164  
FXUS61 KPHI 152214  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
614 PM EDT SUN SEP 15 2019  
   
SYNOPSIS
 
 
A COLD FRONT WILL STALL SOUTH OF OUR AREA THROUGH TODAY WHILE  
HIGH PRESSURE WEAKENS TO OUR WEST. A WEAK AREA OF LOW PRESSURE  
SLIDES NEAR OUR REGION ON MONDAY. HIGH PRESSURE BUILDS ACROSS  
THE NORTHEAST TUESDAY INTO WEDNESDAY, THEN SHIFTS SOUTHWARD  
ACROSS THE MID-ATLANTIC REGION THURSDAY. THE HIGH IS FORECAST TO  
SHIFT TO OUR SOUTH FRIDAY, THEN OFFSHORE NEXT WEEKEND.  
 

 
   
NEAR TERM /THROUGH MONDAY/
 
 
AFTERNOON FORECAST REMAINS ON TRACK, SO WILL MAKE NO SIGNIFICANT  
CHANGES OTHER THAN TO MAKE ADJUSTMENTS BASED ON LATEST SURFACE  
OBS.  
 
NORTHWEST FLOW ALOFT WILL BECOME MORE ESTABLISHED THROUGH  
TONIGHT AS AN UPPER-LEVEL TROUGH IN EASTERN CANADA SHARPENS SOME  
ACROSS THE NORTHEAST. MEANWHILE, A WEAK SURFACE COLD FRONT WILL  
STALL ACROSS THE SOUTHERN PORTIONS OF OUR AREA WITH WEAK HIGH  
PRESSURE REMAINING TO OUR SOUTHWEST. THE SHORT WAVES ASSOCIATED  
WITH THE TROUGH REMAIN TO OUR NORTH THROUGH TONIGHT.  
 
SOME HIGHER LEVEL CLOUDS WILL ARRIVE THROUGH THE NIGHT FROM THE  
WEST WITHIN THE GRADUALLY SHARPENING UPPER-LEVEL FLOW. A SEA  
BREEZE IS RESULTING IN SOME WEAK CONVERGENCE WITHIN AN AREA OF  
LINGERING DEEPER BOUNDARY LAYER MOISTURE, THEREFORE CLOUDINESS  
ASSOCIATED WITH IT WILL DWINDLE LATE THIS AFTERNOON AS THE  
MOISTURE MIXES OUT SOME. THERE ARE SOME HINTS IN THE GUIDANCE,  
MAINLY THE NAM, THAT SOME LOW CLOUDS MAY TRY TO DEVELOP OFFSHORE  
AND MOVE INTO THE COAST OVERNIGHT. THIS IS OF LOW CONFIDENCE.  
LOW TEMPERATURES ARE MOSTLY A BLEND OF THE STATISTICAL GUIDANCE  
AND CONTINUITY.  
 

 
   
SHORT TERM /MONDAY NIGHT THROUGH 6 PM MONDAY/
 
 
AN UPPER-LEVEL TROUGH REMAINS IN PLACE ACROSS EASTERN CANADA  
AND THE NORTHEAST MONDAY. THIS WILL FAVOR NORTHWESTERLY FLOW  
ALOFT AND EMBEDDED WITHIN THIS FLOW IS A WEAK DISTURBANCE WITH A  
WEAK SURFACE LOW REFLECTION. THIS MAY BE THE REMNANT ENERGY  
ASSOCIATED WITH AN MCS YESTERDAY IN THE MIDWEST (ONGOING CLOUD  
DEBRIS MOVING INTO THE OHIO VALLEY). SOME INCREASE IN THE CLOUDS  
ARE EXPECTED, WITH THIS THE MOST PREVALENT ACROSS THE NORTHERN  
PORTIONS OF THE AREA.  
 
