Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 081003 AAA AFDPHI AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 503 AM EST MON FEB 8 2016 .SYNOPSIS... A STRONG AREA OF LOW PRESSURE LOCATED ABOUT 300 MILES EAST OF THE OUTERBANKS OF NORTH CAROLINA WILL MOVE NORTHEAST AND FARTHER OUT TO SEA TODAY. ANOTHER AREA OF LOW PRESSURE IS FORECAST TO DEVELOP TONIGHT NEAR THE SOUTHERN MID-ATLANTIC COAST. AFTER THIS LOW QUICKLY MOVE OUT TO SEA EARLY TUESDAY, A WEAKER AREA OF LOW PRESSURE MAY ORGANIZE TUESDAY AFTERNOON AND NIGHT. AN ARCTIC COLD FRONT WILL APPROACH FROM THE NORTHWEST WEDNESDAY BEFORE MOVING THROUGH THE REGION WEDNESDAY NIGHT. HIGH PRESSURE BUILDS IN FROM THE WEST THURSDAY. A CLIPPER SYSTEM IS EXPECTED TO PASS TO OUR NORTH LATE FRIDAY. IN ITS WAKE, A REINFORCING SHOT OF ARCTIC AIR WILL MAKE IT INTO THE REGION FOR THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... LOW CONTINUES TO LIFT NORTHEAST OFF SHORE. STILL HAVEN`T SEEN PRECIP PROPAGATE WEST FAR ENOUGH TO MOVE ON SHORE. HOWEVER, A BAND HAS BECOME MORE DEFINED IN THE RADAR MOSAIC, AND STILL EXPECT THIS TO MOVE ONTO THE NORTHERN NEW JERSEY SHORE NEAR DAY BREAK. HRRR AND RAP SEEM TO BE HANDLING THIS WELL. SO WILL CONTINUE THE THREE COUNTY WINTER WEATHER ADVISORY FOR GENERALLY ONE TO 3 INCHES WITH THE HIGHEST AMOUNTS CLOSER TO THE SHORE. FOR THE REST OF THE REGION, EXPECT MOSTLY DRY CONDITIONS THROUGH THE DAY. THE OTHER CONCERN WILL BE WINDS. ALREADY WINDS AT THE SHORE ARE GUSTING 30 TO 35 KT (35 TO 40 MPH). HOWEVER, THE PRESSURE GRADIENT SHOULD BE DECREASING QUICKLY AFTER DAY BREAK AS THE LOW PULLS AWAY, SO THE WINDS WE ARE SEEING NOW ARE LIKELY GOING TO BE THE STRONGEST WINDS OF THE DAY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... PRECIPITATION, GENERALLY SNOW OR A RAIN AND SNOW MIX WILL START TO MOVE IN FROM THE SOUTHWEST DURING THE EVENING HOURS AS THE LEADING TROUGH LIFTS INTO THE REGION. THE MAIN UPPER LEVEL LOW WILL REMAIN WELL WEST OF THE REGION THROUGH THIS TIME, SO DO NOT EXPECT THE HEAVIEST SNOW TO BE THROUGH THE OVERNIGHT HOURS, AND THE MODELS HAVE IN FACT TRENDED SLIGHTLY DRIER THROUGH THIS PERIOD. EVEN SO, THE SOUTHERN HALF OF THE REGION COULD SEE AS MUCH AS 4 INCHES OF SNOW IF MESOSCALE BANDS DEVELOP EARLY ENOUGH. && .LONG TERM /TUESDAY THROUGH SUNDAY/... THE SECONDARY COASTAL LOW THAT DEEPENS RAPIDLY OFF THE NC OUTERBANKS MONDAY NIGHT IS EXPECTED TO MOVE TOO FAR OFFSHORE ON TUESDAY TO DIRECTLY IMPACT US. HOWEVER, WE AREN`T OUT OF THE WOODS AS MODELS ARE SHOWING THE PRIMARY SURFACE LOW REORGANIZING AS IT MOVES OFF THE DELMARVA COAST ON TUESDAY. THIS SEEMS LIKE A PLAUSIBLE SCENARIO SINCE THE INITIAL MILLER-B LOW IS EXPECTED TO MOVE WELL OUT TO SEA (LEAVING SOME