340  
FXUS61 KPHI 190924  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
424 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/
 
 
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.  
 

 
   
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 /09Z FRIDAY THROUGH TUESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
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.  
 

 
   
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...JOHNSON  
SHORT TERM...JOHNSON  
LONG TERM...HEAVENER  
AVIATION...HEAVENER/JOHNSON  
MARINE...HEAVENER/JOHNSON  
 
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