THE MAJORITY OF THE GUIDANCE SHOWS SOME SHOWER POTENTIAL WITH  
THE RATHER WEAK SURFACE LOW AS IT TRACKS EAST-SOUTHEAST FROM THE  
UPPER OHIO VALLEY TO START THE DAY TO NEAR DELMARVA BY LATE  
AFTERNOON. THIS WEAK SYSTEM SHOULD TRACK ALONG THE WEAK STALLED  
SURFACE FRONT IN THE VICINITY. THE COMBINATION OF ALL OF THESE  
WEAK SYSTEMS ALONG WITH OUR NORTHERN AREAS BEING NEAR THE RIGHT  
ENTRANCE REGION OF A MID LEVEL JET BY LATE AFTERNOON, SHOULD  
RESULT IN SOME SHOWER ACTIVITY. THE MAIN FOCUS FOR THIS IS  
ACROSS THE WEST AND NORTHERN AREAS WHERE SLIGHT CHANCE TO LOW  
CHANCE POPS ARE MAINTAINED FOR THE AFTERNOON. THE 12Z NAM SHOWS  
A RAPID DEVELOPMENT IN CONVECTION FROM THE BALTIMORE AREA TO  
SOUTHEASTERN PENNSYLVANIA AFTER 21Z, HOWEVER THIS LOOKS  
OVERDONE.  
 
AS FOR THE HIGH TEMPERATURES, OPTED FOR A MODEL BLEND GIVEN SOME  
ADDITIONAL VARIABILITY. HIGHS IN THE MID TO UPPER 80'S SOUTH OF THE  
LINGERING WEAK FRONT. A SEA BREEZE IS EXPECTED ONCE AGAIN.  
 

 
   
LONG TERM /MONDAY NIGHT THROUGH SUNDAY/
 
 
SYNOPTIC OVERVIEW:  
 
AN EXTENDED PERIOD OF QUIET WEATHER LOOKS LIKELY OVER OUR AREA  
FOR THE LONG TERM. AT THE MID-LVLS A FAIRLY AMPLIFIED RIDGE WILL  
RESIDE UPSTREAM OF THE AREA FOR ESSENTIALLY THE ENTIRE LONG-  
TERM PERIOD (ALTHOUGH AT TIMES OSCILLATING IN ORIENTATION AND  
MEAN-POSITION). AT THE SURFACE THE UPSTREAM RIDGE POSITIONING  
WILL PROMOTE ANTICYCLOGENESIS WITH THE INITIAL SURFACE HIGH  
CENTERED NORTH OF THE AREA. BY THE END OF THE WORKWEEK THE HIGH  
WILL RE-ORIENT ITSELF SOUTH OF THE AREA SHIFTING THE LOW-LVL  
FLOW FROM ONSHORE TO OFFSHORE WITH A CORRESPONDING INCREASE IN  
TEMPERATURES EXPECTED.  
 
DAILIES:  
 
MONDAY NIGHT THROUGH TUESDAY: THE ONLY CHANCE OF ANY  
PRECIPITATION THROUGH THE EXTENDED WILL BE IN THE OVERNIGHT  
PERIOD MONDAY INTO TUESDAY MORNING AS A SHORTWAVE LIFTS  
NORTHEAST OF THE AREA AND AN ASSOCIATED WEAK FRONT MOVES THROUGH  
THE AREA. GIVEN THE CLIPPING NATURE OF THE UPPER LEVEL SYSTEM  
CAPPED POPS AT SLIGHT-CHANCE WITH NOTHING SIGNIFICANT EXPECTED.  
THE BOUNDARY WILL BE LARGELY SOUTH OF THE AREA BY TUESDAY  
AFTERNOON WITH HIGHS GENERALLY IN THE 70S AREAWIDE.  
 
WEDNESDAY/THURSDAY: SHOULD BE DRY AND MILD WITH ONSHORE FLOW  
PREVAILING. HIGHS WILL GENERALLY BE NEAR CLIMO (LOW TO MID 70S)  
WITH LOWS IN THE LOW TO MID 50S. MOSTLY SUNNY OUTSIDE OF SOME  
OCCASIONAL STRATUS (MOST PREVALENT NEAR THE COAST).  
 
FRIDAY/SATURDAY: THE HIGH WILL RELOCATE SOUTH OF THE AREA  
TOWARDS THE LATE WEEK-EARLY WEEKEND WITH THE FLOW SHIFTING MORE  
WESTERLY AS A RESULT. THIS WILL USHER IN A WARMING TREND INTO  
THE WEEKEND WITH MAXES INCREASING INTO THE UPPER 70S/LOWER 80S  
ON FRIDAY, AND THEN INCREASING FURTHER INTO THE MID 80S ON  
SATURDAY. PRECIPITATION CHANCES REMAIN ESSENTIALLY NIL. A  
MOSTLY QUIET LONG TERM PERIOD IS EXPECTED, WITH ONLY A SMALL  
CHANCE OF PRECIPITATION AT THE BEGINNING OF THE PERIOD..  
 

