760  
FXUS61 KPHI 261942  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
342 PM EDT WED APR 26 2017  
   
SYNOPSIS
 
 
A WEAKENING COASTAL LOW NEAR LONG ISLAND WILL MOVE SLOWLY NORTHEAST  
OVERNIGHT. A COLD FRONT WILL MOVE ACROSS THE AREA LATE THURSDAY  
NIGHT AND EARLY FRIDAY MORNING BEFORE ANOTHER COLD FRONT CROSSES  
SATURDAY NIGHT. A WARM FRONT IS THEN EXPECTED TO LIFT NORTH ACROSS  
THE AREA SUNDAY NIGHT, FOLLOWED BY ANOTHER COLD FRONT MONDAY NIGHT.  
HIGH PRESSURE IS THEN EXPECTED FOR THE MIDDLE OF NEXT WEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
 
 
REST OF TODAY...CEILINGS SLOWLY LIFTING WITH SOME BREAKS IN OVERCAST  
OR BRIGHTENING AND TEMPS EVER SO SLOWLY WARMING AS THE VERTICALLY  
STACKED LOW PRESSURE SYSTEM OFF THE NJ COAST HEADS EAST. THERE  
MAY STILL BE SOME SPOTTY MIST OR AN ISOLATED SHOWER/ SPRINKLE  
INTO THIS EVENING, MAINLY NE NJ.  
 
TONIGHT....WHERE IT CLEARS...FOG MAY FORM RIGHT AWAY...OTHERWISE  
A DECK OF CLOUDS MAY PERSIST MUCH OF THE NIGHT NEAR 2000 OR 3000  
FT THAT WOULD PREVENT SIGNIFICANT FOG AND STRATUS FORMATION DURING  
THE NIGHT. CONFIDENCE ON STRATUS-FOG FORMATION, EXPANSION/REFORMATION  
IS BELOW AVERAGE BUT WE HAVE MAINTAINED IT IN THE FCST..USING THE  
UPS CROSSOVER TOOL. FCST WAS WAS A 50 50 BLEND OF THE 12Z/26  
GFS/NAM MOS. FCST MINS ARE 8 TO 12 DEGREES ABOVE NORMAL.  
 

 
   
SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/
 
 
MOSTLY CLOUDY TO START...BUT ALL MODEL TSECTIONS FCST A MUCH  
BRIGHTER AND WARMER DAY... WITH A DECENT AMOUNT OF AFTERNOON  
SUNSHINE SO HAVE USED THE 12Z/26 GFS/NAM MOS BLEND FOR THE FCST  
BASIS. FCST TEMPS ARE 7 TO 13F ABOVE NORMAL. MAX T AT PHL MAY  
REACH 82 OR 83.  
 

 
   
LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/
 
 
A COLD FRONT ASSOCIATED WITH LOW PRESSURE MOVING NORTH THROUGH  
EASTERN CANADA IS EXPECTED TO CROSS THE REGION THURSDAY NIGHT, THEN  
MOVE OFF THE COAST FRIDAY MORNING. MAINLY SCATTERED SHOWERS ARE  
EXPECTED AT THIS TIME, PRIMARILY FROM MIDNIGHT THROUGH 6 OR 7 AM. A  
SOUTHERLY FLOW ALOFT WILL MAINTAIN LOW TEMPERATURES IN THE MID TO  
UPPER 40S AND HIGH TEMPERATURES IN THE UPPER 70S TO LOW 80S, ABOVE  
NORMAL FOR THIS TIME OF YEAR. THE DAYTIME HOURS ON FRIDAY WILL  
FEATURE MAINLY DRY WEATHER HAS HIGH PRESSURE BRIEFLY BUILDS INTO  
THE REGION.  
 
