Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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981 FXUS61 KPHI 111959 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 259 PM EST THU FEB 11 2016 .SYNOPSIS... 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. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 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. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... 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. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
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A BITTERLY COLD ARCTIC AIR MASS WILL BE ACROSS THE AREA DURING THE BEGINNING OF THE LONG TERM. A COLD FRONT WILL CROSS THE AREA FRIDAY NIGHT ACCOMPANIED BY SNOW SHOWERS AND GUSTY WINDS. THIS WILL USHER IN THE COLD WINDS WITH TEMPERATURES DROPPING THROUGH THE TEENS IN MOST AREAS AND REACHING THE SINGLE DIGITS ACROSS THE NORTH. THE TEMPERATURES WILL NOT RECOVER MUCH SATURDAY WITH HIGHS MOSTLY IN THE TEENS NORTH AND LOW 20S SOUTH. WIND CHILL VALUES MUCH OF THE DAY WILL BE IN THE SINGLE DIGITS WITH SUB-ZERO READINGS NORTH. WE HAVE ISSUED A WIND CHILL WATCH FOR THE SRN POCONOS AND NW NJ FOR SAT NIGHT INTO SUNDAY MORNING...WHEN THE COLDEST AIR WILL BE OVER THE AREA. WIND CHILL READINGS IN THESE AREAS WILL BE -25 TO -30 DEGREES. A FEW SNOW SHOWERS ACROSS THE HIGHER ELEVATIONS OF NE PA / NRN NJ SATURDAY. TEMPERATURES WILL MODERATE MON AND THEN TREND BACK ABOVE NORMAL FOR TUE/WED. THESE WARMER TEMPS WILL ARRIVE AT THE SAME TIME AS A WET WEATHER SYSTEM APPROACHES FROM THE SW. PRECIPITATION WILL PROBABLY BEGIN MONDAY NIGHT AND CONTINUE INTO WEDNESDAY. MANY OF THE OPERATIONAL MODELS ARE INDICATING ENOUGH OF A WARM-UP SO THAT MOST OF THE PRECIPITATION WILL BE RAIN. IT LOOKS POSSIBLE THAT SOME OF THE PRECIPITATION INITIALLY COULD BE SNOW OR SOME SLEET/FREEZING RAIN. WE WILL JUST HAVE RAIN/SNOW IN THE GRIDS FOR NOW WITH LIMITED CONFID IN PLACEMENT OF ANY FROZEN PCPN. THE STORM WILL PULL AWAY FROM THE REGION NEXT WED AND MORE HIGH PRESSURE WILL ARRIVE LATER IN THE DAY AND LAST INTO THURSDAY. TEMPERATURES FOR THIS PERIOD WILL BE WITHIN A FEW DEGREES OF SEASONAL NORMS.
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&& .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. TUESDAY...WIDESPREAD LOWER CIGS/VSBYS WITH RAIN AND POSSIBLY 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... GALES WILL CONTINUE FRIDAY NIGHT THRU SUNDAY MORNING. CONDITIONS WILL DECREASE BACK TO SCA CONDITIONS FOR AWHILE SUNDAY BEFORE RETURNING TO SUB-SCA CONDITIONS. MORE SCA CONDITIONS POSSIBLE TUE.
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&& .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...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. && $$ SYNOPSIS...O`HARA NEAR TERM...DRAG SHORT TERM...DRAG LONG TERM...O`HARA AVIATION...DRAG/O`HARA/GAINES MARINE...DRAG/O`HARA CLIMATE...

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