Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 180225 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 925 PM EST WED DEC 17 2014 .SYNOPSIS... LOW PRESSURE WILL DEPART TO OUR NORTHEAST THROUGH THURSDAY. HIGH PRESSURE THEN WILL MOVE TO OUR NORTH ON FRIDAY. WEAK LOW PRESSURE WILL DEVELOP IN THE GULF OF MEXICO ON SATURDAY THAT WILL MOVE NORTHEAST ON SUNDAY TO VIRGINA BEACH. A SECOND LOW PRESSURE SYSTEM WILL THEN FORM AND HEAD UP THE EAST COAST MONDAY INTO TUESDAY. ANOTHER COLD FRONTAL BOUNDARY WITH ASSOCIATED LOW PRESSURE SYSTEMS MOVES FROM THE OHIO VALLEY TUESDAY NIGHT INTO OUR REGION ON WEDNESDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... WE DIDNT MAKE TOO MANY CHANGES TO THE OVERNIGHT AS THE FORECAST REMAINS CLOSE LATEST HRRR AND RAP CONTINUE TO BYPASS MEASURABLE IN OUR CWA. SO WE JUST KEPT A CHANCE OF SPRINKLES OR FLURRIES FOR THE OVERNIGHT FAR NORTH NEAR THE PATH OF THE STRONGEST DPVA. NOT MUCH MOISTURE AT ALL ABOVE 850MB SEEMS TO BE THE LIMITING FACTOR. TEMPERATURES WERE FALLING EVER SO SLIGHTLY SLOWER, SO ONLY SLIGHT UPWARD TWEAKS WERE MADE. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... THURSDAY...WE ARE IN SERVICE BACKUP AND STERLING WILL BE WRITING THE FORECASTS STARTING AT ABOUT 8 AM. IT WILL BE A BIT COOLER (STILL ABOVE NORMAL)...ABOUT 8-9F PER MODELED 925MB ABOUT 5C COOLER...WITH GUSTY NW WINDS TO 25 MPH. CONSIDERABLE CLOUDINESS POCONOS WITH MAYBE A FEW FLURRIES? OTHERWISE A MOSTLY SUNNY START IS EXPECTED BECOMING PARTLY SUNNY OR MOSTLY CLOUDY FOR A TIME MIDDAY THEN CLEARING LATE IN THE DAY. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... THURSDAY NIGHT THROUGH SATURDAY: LOW PRESSURE WITH AN ASSOCIATED COLD FRONT WILL BE LOCATED WELL OFFSHORE OVER ATLANTIC CANADA ON THURSDAY. THIS WILL ALLOW FOR CONTINUED NORTH TO NORTHWEST FLOW INTO THE REGION THROUGH FRIDAY. BY SATURDAY WE AWAIT THE APPROACH OF A LOW PRESSURE SYSTEM FROM THE SOUTH WITH INCREASING CLOUDS AND A MORE NORTHEASTERLY FLOW. THIS LOW PRESSURE HAS TRENDED WEAKER AND WEAKER WITH EACH SET OF MODEL RUNS. MANY OF THE 12Z MODELS ONLY BRING VERY LIGHT QPF IF THAT AND ARE FASTER. WILL KEEP POPS IN THE CHANCE CATEGORY HIGHEST ACROSS THE SOUTH. FORECAST TEMPERATURES REFLECT CLOSER TO THE ECMWF AND THE ECMWF MOS IN THESE PERIODS, DID EDGE COOLER FRIDAY NIGHT WITH CLEAR SKIES. SATURDAY NIGHT AND SUNDAY: THE MUCH ANTICIPATED LOW PRESSURE SYSTEM WILL PASS TO OUR SOUTHEAST SATURDAY NIGHT INTO SUNDAY. CONSIDERABLE DIFFERENCES FROM WHERE THE MODELS AND THERE RESPECTIVE ENSEMBLES WERE A FEW DAYS AGO, PARTICULARLY WITH THE ECMWF. THE ECMWF HAS TRENDED ABOUT 20 MB WEAKER WITH THE LOW PRESSURE CENTER TOWARD THE DRIER GFS AND CMC