Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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552 FXUS61 KPHI 111714 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1214 PM EST THU FEB 11 2016 .SYNOPSIS... HIGH PRESSURE WILL BUILD EASTWARD INTO THE REGION TODAY AND THEN MOVE THROUGH THE REGION TONIGHT. AN ARCTIC COLD FRONTAL BOUNDARY WILL THEN MOVE THROUGH THE AREA FRIDAY NIGHT. BY SUNDAY, ANOTHER AREA OF HIGH PRESSURE WILL BUILD SOUTHWARD INTO THE REGION AS LOW PRESSURE FORMS ACROSS THE SOUTHERN UNITED STATES BY MONDAY. THIS AREA OF LOW PRESSURE WILL THEN TRACK UP THE EAST COAST TUESDAY INTO WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... 1140 AM ESTF: HAVE UPDATED THE AFTN PACKAGE AND ONLY CHANGES FORTHCOMING WITH THE STANDARD 1230PM MIGHT BE A SLIGHT UPWARD ADJUSTMENT OF SNOW AMTS IN THE POCONOS AND SUSSEX COUNTY NJ. WE HAVE WIDESPREAD 1/2 INCH IN THE GRIDS FOR THE REGION I-78 NORTH BUT THE LEGACY READS FOR THE MOST PART, LITTLE OR NO. "HEAVY" WORDING NOW RESERVED FOR I-78 REGION NORTH THIS AFTN. UPDATED SNOW MAP POSTED. COLD... MINOR ADJUSTMENTS TO THE MID SHIFT TEMPS AND DEWS. WINDS WERE BOOSTED ABOUT 5 MPH ON THE LAND....GUSTS 25-35 MPH. 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 SNOWSQL PARM TOOLS SHOW HUGE VALUES BOTH THIS MORNING, THIS AFTERNOON AND PROBABLY AGAIN SATURDAY WITH REAL DEAL TRUE ARCTIC PLUNGE. TONIGHT...SNOW SHOWERS TRAIL OUT TO SEA AND DISSIPATE 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. WE WILL RUN A 50 50 BLEND OF 12Z/11 GFS/NAM MOS BUT WILL PROBABLY ALLOW FOR COOLER THAN THIS FCST BY SEVERAL DEGREES OVER E PA AND NW NJ RADIATORS. SHOULD GET CLOSE TO 3 ABOVE IN PARTS OF E PA RADIATIORS PER GFS 2M TEMPS. WESTERLY WINDS BECOME LIGHT LATE. && .SHORT TERM /FRIDAY/... SUNNY, THEN INCREASING CLOUDS...MAINLY HIGH CLOUDS. WINDS TURN SW AND THE UNSTABLE AIR 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 AFTER 5 PM. SW WIND. 50 50 BLENDED 12Z/11 GFS/NAM MOS GUIDANCE. && .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 /18Z THURSDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THIS AFTERNOON...VFR SCT-BKN AOA 4000 FT. BRIEF IFR CONDS IN SNOW SHOWERS DEVELOP KTTN/KRDG AND KABE DURING MID AFTN AND MAY SLIP SOUTH TO VCNTY KPHL AND KACY AROUND 22Z. WEST WIND GUSTY AROUND 30 KT, ISOLATED 35 KT. 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). WEST WIND GUSTS INCREASING TO 30 KT BY 16Z. ISOLATED 35 KT POSSIBLE. TONIGHT...VFR SCT-BKN CLOUDS AOA 4000 FT DURING THE EVENING BECOMING CLEAR. ANY LEFTOVER SNOW SHOWERS SHOULD END BY 02Z. GUSTY WNW WINDS 20-30 KT SLOWLY DIMINISHING DURING THE NIGHT. FRIDAY...VFR. CIRRUS CIGS ARRIVE AND THEN LOWER DURING THE AFTN. SW WIND. 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. && .MARINE... 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... OUR MID AFTERNOON MARINE PRODUCTS WILL HEADLINE A NEW HIGH CONFIDENCE GALE WATCH FOR THE PERIOD ROUGHLY 4 AM SATURDAY THROUGH 8 AM SUNDAY. 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. && .CLIMATE... 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. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...GALE WARNING UNTIL 1 AM EST FRIDAY FOR ANZ450>455. GALE WARNING UNTIL 11 PM EST THIS EVENING FOR ANZ430-431. && $$ SYNOPSIS...FRANCK NEAR TERM...DRAG 1214 SHORT TERM...DRAG 1214 LONG TERM...GAINES AVIATION...DRAG/GAINES 1214 MARINE...DRAG/GAINES 1214 CLIMATE...1214

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