 
   
AVIATION /22Z SUNDAY THROUGH FRIDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
TONIGHT...VFR OVERALL. THERE IS SOME POTENTIAL THAT LOW CLOUDS  
DEVELOP OVERNIGHT NEAR THE COAST AND REACH ACY, HOWEVER THIS IS  
OF LOW CONFIDENCE. LIGHT AND VARIABLE TO LOCALLY CALM WINDS.  
 
MONDAY...SOME LOW CLOUDS POSSIBLE NEAR THE COAST EARLY,  
OTHERWISE VFR WITH ANY CEILINGS MAINLY ABOVE 8000 FEET. SOME  
SHOWERS POSSIBLE IN THE AFTERNOON MAINLY NEAR AND NORTH/WEST OF  
ABE AND RDG. LIGHT AND VARIABLE WINDS BECOMING WEST-NORTHWEST  
4-8 KNOTS IN THE MORNING, THEN TURNING SOUTHWESTERLY BEFORE  
BECOMING NORTHWEST TOWARD EARLY EVENING.  
 
OUTLOOK...  
 
MONDAY NIGHT...GENERALLY VFR ALTHOUGH SOME SUB-VFR CONDITIONS  
POSSIBLE IN SHOWERS/LOWER CLOUDS. WINDS NORTH-NORTHEAST 5-10KTS.  
 
TUESDAY-WEDNESDAY NIGHT...MOSTLY VFR DURING THE DAY, WITH A  
CHANCE OF MVFR CONDITIONS OVERNIGHT IN STRATUS. EAST TO  
NORTHEAST WINDS 5-10 KNOTS  
 
THURSDAY-THURSDAY NIGHT...GENERALLY VFR CONDITIONS EXPECTED WITH  
EAST-SOUTHEAST WINDS 5-10 KTS.  
 

 
   
MARINE
 
 
CONDITIONS WILL REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA  
THROUGH MONDAY. A STALLED WEAK FRONT IN THE VICINITY WILL RESULT  
IN LIGHT ENOUGH FLOW FOR SEA/BAY BREEZE INFLUENCES AND  
THEREFORE WIND SHIFTS TO MORE SOUTHERLY.  
 
OUTLOOK...  
 
MONDAY NIGHT THROUGH TUESDAY MORNING...CONDITIONS ARE EXPECTED  
TO REMAIN BELOW ADVISORY LEVELS WITH SEAS AROUND 3-4 FT. AND NE  
WINDS INCREASING TO AROUND 15 KTS BY TUESDAY MORNING.  
 
TUESDAY-THURSDAY...SCA CONDITIONS POTENTIALLY DEVELOPING AS  
EARLY AS TUESDAY BUT LIKELY BY WEDNESDAY. SEAS WILL INCREASE TO  
5-7 FT BY LATE WEDNESDAY WITH NORTHEASTERLY WIND GUSTS LIKELY  
INCREASING TO 25 KTS OR SO AS WELL.S  
 
RIP CURRENTS...  
 
A MODERATE RISK OF DANGEROUS RIP CURRENTS CONTINUES INTO THIS  
EVENING FOR THE NEW JERSEY AND DELAWARE BEACHES. SOUTHEASTERLY WINDS  
AROUND 10 MPH WITH WAVES 3 TO 4 FEET IN THE SURF ZONE.  
 
FOR MONDAY, A LOW RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS  
IS ANTICIPATED DUE TO LIGHT SOUTHERLY FLOW AND WAVES OF 2-3 FEET IN  
THE SURF ZONE.  
 

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

 
 

 
SYNOPSIS...CARR  
NEAR TERM...GORSE/MPS  
SHORT TERM...GORSE  
LONG TERM...CARR  
AVIATION...CARR/GORSE/MPS  
MARINE...CARR/GORSE/MPS  
 
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