLY BRIEFLY HEAVY WITH BRIEF SMALL ACCUMULATIONS. I THINK MOSTLY HIGHER TERRAIN UNLESS WE CAN SEE SOME BANDS ORGANIZE LATE THIS AFTERNOON. NOT GIVING UP, THOUGH DRIER DEWPOINTS AND 20+ TT/TD SPREADS ARGUE AGAINST ACCUMS ANYWHERE SE OF A KABE-KMMU LINE. HOWEVER, HAVE SEEN BANDS ORGANIZE BEFORE AND A SLIGHT INCREASE IN RH CAN PERMIT PROBLEM SNOW SQUALLS. WILL CHECK AT 320 PM FOR A FINAL DECISION ON HOW TO HOPEFULLY BEST FORECAST THE PERIOD 330 PM TO 8 PM. THE SCIENCE BEHIND THE SNOW SHOWERS...EXTREME AND MOIST BOUNDARY LAYER LAPSE RATES ASSOCIATED WITH THE COLD POOL UP THROUGH MID LVLS--- ROUGHLY 500MB. BOTH THE BGM WINDEX TOOL AND THE BTV SNOWSQUALL PARM TOOLS INDICATED HUGE VALUES BOTH THIS MORNING, THIS AFTERNOON AND PROBABLY AGAIN SATURDAY WITH REAL DEAL TRUE ARCTIC PLUNGE. TONIGHT...SNOW SHOWERS DRY OUT OR TRAIL ESEWD OUT TO SEA THIS EVENING AS THE SFC HEATING WANES AND THE COLD POOL ALOFT WARMS A BIT. SKIES CLEAR MOST OF THE AREA AND WINDS DIMINISH AS A RIDGE OF HIGH PRESSURE POKES FROM THE SOUTHWEST IN WITH SOME RADIATIONAL COOLING ON TODAYS FRESHENED SNOW COVER. RAN A 50 50 BLEND OF 12Z/11 GFS/NAM MOS BUT WILL PROBABLY ALLOW FOR COOLER THAN THIS FCST BY 2-3 DEGREES OVER E PA AND NW NJ RADIATORS. SHOULD GET CLOSE TO ZERO IN PARTS OF E PA RADIATIORS PER GFS 2M TEMPS. WESTERLY WINDS DIMINISH AND BECOME LIGHT LATE. CONFIDENCE: AVERAGE.
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&& .SHORT TERM /FRIDAY/...
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SUNNY, THEN INCREASING AND THICKENING CLOUDS AHEAD OF THE JAMES BAY ARCTIC VORTEX DIVING SEWD...MAINLY HIGH CLOUDS UNTIL LATE IN THE DAY. WINDS TURN SW AND THE UNSTABLE AND MOISTENING BOUNDARY LAYER LAPSE RATES OVER THE STILL OPEN WATERS OF THE BAYS MAY YIELD SOME BAY EFFECT FLURRIES LATE IN THE DAY. OTHERWISE, SNOW SHOWERS IN THE WAA PATTERN IN PA COULD DEVELOP FLURRIES OR SNOW SHOWERS IN THE POCONOS NEAR 5 PM. SW WIND. 50 50 BLENDED 12Z/11 GFS/NAM MOS GUIDANCE. CONFIDENCE: AVERAGE.