SEPARATION BETWEEN THE TWO) AND THERE LOOKS TO BE ANOTHER MID-LEVEL SHORTWAVE TROUGH ROTATING AROUND THE UPPER LOW THAT WOULD CONTRIBUTE TO HEIGHT FALLS AND COASTAL CYCLOGENESIS. IN THESE TYPES OF SETUPS, ENHANCED FRONTOGENETICAL LIFT AND MESOSCALE BANDING IS FAVORED ON THE NWRN SIDE OF THE LOW. THE 00Z GUIDANCE HAD COME INTO BETTER AGREEMENT AND SHOWS THE POTENTIAL FOR MESOSCALE BANDING IN THEIR MASS/THERMAL FIELDS THAT PRODUCES A RELATIVELY NARROW WEST-EAST ORIENTED BAND OF HEAVIER QPF OVER THE NRN DELMARVA/SERN PA/SRN NJ. PARTIAL THICKNESSES IMPLY ALL SNOW. HOWEVER, THE CURRENT FORECAST OF HIGHS IN THE UPPER 30S FOR THESE AREAS OF CONCERN IMPLY THE LOWER BOUNDARY LAYER IS MARGINALLY SUPPORTIVE OF SNOW. THERE IS CERTAINLY A POTENTIAL THAT SOME RAIN MIXES IN AND/OR SNOW HAS A TOUGH TIME ACCUMULATING...BUT ONLY IF THE INTENSITY OF THE PRECIP IS LIGHT. IF THE HEAVIER SNOW DOES MATERIALIZE, THEN DYNAMICAL COOLING SHOULD BE ENOUGH TO OVERCOME THIS ISSUE. AFTER COORDINATION WITH WPC AND NEIGHBORING WFOS, WE DECIDED IT WAS BEST TO ISSUE A WINTER STORM WATCH FOR FAR SERN PA, NRN DELMARVA AND SRN NJ. THE WHOLE AREA IN THE WATCH WILL LIKELY NOT SEE WARNING CRITERIA SNOWFALL (AND SOME MAYBE SIGNIFICANTLY LESS) BUT THIS IS WHERE THE GREATEST POTENTIAL FOR 5 OR MORE INCHES OF SNOWFALL EXISTS IN A RATHER NARROW SWATH SOMEWHERE APPROXIMATELY AS FAR NORTH AS PHILADELPHIA AND AS FAR SOUTH AS DOVER. ANOTHER CHALLENGE WITH THIS EVENT IS TRYING TO PINPOINT THE TIMING OF THE HEAVIER SNOW. THE WATCH GOES STARTS LATE TONIGHT AND CONTINUES 28 HOURS THROUGH TUESDAY NIGHT. WE ARE NOT EXPECTING A LONG DURATION EVENT BUT WE WENT WIDE IN TIME TO ACCOUNT FOR THE UNCERTAINTY IN WHEN THE HEAVIER SNOW BAND DEVELOPS. ONE CAMP OF MODELS INDICATE IT WILL OCCUR LATE TONIGHT INTO TUESDAY MORNING WHILE OTHER CLUSTER FAVORS LATER TUESDAY AFTERNOON AND NIGHT. FARTHER NORTH INTO NERN PA AND NWRN NJ, WHERE THE POSSIBILITY FOR HEAVIER SNOW IS LOOKING LESS LIKELY AT THIS POINT, LIGHT SNOW MAY ONLY ACCUMULATE AN INCH OR TWO TUESDAY-TUESDAY NIGHT. HOWEVER, WE`LL STILL NEED TO MONITOR FOR THE POSSIBILITY OF THE HEAVIER SNOW BAND SHIFTING NORTHWARD. VERY FEW SCENARIOS CAN BE RULED OUT AT THIS POINT. THE UPPER LOW EVENTUALLY OPENS UP AND THE WAVE PASSES THRU THE AREA ON WEDNESDAY. A KICKER SYSTEM WILL QUICKLY FOLLOW WEDNESDAY NIGHT/EARLY THURSDAY. WE WILL KEEP A LOW CHANCE FOR SNOW SHOWERS DURING THIS TIME BUT ADDITIONAL SNOWFALL ACCUMULATIONS WOULD BE MINOR. THIS SECOND DISTURBANCE WILL ALSO BE ACCOMPANIED BY THE A COLD FRONTAL PASSAGE. IN ITS WAKE, THE SOUTHERN FRINGE OF ARCTIC AIR WILL MAKE ITS WAY INTO THE MID ATLANTIC. TEMPS THURSDAY AND FRIDAY WILL STRUGGLE TO GET ABOVE FREEZING IN THE COASTAL