MODELS. STRONG AGREEMENT FROM IT`S ENSEMBLE MEAN AND THE 06Z GEFS EXIST AS WELL. ALSO, MORE FEATURES ASSOCIATED WITH THIS SYSTEM WILL BE BETTER SAMPLED BY THE UPPER AIR NETWORK, ADDING MORE INITIAL DATA. BOTTOM LINE IS THAT CONFIDENCE CONTINUES TO INCREASE LITTLE BY LITTLE ON EACH FORECAST PACKAGE FOR A RATHER LIGHT EVENT FOCUSED ON SATURDAY EVENING. SUNDAY NIGHT THROUGH TUESDAY: AS THE PREVIOUS STORM DEPARTS WE SHOULD HAVE A DRY WINDOW SUNDAY NIGHT. SOME OF THE MID-LEVEL ENERGY DESTINED FOR THE PREVIOUS STORM WILL STAY OVER THE SOUTHEAST AND SPAWN ANOTHER LOW PRESSURE SYSTEM WHICH HEADS UP THE COAST FOCUSED ON MONDAY NIGHT FOR OUR REGION. THIS IS A NEW WRINKLE IN THE MODEL GUIDANCE TODAY AND WILL NOT GO MUCH ABOVE CHANCE POP TILL MORE CONSISTENCY IS SHOWN. THE POCONOS AND NORTHWEST NJ HAVE A CHANCE TO SEE MIXED PRECIPITATION. HOWEVER, A SUBSTANTIAL WARM LAYER LOOKS TO BE IN PLACE WHICH COULD LEAD TO MIXED PRECIPITATION QUICKLY CHANGING TO RAIN. FOR NOW GENERAL RAIN/SNOW TO RAIN FOR THE POCONOS AND ALL RAIN ELSEWHERE. WITH THE RAIN POSSIBLE NOT MUCH SPREAD IN THE MODELED TWO METER TEMPERATURES AND MOS GUIDANCE, DID NOT STRAY FROM THESE ON TEMPERATURES. TUESDAY NIGHT THROUGH CHRISTMAS EVE: A STRONG COLD FRONTAL BOUNDARY WILL MOVE INTO THE OHIO VALLEY INTO THE DEEP SOUTH ON TUESDAY DEVELOPING A LOW PRESSURE SYSTEM TO OUR WEST BY TUESDAY NIGHT WHICH DEEPENS AS THE TROUGH LIKELY BECOMES NEGATIVELY TILTED. EASTERLY WINDS WILL GRADUALLY STRENGTHEN AND SWITCH TO SOUTHEASTERLY BY WEDNESDAY MORNING. WAA AHEAD OF THE LOW IS LIKELY TO PICK UP AS WELL WITH A STRONG LLJ. WENT ABOVE WPC GUIDANCE ON THE WINDS. ALSO, THINK THE WINDS DUE TO DEEPENING LOW PRESSURE MAY BE HIGHER THAN CURRENTLY FORECASTED. THIS FORECAST DOES NOT COMMIT TO A TIME PERIOD OF MUCH HIGHER WINDS SINCE WE`RE STILL SEVEN DAYS OUT. WITH TEMPERATURES WELL ABOVE FREEZING, RAIN IS EXPECTED. THIS DEEPENING LOW PRESSURE COULD PROMOTE HEAVY RAINFALL, COASTAL FLOODING AND A FEW RUMBLES OF THUNDER DEPENDING ON THE EXACT EVOLUTION OF THE LOW PRESSURE SYSTEM. THE FORECAST FOR THIS TIME PERIOD WILL CONTINUE TO BE ADJUSTED AS NEW DATA BECOMES AVAILABLE WHILE LIKELY NOT SNOW, RAIN AND WIND MAY STILL CREATE TRAVEL PROBLEMS IN THIS PERIOD. WPC GUIDANCE ON TEMPERATURES CAPTURES THE POTENTIAL SHORT WARM-UP WELL. IN TERMS OF TRACK ALL OF THE MODELS AND RESPECTIVE ENSEMBLES SHOW A SPREAD GOING UP EITHER SIDE OF THE APPALACHIANS WITH THE LOW BEING THE STRONGEST OVER THE LAKES ON WEDNESDAY. WITH THE FORECAST IN MIND IT DOESN`T TAKE MUCH TO GO SLIGHTLY FORWARD IN TIME. WITH ANY LIGHT SNOW MELTING FROM THE WEEKEND AND WARM CONDITIONS ON CHRISTMAS EVE THE PROSPECTS FOR A WHITE CHRISTMAS ARE NOT THAT GOOD ATTM. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. A VFR 00Z TAF ISSUED. FOR THIS EVENING AND OVERNIGHT...SOME VFR CIGS ARE LIKELY FROM KPHL TERMINAL AREA NORTHWARD UNTIL AN UPPER AIR DISTURBANCE CLEARS THE AREA. WE ARE NOT EXPECTING PCPN TO REACH OR IMPACT TERMINALS, ALTHOUGH THERE MIGHT BE SOME MVFR CONDITION AT POCONO AIRPORTS DUE TO SNOW. FARTHER TO THE SOUTH, NO CIGS ARE PREDICTED, VERY FEW CLOUDS AT ALL. WEST TO NORTHWEST WINDS WILL AVERAGE 10 TO 15 KNOTS. WHILE WE ARE CARRYING GUSTS IN THE TAFS, THEY SHOULD NOT CONTINUOUSLY OCCUR. IT WILL BE PRETTY WINDY BETWEEN 2K AND 4K (WINDS GREATER THAN 30 KTS) AND WE BELIEVE THAT WILL BE ENOUGH TO TRIGGER GUSTS REACHING AROUND 20 KTS FROM TIME TO TIME OVERNIGHT. ON THURSDAY. A VFR CIG IS PREDICTED TO REFORM FROM KABE-KRDG NORTHWARD. ELSEWHERE A SCATTERED DECK OF FLAT STRATOCUMULUS CLOUDS AROUND 4500 FEET SHOULD OCCUR. SUSTAINED WEST TO NORTHWEST WINDS SHOULD INCREASE TO NEAR 15 KTS WITH PEAK GUSTS OF AROUND 25 KTS. WINDS SHOULD DECREASE SECOND HALF OF THURSDAY AFTERNOON AND WE DROPPED THE GUSTINESS AND REDUCED CLOUD COVERAGE AT THE START OF THE EVENING. OUTLOOK... THURSDAY NIGHT THROUGH SATURDAY: VFR WITH INCREASING CLOUDS SATURDAY. SATURDAY NIGHT AND SUNDAY: SOME RESTRICTIONS TO MVFR IN LIGHT SNOW SHOWERS AND LIGHT RAIN/SNOW SHOWER MIX FOR PHL,ILG, MIV AND ACY. SUNDAY NIGHT: VFR. && .MARINE... SCA POSTED. SCA VERIFICATION OCCURRING MOST OF THE COAST. WINDS SHOULD SUBSIDE SOMEWHAT THIS EVENING THEN MAY PULSE UP DURING THE NIGHT WITH ISOLATED GUSTS 30-33 KT POSSIBLE BY MORNING. WINDS ON THURSDAY SHOULD BE STRONGEST DURING THE MORNING THEN MAY SUBSIDE A BIT DURING MID AND LATE AFTERNOON. THE SCA ON DE BAY HAS BEEN EXTENDED. STRONG WINDS ARE FORECAST ABOVE THE BOUNDARY LAYER WHICH SHOULD BECOME MORE EASILY MIXED DOWNWARD AS THE NIGHT PROGRESSES PEAKING THURSDAY MORNING. BUOY 44009 FULL SERVICE RESTORATION PROBABLY DELAYED TIL FEBRUARY 2015. OUTLOOK... WIND GUSTS CLOSE TO 25 KNOTS IN SPOTS THURSDAY NIGHT AND FRIDAY WITH NORTHWEST FLOW. NOT ENOUGH CONFIDENCE TO EXTEND SCA ATTM. OTHERWISE, CONDITIONS WILL BE BELOW SCA CRITERIA THROUGH MONDAY. WEAK LOW PRESSURE PASSING TO OUR SOUTH SHOULD NOT LEAD TO SEAS HIGHER THAN FOUR FEET ON THE OCEAN. SOUTHERLY WINDS MONDAY. WINDS SHIFTING TO NORTH OR NORTHEAST SATURDAY INTO THE WEEKEND. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 5 PM EST THURSDAY FOR ANZ450>455. SMALL CRAFT ADVISORY UNTIL NOON EST THURSDAY FOR ANZ430-431. && $$ SYNOPSIS...GAINES NEAR TERM...GIGI SHORT TERM...DRAG LONG TERM...GAINES AVIATION...GAINES/GIGI MARINE...DRAG/GAINES/GIGI

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