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&& .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... OUR UPDATED BRIEFING PACKAGE AT MIDDAY WILL INCLUDE MORE INFORMATION ON THE UPCOMING DANGEROUS COLD, INCLUDING A POSSIBLE WIND CHILL WATCH FOR SAT NIGHT WHICH IS ALREADY A HIGH CONFIDENCE LIKELIHOOD. THE EXTENDED WILL FEATURE BOTH THE PROSPECTS FOR THE COLDEST AIR OF THE SEASON CENTERED ON SUNDAY MORNING AND A STRENGTHENING LOW PRESSURE SYSTEM TRACKING UP THE EAST COAST EARLY NEXT WEEK. FRIDAY AND SATURDAY: HIGH PRESSURE WILL MOVE THROUGH THE REGION ON FRIDAY. THIS HIGH PRESSURE SYSTEM WILL GIVE WAY TO ANOTHER ARCTIC COLD FRONT FRIDAY NIGHT. THE COLD FRONT SHOULD PROVIDE ENOUGH LIFT AND MOISTURE FOR SOME SCATTERED SNOW SHOWERS TO DEVELOP. THESE MAY PRODUCE SOME LIGHT ACCUMULATIONS OF UNDER AN INCH. BEHIND THE FRONT, IT WILL BE A VERY COLD AND WINDY PERIOD WITH SOME ADDITIONAL SNOW SHOWERS AND/OR FLURRIES IN ASSOCIATION WITH THE NW FLOW OFF OF THE EASTERN GREAT LAKES. THE FAVORED REGIONS TO SEE SNOW SHOWERS ARE IN THE HIGH TERRAIN AREAS OF EASTERN PA AND NW NJ. BUFKIT ANALYSIS YIELDS THE POTENTIAL FOR 30-40 MPH GUSTS SATURDAY AFTERNOON ACROSS THE REGION WITH THE GFS BEING THE MOST AGGRESSIVE WITH THE GUST POTENTIAL. THE STRONG CAA WILL NOT ALLOW TEMPERATURES TO RISE MUCH DURING THE DAY. SATURDAY NIGHT THROUGH SUNDAY NIGHT: ANOTHER POTENT AREA OF ARCTIC HIGH PRESSURE WILL BUILD INTO THE REGION WITH THE COLDEST SHOT OF AIR OF THE SEASON SO FAR. MODELING HAS BEEN HOLDING STEADY ON THE IDEA THAT 850 MB TEMPERATURES LOOK TO DIVE BELOW -25C. WILL NUDGE TEMPERATURES A COUPLE OF DEGREES COOLER THAN MOST ENSEMBLE GUIDANCE THROUGH THE WEEKEND DUE TO THE DEGREE OF THE COLD AIR BEING MODELED. STRONG NORTHWEST WIND GUSTS, THOUGH NOT AS STRONG AS ON SATURDAY WILL CONTINUE IN THE WAKE OF THE DEPARTING SYSTEM. THE COLD AND WIND WILL RESULT IN WIND CHILLS FROM -10 TO -30 BELOW ZERO SATURDAY NIGHT AND SUNDAY MORNING. PLEASE TO MAKE SURE TO PREPARE FOR THE COLD WEATHER THAT IS COMING. PREPARATIONS INCLUDE CHECKING PIPES AND MAKING SURE YOUR VEHICLE IS IN GOOD WORKING CONDITION. LOW TEMPERATURES SUNDAY MORNING WILL LIKELY NEAR OR BELOW ZERO AS WELL. PLEASE REFER TO THE CLIMATE SECTION ON RECORD POTENTIAL. PRESIDENTS DAY THROUGH TUESDAY NIGHT: HIGH PRESSURE WILL GRADUALLY MOVE EAST OF THE REGION AND WILL GIVE WAY TO A STORM SYSTEM THAT IS CURRENTLY MODELED TO FORM ACROSS THE SOUTHERN UNITED STATES AND INTENSIFY AS IT MOVES UP THE EAST COAST. THE 00Z 2/11 OPERATIONAL MODELS HAVE NARROWED THE GOAL POSTS OF POSSIBLE TRACKS FROM EARLIER MODEL RUNS. THIS ALSO MATCHES OR IS JUST EAST OF THE 12Z 2/10 ECMWF ENSEMBLE MEAN TRACK. THIS TRACK GOES FROM SOUTH CENTRAL AL/GA NORTHEAST TO THE CAROLINA COASTLINE THEN DUE NORTH UP THE EAST COAST INTO SOUTHERN NEW ENGLAND. TWO MAIN FEATURES ARE PRESENT TO TRACK WITH REGARDS TO MODELS OR RESPECTIVE ENSEMBLES CHANGING THE FORECAST TRACK OF THIS SYSTEM IN FUTURE RUNS. THIS FIRST IS A LEADING SHORTWAVE WHICH MOVES INTO THE THE OHIO VALLEY ON MONDAY AND THE SECOND IS THE DEGREE OF MID- LEVEL HEIGHT RISES THAT OCCUR AHEAD OF THE STORM