BY FRIDAY NIGHT, ANOTHER FRONTAL BOUNDARY IS FORECAST TO BEGIN  
APPROACHING THE AREA FROM THE NORTHWEST AS IT CROSSES PENNSYLVANIA  
AND NEW YORK. THE FRONT WILL SAG SOUTH THROUGH THE AREA DURING THE  
DAY SATURDAY, BRINGING WITH IT SOME ADDITIONAL SHOWER ACTIVITY, THEN  
STALL TO OUR SOUTH SATURDAY NIGHT INTO SUNDAY. THE SUBSEQUENT  
ONSHORE FLOW WILL COOL TEMPERATURES DOWN TO THE 60S NORTH AND LOW  
70S SOUTH ON SUNDAY,BUT WITH MAINLY DRY CONDITIONS. THIS FRONT IS  
THEN EXPECTED TO LIFT BACK NORTH AS A WARM FRONT SUNDAY NIGHT INTO  
MONDAY MORNING, WITH AN INCREASING CHANCE OF SHOWERS AS THE DAY  
WEARS ON WITH THE APPROACH OF A COLD FRONT FROM THE WEST LATE IN THE  
DAY. SHOWERS AND THUNDERSTORMS MAY ACCOMPANY THIS FRONT...ESPECIALLY  
LATER MONDAY NIGHT INTO TUESDAY MORNING. INSTABILITY IN THE WARM  
SECTOR AHEAD OF THIS FRONT COULD EVEN PRODUCE SHOWER AND  
THUNDERSTORM ACTIVITY AS EARLY AS MONDAY AFTERNOON. HIGH  
TEMPERATURES IN THE 70S ARE EXPECTED ON MONDAY.  
 
THE FRONT WILL MOVE OFFSHORE BY TUESDAY MORNING, BUT A SECONDARY  
SURFACE TROUGH MAY MOVE ACROSS THE AREA DURING THE DAY. WITH A SHORT  
WAVE/VORTICITY MAX MOVING ACROSS THE AREA DURING THE DAY, THERE  
COULD BE SOME ISOLATED SHOWERS ACROSS NORTHEASTERN PENNSYLVANIA AND  
NORTHERN NEW JERSEY. COOLER TEMPERATURES ARE EXPECTED THROUGH MID  
WEEK, WITH LOWS GENERALLY IN THE 50S AND HIGHS IN THE 70S.  
 

 
   
AVIATION /20Z WEDNESDAY THROUGH MONDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
REST OF THIS AFTERNOON...CIGS 1000 TO 2500 FEET CONTINUE TO IMPROVE-  
RISE-LIFT. LIGHT NORTH TO NORTHEAST WIND.  
 
TONIGHT...PROBABLY MVFR CIGS TO START BUT MAY DETERIORATE TO IFR  
CONDITIONS IN ST/FOG WITH A NEARLY CALM WIND SOMETIME BETWEEN  
06Z AND 12Z/27. PLEASE SEE TAFS FOR DETAILS.  
 
THURSDAY...IFR OR MVFR CONDS IN ST/FOG TO START THE DAY, PROBABLY  
IMPROVES TO VFR SCT-BKN CLOUDS AOA 3500 FEET DURING THE AFTERNOON.  
WIND BECOMING SOUTHEAST TO SOUTH WITH MID AFTERNOON GUSTS 15-20KT.  
 
OUTLOOK...  
 
THURSDAY NIGHT...GENERALLY VFR. A CHANCE OF SHOWERS OVERNIGHT  
WHICH COULD TEMPORARILY REDUCE CONDITIONS TO MVFR.  
 
FRIDAY...VFR CONDITIONS EXPECTED.  
 
FRIDAY NIGHT...VFR EARLY. PATCHY FOG AND LOW CIGS MAY DEVELOP  
OVERNIGHT.  
 
SATURDAY...BECOMING VFR DURING THE MORNING, THEN A CHANCE OF  
SHOWERS DURING THE AFTERNOON. CONDITIONS MAY TEMPORARILY BE  
REDUCED WITH ANY SHOWERS.  
 
