357  
FXUS61 KPHI 240722  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
322 AM EDT WED AUG 24 2016  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL CONTINUE TO BUILD OFFSHORE TODAY AND OUT TO SEA  
THURSDAY. A COLD FRONT WILL MOVE ACROSS THE AREA FRIDAY AND STALL TO  
OUR SOUTH OVER THE WEEKEND. HIGH PRESSURE BUILDS TO OUR NORTH OVER  
THE WEEKEND, THEN OFFSHORE MONDAY. AN AREA OF LOW PRESSURE MAY PASS  
TO OUR NORTH MONDAY, BRINGING A FRONT ACROSS THE AREA MONDAY INTO  
TUESDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
AN UPPER-LEVEL RIDGE, STRETCHED ACROSS THE SOUTHERN STATES, WILL  
HAVE AN EXTENSION ON ITS NORTHEASTERN SIDE MOVE ACROSS OUR REGION  
DURING THE COURSE OF TODAY. AS THIS OCCURS, SURFACE HIGH PRESSURE  
OVER THE AREA WILL BECOME MORE CENTERED OFFSHORE. THIS WILL RESULT  
IN LIGHT WINDS FOR AWHILE THIS MORNING, HOWEVER A MORE SOUTHERLY  
WIND WILL THEN OCCUR. THE PRESSURE GRADIENT IS NOT ALL THAT TIGHT  
AND THEREFORE THE FLOW IS ON THE WEAKER SIDE, THEREFORE WITH AMPLE  
HEATING OF THE BOUNDARY LAYER THIS AFTERNOON THERE SHOULD BE SEA  
BREEZE DEVELOPMENT. THIS WILL BACK THE WINDS A BIT MORE  
SOUTH-SOUTHEAST ALONG THE COAST.  
 
AS THE RIDGE EXPANDS NORTHEASTWARD SOME TODAY, THERE WILL BE SOME  
WARMING ALOFT AS REFLECTED BY AN INCREASE IN THE THICKNESSES. THIS  
WILL RESULT IN A WARMER AFTERNOON FOR MANY PLACES FROM WHAT WAS  
OBSERVED YESTERDAY. OVERALL A WARM AFTERNOON, HOWEVER DEW POINTS  
WHILE A BIT HIGHER ARE EXPECTED TO REMAIN BELOW HUMID THRESHOLDS FOR  
MUCH OF THE REGION. DESPITE SOME RIDGING INTO THE AREA TODAY,  
CONVECTION IN THE MIDWEST EARLY THIS MORNING WILL SEND SOME HIGH  
LEVEL DEBRIS CLOUDS DOWNSTREAM SOME OF WHICH WILL MOVE THROUGH PARTS  
OF OUR AREA AT TIMES.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/
 
 
THE NORTHEASTERN EXTENSION OF THE SOUTHERN STATES RIDGE SHIFTS  
OFFSHORE TONIGHT AS A WEAKENING SHORT WAVE TROUGH SLIDES ACROSS THE  
GREAT LAKES REGION. THIS IS ACCOMPANIED BY A SURGE IN LOW-LEVEL WARM  
AIR ADVECTION UP THE OHIO VALLEY. THE SOUTHWESTERLY FLOW WILL ALSO  
START TO BRING IN SOME INCREASE TO THE LOW-LEVEL MOISTURE AS WE GO  
THROUGH TONIGHT, HOWEVER THIS DOES NOT APPEAR TO BE REAL ROBUST. IT  
LOOKS LIKE THE BEST FORCING REMAINS WELL TO OUR WEST MORE IN THE  
OHIO VALLEY DUE TO THE WARM AIR ADVECTION WITH THE AFOREMENTIONED  
SHORT WAVE TROUGH, PLUS A WIND SHIFT IS NOTED AROUND 850 MB. AS A  
RESULT, WE KEPT THE FORECAST DRY WITH THE EXPECTATION THAT ANY  
CONVECTION ASSOCIATED WITH THIS REMAINS WELL TO OUR WEST.  
 
WE ARE ANTICIPATING SOME HIGH LEVEL CLOUDS AROUND AT TIMES,  
OTHERWISE A BIT WARMER NIGHT DUE TO SOME UPTICK IN THE DEW POINTS.  
THIS MAY ALSO RESULT IN PATCHY FOG IN THE VALLEY AREAS AS WELL AS  
SOME RURAL SPOTS.  
 

 
   
LONG TERM /THURSDAY THROUGH TUESDAY/
 
 
HIGH PRESSURE CONTINUES TO MOVE OUT TO SEA THURSDAY, WHICH WILL LEAD  
TO RETURN FLOW AROUND THE WESTERN SIDE OF THE HIGH. THIS WILL ALLOW  
TEMPERATURES TO WARM AND MOISTURE TO BEGIN INCREASING. THERE WILL BE  
A CHANCE OF SHOWERS/THUNDERSTORMS THURSDAY INTO THURSDAY EVENING AS  
A COUPLE OF SHORT WAVE/VORTICITY IMPULSES SLIDE ACROSS THE AREA.  
 
THE RETURN FLOW WILL CONTINUE INTO FRIDAY AHEAD OF AN APPROACHING  
FRONTAL BOUNDARY. THERE WILL AGAIN BE A CHANCE FOR ISOLATED SHOWERS  
TO DEVELOP DURING THE DAY, BUT OVERALL CHANCES ARE SMALL AT THIS  
TIME. 925/850 MB TEMPERATURES AND THICKNESSES WILL CONTINUE TO  
INCREASE, MAKING FRIDAY THE WARMEST AND MOST HUMID DAY OF THE WEEK.  
 
