Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 251954 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 354 PM EDT SAT OCT 25 2014 .SYNOPSIS...
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A COLD FRONT WILL PASS THROUGH THE AREA TONIGHT. THE MID-ATLANTIC REGION WILL BE SITUATED BETWEEN LOW PRESSURE OVER EASTERN CANADA AND HIGH PRESSURE BUILDING IN FROM THE TENNESSEE VALLEY ON SUNDAY. THEN THE HIGH PRESSURE SYSTEM WILL RIDGE INTO THE AREA SUNDAY NIGHT AND MONDAY. A WARM FRONT WILL LIFT NORTH OF THE AREA TUESDAY BEFORE A COLD FRONT MOVES THROUGH WEDNESDAY. ANOTHER HIGH PRESSURE SYSTEM BRIEFLY RETURNS TO THE AREA ON THURSDAY. A COLD FRONT IS EXPECTED TO PASS THROUGH THE NORTHEAST ON FRIDAY WITH A LOW PRESSURE SYSTEM FORMING ALONG IT. CANADIAN HIGH PRESSURE WILL THEN BUILD EAST FOR NEXT WEEKEND.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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A RELATIVELY DRY COLD FRONT WILL MOVE ACROSS THE AREA TONIGHT, ALONG WITH A FAIRLY STRONG SHORT WAVE/VORTICITY MAX. HOWEVER, WITH A LACK OF VERTICAL MOISTURE ASSOCIATED WITH THE SYSTEM, WE DO NOT EXPECT ANY PRECIPITATION ACROSS THE AREA, MOSTLY AN INCREASE IN CLOUD COVER OVERNIGHT. THE MORE LIKELY MEASURABLE PRECIPITATION IS EXPECTED TO PASS NORTH OF THE AREA. THERE COULD BE A FEW SPRINKLES MOVE ACROSS THE NORTHERN TIER OF THE AREA, BUT FOR NOW WE WILL KEEP THE FORECAST PRECIP FREE. TEMPERATURES WILL COOL THROUGH THE NIGHT, ESPECIALLY BEHIND THE FRONTAL BOUNDARY WHICH SHOULD MOVE THROUGH AFTER MIDNIGHT. OVERNIGHT LOWS WERE A BLEND OF MAV/MET MOS AND MOSGUIDE.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
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STRONG NORTHWEST FLOW BETWEEN LOW PRESSURE TO THE NORTHEAST AND HIGH PRESSURE BUILDING BUILDING IN FROM THE SOUTHWEST WILL BE THE MAIN CONCERN ON SUNDAY. LOOKING AT SOUNDINGS, GUSTS OF AT LEAST 25-30 MPH, WITH GUSTS OF 35-40 MPH POSSIBLE, CAN BE EXPECTED FROM MID-MORNING INTO THE LATE AFTERNOON. NO PRECIPITATION IS EXPECTED, ALTHOUGH THERE COULD BE AN INCREASE IN CLOUD COVER DURING THE DAY. HIGHS ARE EXPECTED TO BE A LITTLE ABOVE NORMAL FOR MOST PLACES. WE USED A BLEND OF MIXED 925MB ECMWF TEMPS, MAV/MET MOS, AND MOSGUIDE FOR DAYTIME HIGHS.