SATURDAY NIGHT-MONDAY...LOW CLOUDS AND FOG MAY DEVELOP  
OVERNIGHT SATURDAY AND CONTINUE INTO SUNDAY LEADING TO REDUCED  
CONDITIONS. THERE WILL ALSO BE A CHANCE OF SHOWERS.  
 

 
   
MARINE
 
 
THE SMALL CRAFT ADVISORY HAZARDOUS SEAS CONTINUES THROUGH  
THURSDAY. WAVES (VIRTUALLY ALL SE SWELL AT 10-11 SECONDS) ARE  
CURRENTLY AROUND 7 FT AND WILL GRADUALLY SUBSIDE THROUGH  
THURSDAY. HOW MUCH MARINE FOG DEVELOPS THE NEXT DAY OR SO.?  
UNSURE...SO FCST THE FOG CONSERVATIVELY FOR NOW.  
 
OUTLOOK...  
 
THURSDAY NIGHT...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS  
THROUGH THURSDAY NIGHT.  
 
FRIDAY...WINDS EXPECTED TO REMAIN BELOW ADVISORY LEVELS, BUT  
SEAS MAY REMAIN ELEVATED TO ADVISORY LEVELS.  
 
FRIDAY NIGHT-MONDAY...WINDS ARE EXPECTED TO REMAIN BELOW  
ADVISORY LEVELS. SEAS MAY APPROACH 5 FEET AT TIMES, BUT MOSTLY  
REMAIN AROUND 4 FEET.  
 

 
   
TIDES/COASTAL FLOODING
 
 
TIDES FCST NEAR ADVISORY THRESHOLD THIS EVENING. HOLDING OFF ON  
AN ADVISORY FOR NOW BUT MAY NEED TO ISSUE FOR MINOR COASTAL  
FLOODING AROUND 6 OR 7PM IF DEPARTURES DO NOT FURTHER DECREASE.  
 
WE WILL CONTINUE TO MONITOR THE HIGH TIDE THIS EVENING SINCE IT  
WILL BE THE HIGHER ONE THAT OCCURS WITH A NEW MOON. IF THE WATER  
DOES NOT DRAIN AWAY FROM THE COAST FAST ENOUGH, WE COULD SEE  
SOME LOCALIZED MINOR FLOODING AT THAT TIME.  
 

 
   
CLIMATE
 
 
PRESUMING OUR FORECAST TEMPS THESE LAST 5 DAYS OF APRIL ARE ACCURATE,  
WE ARE ASSURED OF A TOP 3 WARMEST APRIL ON RECORD IN MUCH OF OUR  
FORECAST AREA. SUNDAY IS THE CRITICAL DAY FOR DETERMINING RECORD  
OR NOT.  
 
BELOW: APRIL PROJECTED WITHIN THE TOP APRIL AVG TEMPS, THE  
NORMAL FOR APRIL AND THE PERIOD OF RECORD (POR).  
 
PHL NORMAL 54.0 POR 1874  
 
59.4 1994  
59.2 2017?  
58.5 1921  
58.4 2010  
57.9 1941  
 
ABE NORMAL 49.9 POR 1922  
 
56.6 PROJECTING RECORD  
56.4 1941  
54.7 1994  
 
ACY NORMAL 51.7 POR 1874  
 
57.2 PROJECTING RECORD  
56.3 2010  
56.1 2011  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...NONE.  
DE...NONE.  
MD...NONE.  
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT FRIDAY  
FOR ANZ450>455.  
 

 
 

 
SYNOPSIS...MIKETTA  
NEAR TERM...DRAG 342  
SHORT TERM...DRAG  
LONG TERM...MIKETTA  
AVIATION...DRAG/MIKETTA 342  
MARINE...DRAG/MIKETTA  
TIDES/COASTAL FLOODING...  
CLIMATE...  
 
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