Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 202048 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 348 PM EST THU NOV 20 2014 .SYNOPSIS...
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A COLD FRONT WILL SHIFT TO OUR EAST THROUGH EARLY THIS EVENING, THEN HIGH PRESSURE FROM THE LOWER OHIO VALLEY WILL BUILD INTO OUR AREA LATER FRIDAY. THE HIGH WILL MOVE OFFSHORE SATURDAY, THEN A WARM FRONT LIFTS ACROSS OUR AREA SUNDAY NIGHT AND MONDAY AS A STRONG LOW PRESSURE SYSTEM TRACKS INTO THE GREAT LAKES REGION. A COLD FRONT IS FORECAST TO MOVE THROUGH LATER MONDAY NIGHT AND TUESDAY, FOLLOWED BY HIGH PRESSURE LATE WEDNESDAY AND THURSDAY.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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A COLD FRONT HAS BEEN SLOW TO MOVE THROUGH OUR REGION TODAY. AS A RESULT, WE WERE ABLE TO GET A FEW HOURS OF MORE SOUTHERLY FLOW AND A FEW DEGREES TACKED ON TO THE HIGH TEMPERATURES. A NICE BREAK FROM THE EARLY SEASON COLD. HOWEVER, TONIGHT WITH THE PASSAGE OF THE FRONT, WINDS WILL GO BACK MORE NORTHWESTERLY WITH ANOTHER SHOT OF ARCTIC AIR ENTERING THE REGION. A DRY AIRMASS WILL CONTINUE TO PREVENT ANY CHANCES FOR PRECIPITATION. FOR TEMPERATURES, STARTED WITH LAV GUIDANCE THROUGH THE EVENING SINCE IT HAS A BETTER HANDLE ON RECENT TEMPERATURE TRENDS. WENT AT OR A TOUCH COOLER IN SPOTS WITH LOWS, SUSTAINED WINDS ARGUE FOR WARMER LOWS BUT THE DEGREE OF THE AIRMASS MAY BE UNDERESTIMATED BY STAT GUIDANCE.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
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HIGH PRESSURE WILL MOVE FROM THE OHIO VALLEY INTO OUR REGION THROUGHOUT THE DAY. CONTINUED DRY WITH MOSTLY SUNNY SKIES OUTSIDE OF THE POCONOS AND NW NJ. NORTHWEST FLOW WILL CONTINUE WITH SOME MOISTURE OFF THE GREAT LAKES POSSIBLY INTERACTING WITH THE HIGHER TERRAIN AREAS. MAINTAINING SOME SCATTERED FLURRIES IN THE GRIDS FOR NW NJ AND THE POCONOS. MODELED TWO METER TEMPERATURES AND 850/925 MB TEMPS ALONG WITH MET AND MAV GUIDANCE SETS SHOW OUR REGION ONLY HAVING THE POTENTIAL FOR HIGHS IN THE MID 30`S ON FRIDAY. GIVEN THE STRONG CAA, THAT SEEMS REASONABLE.