SYSTEM. A STRONGER SHORTWAVE WOULD TEND TO PUSH THE OVERALL TROUGH WITH THIS STORM FURTHER EAST. WHILE A WEAKER SHORTWAVE WOULD ALLOW FOR HIGHER MID- LEVEL HEIGHT RISES LEADING TO A FURTHER WEST TRACK OF THE LOW. RIGHT NOW THE FAVORED TRACK WOULD RESULT IN SNOW CHANGING TO RAIN ACROSS MOST OF THE REGION WITH THE HIGHEST CHANCES FOR PRECIPITATION MONDAY NIGHT AND TUESDAY. IT WILL LIKELY BE WINDY AS WELL WITH THE STRENGTHENING LOW PRESSURE SYSTEM TRACKING NEAR THE REGION. WEDNESDAY: THE REGION SHOULD GRADUALLY BEGIN TO CLEAR OUT AS ANOTHER HIGH PRESSURE SYSTEM BUILDS EASTWARD TOWARD THE REGION. SOME UNCERTAINTY THOUGH AS 2/11 00Z ECMWF BRINGS ANOTHER SYSTEM INTO THE REGION BY THIS PERIOD. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. REST OF TODAY...VFR SCT-BKN AOA 4000 FT. BRIEF MVFR/IFR CONDS IN SNOW SHOWERS MAY DEVELOP AROUND KABE/KRDG AND KTTN DURING MID TO LATE AFTERNOON AND MAY SLIP SOUTH TOWARD THE VICINITY OF KPHL AND KPNE AROUND 22Z. A WESTERLY WIND WILL CONTINUE TO BE QUITE GUSTY TO AROUND 30 KNOTS, WITH A FEW ISOLATED GUSTS TO 35 KNOTS. THE SNOW SHOWERS ARE ASSOCIATED WITH EXTREMELY LARGE AND MOIST LOW LVL LAPSE RATES. ALSO AIDING MAY BE THE LAKE ERIE MOISTURE PLUME (RECENTLY LARGELY NON ICE COVERED). THIS EVENING AND TONIGHT...VFR SCT-BKN CLOUDS AOA 4000 FT DURING THE EVENING BECOMING MAINLY CLEAR OR WITH JUST A LITTLE CIRRUS OVERHEAD. ANY LEFTOVER SNOW SHOWERS SHOULD END BETWEEN ABOUT 0Z TO 02Z. GUSTY WNW WINDS 20-30 KT INTO THE EVENING WILL SLOWLY DIMINISH LATER DURING THE NIGHT. FRIDAY...VFR CONDITIONS ARE EXPECTED. CIRRUS CIGS ARRIVE AND THEN LOWER DURING THE AFTN. SOUTHWESTERLY WINDS ARE EXPECTED, MAINLY AROUND 10 KNOTS OR LESS. OUTLOOK... FRIDAY NIGHT AND SATURDAY: MAINLY VFR, POSSIBLE MVFR RESTRICTIONS IN SCATTERED SNOW SHOWERS. NORTHWEST WINDS INCREASING SATURDAY FROM 15-25 KNOTS WITH GUSTS UP TO 40 KNOTS SATURDAY AFTERNOON. SATURDAY NIGHT AND SUNDAY...VFR CONDITIONS EXPECTED. NORTHWEST WINDS 10 TO 25 KNOTS. MONDAY...VFR CONDITIONS FOR MOST OF THE DAY THEN BECOMING MVFR AND IFR BY EVENING WITH RAIN AND SNOW.
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&& .MARINE...
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GALES IN PROGRESS AND GLW CONTINUES AS POSTED. AN SCA WILL BE NEEDED FOR MUCH IF NOT ALL OF THE OVER NIGHT HOURS ONCE THE GALES SUBSIDE. LIGHT FREEZING SPRAY IS OCCURRING AND CONTINUES TO BE EXPECTED ON THE BAY AS WELL AS THE NEAR COASTAL WATERS THROUGH TONIGHT. FRIDAY NO HEADLINE! A GOOD DAY TO FINISH UP ANY MARINE RELATED ACTIVITY. OUTLOOK... SO WHILE, SEAS AND WINDS WILL START OUT FAIRLY LIGHT ON FRIDAY. HOWEVER, A QUICK RAMP UP IS EXPECTED AFTER THE PASSAGE OF AN ARCTIC COLD FRONTAL BOUNDARY FRIDAY NIGHT. NORTHWEST WINDS WILL INCREASE AND REACH GALE FORCE BY SATURDAY AND CONTINUE GALE FORCE THROUGH SATURDAY NIGHT. CONFIDENCE FOR GALES ON SATURDAY IS VERY HIGH. SEAS WILL RISE TO BETWEEN 5 AND 7 FEET FOR A PERIOD AS WELL ON SATURDAY. SEAS AND WINDS ARE EXPECTED TO DECREASE ON SUNDAY. WAVE HEIGHTS WILL LIKELY START INCREASING AGAIN BY MONDAY NIGHT IN RESPONSE TO A DEVELOPING LOW PRESSURE SYSTEM TO OUR SOUTH.
