153  
FXUS61 KPHI 281323  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
923 AM EDT WED JUN 28 2017  
   
SYNOPSIS
 
 
HIGH PRESSURE OVER OUR REGION TODAY WILL SHIFT OFFSHORE THIS  
EVENING, THEN REMAIN THERE THROUGH FRIDAY. A WEAK COLD FRONT IS  
FORECAST TO ARRIVE LATER SUNDAY, HOWEVER THIS BOUNDARY MAY THEN  
STALL ACROSS OUR REGION EARLY NEXT WEEK.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
NO MAJOR CHANGES WITH THE 930 AM FORECAST UPDATE. AGREE WITH THE  
PREVIOUS SHIFT THAT THERE MAY BE MEAGER INSTABILITY AND ENOUGH  
MOISTURE TO SUPPORT LIGHT SHOWERS AROUND AND NORTH OF THE I80  
CORRIDOR THIS AFTERNOON. HOWEVER, SYNOPTIC SCALE SUBSIDENCE  
MAKES IT TOO UNLIKELY TO INCLUDE IN THE FORECAST AT THIS TIME.  
 
TODAY...SUNNY OR MOSTLY SUNNY AND COMFORTABLY COOL FOR SUMMER  
WITH FEW OR SCT SC 16Z-21Z AOA 5000 FT, MAINLY NORTHWEST OF  
I-95. WEST NORTHWEST WIND GUSTING 15-20 MPH THIS MORNING  
BECOMING MORE WESTERLY THIS AFTERNOON AND DIMINISHING SLIGHTLY.  
DEWPOINTS IN THE 40S WHILE MAX TEMPS 2 TO 7 DEGREES BELOW  
NORMAL. ONE OF THE NICEST DAYS WE'LL SEE FOR QUITE A WHILE.  
 
FORECAST BASIS: A 50 50 BLEND OF THE 00Z/28 GFS/NAM MOS.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/
 
 
TONIGHT...MOSTLY CLEAR WITH SOME CIRRUS AFTER MIDNIGHT, ESPECIALLY  
NORTHWEST OF I-95. LOWERED THE 50 50 BLENDED 00Z/28 MOS GFS/NAM  
TEMPS A DEGREE OR TWO FROM THAT GUIDANCE DUE TO LIGHT WIND.  
THESE TEMPS 1 TO 4 DEGREES BELOW NORMAL.  
 

 
   
LONG TERM /THURSDAY THROUGH TUESDAY/
 
 
SUMMARY...INCREASING HEAT AND HUMIDITY FRIDAY INTO SUNDAY, THEN THE  
HUMIDITY SHOULD LOWER SOME EARLY NEXT WEEK FOR MUCH OF THE AREA. THE  
DETAILS THOUGH WILL DEPEND ON THE TIMING AND LOCATION OF A WEAK COLD  
FRONT THAT MAY END UP STALLING ACROSS OUR REGION.  
 
SYNOPTIC OVERVIEW...A MORE ZONAL FLOW ALOFT THURSDAY WILL GIVE WAY  
TO SOME AMPLIFICATION ACROSS THE NORTHEAST. THIS CHANGE WILL BE DUE  
TO A STRONG SHORT WAVE CARVING OUT A TROUGH IN THE MIDWEST AND GREAT  
LAKES FRIDAY AND SATURDAY, WHICH THEN GRADUALLY SHIFTS EASTWARD  
LATER IN THE WEEKEND AND EARLY NEXT WEEK. THERE MAY BE SEVERAL  
STRONGER SHORT WAVES WITHIN THIS TROUGH, WHICH WILL IMPACT THE  
SHARPNESS AND TIMING EASTWARD. AT THE SURFACE, HIGH PRESSURE REMAINS  
ANCHORED OFFSHORE WHICH WILL RESULT IN A HOT AND HUMID SOUTHWEST  
FLOW FOR A TIME. THE MAIN FEATURE IS A WEAK COLD FRONT THAT WILL  
SETTLE INTO OUR AREA LATER SUNDAY, HOWEVER IT MAY THEN STALL IN OUR  
VICINITY THROUGH EARLY NEXT WEEK. THE PRESENCE OF THE INCOMING FRONT  
AND TROUGH NEARBY WILL RESULT IN SOME CONVECTION. WE USED A  
MODEL/CONTINUITY BLEND FOR THURSDAY THROUGH FRIDAY NIGHT, THEN  
BLENDED IN THE 00Z WPC GUIDANCE THEREAFTER. SOME ADJUSTMENTS WERE  
THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH OUR NEIGHBORING  
OFFICES.  
 
