Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 191452 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 952 AM EST FRI DEC 19 2014 .SYNOPSIS... HIGH PRESSURE OVER THE NORTHERN GREAT LAKES WILL MOVE INTO THE OHIO VALLEY THIS MORNING. LOW PRESSURE IS EXPECTED TO FORM OVER THE GULF STATES LATE TONIGHT AND TRACK ACROSS GEORGIA SATURDAY. A STRONG LOW PRESSURE SYSTEM AND COLD FRONT MAY MOVE THROUGH THE EASTERN SEABOARD ON CHRISTMAS EVE. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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MID-MORNING UPDATE...LOW CLOUDS COVER THE ENTIRE FCST AREA FROM NW NJ AND THE POCONOS TO SRN DE. MORNING SOUNDS SHOW THE SUBSIDENCE INVERSION BETWEEN 800 AND 850 MB WITH MOISTURE TRAPPED BELOW. THE CLOUD LAYER IS RATHER THIN ESPECIALLY NEAR THE SRN EDGE OVER DELVARVA AND SRN NJ. GUIDANCE INDICATES CLEARING TODAY BUT THINK THIS MAY BE TOO OPTIMISTIC. DEC SUN WILL NOT HAVE MUCH EFFECT. HAVE INCREASED CLOUD COVER IN THE GRIDS BUT RETAIN PARTIAL CLEARING SOUTH. MAX TEMPS THIS AFTN WILL BE ONLY A FEW DEGS HIGHER THAN CURRENT READINGS. PREVIOUS DISCUSSION BELOW... SURFACE HIGH CONTINUES TO SLIDE CLOSER TO THE REGION TODAY. HOWEVER, LIKE LAST WEEK, THERE APPEARS TO BE ABUNDANT MOISTURE BELOW THE INVERSION, SO DESPITE THE SYNOPTIC SCALE SUBSIDENCE, SHOULD STILL SEE QUITE A BIT OF CLOUD COVER. WITH LITTLE CHANGE IN THE AIR MASS, EXPECT HIGHS NEAR MAX TEMPS YESTERDAY WHICH ARE NEAR OR JUST BELOW NORMALS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... THE BIGGEST CHANGE TONIGHT FROM THE LAST FEW NIGHTS IS THAT WITH THE HIGH INCHING CLOSER AND THUS THE PRESSURE GRADIENT ACROSS THE REGION DECREASING, WINDS SHOULD BE LIGHT. THOUGH WE WOULD TYPICALLY EXPECT TO SEE CLEARING SKIES IN THIS PATTERN, WITH THE LOW LEVEL MOISTURE LIKELY STILL IN PLACE, COULD STILL SEE QUITE A BIT OF CLOUD COVER, ESPECIALLY OVER THE NORTHERN HALF OF THE REGION. && .LONG TERM /SATURDAY THROUGH THURSDAY/... MID-LEVEL FLOW THE NEXT COUPLE OF DAYS IS RATHER FLAT THOUGH A CHANGE TO THAT PATTERN APPEARS LIKELY BY THE END OF THE WEEKEND. A DEEP TROUGH EMERGES ACROSS THE CENTRAL U.S. BY TUESDAY AS MULTIPLE PACIFIC NORTHWEST WAVES ROUND THE BASE OF THE TROUGH AND ACROSS OUR REGION...WE ARE HEADING FOR A VERY UNSETTLED PERIOD BY EARLY NEXT WEEK. SATURDAY - SUNDAY...LOOKS MOSTLY DRY BOTH DAYS WITH HIGH PRESSURE ANCHORED TO OUR NORTHEAST. THERE IS SOME NORTHERN STREAM ENERGY TO CONTEND WITH LATE SATURDAY NIGHT WITH THE HELP OF A WEAK INVERTED TROUGH OFFSHORE. THIS COMBINATION COULD TOUCH OFF A FEW SHOWERS AS ALONG THE NORTHEASTERN NEW JERSEY COAST BUT WILL BE OF LITTLE CONSEQUENCE. ONSHORE FLOW WILL HELP TO KEEP AMPLE LOW-LEVEL MOISTURE STREAMING INTO THE REGION, UNDER THE SUBSIDENCE INVERSION. SATURDAY COULD BE THE SUNNIER DAY THAN SUNDAY, BUT EACH DAY THE CONVECTIVE TEMPERATURES LOOK TO BE REACHED SO IT MAY BE SHORT LIVED. MONDAY - TUESDAY...ONCE THE AFOREMENTIONED SYSTEM ABOVE DEPARTS ANOTHER, BETTER DEFINED SYSTEM MOVES OFF THE CAROLINA COAST AND OUT TO SEA ON TUESDAY. WEAK BAROCLINIC ZONE OFF THE MID-ATLANTIC COAST WILL ALLOW FOR AMPLE MOISTURE TO ADVECT IN FROM THE SOUTH. AS THE WAVE OF LOW PRESSURE MOVES BY IT WILL TAP INTO THE MOISTURE FEED