PLAIN AND LIKELY REMAIN IN THE 20S NORTH AND WEST OF THE FALL LINE. A CLIPPER SYSTEM IS EXPECTED TO PASS TO OUR NORTH LATE FRIDAY. A SECONDARY WAVE OF LOW PRESSURE MAY DEVELOP FARTHER SOUTH TOWARD THE BASE OF THE LARGE-SCALE TROUGH AND ON THE SOUTHERN FRINGE OF THE POLAR AIRMASS. FOR THE MOST PART, MODELS ARE SUPPRESSING THE TRACK OF THE LOW TO OUR SOUTH AND DEEPENING IT TOO FAR OFFSHORE TO BRING THE DEEPER ATLANTIC MOISTURE BACK INTO OUR AREA. HOWEVER, THE 00Z ECMWF, WITH SUPPORT FROM SOME OF ITS ENSEMBLE MEMBERS, ARE SHOWING A DEEPER AND MORE NORTHERN SYSTEM, WHICH COULD BRING YET ANOTHER ROUND OF AT SNOW TO OUR REGION. A REINFORCING SHOT OF ARCTIC AIR WILL MAKE IT INTO THE REGION FOR THE WEEKEND. TEMPERATURES COULD BE 15-20F BELOW NORMAL NEXT WEEKEND AND WIND CHILL VALUES BELOW ZERO IN THE HIGHER ELEVATIONS. && .AVIATION /10Z MONDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. FOR THE DELAWARE VALLEY TAF SITES (KPHL, KPNE, KTTN, KILG) AND THE WESTERN TAF SITES (KABE AND KRDG) - MOSTLY VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 21Z. AFTER THAT, AN APPROACHING TROUGH WILL BRING LOWER CEILINGS, AND EVENTUALLY LOWER VISIBILITIES WITH SNOW. LOWER CEILINGS COULD START TO MOVE IN BETWEEN 21 AND 00Z, BUT DO NOT EXPECT THE SNOW TO MOVE IN UNTIL AFTER 00Z. ONCE SNOW BEGINS TO MOVE IN, EXPECT WIDESPREAD IFR CONDITIONS. OUTLOOK... TUESDAY AND TUESDAY NIGHT...PERIODS OF SNOW EXPECTED. THE SNOW MAY MIX WITH RAIN AT MIV AND ACY DURING THE DAY TUESDAY ESPECIALLY AT TIMES WHEN IT IS LIGHTER. THERE IS STILL PLENTY OF UNCERTAINTY REGARDING THE TIMING AND OVERALL IMPACTS AT THE AIRPORTS BUT WE CAN SAY THAT CONFIDENCE HAS INCREASED THAT A NARROW BAND OF HEAVIER SNOW WILL DEVELOP SOMETIME DURING THE PERIOD NEAR THE ILG-PHL-ACY CORRIDOR. EXPECT WIDESPREAD MVFR/IFR CONDS AND THE POSSIBILITY FOR LIFR IF THE HEAVIER SNOW BAND DEVELOPS. WEDNESDAY...LEFTOVER SNOW SHOWERS WILL TAPER OFF FROM WEST TO EAST DURING THE DAY, THEN CONDITIONS IMPROVE TO VFR. BREEZY WLY WINDS GUSTING TO 25 KT. THURSDAY...VFR AND BREEZY NW WINDS GUSTING AOA 30 KT. CONFIDENCE IS HIGH. FRIDAY...CURRENTLY FORECASTING VFR BUT WE ARE WATCHING THE POTENTIAL FOR ANOTHER STORM SYSTEM TO DEVELOP NEAR THE MID-ATLANTIC COAST AND BRING MORE SNOW INTO THE AREA. CONFIDENCE IS LOW. && .MARINE... A GALE WARNING CONTINUES ALONG THE COASTAL WATERS. HAVE ALREADY SEEN SEVERAL LOCATIONS ALONG THE COAST REPORT GALE GUSTS. EXPECT THESE STRONG WINDS TO CONTINUE THROUGH MID DAY BEFORE DROPPING OFF SHARPLY. ALTHOUGH SCA CONDITIONS FOR SEAS AND WINDS MAY LINGER FOR MUCH OF THE DAY. ON THE DELAWARE BAY, EXPECT SCA CONDITIONS TO CONTINUE THROUGH AT LEAST SUNRISE. THERE IS LOW CONFIDENCE THAT THEY MAY LINTER FOR A FEW