FOR THURSDAY AND FRIDAY...HIGH PRESSURE ANCHORED OFFSHORE WILL DRIVE  
AN INCREASING SOUTHWESTERLY WIND ACROSS OUR AREA. THE FLOW ALOFT IS  
MAINLY ZONAL, WITH THE MAIN SHORT WAVE ENERGY TRACKING TO OUR NORTH  
THURSDAY. THERE IS INCREASING LOW-LEVEL WARM AIR ADVECTION FORECAST  
DURING THURSDAY, WHICH WILL BOOST TEMPERATURES WELL INTO THE 80S.  
THE SOUTHWESTERLY FLOW WILL ALSO START TO TRANSPORT INCREASING LOW-  
LEVEL MOISTURE OUR WAY ESPECIALLY AS A 40-50 KNOT LOW-LEVEL JET  
MOVES THROUGH THURSDAY NIGHT. THIS MOISTURE INCREASE SHOULD BE  
GRADUAL DURING THE DAY THURSDAY RESULTING IN A NOT SO HUMID FEEL  
OVERALL. THIS WILL CHANGE HOWEVER THURSDAY NIGHT AND FRIDAY AS DEW  
POINTS ARE FORECAST TO INCREASE INTO THE 60S. AS THE LOW-LEVEL WARM  
AIR ADVECTION CONTINUES IN ADDITION TO PERHAPS SOME SUBSIDENCE ON  
THE NORTHWEST SIDE OF OFFSHORE HIGH PRESSURE, DAYTIME HIGHS ON  
FRIDAY WILL EDGE INTO THE LOWER 90S FOR SEVERAL AREAS. THIS COMBINED  
WITH HIGHER DEW POINTS WILL RESULT IN HEAT INDICES INTO THE MID 90S  
DURING PEAK HEATING. THERE WILL BE A SOUTHWESTERLY BREEZE, AND AS  
MIXING DEEPENS THE DEW POINTS MAY LOCALLY LOWER SOME DURING PEAK  
HEATING WHICH IN THIS CASE WOULD KEEP THE HEAT INDICES A BIT LOWER.  
THURSDAY LOOKS TO BE A DRY DAY FOR MUCH OF THE REGION, ALTHOUGH SOME  
UPSTREAM CONVECTION MAY GET INTO OUR NORTHWESTERN ZONES LATER IN THE  
DAY AND IN THE EVENING. A LEAD SHORT WAVE CROSSING THE NORTHERN  
AREAS FRIDAY AFTERNOON MAY ALLOW FOR SOME CONVECTION. THIS LOOKS TO  
BE FOCUSED NEAR THE HIGHER TERRAIN AREAS OF OUR NORTHWESTERN ZONES.  
WE WILL CONTINUE TO CARRY SLIGHT CHANCE TO LOW CHANCE POPS  
ESPECIALLY FRIDAY AFTERNOON AND EVENING.  
 
FOR SATURDAY AND SUNDAY...LOW PRESSURE IS FORECAST TO TRACK FROM THE  
GREAT LAKES SATURDAY MORNING TO JUST EAST OF JAMES BAY CANADA BY  
LATER SUNDAY. THIS WILL PULL A COLD FRONT SLOWLY EASTWARD, AND IT  
CURRENTLY IS NOT FORECAST TO ARRIVE INTO OUR AREA UNTIL LATER  
SUNDAY. THE SYNOPTIC SETUP WOULD SUGGEST THOUGH THAT A LEE-SIDE  
TROUGH WILL BE IN PLACE, WITH THIS POTENTIALLY BEING LOCATED NEAR  
THE I-95 CORRIDOR BOTH DAYS. THERE WILL BE A HOT AND HUMID AIRMASS  
IN PLACE, ESPECIALLY SATURDAY WHERE THE HUMIDITY SHOULD PEAK. THE  
MAIN UPPER-LEVEL TROUGH IS FORECAST TO HANG BACK OVER THE GREAT  
LAKES FOR SATURDAY, THEN MORE EASTWARD PROGRESS OCCURS SUNDAY. THIS  
WILL SETTLE A WEAK COLD FRONT INTO OUR AREA LATER SUNDAY. THE BULK  
OF THE CONVECTION SATURDAY MAY RESIDE TO OUR WEST CLOSER TO THE  
FRONTAL ZONE, HOWEVER SOME CONVECTION IS ANTICIPATED TIED TO THE LEE-  
SIDE TROUGH. GIVEN THE HIGHER HEAT AND HUMIDITY ON SATURDAY A HEAT  
ADVISORY MAY BE NEEDED, ESPECIALLY FOR THE URBAN CORRIDOR FROM  
WILMINGTON TO PHILADELPHIA/CAMDEN TO TRENTON, AS HEAT INDICES MAY  
APPROACH 100 DEGREES DURING PEAK HEATING. THE CONVECTIVE EVOLUTION  
DURING THIS TIME FRAME IS LESS CERTAIN, AS THE TIMING OF THE FRONT  
WILL BE KEY AND ALSO HOW MUCH CAN DEVELOP NEAR OR ALONG THE LEE-SIDE  
TROUGH. THERE IS SOME POTENTIAL THAT UPSTREAM ORGANIZED CONVECTION  
MOVES ACROSS MUCH OF OUR AREA SATURDAY NIGHT. GIVEN LESS CERTAINTY,  
HELD POPS NO HIGHER THAN THE CHANCE RANGE.  
 