ALLOWING FOR BETTER CHANCES OF PRECIPITATION. CONTINUED ONSHORE FLOW AHEAD OF THE SYSTEM WILL ALLOW FOR A WARMING LOW-LEVEL THERMAL PROFILE SO ANY PRECIPITATION WILL BE LIQUID WITH SOME MIXING POSSIBLE IN THE FAR NORTHWESTERN ZONES. IT IS ENTIRELY POSSIBLE THAT A WEAK CAD SETUP OCCURS LATE MONDAY NIGHT WITH A NORTHERLY BOUNDARY LAYER AGEOSTROPHIC WIND COMPONENT. MODELS HAVE BEEN KNOWN TO WARM THE SURFACE LAYER TOO FAST WITH A RATHER LARGE NEW ENGLAND HIGH PRESSURE IN PLACE, OR THEY PUSH THE HIGH OUT FASTER ALLOWING A SOUTHEAST RETURN FLOW. EITHER WAY IT COULD BE A MESSY TUESDAY MORNING COMMUTE ACROSS OUR NORTHWEST ZONES. SYSTEM MOVES OFF TOWARDS THE NORTHEAST ON TUESDAY, WITH RAIN STILL ONGOING, BUT WE ARE GEARING UP FOR THE BIGGER EVENT ON CHRISTMAS EVE. WEDNESDAY...STILL WATCHING A LARGE LOW PRESSURE FORM TO OUR WEST AND TRACK INTO THE GREAT LAKES REGION ON WEDNESDAY. THIS WOULD KEEP OUR REGION UNDER A WARMING THERMAL PROFILE WITH A LOT OF MOISTURE TO WORK WITH...AN ALL LIQUID EVENT IS EXPECTED AT THIS POINT. GUIDANCE CONTINUES TO SHOW A WEAKER SECONDARY DEVELOPMENT ALONG A TRIPLE POINT OVER OUR REGION DURING THE DAY. THIS WOULD HELP TO INTENSIFY RAINFALL AMOUNTS AND ENHANCE THE LOW-LEVEL PRESSURE GRADIENT. HEAVY RAIN WITH STRONG WINDS ARE EXPECTED SO IT IS ENTIRELY POSSIBLE WE ARE LOOKING AT ANOTHER MULTIPLE HEADLINE EVENT. COASTAL FLOODING COULD ALSO BECOME AN ISSUE WITH THE STRONGER ONSHORE WINDS DURING WEDNESDAY`S HIGH TIDE. HAVE GONE WITH CATEGORICAL POPS FOR THAIS TIMEFRAME. WE WILL CONTINUE TO HAVE WORDING IN THE HWO FOR THIS EVENT. LOOKS LIKE RUDOLPH AND THE OTHER REINDEER WILL HAVE THEIR WORK CUT OUT FOR THEM THIS CHRISTMAS EVE. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. LOW-END VFR CIGS CONTINUE AT ALL TAF SITES THIS MORNING. NO PROBLEMS WITH VSBYS. A FEW NW WINDS GUSTS ARE POSSIBLE TODAY BUT THIS GUSTINESS IS LOOKING LESS LIKELY WITH TIME. MOSTLY VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. THERE SHOULD BE PERSISTENT CLOUDS BETWEEN 3000 AND 5000 FT AGL FOR MUCH OF THE DAY, SO COULD SEE LOCALIZED MVFR CEILINGS RIGHT AT 3000 FT, BUT MOSTLY CEILINGS SHOULD BE BETWEEN 3500 AND 4000 FT. NORTHWESTERLY WINDS MAY GUST AT TIMES TO 20KT THROUGH EARLY THIS AFTERNOON, BUT BY TONIGHT SHOULD BE LESS THAN 10KT. OUTLOOK... SATURDAY - SUNDAY...VFR. NORTH-NORTHEAST WINDS EXPECTED. CIGS COULD BE LOWERING THROUGHOUT THE DAY MONDAY - TUESDAY...SUB-VFR EXPECTED WITH SCATTERED RAIN/SNOW SHOWERS, BECOMING ALL RAIN BY TUESDAY.
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&& .MARINE... WINDS AND SEAS SHOULD STAY BELOW SCA CRITERIA. HOWEVER, GUSTS NEAR OR JUST ABOVE 20KT WILL BE POSSIBLE THROUGH THIS EVENING. OUTLOOK... SATURDAY - SUNDAY...SUB-SCA EXPECTED FOR THE MOST PART. SEAS REMAIN AROUND 3 TO 4 FEET. CONFIDENCE: AVERAGE TO SLIGHTLY BELOW AVERAGE. MONDAY - TUESDAY...SCA CONDITIONS SHOULD PRESENT THEMSELVES LATER ON MONDAY UNDER A STRENGTHENING EASTERLY FLOW AND BUILDING SEAS. CONFIDENCE: AVERAGE. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GIGI NEAR TERM...AMC/JOHNSON SHORT TERM...JOHNSON LONG TERM...HEAVENER AVIATION...AMC/HEAVENER/JOHNSON MARINE...HEAVENER/JOHNSON

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