MORE HOURS BEYOND SUNRISE. WINDS WILL BEGIN TO INCREASE AGAIN LATE TONIGHT/EARLY TUESDAY MORNING AHEAD OF THE NEXT LOW MOVING IN FROM THE WEST. OUTLOOK... TUESDAY AND WEDNESDAY...ANOTHER AREA OF LOW PRESSURE WILL DEVELOP OFF THE MID-ATLANTIC COAST. SCA CONDITIONS EXPECTED WITH HAZARDOUS SEAS AND PERIODS OF 25 KT GUSTS. THERE COULD BE A TEMPORARY LULL IN THE WINDS ON TUESDAY CLOSE TO WHERE THE LOW DEVELOPS. THURSDAY AND FRIDAY...SOLID SCA CONDITIONS EXPECTED. GALES ARE CERTAINLY A POSSIBLE WITH GUSTY NW WINDS AND STEEP LAPSE RATES BEHIND A COLD FRONT. && .TIDES/COASTAL FLOODING... ***MODERATE COASTAL FLOODING IS LIKELY AT SANDY HOOK FOR BOTH HIGH TIDE CYCLES TODAY. MINOR COASTAL FLOODING IS LIKELY NEAR THE THIS MORNINGS HIGH TIDE FOR OTHER LOCATIONS. THERE IS INCREASING POTENTIAL FOR MODERATE COASTAL FLOODING NEAR THE TUESDAY MORNING HIGH TIDE.*** HIGH PRESSURE WILL ANCHOR OVER EASTERN QUEBEC/LABRADOR WHILE LOW PRESSURE PASSING OFFSHORE WELL TO THE SOUTHEAST UNDERGOES EXPLOSIVE DEEPENING THROUGH TODAY. WITH THE AFOREMENTIONED HIGH REMAINING TO OUR NORTH, A BROAD AREA OF LOW PRESSURE WILL DEVELOP OFF THE OUTER BANKS TONIGHT AND PASS OFFSHORE SOUTHEAST OF OUR REGION DURING THE DAY TOMORROW. THESE TWO SYSTEMS WILL MAINTAIN AN ONSHORE FLOW ALONG THE COAST THRU TUESDAY, WITH ONLY A BRIEF PAUSE THIS AFTERNOON AND VERY EARLY TONIGHT, AS THE PRESSURE GRADIENT RELAXES BETWEEN SYSTEMS. ADDING TO THE TIDAL FLOODING POTENTIAL, ASTRONOMICAL TIDES WILL BE HIGH DUE TO THE NEW MOON TODAY. AT SANDY HOOK, WE ALREADY SAW A LARGE DEPARTURE WITH THE LOW TIDE EARLIER, AND WINDS HAVE INCREASED SHARPLY AND ARE EXPECTED TO CONTINUE THROUGH THE HIGH TIDE CYCLE. THUS, MODEL GUIDANCE AND A LOCAL REGRESSION PROGRAM INDICATE THAT A DEPARTURE OF OVER 2 FEET IS POSSIBLE WITH THE NEXT HIGH TIDE, OR JUST ENOUGH TO REACH MODERATE FLOODING THRESHOLDS. WITH THE CONTINUED NORTHEAST FLOW AND HIGH WAVE ACTION, EXPECT THAT IT COULD BE A SIMILAR STORY FOR TONIGHT`S HIGH TIDE, THOUGH THAT IS THE LOWER OF THE ASTRONOMICAL TIDES. THUS THE WARNING INCLUDES BOTH HIGH TIDE CYCLES TODAY. CONTINUED THE WATCH FOR TOMORROW`S HIGH TIDE CYCLE. FOR THE REST OF THE COAST...WITH HIGH ASTRONOMICAL TIDES, WE EXPECT A SURGE OF 1 TO 2 FT THIS MORNING. WE HAVE HIGH CONFIDENCE IN WIDESPREAD MINOR COASTAL FLOODING. WE HAVE ALSO TEMPERED DOWN THE HIGH-BIASED ET AND ESTOFS GUIDANCE DUE TO A RESIDUAL BIAS OF NEARLY 1 FOOT IN SPOTS. A COASTAL FLOOD ADVISORY HAS BEEN ISSUED FOR THIS MORNING`S HIGH TIDE ALONG THE SOUTHERN NJ AND DE OCEANFRONT, AS WELL AS DELAWARE BAY. THERE IS A BIT MORE UNCERTAINTY ON WHETHER WE REACH THE MINOR THRESHOLD AT REEDY POINT, WHICH IS LARGELY DEPENDENT ON EKMAN TRANSPORT IN A NORTHEAST FLOW, BUT WE