FOR MONDAY AND TUESDAY...THE MAIN PART OF AN UPPER-LEVEL TROUGH MAY  
LIFT INTO NORTHERN NEW ENGLAND DURING THIS TIME FRAME, THEREFORE THE  
FLOW IS MORE PARALLEL TO A SURFACE FRONT IN THE VICINITY. AS A  
RESULT, OUR SENSIBLE WEATHER WILL BE DEPENDENT ON THE LOCATION OF  
THIS FRONT AS IT STALLS OUT. SOME LINGERING LOW-LEVEL CONVERGENCE  
COMBINED WITH INSTABILITY AND SOME SHORT WAVES ALOFT MAY RESULT IN  
SOME CONVECTION ESPECIALLY EACH AFTERNOON AND EVENING. THE OVERALL  
TIMING THOUGH AND ESPECIALLY COVERAGE IS LESS CERTAIN. WHILE IT WILL  
STILL BE RATHER WARM, A BIT OF COOLING IS ANTICIPATED BASED ON THE  
FRONT IN THE AREA AND THE DEW POINTS SHOULD BE A LITTLE LOWER AS  
WELL.  
 

 
   
AVIATION /14Z WEDNESDAY THROUGH SUNDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
THROUGH TODAY....VFR. FEW OR SCT CLOUDS AOA 6000 FT. WEST NORTHWEST  
WIND GUST AROUND 15 KTS BACKING A BIT THIS AFTERNOON.  
 
TONIGHT...VFR. BROKEN CIRRUS PROBABLY ARRIVES TOWARD DAWN THURSDAY.  
LIGHT SOUTHWEST WIND.  
 
OUTLOOK...  
THURSDAY AND FRIDAY...VFR OVERALL. A SHOWER OR THUNDERSTORM IS  
POSSIBLE THURSDAY AFTERNOON AND EVENING MAINLY NORTH AND WEST OF  
KABE, THEN THIS MAY SPREAD SOUTH AND EAST SOME THROUGH FRIDAY.  
SOUTHWEST WINDS INCREASE EACH DAY TO 10-15 KNOTS, WITH LOCAL GUSTS  
UP TO 20 KNOTS EACH AFTERNOON.  
 
SATURDAY AND SUNDAY...TIMES OF LOWER CONDITIONS POSSIBLE DUE TO SOME  
SHOWERS AND THUNDERSTORMS, ESPECIALLY EACH AFTERNOON AND EVENING.  
 

 
   
MARINE
 
 
NO HEADLINES THROUGH TONIGHT. NORTHWEST WIND GUST 15-20 KT AT  
TIMES DURING THE DAYLIGHT HOURS BECOMES SOUTH TO SOUTHWEST LATE  
THIS AFTERNOON AND CONTINUES TONIGHT. LOCAL SEA BREEZES SHOULD  
DEVELOP 15-18Z. GUSTS TO 25 KT POSSIBLE LATE THIS AFTERNOON NNJ  
WATERS.  
 
