Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 271440 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 940 AM EST SAT DEC 27 2014 .SYNOPSIS... A HIGH PRESSURE SYSTEM CENTERED OVER THE CAROLINAS WILL DRIFT SLOWLY OUT TO SEA TODAY. A COLD FRONT WILL CROSS THE AREA ON SUNDAY, THEN STALL TO OUR SOUTH AS A LOW PRESSURE SYSTEM RIDES ALONG IT MONDAY AND MONDAY NIGHT. A STRONG CANADIAN HIGH PRESSURE SYSTEM WILL REACH THE NORTHERN PLAINS BY TUESDAY AND IS THEN EXPECTED TO GRADUALLY BUILD SOUTH AND THEN EAST REACHING KANSAS ON WEDNESDAY AND THE CAROLINAS ON FRIDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... NOT MUCH CHANGE TO THE FORECAST FOR TODAY WITH HIGH PRESSURE SLOWLY MOVING EASTWARD, TO OUR SOUTHEAST. SHOULD DEVELOP A BETTER WEST-SOUTHWEST FLOW BY LATER THIS MORNING, THOUGH STILL BELOW 10 KNOTS EXPECTED. SKIES WILL BE PARTLY TO MOSTLY SUNNY AND TEMPERATURES WILL ONCE AGAIN BE FAIRLY MILD FOR LATE DECEMBER. READINGS WILL TOP OUT IN THE LOW/MID 50S FOR MOST AREAS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... THE HIGH SLIDES EAST INTO THE ATLANTIC TONIGHT AND THIS ALLOWS THE NEXT SYSTEM TO APPROACH FROM THE WEST. LOW PRESSURE WILL ADVANCE ACROSS SOUTHERN CANADA AND CAUSE A COLD FRONT TO PUSH IN FROM THE WEST. INCREASING CLOUDS ARE EXPECTED OVERNIGHT AND THERE IS A CHC FOR SOME SHOWERS ACROSS THE WRN/NWRN AREAS AFTER MIDNIGHT. SMALLER SLGT CHC POPS ARE IN THE GRIDS FOR NRN DELAWARE...THE DEL VALLEY INTO CNTRL NJ. LOWS TONIGHT WILL BE IN THE UPPER 30S AND LOW 40S ACROSS THE AREA. && .LONG TERM /SUNDAY THROUGH FRIDAY/... A LOWER CONFIDENCE LONG TERM FORECAST CONTINUES FOR THE WAVE ON THE COLD FRONT AS WE KICKED THE PROBLEMATICAL PTYPE CAN FROM SUNDAY NIGHT TO MONDAY NIGHT. OTHER THAN THE OPERATION ECMWF, THE MODELING CONSENSUS IS COMING CLOSER TO OUR CWA BEING AFFECTED BY A WAVE OF LOW PRESSURE FORMING ON THE CDFNT. THIS FRONT WILL COME THRU OUR AREA ON SUNDAY. THERE ARE STILL MULTIPLE ISSUES OF STRENGTH, TIMING AND THERMAL FIELDS. A FASTER PROGRESSING SYSTEM LIKE THE UKMET HAS IS WARMER AND RAINIER, SLOWER PROGRESSING SYSTEM LIKE THE CAN GGEM HAS IT SNOWIER. THE WRF-NMMB IS BOTH SLOWER AND WARMER WHICH LOOKS LIKE ITS USUAL MODEL BIAS OF PLACING LOWS TOO DEEP IN THE COLD AIR. ADD TO THE MIX THE OP ECMWF STILL HAS NO SECOND SYSTEM AT ALL. THE ENSEMBLING CLUSTERING PUTS THE OP GFS IN THE MIDDLE OF THE ROAD. ABOUT A QUARTER OF THE MEMBERS ARE WETTER FARTHER TO THE NORTHWEST WHILE A QUARTER OF THE MEMBERS ARE SIMILAR TO THE ECMWF SOLUTION. CONVERSELY MOST OF THE 20 CAN GGEM ENSEMBLE MEMBERS ARE MORE MUTED THAN THE OP OR CONTROL, ONLY ABOUT ONE OR TWO ARE MORE BULLISH. THE "NOISE` IN THE ECMWF ENSEMBLE MEAN IS STILL