705  
FXUS61 KPHI 270359  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
1159 PM EDT WED APR 26 2017  
   
SYNOPSIS
 
 
A WEAKENING LOW NEAR LONG ISLAND THIS EVENING 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/
 
 
AS THE WEAK LOW DRIFTS NORTHEASTWARD, SOME CLEARING TOOK PLACE  
OVER EASTERN PENNSYLVANIA. HOWEVER, THE CLOUDS BEGAN TO BUILD  
BACK TO THE WEST ONCE THE SUN SET WHICH IS A BIT FASTER THAN  
PREVIOUSLY THOUGHT. WE WILL FORECAST A CLOUDY TO MOSTLY CLOUDY  
SKY FOR THE BALANCE OF THE NIGHT THROUGHOUT OUR COUNTIES IN  
EASTERN PENNSYLVANIA, NEW JERSEY, DELAWARE AND NORTHEASTERN  
MARYLAND. THE QUICK RETURN OF THE CLOUD COVER SHOULD LIMIT THE  
AMOUNT OF FOG WE HAVE OVERNIGHT. WE WILL CONTINUE TO MENTION  
ONLY PATCHY FOG IN SPOTS.  
 
THE WIND IS FORECAST TO REMAIN LIGHT AND VARIABLE. MINIMUM  
TEMPERATURES SHOULD FAVOR THE LOWER AND MIDDLE 50S.  
 

 
   
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 /04Z THURSDAY THROUGH MONDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
MVFR CEILINGS WERE BEING REPORTED AROUND 0130Z AT ALL EIGHT OF  
OUR TAF SITES. THE CLEARING THAT TOOK PLACE IN EASTERN  
PENNSYLVANIA HAS PROVEN MORE SHORT LIVED THAN WE ORIGINALLY  
THOUGHT IT WOULD BE. AS A RESULT, WE HAVE ADJUSTED THE TAFS  
ACCORDINGLY.  
 
WE ARE EXPECTING MVFR CEILINGS TO PREVAIL DURING THE FIRST PART  
OF THE NIGHT. CEILINGS MAY LOWER NEAR 1000 FEET LATE TONIGHT  
AND THEY COULD EVEN DROP A BIT BELOW THAT LEVEL IN SPOTS. OUR  
CONFIDENCE IN THAT OCCURRING AND WHERE IT WOULD HAPPEN IS LOW,  
SO WE HAVE LIMITED OUR DECREASE IN CEILING HEIGHTS TO THE 1000  
FOOT LEVEL. THE CLOUD COVER SHOULD PREVENT ANY DENSE FOG FROM  
FORMING AT OR NEAR OUR TAF SITES.  
 
WE ARE ANTICIPATING THAT CONDITIONS WILL IMPROVE THROUGH MVFR  
LATE ON THURSDAY MORNING INTO THE VFR CATEGORY FOR THURSDAY  
AFTERNOON.  
 
A LIGHT AND VARIABLE WIND OVERNIGHT IS FORECAST TO SETTLE INTO  
THE SOUTHEAST AND SOUTH ON THURSDAY WITH SPEEDS INCREASING TO 5  
TO 10 KNOTS.  
 
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
 
 
STARTING TO SEE VISIBILITIES ALONG THE COAST TO DECREASE NEAR  
ONE MILE. THUS, HAVE ISSUED A MARINE DENSE FOG ADVISORY THROUGH  
14Z. HARD TO DETERMINE HOW FAR OFF THE COAST THE FOG GOES, BUT  
EXPECT WIDESPREAD FOG AT LEAST NEAR THE SHORE. WILL CONTINUE TO  
MONITOR THROUGH THE NIGHT.  
 
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.  
 
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.  
 

 
   
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...DENSE FOG ADVISORY UNTIL 10 AM EDT THURSDAY FOR ANZ430-431-  
450>455.  
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT FRIDAY  
FOR ANZ450>455.  
 

 
 

 
SYNOPSIS...MIKETTA  
NEAR TERM...IOVINO  
SHORT TERM...DRAG  
LONG TERM...MIKETTA  
AVIATION...IOVINO/MIKETTA  
MARINE...DRAG/JOHNSON/MIKETTA  
CLIMATE...  
 
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