OUTLOOK...  
THURSDAY AND FRIDAY...A LOW-LEVEL JET IS FORECAST TO MOVE ACROSS THE  
AREA THURSDAY NIGHT INTO FRIDAY, HOWEVER THE FORECAST SOUNDINGS SHOW  
VERTICAL MIXING IS NOT ALL THAT EFFICIENT DUE TO A VERY WARM AIRMASS  
IN PLACE. HOWEVER, STRONGER WINDS ARE NOT THAT FAR ABOVE THE  
SURFACE. AS A RESULT, WIND GUSTS UP TO 30 KNOTS ARE POSSIBLE FOR A  
TIME ESPECIALLY ON THE OCEAN ZONES. THIS STRONGER SOUTHWESTERLY FLOW  
WILL ALSO BUILD THE SEAS. A SMALL CRAFT ADVISORY THEREFORE MAY BE  
NEEDED STARTING THURSDAY AFTERNOON AND CONTINUING INTO FRIDAY. THE  
WINDS AND SEAS SHOULD DIMINISH FRIDAY NIGHT.  
 
SATURDAY AND SUNDAY...THE WINDS AND SEAS ARE FORECAST TO BE MOSTLY  
BELOW SMALL CRAFT ADVISORY CRITERIA.  
 
RIP CURRENTS...  
 
THIS MORNINGS OBSERVATION FROM LBI INDICATED A WATER TEMP IN THE  
LOWER 60S AND IT MIGHT BE COLDER THAN THAT ON PARTS OF THE NJ  
COAST FROM OCEAN COUNTY DOWN TO CAPE MAY AS EVALUATED BY THE  
0822Z RUTGERS IMCS SATELLITE IMAGERY.  
 
THE FORECAST IS FOR A LOW RISK FOR THE FORMATION OF DANGEROUS  
RIP CURRENTS TODAY. OFFSHORE WINDS THIS MORNING TURN SOUTHERLY  
THIS AFTERNOON AND INCREASE CONSIDERABLY LATE IN THE DAY,  
ESPECIALLY OCEAN AND MONMOUTH COUNTIES. SO A CLEARLY DEFINED LOW  
RISK MORNING-MIDDAY MAY BECOME LOW ENHANCED LATE THIS  
AFTERNOON, ESPECIALLY AS HEAD TO THE LATE AFTERNOON LOW TIDE. WE  
RAN A LATE DAY SWELL SCENARIO OF 1 FT 9 SEC OR 2 FEET 5  
SECONDS, WITH A SOUTH WIND OF 19 KNOTS AND STILL CAME UP WITH  
LOW RISK.  
 
LOW RISK DOES NOT MEAN NO RISK AND IT IS ALWAYS ADVISED FOR ULTIMATE  
SAFETY, SWIM IN THE PRESENCE OF THE LIFEGUARDS. THEY HAVE THE  
FLOTATION DEVICES THAT CAN MORE EASILY SAVE A LIFE.  
 
WHERE THE SURF ZONE WATERS ARE STEEPER, THERE MAY BE FEWER RIP  
CURRENTS, BUT THERE, THE DANGER OF WAVE RELATED INJURY INCREASES.  
 
AN ONGOING DE 6+ YEAR STUDY SHOWS THE 10-20 YEAR AND 40-60 YEAR  
AGE GROUPS MOST VULNERABLE. THE 10-20 YEAR OLDS SURF ZONE INJURIES  
ARE ASSOCIATED WITH BODY BOARDING AND BODY SURFING, WHILE THE  
40-60 YEAR OLD WADERS ARE KNOCKED DOWN BY WAVE ACTION, ESPECIALLY  
WITH BACK TURNED TO THE OCEAN.  
 
MALES ARE STATISTICALLY FAR MORE LIKELY TO BE INJURED OR LOSE  
THEIR LIFE IN THE SURF ZONE BUT AS JUNE 15 REMINDS US...ANYONE  
IS VULNERABLE.  
 

 
   
CLIMATE
 
 
MONTHLY AVG TEMP FOR JUNE  
 
PHL PROJECTING 74.5 OR 1.2 DEGREES ABOVE THE AVERAGE OF 73.3  
 
ABE PROJECTING 70.8 OR 1.7 DEGREES ABOVE THE AVERAGE OF 69.1  
 
SEVEN OF OUR EIGHT LONG TERM CLIMATE SITES WILL AVERAGE ABOVE  
NORMAL PROBABLY FROM ABOUT 8 TENTHS OF A DEGREE FOR TTN/ILG TO  
AS MUCH AS 2 DEGREES FOR GED.  
 
MOUNT POCONO IS OUR ONLY BELOW NORMAL AVERAGE AND PROJECTING  
1-1.5 BELOW).  
 
THESE PROJECTIONS ARE BASED ON OUR 330 AM FORECAST.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...NONE.  
DE...NONE.  
MD...NONE.  
MARINE...NONE.  
 

 
 

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