NORTHWEST OF THE OP. BUT NOT AS MUCH AS THE 12Z RUN WAS. PART OF THE ISSUE REMAINS THE POSSIBILITY OF CONVECTION IN THE NORTHWEST GULF. ALSO WHILE THE LOW IS HEADING TOWARD A CONFLUENT FLOW, NOT SURE THE SYSTEM WILL GET AS SUPPRESSED AS THE OP ECMWF. FOR THIS FCST PACKAGE WE ARE CLOSEST TO THE PGFS WHICH HAS A SLIGHTLY SLOWER AND LESS ROBUST SOLUTION THAN THE OP GFS. WE HAVE GAINED ANOTHER DAY TO GET A BETTER HANDLE, WHICH WE HOPE SUBSEQUENT SOUNDING RUNS WILL DO. THE SOUNDING INITIALIZATION IN THE SOUTHWEST LOOKED GOOD. THE TROF ITSELF LOOKS BAGGIER, BUT THE INITIAL ENERGY SURGE IS HEADING TO THE GREAT LAKES. ITS THE SHORT WAVES ALONG THE CALIFORNIA COAST THAT WILL INITIATE THE SECONDARY LOW. THERMALLY THE GFS LOOKED BETTER AT BOTH 850MB AND 925MB. ANOTHER REASON MONDAY NIGHT WE WERE NOT AS WARM AS THE WRF-NMMB. BETTER MODELING CONSENSUS ON SUNDAY AND SUNDAY NIGHT. THE INITIAL SURGE OF MOISTURE IS EXITING FASTER AND LESS OF A PTYPE ISSUE IS EXPECTED ON SUNDAY NIGHT. IN FACT NORTHWEST OF THE FALL LINE/I95 CORRIDOR IT LOOKS LIKE A RACE FOR WHICH WILL HAPPEN FIRST, PCPN END OR A CHANGE TO SNOW JUST BEFORE ENDING. WHERE PCPN SHOULD LINGER DEEPER INTO THE NIGHT, THERMAL FIELDS SUPPORT JUST RAIN SOUTH. BACKING UP TO SUNDAY DAY, THERE IS DECENT MODEL CONSENSUS OF A SHORT WAVE MOVING THROUGH THE SOUTHERN HALF OF OUR CWA DURING THE AFTERNOON AND WE UPPED POPS TO LIKELY SOUTH. LIKELY POPS WERE CARRIED INTO THE EVENING SOUTH AS THE PCPN TAKES MORE OF AN ANAFRONT LOOK TO IT. A PRECIPITATION BREAK IS EXPECTED ON MONDAY, OUR BREAK TIMING IS CENTERED AROUND THE MIDDLE OF THE DAY. THERE MIGHT BE SOME SUNSHINE NORTH, LESS CONFIDENT ABOUT SEEING THE SUN SOUTH. ONCE THE BREAK ENSUES, DRIER AIR WILL START WORKING ITS WAY SOUTHWARD. THIS WILL MAKE IT EASIER FOR THE NORTHERN PART OF THE PCPN TO TRANSITION TO SNOW AFTER BOUNDARY LAYER TEMPERATURES FALL. FOR NOW WE ARE CENTERING THE BEST CHANCE FOR PCPN ASSOCIATED WITH THE FRONT TO OCCUR ON MONDAY NIGHT. THERE ARE MANY MOVING PARTS TO THIS FORECAST, BUT SUFFICE THAT THE POSSIBILITY FOR ACCUMULATING SNOW WHICH WAS NORTHWEST ON SUNDAY NIGHT HAS SHIFTED TO AROUND THE DELAWARE VALLEY CORRIDOR ON MONDAY NIGHT. BASICALLY A TIGHTENING FGEN BAND COUPLED WITH A JET STREAK ALOFT IS THE TRIGGER FOR PCPN IN OUR AREA. ISENTROPIC LIFT IS NOT THERE AND NEITHER IS A TROWAL. THE PREDICTED MOISTURE TRANSPORT AT 290K IS ABOUT A FOURTH OF WHAT IS HEADING OUR WAY ON SUNDAY WHICH MAY STAND AS A GOOD PCPN FCST PROXY. SOME OF THE MORE AGGRESSIVE MODELS BRING A COUPLE OF INCHES OF SNOW TO OUR REGION. WE SHIFTED OUR HWO MENTION TO THE DELAWARE VALLEY AND IF THERE WAS TO BE AN IMPACT WOULD BE WITH THE TUESDAY MORNING COMMUTE, WE LINGER A CHANCE OF MAINLY SNOW SOUTHEAST ON TUESDAY MORNING, MORE SO FOR TIMING INCONSISTENCIES AND NOT THAT IT WOULD BE THAT A PROTRACTED A PCPN EVENT. REGARDLESS OF THE PTYPE OUTCOME INTO TUESDAY MORNING, THE REST OF THE WEEK WILL FEATURE COLDER WEATHER. THE VORT MAX ON WEDNESDAY LOOKS MORE CHANNELIZED THAN WAS PREDICTED YESTERDAY, SO A COLD, BUT DRY END OF THE LONG TERM WAS CONTINUED. