Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 261435 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 935 AM EST FRI DEC 26 2014 .SYNOPSIS... A HIGH PRESSURE SYSTEM OVER NORTH CAROLINA WILL SLOWLY MOVE EAST TODAY THROUGH SATURDAY AND BE WELL OFFSHORE BY SATURDAY NIGHT. A COLD FRONT IS FORECAST TO MOVE THROUGH OUR AREA SUNDAY BEFORE SLOWING ITS SOUTHWARD PROGRESSION AS A WAVE OF LOW PRESSURE MOVES ALONG IT ON MONDAY. A STRONG CANADIAN HIGH PRESSURE SYSTEM WILL SLOWLY SINK SOUTH AND REACH THE NORTHERN PLAINS ON TUESDAY AND THE GULF COAST STATES ON THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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930 AM UPDATE...NO MAJOR CHANGES IN THE NEAR TERM. THOUGH A FEW PLACES WERE COLDER THIS MORNING THAN EXPECTED, WITH CLEAR SKIES AND DOWNSLOPING WINDS, TEMPS SHOULD HAVE NO TROUBLE CLIMBING INTO THE 40S AND 50S. PREVIOUS NEAR TERM DISCUSSION...GREAT WEATHER EXPECTED ACROSS THE MIDDLE ATLANTIC REGION TODAY. HIGH PRESSURE ACROSS THE SOUTHEAST STATES WILL RIDGE ACROSS THE AREA AS UPPER HEIGHTS SLOWLY BUILD. THIS WILL RESULT IN MOSTLY SUNNY SKIES AND MORE ABOVE NORMAL TEMPS FOR THE REGION. HIGHS WILL RANGE FROM THE UPPER 40S TO LOW 50S ACROSS MOST AREAS. WINDS WILL BE LIGHT FROM THE W/NW THIS MORNING...THEN W/SW BY SUNSET.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... MORE FAIR WEATHER TONIGHT WITH THE SFC HIGH MOVING OFF THE COAST. SKIES WILL REMAIN MOSTLY CLR AND TEMPS WILL CONTINUE ABOVE NORMAL. LOWS TONIGHT WILL BE IN THE LOW/MID 30S IN MOST AREAS. WINDS WILL BE LIGHT. && .LONG TERM /SATURDAY THROUGH THURSDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THE LONG TERM PERIOD WILL BRING COLDER WEATHER BACK INTO OUR CWA WITH A TRANSITIONAL PCPN EVENT SUNDAY INTO MONDAY. THE GFS INITIALIZATION AT 500MB LOOKS BETTER THAN IT DID LAST NIGHT AND WAS ON PAR WITH THE ECMWF AND WRF-NMMB. DOMESTICALLY THE WRF-NMMB LOOKED BETTER AT 850MB AND BOTH MODELS COMPARABLE AT 925MB. WHILE THE MODELS HAVE COME CLOSER, THERE ARE STILL TIMING AND INTENSITY DIFFERENCES THAT ONLY SUBTLE CHANGES INITIATED. WHILE WE THOUGHT WE HAD THE DIURNAL BIAS OF FLATTER SOLUTIONS NIGHT SOUNDING RUNS, MORE ROBUST SOLUTIONS DAY SOUNDING RUNS, THE ECMWF FLIPPED ON US TONIGHT BECAUSE ITS DECAY OF ITS SOUTHWESTERN TROF IS SLOWER. THE ECMWF ENSEMBLES INFER A SLIGHTLY NORTHWEST AND WARMER TRACK. GREATEST UNCERTAINTY IS SMACK AT THE BASE OF THE SHORT WAVE TROF. THERE WERE ABOUT 5 GEFS MEMBERS THAT WERE WETTER THAN THE OP AND THE CAN GEFS, TWO MEMBERS WERE STRONGER, TWO COMPARABLE AND ABOUT 16 WEAKER THAN THE OP MODEL. NO WEATHER ISSUES ON