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&& .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
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THE GFS INITIALIZATION LOOKED BETTER THAN THE WRF-NMMB AT 500MB WHILE THERMALLY THERE WERE ISSUES IN THE LOCAL AREA, BUT UPWIND BOTH LOOKED VERY GOOD. THERE IS PRETTY GOOD MODELING CONSENSUS CONCERNING THE COLD FRONT ON WEDNESDAY, MUCH LESS CONSENUS WITH THE EVOLUTION OF THE DEEPENING TROF FOR NEXT WEEKEND. THE GEFS MEAN IS MORE PROGRESSIVE THAN THE GFS WHICH BY ITSELF IS AT ONE END OF THE PROGRESSIVE SPECTRUM. THE LATEST ECMWF CONTINUES THE 00Z RUN IDEA OF A CLOSING CUT-OFF LOW AND NOR`EASTER. ITS 00Z ENSEMBLE MEAN WAS MORE PROGRESSIVE, ALTHOUGH THE SD(S) AT THE BASE OF THE TROF SHOW THERE ARE BIG DIFFERENCES IN TROF STRENGTH AMONG ITS MEMBERS. THE BIGGEST DIFFERENCES ARE BEYOND SATURDAY AT THIS POINT AND WE HAVE OPTED FOR A MODEL BLEND EARLY AND THEN A CAN GGEM/WPC CONSENSUS FOR FRIDAY AND SATURDAY. ON SUNDAY NIGHT THE GRADIENT WILL BE RELAXING. FCST BOUNDARY LAYER WINDS SUGGEST DECOUPLING BY MORNING. WITH GENERALLY CLEAR SKIES, WE OPTED FOR THE COOLER GFS MOS MINS BECAUSE OF THIS. ANY FROST THAT DOES OCCUR IS EXPECTED TO BE NORTH WHERE THE GROWING SEASON HAS ENDED. ON MONDAY THERE WILL BE SOME WAA CLOUDS, ESPECIALLY NORTH. MOST LOOK TO BE AT HIGH ALTOCU OR CIRRUS LEVEL. LESS OVERALL SOUTH. WHILE THERE IS A PREDICTED SHORT WAVE LATE, WE STILL HAVE RIDGING INCREASING, SO OVERALL THE DAY SHOULD BE MOSUNNY. BASED ON FCST 925MB AND 850MB TEMPS (EVEN THE WRF`S), GFS MOS MAX TEMPS LOOKED BETTER AND MAX TEMPS WERE NOT TOUCHED MUCH. ON MONDAY NIGHT A WEAK WARM WILL START MOVING TOWARD OUR AREA. NOT MUCH MOISTURE PREDICTED WITH IT, MAINLY AT CIRRUS LEVELS AGAIN. GIVEN THIS IS GETTING FURTHER IN TIME, WE WERE NOT AS AGGRESSIVE WITH RADIATING THE MINS. THE SFC GRADIENT IS LOOSE ENOUGH THAT WINDS WOULD DECOUPLE. AS THE WARM FRONT MOVES NORTH OF OUR CWA TUESDAY, A POCKET OF EXTREMELY WARM AIR FOR LATE OCTOBER WILL BE MOVING INTO OUR CWA. 925MB AND 850MB TEMPS OF THIS LEVEL IN SUMMER WOULD GET US INTO THE 80S IN A BIG CHUNK OF OUR CWA. MODEL FCST SOUNDINGS ARE NOT IN MUCH OF A MIXING MOOD, MAYBE TOO MUCH OF AN EXTENT BECAUSE THE SW GRADIENT DOES NOT LOOK THAT FEEBLE. AGAIN THIS IS GETTING OUT THERE IN TIME, BUT PREDICTED 1000-850MB THICKNESSES OVER US TUE IN THE CONUS YDA GAVE HIGHS NEAR 80F. THE SOUNDING MAXT MACROS ARE IN THE UPPER 70S TO MID 80S. SO WE COMPROMISED UPWARD BETWEEN THE LATTER AND CONTINUITY. TUE RECORD HIGHS ARE MAINLY IN THE LOWER TO MID 80S. FOR TUESDAY NIGHT AND WEDNESDAY WE FOLLOWED THE USUAL MODEL TIMING BIAS FOR THE TIMING OF THE COLD FRONT AND SHOWERS. MAINTAINED THE THOUGHT OF HIGHER POPS AS THE PREDICTED ENTRANCE REGION OF THE 250MB JET SHOULD ENHANCE UPWARD MOTION/PCPN CHANCES OVER OUR CWA. TIMING IS CLOSEST TO THE CAN GGEM SOLUTION. WHILE THE GFS HAS EDGED FASTER, ITS 12Z GEFS MEAN IS NOW SLOWER THAN THE OP MODEL. WITH A TIGHTER TIMING SOLUTION, WE REMOVED MOST OF THE POPS FOR WEDNESDAY NIGHT. TUESDAY NIGHT COULD BE WARMER WITH A DECENT SW GRADIENT AND NOT SURE ABOUT HOW MUCH OF A COOL OFF ON WEDNESDAY AS OUR STARTING POINT WILL BE RELATIVELY HIGH. THE COLD FRONT TREND FOR THURSDAY IS FOR MORE OF A SOUTHERN PROGRESSION. THAT STARTED ON THE 00Z RUN AND CONTINUED WITH THE 12Z RUN. A DRY DAY WITH NEAR SEASONAL TEMPERATURES ARE PREDICTED. FRIDAY INTO THE WEEKEND HAS LOOKED PRETTY DYNAMIC FOR A WHILE, ITS THE PLAYERS ON THE TEAM THAT HAVE BEEN TRADED ALL OVER THE PLACE. A COLD FRONT IS EXPECTED TO APPROACH AS THE TROF BEGINS DIGGING ON FRIDAY. SOUTHERN STREAM CYCLOGENESIS IS INDICATED BY BOTH THE CAN GGEM AND ECMWF. THOSE RESULTS FOR FRIDAY NIGHT/SATURDAY ARE ABOUT THE SAME WITH AN INVERTED TROF PREDICTED OVER OUR CWA AND A CHANCE FOR RAIN. THE BIGGER MODELING DIFFERENCES ARE BEYOND SATURDAY. EITHER WAY NEXT WEEKEND DOES NOT LOOK AS INVITING AS THIS WEEKEND.