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&& .CLIMATE...
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NEAR RECORD COLD IS EXPECTED FOR PORTIONS OF OUR AREA SUNDAY MORNING AND BY FAR THE COLDEST AIR OF THE SEASON SO FAR. ANTICIPATING TEMPS THROUGHOUT OUR FORECAST AREA WITHIN SEVERAL DEGREES OF ZERO (WIND IS THE EQUALIZER) ANYTIME FROM MIDNIGHT THROUGH 8 AM SUNDAY EXCEPT COLDER KMPO (NEAR -12F). THIS HAS BEEN ADVERTISED BY THE GFS/ECMWF 2M TEMPS CYCLICALLY SINCE AT LEAST THE 00Z/7 OPERATIONAL CYCLES. THEREFORE, BEST CHANCE FOR RECORD EQUALING OR EXCEEDING FOR VALENTINES DAY THE 14TH WOULD BE KABE, KTTN, KPHL AND KMPO. SNOW COVER MAY HELP A BIT I-95 NORTHWESTWARD...AND WE`LL SEE WHERE WE ARE WITH SNOW COVER BY THURSDAY EVENING. NEW DUSTINGS APPEAR ON THE WAY THROUGH FRIDAY NIGHT. PLEASE NOTE... GUIDANCE IN PART IS BEING CLIMO BIASED HIGHER THAN WHAT THE ONCOMING GFS/ECMWF LITERAL AIRMASS AND 2M TEMPS ARE INDICATING FOR SUNDAY MORNING. TEMPS SUNDAY MORNING IN THE URBAN AREAS SHOULD BE ABOUT 25 COLDER THAN NORMAL. THAT MEANS GUIDANCE TEMPS FOR PHL OF 5 AND 6 DEGREES APPEAR TOO WARM...ESPECIALLY WITH A NORMAL PHILADELPHIA LOW ON SUNDAY OF 28. HAVE SEEN THE 12Z/11 2M TEMPS FOR PHL...1 ABOVE RANGING DOWN TO -11 AT KMPO AND AM LIKING THOSE VALUES AS WITHIN 2F OF THE UPCOMING REALITY. RECORD LOW MAX`S CAN ONLY OCCUR FOR THIS EVENT ON SUNDAY THE 14TH, IF THEN. THOSE HAVE BEEN ADDED RECENTLY BELOW. SITE 2015-16 COLDEST SO FAR RECORD LOW FEB. 14TH ----RER LOW MAX ---------------------- -------------------- ABE 8 -1 IN 1979 14-1979 ACY 10 -6 IN 1979 13-1979 PHL 12 +2 IN 1979 14-1979 ILG 12 -4 IN 1979 13-1979 RDG 10 -4 IN 1983 TTN 9 0 IN 1916 GED 13 -7 IN 1979 MPO -1 -12 IN 1970 SO, THIS WILL BE WIND DRIVEN COLD WITH MANY AREAS EXPERIENCING WIND CHILL VALUES OF 15 TO 25 BELOW ZERO...POSSIBLY 30 BELOW IN THE HILLS AND MOUNTAINS OF NORTHWEST NEW JERSEY AND NORTHEAST PENNSYLVANIA.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...WIND CHILL WATCH FROM SATURDAY EVENING THROUGH SUNDAY MORNING FOR PAZ054-055. NJ...WIND CHILL WATCH FROM SATURDAY EVENING THROUGH SUNDAY MORNING FOR NJZ001. DE...NONE. MD...NONE. MARINE...GALE WATCH FROM LATE FRIDAY NIGHT THROUGH SUNDAY MORNING FOR ANZ430-431-450>455. GALE WARNING UNTIL 1 AM EST FRIDAY FOR ANZ450>455. GALE WARNING UNTIL 11 PM EST THIS EVENING FOR ANZ430-431.
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&& $$ SYNOPSIS...O`HARA 252 NEAR TERM...DRAG 252 SHORT TERM...DRAG 252 LONG TERM...GAINES AVIATION...DRAG/GAINES/KLINE 252 MARINE...DRAG/GAINES 252 CLIMATE...

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