SATURDAY AS THE HIGH PRESSURE SYSTEM SHOULD BE OFF THE NORTH CAROLINA COAST AND THE APPROACHING COLD FRONT STILL WELL TO OUR WEST. THE PREDICTED CONVECTIVE TEMPERATURES OFF THE SOUNDINGS ARE STILL IN THE 90S AND LOW 100S AND LOW LEVEL MOISTURE EVEN ON THE WRF-NMMB IS NOT THAT PLENTIFUL. WE ARE EXPECTING A MOSUNNY DAY WITH MAXIMUM TEMPERATURES A COUPLE OF DEGREES HIGHER THAN TODAY. ONCE AGAIN THE FULL SUN MACROS OFF THE WRF-NMMB MODEL SUPPORT GFS MOS MORE THAN ITS OWN NAM MOS (WHICH WAS NOT UTILIZED). SATURDAY NIGHT CLOUDINESS ASSOCIATED WITH THE COLD FRONT`S PRECIPITATION SHOULD START ARRIVING IN THE AREA. MIN TEMP CONFIDENCE IS LOWER THAN AVERAGE BECAUSE OF THIS AND ACTUAL MINS MIGHT OCCUR EARLIER AT NIGHT WITH A BUMP UP IN TEMPS AS CLOUDS ARRIVE. FAR NORTHWEST CWA ONLY AREA THAT GETS PREDICTED OMEGA AND LOCATION OF LIQUID POPS LATE. THE CDFNT IS PREDICTED TO PASS THROUGH OUR CWA ON SUNDAY AND SUNDAY EVENING. MODELS NOT OVERLY ENTHUSED ABOUT SHOWER/PCPN POTENTIAL. WE DO SEE THE BEST PREDICTED MID LEVEL QVEC CONVERGENCE WITH THE PCPN POTENTIAL OCCURRING DURING THE DAY AND HIEST RELATIVELY SPEAKING INSTABILITY. NOT MUCH DPVA OR REFLECTED OMEGA, SO WE KEPT POPS AS CHANCE AND MENTION OF PCPN AS SCATTERED SHOWERS. WE DID NOT SWAY MUCH FROM STAT GUIDANCE FOR MAX TEMPS. THERE ARE FORCING SIMILARITIES WITH THE WAVE ON THE FRONT. SINCE ITS PREDICTED TO BE RELATIVELY WEAK WE ARE NOT SEEING MUCH MID LEVEL WAA PAST 12Z MON AND NOT MUCH PREDICTED ISENTROPIC LIFT. BUT, OUR CWA WILL BE IN AN EXCELLENT ENTRANCE REGION OF A 180KT 250MB JET AND THE 700MB JET ALSO IS PREDICTED TO PASS ACROSS THE SOUTHERN PART OF OUR CWA. MID LEVEL QVEC CONVERGENCE GETS REPLACED BY MID LEVEL FGEN FORCING AS A PCPN PROCESSOR (AGAIN LEANING SOUTH). DIFFERENCES COME AROUND WITH TIMING AND HOW STRONG THESE PROCESSES WILL BE. THE ADDED ELEMENT IS THAT COLDER AIR WILL BE ADVECTING INTO THIS SYSTEM AND A CHANGE TO NON LIQUID PTYPE IS EXPECTED TO OCCUR. BUT LIKE LAST NIGHT, THE MOST LIKELY PLACES TO SEE A TRANSITION TO SLEET (ADDED IT PER WRF FCST SOUNDINGS) AND SNOW (GENERALLY NORTHWEST OF THE FALL LINE/I95 CORRIDOR AND WEST OF 287 IN NJ) ARE EXPECTED TO SEE THE LOWEST AMOUNTS OF PCPN. IN ADDITION WARM WEATHER LEADING INTO THIS EVENT AND SUPPOSIVE LIGHT PCPN INTENSITY SHOULD REDUCE ACCUMULATION EFFICIENCY. ON THE OTHER HAND, PCPN TRANSITION OCCURRING AT NIGHT WILL NOT HURT. RIGHT NOW ANY ACCUMS DONT LOOK TO BE MUCH, BUT MIGHT COINCIDE WITH THE MONDAY MORNING COMMUTE. WE WILL ADD A MENTION IN THE HWO GIVEN THERE ARE STILL UNCERTAINTIES TO THE STRENGTH OF THE SYSTEM AND DO NOT WANT TO SELL IT SHORT. TIMING WE ARE