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&& .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
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THE OVERALL SYNOPTIC SETUP FEATURES A PATTERN CHANGE, WHICH IS A RESULT OF ENERGY DRIVING ACROSS THE SOUTHWESTERN U.S. FRIDAY NIGHT WHICH EJECTS INTO THE SOUTHERN PLAINS SATURDAY. THIS WILL ALLOW DOWNSTREAM RIDGING TO PUSH EASTWARD AS AN UPPER-LEVEL TROUGH LIFTS OUT OF THE EAST. THE SOUTHERN ENERGY LOOKS TO AMPLIFY AN UPPER-LEVEL TROUGH ACROSS THE CENTRAL PORTION OF THE NATION EARLY NEXT WEEK, WITH THE POTENTIAL FOR A DEEP CYCLONE TRACKING UP ACROSS THE GREAT LAKES REGION. THIS TROUGH EVENTUALLY ARRIVES IN THE EAST LATE TUESDAY AND WEDNESDAY, ALTHOUGH IT MAY DEAMPLIFY INTO THURSDAY. WE USED A MODEL BLEND OVERALL FOR FRIDAY NIGHT THROUGH SUNDAY, THEN THE 12Z WPC GUIDANCE THEREAFTER. SOME ADJUSTMENTS WERE MADE FOLLOWING ADDITIONAL COLLABORATION WITH OUR SURROUNDING OFFICES. FOR FRIDAY NIGHT AND SATURDAY...A PATTERN CHANGE GETS UNDERWAY AS A STRONG UPPER-LEVEL TROUGH LIFTS OUT OF THE NORTHEAST THROUGH FRIDAY NIGHT. AS THIS OCCURS, STRONG HIGH PRESSURE AT THE SURFACE IS FORECAST TO SETTLE NEARLY RIGHT OVER THE MID ATLANTIC FRIDAY NIGHT BEFORE SHIFTING OFFSHORE DURING SATURDAY. THIS SHOULD RESULT IN GOOD RADIATIONAL COOLING CONDITIONS FRIDAY NIGHT. AS THE UPPER-LEVEL TROUGH DEPARTS, THE FLOW IS FORECAST TO START BACKING ALLOWING WAA TO GET UNDERWAY. THIS RIBBON OF WAA ALONG WITH AN INCREASE IN THE FLOW JUST TO OUR NORTHWEST ESPECIALLY WILL TEAM UP WITH A WEAKENING SURFACE FRONTAL BOUNDARY. THIS THERMAL BOUNDARY IS MORE DEFINED AROUND 850 MB THOUGH AND THERE APPEARS TO BE ENOUGH LIFT TO GENERATE SOME LIGHT QPF AROUND THE GREAT LAKES. SOME OF THIS MAY SETTLE SOUTHEASTWARD DURING SATURDAY NIGHT BEFORE WEAKENING. GIVEN THE WARMING ALOFT, ANY LIGHT QPF THAT CAN GET TO OUR FAR NORTH/NORTHWEST ZONES COULD BE A LITTLE FREEZING RAIN. THIS LOOKS LIKE A LOW PROBABILITY ATTM ALONG WITH LOW CONFIDENCE AND THEREFORE KEPT POPS AT 30 PERCENT OR LESS. THE SOUTHWESTERLY FLOW ALONG WITH THE WAA WILL ALLOW SOME MODERATION IN THE SURFACE TEMPERATURES SATURDAY, ALTHOUGH THERE SHOULD ALSO BE HIGH CLOUDINESS AROUND. FOR SUNDAY AND MONDAY...AN AMPLIFYING UPPER-LEVEL TROUGH ACROSS THE PLAINS AND MIDWEST WILL DRIVE A DEEPENING SURFACE LOW INTO THE GREAT LAKES REGION LATE SUNDAY AND MONDAY. DOWNSTREAM, INCREASING WAA AND THETA-E ADVECTION WILL COMBINE WITH AN AREA OF LARGE SCALE LIFT TO PRODUCE SOME RAIN. THIS WILL BE WITH A WARM FRONT LIFTING NORTH SUNDAY NIGHT AND MONDAY. THIS SHOULD BE AIDED BY AN INCREASING LOW-LEVEL JET, AND IT IS POSSIBLE THAT SOME CONVECTIVE ELEMENTS DEVELOP WITHIN THE OVERRUNNING REGIME WITH A WARMER AND MORE MOIST AIRMASS SURGING NORTHWARD. AS THE DEEPENING SURFACE LOW TRACKS ACROSS THE GREAT LAKES MONDAY, A COLD FRONT SHOULD ARRIVE IN OUR AREA