THE FRONTAL BOUNDARY WILL SAG SOUTH OF THE AREA FRIDAY NIGHT, AND  
STALL JUST TO OUR SOUTH OVER THE WEEKEND WHILE HIGH PRESSURE BUILDS  
TO OUR NORTH. THIS HIGH WILL KEEP DRY WEATHER IN PLACE ACROSS THE  
AREA THROUGH THE WEEKEND.  
 
THE HIGH PRESSURE WILL BUILD OFFSHORE OF NEW ENGLAND BY MONDAY, AND  
A COLD FRONT WILL BEGIN APPROACHING THE AREA MONDAY INTO TUESDAY AS  
AN AREA OF LOW PRESSURE SKIRTS TO OUR NORTH. THERE ARE A COUPLE OF  
SHORT WAVE/VORTICITY IMPULSES FORECAST EARLY NEXT WEEK, SO THERE  
WILL CONTINUE TO BE A CHANCE FOR ISOLATED SHOWERS OR THUNDERSTORMS  
MONDAY INTO TUESDAY.  
 

 
   
AVIATION /07Z WEDNESDAY THROUGH SUNDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
TODAY...VFR. LIGHT AND VARIABLE TO CALM WINDS OVERALL TO START THIS  
MORNING, BECOME SOUTHWESTERLY AT 5-10 KNOTS. A TURN TO SOUTH OR  
SOUTHEAST AT ACY AND ILG SHOULD OCCUR BY LATE AFTERNOON AS A SEA/BAY  
BREEZE DEVELOPS.  
 
TONIGHT...VFR OVERALL. SOUTHERLY WINDS BECOMING LIGHT AND VARIABLE  
AT MOST TERMINALS DURING THE EVENING. LOCAL MVFR VISIBILITY IS  
POSSIBLE TOWARD DAYBREAK THURSDAY DUE TO LIGHT FOG, MAINLY AT RDG,  
ABE AND MIV.  
 
OUTLOOK...  
 
THURSDAY-FRIDAY...GENERALLY VFR CONDITIONS EXPECTED. A CHANCE OF  
ISOLATED SHOWERS AND THUNDERSTORMS WHICH MAY LEAD TO TEMPORARY LOWER  
CONDITIONS.  
 
FRIDAY NIGHT THROUGH SUNDAY...VFR CONDITIONS EXPECTED.  
 

 
   
MARINE
 
 
HIGH PRESSURE AT THE SURFACE EASES MORE OFFSHORE THROUGH TODAY AND  
TONIGHT. THIS WILL ALLOW FOR THE SURFACE FLOW TO TURN MORE SOUTHERLY  
TODAY AND CONTINUE TONIGHT. WHILE THE FLOW IS NOT FORECAST TO BE ALL  
THAT STRONG WITH THE DEPARTING SURFACE HIGH, THE SOUTHERLY FLOW WILL  
INCREASE ESPECIALLY BY LATE THIS AFTERNOON ACROSS THE NORTHERN  
COASTAL WATERS. THERE SHOULD BE SOME NEARSHORE ENHANCEMENT  
PARTICULARLY THIS AFTERNOON AND EARLY EVENING AS A SEA/BAY BREEZE  
CIRCULATION OCCURS, HOWEVER THE SPEEDS (ALSO SEAS) ARE EXPECTED TO  
BE BELOW SMALL CRAFT ADVISORY CRITERIA THROUGH TONIGHT.  
 
OUTLOOK...  
 
THURSDAY THROUGH FRIDAY...WINDS MAY APPROACH SMALL CRAFT ADVISORY  
LEVELS THURSDAY INTO THURSDAY NIGHT. WINDS WILL BEGIN DIMINISHING  
FRIDAY MORNING.  
 
FRIDAY NIGHT THROUGH SUNDAY...SUB-SMALL CRAFT ADVISORY CONDITIONS  
EXPECTED TO CONTINUE ACROSS THE WATERS.  
 
RIP CURRENTS...FOR TODAY, THE RISK FOR THE FORMATION OF DANGEROUS  
RIP CURRENTS IS LOW. HOWEVER, CONDITIONS MAY REACH MODERATE THIS  
AFTERNOON AND EVENING ESPECIALLY IF THE WAVES IN THE SURF ZONE  
INCREASE TO 2-3 FEET COMBINED WITH THE SOUTH-SOUTHEAST WINDS  
INCREASING FASTER.  
 
THIS COMING SUN-TUE...MODEL ENSEMBLE GUIDANCE ON EVERY SUCCESSIVE  
CYCLE CONTINUES TO SEND 2-4 FT LONG PERIOD (15 TO 17 SECOND) EAST  
SOUTHEAST SWELL INTO OUR WATERS FROM THE CENTRAL ATLANTIC. IF THAT  
OCCURS, SWIMMING AND WADING DANGERS WILL INCREASE MARKEDLY.  
 

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

 
 

 
SYNOPSIS...ROBERTSON  
NEAR TERM...GORSE  
SHORT TERM...GORSE  
LONG TERM...ROBERTSON  
AVIATION...GORSE/ROBERTSON  
MARINE...GORSE/ROBERTSON  
 
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