CLOSEST TO THE PARALLEL GFS. THERMAL FIELDS WITH THE GFS AND ECMWF WERE FAIRLY CLOSE AND 925S AND 850S TEMPS WERE USED AS THE DEMARCATION OF NON-LIQUID. AS PCPN INTENSITY DECREASES AS MONDAY CONTINUES, A BACKWARD CHANGE OR MIX TO SOME RAIN MIGHT OCCUR. GIVEN THE FASTER TREND, WE DECIDED TO REMOVE THE MENTION OF POPS FOR MONDAY NIGHT. THE SHORT WAVE ON TUESDAY IS PREDICTED TO BE SO CHANNELIZED AND RELATIVELY WEAKER, WE ONLY KEPT THE MENTION OF FLURRIES IN NORTHWEST. WE DID ADD FLURRIES IN AS A STARTER FOR WEDNESDAY AS A MUCH STRONGER AND MORE ORTHOGONAL SHORT WAVE TROF IS PREDICTED TO MOVE THROUGH. BY TUESDAY AND NEW YEARS EVE TEMPERATURES SHOULD BECOME COLDER THAN NORMAL. NO CHANGE TO THURSDAY (NEW YEARS DAY) FORECAST WAS MADE AS 2015 IS EXPECTED TO COMMENCE RELATIVELY QUIETLY. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. WONDERFUL FLYING CONDITIONS TODAY AND TONIGHT AS HIGH PRESSURE RULES THE WEATHER PICTURE. SKIES WILL FEATURE JUST SOME HIGH CLOUDINESS AT TIMES TODAY. WINDS WILL BE WRLY/NWRLY AROUND 5 KNOTS EARLY TODAY AND THEN WINDS WILL SHIFT MORE SWRLY AT 5 TO 10 KNOTS LATER THIS AFTERNOON. TONIGHT SKC AND CALM OR VRY LGT SW WINDS. OUTLOOK... SATURDAY...VFR. SATURDAY NIGHT...SOME MVFR CIGS POSSIBLE NORTHWEST AIRPORTS, VFR CIGS ELSEWHERE. SUNDAY INTO MONDAY...MVFR, POSSIBLY IFR, CONDITIONS POSSIBLE AT TIMES AS WAVES OF PRECIPITATION MOVE FROM NORTH TO SOUTH ACROSS THE AREA. THE NORTHERN PART OF THE PRECIPITATION SHIELD COULD BE SNOW. MONDAY NIGHT AND TUESDAY...VFR. && .MARINE... HIGH PRESSURE OFF TO THE SOUTH WILL BUILD ACROSS THE WATERS TODAY AND THEN MOVE TO THE EAST TONIGHT. WINDS AND SEAS WILL REMAIN SUB- SCA CONDITIONS THROUGH THE PERIOD. WINDS WILL BE W OR NW THIS MORNING AND THEN BACK TO MORE OF A W OR SW DIRECTION TONIGHT. SPEEDS WILL BE AROUND 10 KNOTS TODAY AND CLOSER TO 5 KNOTS TONIGHT. SEAS ON THE OCEAN 2 TO 3 FT AND 1 TO 2 FT OVER DEL BAY. OUTLOOK... SATURDAY AND SATURDAY EVENING...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED. SATURDAY NIGHT INTO 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 AND MONDAY NIGHT...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED. LOWER CONFIDENCE AS A WAVE OF LOW PRESSURE IS PREDICTED TO FORM SOUTH OF THE AREA WATERS ON THE MENTIONED FRONT. ITS POSSIBLE THAT SMALL CRAFT ADVISORY CONDITIONS MIGHT OCCUR IF THIS LOW INTENSIFIES FASTER THAN WE ARE CURRENTLY FORECASTING. TUESDAY...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...JOHNSON/O`HARA SHORT TERM...O`HARA LONG TERM...GIGI AVIATION...GIGI/MIKETTA/O`HARA MARINE...GIGI/O`HARA

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