LATE. HOWEVER, A DRY SLOT LOOKS TO OVERSPREAD OUR AREA DURING MONDAY THEREFORE AFTER SOME EARLY RAIN THE CHC OF LINGERING SHOWERS LOOKS ON THE LOW SIDE. WE CARRIED CATEGORICAL POPS SUNDAY NIGHT, THEN THESE TAPER DOWN RAPIDLY AROUND DAYBREAK MONDAY. GIVEN THE STRONG LOW-LEVEL FLOW AND WAA, A SURGE IN THE SURFACE TEMPERATURES ARE ANTICIPATING WITH SOME AREAS NEARING 70 DEGREES FOR A TIME DESPITE BEING THE SECOND HALF OF NOVEMBER. THE RECORD HIGHS FOR MONDAY ARE MAINLY IN THE UPPER 60S TO LOWER 70S, AND IF WE CAN GET ENOUGH SUNSHINE AND MIX DECENTLY THEN SOME SPOTS COULD HAVE A SHOT AT THESE RECORDS. FOR TUESDAY THROUGH THURSDAY...A COLD FRONT IS FORECAST TO BE SHIFTING GRADUALLY OFFSHORE AND THIS WILL ALLOW CAA TO KICK IN AS THE UPPER-LEVEL TROUGH ARRIVES. THE ACTUAL TROUGH AXIS LOOKS TO REMAIN TO OUR WEST, AND THIS COULD SLOW THE FRONT DOWN AS IT EASES OFFSHORE. SOME SHORT WAVE ENERGY ROUNDING THE BASE OF THE TROUGH MAY INDUCE A SURFACE LOW ALONG THE FRONT. THIS FEATURE HOWEVER LOOKS TO TRACK OFFSHORE THOUGH TUESDAY INTO WEDNESDAY. WE MOSTLY FOLLOWED THE 12Z WPC POPS DURING THIS TIME FRAME. THERE BECOMES MORE UNCERTAINTY WITH THE UPPER-LEVEL TROUGH MOVING ACROSS THE EAST, DUE TO WHAT OCCURS ACROSS THE WEST. SOME GUIDANCE SHOWS A MUCH STRONGER TROUGH DIGGING ACROSS THE EAST LATE WEDNESDAY AND THURSDAY. AS OF NOW, WE WENT MUCH CLOSER TO THE 12Z WPC GUIDANCE WHICH FAVORED A BLEND OF CONTINUITY AND THE ECMWF MEAN FOR WEDNESDAY AND THURSDAY.
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&& .AVIATION /21Z THURSDAY THROUGH TUESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. ONLY SCATTERED MID-LEVEL CLOUDS ARE EXPECTED THROUGH FRIDAY. HOWEVER, THE MAIN STORY WILL BE GUSTY WINDS. SPORADIC GUSTS AROUND 25 KNOTS HAVE OCCURRED THIS AFTERNOON AND WILL CONTINUE GUSTS IN THE TAFS THROUGH 22Z. THE ENVIRONMENT IS FAVORABLE AGAIN FRIDAY FOR AFTERNOON WIND GUSTS AROUND 25 KNOTS. THE WIND DIRECTION WILL BE MORE NORTH OF WEST ON FRIDAY AROUND 300 COMPARED TO THE SOUTH OF WEST TODAY AROUND 250/260. OUTLOOK... FRIDAY NIGHT AND SATURDAY...VFR, WITH SOME INCREASE IN HIGH LEVEL CLOUDS LATE SATURDAY. NORTHWEST WINDS LESS THAN 10 KNOTS FRIDAY NIGHT BECOMING SOUTHWEST, THEN SOUTHWEST AROUND 10 KNOTS DURING THE DAY SATURDAY. SUNDAY AND MONDAY...VFR FOR AWHILE SUNDAY WITH AN INCREASE IN CLOUDS, THEN CEILINGS LOWERING TO MVFR /POTENTIALLY IFR/ SUNDAY NIGHT INTO MONDAY AS A PERIOD OF RAIN MOVES ACROSS THE AREA. THE CEILINGS MAY IMPROVE TO VFR DURING MONDAY ALTHOUGH A FEW SHOWERS MAY LINGER. SOUTHWESTERLY WINDS MAY GUST TO AROUND 20 KNOTS EACH AFTERNOON. A PERIOD OF LOW-LEVEL WIND SHEAR MAY OCCUR SUNDAY NIGHT INTO MONDAY AS A LOW-LEVEL SOUTHERLY JET AROUND 50 KNOTS MOVES THROUGH. TUESDAY...MOSTLY VFR WITH A SHOWER POSSIBLE ESPECIALLY CLOSER TO THE COAST AS A COLD FRONT SHIFTS OFFSHORE. THE WINDS BECOMING WEST-SOUTHWEST.