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. HIGH PRESSURE ACROSS THE AREA THIS MORNING WILL MOVE EAST LATER TODAY. A LOW PRESSURE SYSTEM AND FRONT WILL AFFECT THE AREA SUNDAY. IN BETWEEN THESE SYSTEMS WE WILL FIND ANOTHER GOOD FLYING WEATHER DAY WITH VFR EXPECTED TODAY AND TONIGHT. THERE WILL BE SOME HIGH CLOUDS ACROSS THE AREA TODAY AND SOME MID LEVEL CLOUDINESS WILL ARRIVE OVERNIGHT. NO PCPN IS EXPECTED IN THE TAF PERIOD. WINDS WILL BE LIGHT TODAY AND TONIGHT...FAVORING A SW DIRECTION MUCH OF THE TIME. OUTLOOK... SUNDAY AND SUNDAY NIGHT...MVFR, POSSIBLY IFR, CONDITIONS POSSIBLE AT TIMES AS A COLD FRONT MOVES THROUGH THE REGION WITH SHOWERS. MONDAY AND MONDAY NIGHT...LOW CONFIDENCE. A SECOND WAVE OF PRECIPITATION COULD BRING MVFR TO IFR CONDITIONS BACK INTO THE REGION. MOST LIKELY TO OCCUR AT SOUTHERN AIRPORTS AND TERMINALS. SOME PRECIPITATION COULD FALL AS SNOW. TUESDAY...VFR NORTH, BECOMING VFR SOUTH. TUESDAY NIGHT AND WEDNESDAY...VFR. && .MARINE... ANOTHER GOOD DAY TO BE ON THE WATERS AS HIGH PRESSURE REMAIN IN CONTROL OF THE WEATHER. THE HIGH SLIDES TO THE EAST TONIGHT. DRY WEATHER WITH INCREASING CLOUDS EXPECTED TODAY AND TONIGHT. WINDS WILL BE MOSTLY SWRLY 5 TO 10 KNOTS TODAY AND 10 TO 15 KNOTS TONIGHT. A FEW GUSTS CLOSER TO 20 KNOTS POSSIBLE TONIGHT. SEAS TODAY AROUND 2 FT ON THE OCEAN AND 1 TO 2 ACROSS DEL BAY. OUTLOOK... SUNDAY MORNING...A SLIGHTLY STRONGER SOUTHWEST FLOW PRECEDING A COLD FRONT WILL BRING WIND GUSTS CLOSER TO SMALL CRAFT ADVISORY CRITERIA ON THE OCEAN. SUNDAY AFTERNOON AND NIGHT...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED. MONDAY THROUGH TUESDAY...THERE IS A CHANCE FOR SEAS TO REACH SMALL CRAFT ADVISORY CRITERIA MONDAY NIGHT AND TUESDAY. SUB SMALL CRAFT ADVISORY WINDS ARE STILL PREDICTED. LOWER CONFIDENCE AS A WAVE OF LOW PRESSURE WILL FORM SOUTH OF THE AREA WATERS ON THE PREVIOUSLY MENTIONED FRONT. ITS POSSIBLE THAT WIND RELATED SMALL CRAFT ADVISORY CONDITIONS MIGHT ALSO OCCUR IF THIS LOW INTENSIFIES FASTER THAN WE ARE CURRENTLY FORECASTING. TUESDAY NIGHT THROUGH WEDNESDAY...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GIGI/MIKETTA NEAR TERM...HEAVENER/O`HARA SHORT TERM...O`HARA LONG TERM...GIGI AVIATION...GIGI/MIKETTA/O`HARA MARINE...GIGI/MIKETTA/O`HARA

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