EXPECT IT TO BE CLOSE NONETHELESS. THE COASTAL FLOOD ADVISORY CONTINUES FOR THE CENTRAL AND SOUTHERN NJ AND DE OCEANFRONT FOR THIS EVENING`S HIGH TIDE. FOR THE TUESDAY MORNING HIGH TIDE, A MORE EASTERLY COMPONENT/LONGER FETCH TO THE WIND WILL HAVE A GREATER IMPACT ALONG THE ENTIRE COAST, INCLUDING DELAWARE BAY, AND PORTIONS OF THE TIDAL DELAWARE. WE AGREE WITH THE STRONGER GFS WINDS, ESPECIALLY GIVEN THE SYNOPTIC SETUP. THE MAIN UNCERTAINTY IS REGARDING A BROAD LOW PRESSURE/TROUGH MOVING NORTHEASTWARD ALONG THE COAST, WHICH MAY ALLOW WINDS TO QUICKLY RELAX NEAR THE TIME OF HIGH TIDE, PARTICULARLY DELMARVA AND FAR SOUTHERN NJ. NEVERTHELESS, ASIDE FROM A BRIEF LULL IN THE FLOW MONDAY AFTERNOON AND VERY EARLY MONDAY NIGHT, WE`LL HAVE HAD NEARLY 48 HOURS DURATION OF ONSHORE FLOW, WHICH WILL MAKE FOR HIGHER TIDAL DEPARTURES COMPARED TO MONDAY MORNING, IN ADDITION TO THE ASTRONOMICALLY HIGHER TIDES. IN TERMS OF GUIDANCE, WE SIDED MORE WITH THE HIGHER ETSS SURGE OF 2 TO 2.5 FEET, EVEN CONSIDERING THE AFOREMENTIONED RESIDUAL. A COASTAL FLOOD WATCH REMAINS IN EFFECT FOR THE TUESDAY MORNING HIGH TIDE FOR THE NJ AND DE OCEANFRONT WITH THE HIGHEST CONFIDENCE IN WIDESPREAD MODERATE COASTAL FLOODING FOR CENTRAL AND NORTHERN NJ. ELSEWHERE, WIDESPREAD MINOR COASTAL FLOODING IS ANTICIPATED, PERHAPS UP TO PHILADELPHIA, GIVEN THE MORE EASTERLY FLOW UP DELAWARE BAY. FOR THESE AREAS, A COASTAL FLOOD ADVISORY WILL LIKELY BE NEEDED. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT FOR PAZ070-071-101-102. NJ...WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR NJZ012>014-020-026. COASTAL FLOOD WATCH FROM LATE TONIGHT THROUGH TUESDAY AFTERNOON FOR NJZ012>014-020>027. COASTAL FLOOD ADVISORY UNTIL 4 AM EST TUESDAY FOR NJZ020>027. COASTAL FLOOD ADVISORY FROM 9 AM THIS MORNING TO 1 PM EST THIS AFTERNOON FOR NJZ016. WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT FOR NJZ016>023-027. COASTAL FLOOD WARNING UNTIL 10 PM EST THIS EVENING FOR NJZ012>014. DE...COASTAL FLOOD WATCH FROM LATE TONIGHT THROUGH TUESDAY AFTERNOON FOR DEZ002>004. COASTAL FLOOD ADVISORY UNTIL 4 AM EST TUESDAY FOR DEZ002>004. COASTAL FLOOD ADVISORY FROM 9 AM THIS MORNING TO 1 PM EST THIS AFTERNOON FOR DEZ001. WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT FOR DEZ001-002. MD...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT FOR MDZ008-012-015. MARINE...GALE WARNING UNTIL NOON EST TODAY FOR ANZ450>455. SMALL CRAFT ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR ANZ430-431. && $$ SYNOPSIS...KLEIN NEAR TERM...JOHNSON SHORT TERM...JOHNSON LONG TERM...KLEIN AVIATION...JOHNSON/KLEIN MARINE...JOHNSON/KLEIN TIDES/COASTAL FLOODING...

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