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&& .MARINE...
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SEAS WILL CONTINUE TO BE AT OR OVER FIVE FEET THROUGH A GOOD PORTION OF FRIDAY. ONCE AGAIN THE POTENTIAL IS PRESENT FOR GUSTY WEST TO NORTHWEST TO INCREASE TONIGHT TO AROUND 35 KNOTS WITH THE HIGHEST CHANCE FROM 07-11Z. SOME UNCERTAINTY IS PRESENT IN EXACTLY WHEN THE WINDS WILL START TO SLACKEN OFF BETWEEN 12 AND 16Z FRIDAY. GIVEN THE UNCERTAINTY WILL ONLY HAVE THE GALE WARNING GO TO 12Z FRIDAY ATTM. OUTLOOK... FRIDAY NIGHT AND SATURDAY...SOME GUSTS NEAR 25 KNOTS FRIDAY EVENING, THEN GENERALLY THE CONDITIONS ARE ANTICIPATED TO BELOW SMALL CRAFT ADVISORY CRITERIA. AN INCREASING SOUTHERLY FLOW HOWEVER MAY ALLOW WIND GUSTS TO NEAR 25 KNOTS SATURDAY NIGHT. SUNDAY AND MONDAY...A STRONG SOUTH-SOUTHWEST LOW-LEVEL JET IS FORECAST TO MOVE ACROSS THE AREA SUNDAY NIGHT INTO MONDAY. THIS WILL BE ASSOCIATED WITH A WARMER AIRMASS THAT IS MOVING IN, WHICH TENDS TO NOT ALLOW FOR A FAVORABLE MIXING SETUP. THEREFORE, KEPT GUSTS BELOW GALE CRITERIA. GIVEN THE SOUTHWESTERLY FLOW, DID GO BELOW WAVEWATCH BY ABOUT A FOOT AS IT TENDS TO OVERDO THE SEAS WITHIN THIS FLOW REGIME. TUESDAY...THE WINDS ARE ANTICIPATED TO BE BELOW ADVISORY CRITERIA, AND THE SEAS SHOULD BE SUBSIDING BELOW 5 FEET.
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&& .TIDES/COASTAL FLOODING...
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A STRONG OFFSHORE FLOW WILL DEVELOP OVER THE AREA AS THE COLD FRONT MOVES OFF THE COAST. THIS FLOW WILL CREATE LOW WATER CONDITIONS ALONG THE COAST AND ASSOCIATED INLETS TONIGHT THROUGH FRIDAY AFTERNOON. THERE IS EVEN SOME CONCERN FOR BLOWOUT TIDES NEAR THE TIME OF HIGH TIDE...WHICH TONIGHT OCCURS WITHIN AN HOUR EITHER SIDE OF MIDNIGHT ALONG THE COAST...AND LATER TONIGHT IN THE DELAWARE BAY. DBOFS AND CBOFS INDICATE WATER LEVELS GETTING WITHIN A TENTH OF A FOOT OR SO OF BLOWOUT CONDITIONS (MINUS 1.8 FEET MLLW), WHILE ETSURGE GUIDANCE IS NOT NEARLY AS AGGRESSIVE. BASED ON THE FACT THAT ONE MODEL IS JUST BARELY BRINGING US TO BLOWOUT CONDITIONS AND ANOTHER ISN`T SO CLOSE, WE WILL HOLD OFF ON ANY STATEMENTS AT THIS POINT IN TIME. WE WILL OBVIOUSLY BE WATCHING THE SITUATION THIS EVENING AND ISSUE LATER STATEMENTS, IF NECESSARY.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...GALE WARNING FROM MIDNIGHT TONIGHT TO 7 AM EST FRIDAY FOR ANZ431-450>455. SMALL CRAFT ADVISORY UNTIL 6 PM EST FRIDAY FOR ANZ430.
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&& $$ SYNOPSIS...GORSE NEAR TERM...GAINES SHORT TERM...GAINES LONG TERM...GORSE AVIATION...GAINES/GORSE MARINE...GAINES/GORSE TIDES/COASTAL FLOODING...MIKETTA

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