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&& .AVIATION /20Z SATURDAY THROUGH THURSDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. GUSTY WESTERLY WINDS GENERALLY AROUND 15-20 KNOTS WILL CONTINUE FOR THIS AFTERNOON, BEFORE GUSTS DROP OFF LATE THIS AFTERNOON/EARLY THIS EVENING. A STEADY WEST BREEZE OF 10 KNOTS OR LESS IS EXPECTED THROUGH MOST OF THE OVERNIGHT BEFORE WINDS INCREASE AND GUSTS INCREASE SUNDAY MORNING BEHIND THE FRONTAL BOUNDARY. WIND GUSTS OF 25-30 KNOTS ARE EXPECTED DURING THE DAY SUNDAY, WITH GUSTS AS HIGH AS 35 KNOTS POSSIBLE. OUTLOOK... SUNDAY NIGHT THROUGH TUESDAY...VFR. TUESDAY NIGHT AND WEDNESDAY...PREDOMINATELY VFR. ALTHOUGH A BRIEF PERIOD OF MVFR AND SHRA POSSIBLE WITH COLD FROPA. WEDNESDAY NIGHT AND THURSDAY...VFR.
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&& .MARINE...
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SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR TONIGHT AND SUNDAY AS STRONG WEST-NORTHWEST WINDS WILL INCREASE TONIGHT AND ESPECIALLY SUNDAY BEHIND A COLD FRONTAL PASSAGE. WIND GUSTS OF AROUND 30 KNOTS ARE EXPECTED OVERNIGHT INTO SUNDAY. IT IS POSSIBLE AN OCCASIONAL GUST NEAR 34 KNOTS MAY OCCUR DURING THE DAY SUNDAY, BUT WE DO NOT EXPECT IT TO BE FREQUENT ENOUGH TO NEED A GALE WARNING. OUTLOOK... SUNDAY NIGHT...WE EXTENDED THE SMALL CRAFT ADVISORY IN THE SOUTHERN ATLANTIC WATERS THROUGH SUNDAY NIGHT AS THE GRADIENT IS PREDICTED TO RELAX SLIGHTLY LATER. MONDAY THROUGH TUESDAY...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED. THE SOUTHWEST FLOW IS PREDICTED TO START INCREASING ON TUESDAY. TUESDAY NIGHT AND WEDNESDAY...THERE IS A CHANCE FOR SMALL CRAFT ADVISORY CONDITIONS, HIGHER CHANCE ON THE OCEAN. THE SOUTHWEST FLOW IS EXPECTED TO INCREASE FURTHER, ALTHOUGH THE MODELS TEND TO BE A BIT TOO BULLISH IN THIS REGARD AND SUBSEQUENTLY WITH THE SEAS. WEDNESDAY NIGHT THROUGH THURSDAY...A RETURN OF SUB SMALL CRAFT ADVISORY CONDITIONS.
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&& .FIRE WEATHER...
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SUNDAY WILL BE VERY GUSTY AND RELATIVE HUMIDITY LEVELS WILL DROP TO AROUND 30-35 PERCENT FOR MANY LOCATIONS ACROSS SOUTHEAST PENNSYLVANIA, CENTRAL/SOUTHERN NEW JERSEY, AND DELMARVA. HOWEVER, WITH THE RECENT RAINS IN THE LAST WEEK, FUELS ARE STILL FAIRLY MOIST, SO WE ARE NOT ISSUING ANY ENHANCED FIRE WEATHER STATEMENTS.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 6 AM EDT MONDAY FOR ANZ450>455. SMALL CRAFT ADVISORY FROM 8 AM TO 9 PM EDT SUNDAY FOR ANZ430- 431.
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&& $$ SYNOPSIS...GIGI/KLEIN NEAR TERM...ROBERTSON SHORT TERM...ROBERTSON LONG TERM...GIGI AVIATION...GIGI/KLEIN/ROBERTSON MARINE...GIGI/KLEIN/ROBERTSON FIRE WEATHER...ROBERTSON

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