365  
FXUS61 KPHI 271946  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
346 PM EDT MON JUL 27 2015  
   
SYNOPSIS
 
 
A NEARLY STALLED FRONTAL BOUNDARY WILL CONTINUE TO DISSIPATE IN  
OUR REGION TONIGHT. WEAK HIGH PRESSURE BUILDING EASTWARD FROM THE  
GREAT LAKES IS FORECAST TO INFLUENCE OUR WEATHER FOR TUESDAY AND  
WEDNESDAY. A FRONTAL BOUNDARY FROM THE NORTHWEST IS EXPECTED TO  
ARRIVE ON THURSDAY NIGHT FOLLOWED BY HIGH PRESSURE FOR FRIDAY AND  
THE WEEKEND. ANOTHER FRONT MAY APPROACH FROM THE NORTHWEST ON  
MONDAY.  
 

 
   
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
 
 
MOST OF THE REGION REMAINS DRY THIS AFTERNOON AND EVENING WHILE  
CLOSER THE NEW JERSEY COAST SEA BREEZE CIRCULATION HAS IGNITED  
SCATTERED SHOWERS WITH EMBEDDED THUNDER. LIKE DAYS PAST THERE IS  
VERY LITTLE IN THE WAY OF SHEAR AS THE WINDS ALOFT REMAIN  
RELATIVELY LIGHT SO VERY LITTLE IN THE WAY OF ANY DOWNWIND  
PROPAGATION. SOME ISOLATED SHOWERS ALONG THE HIGHER TERRAIN IN OUR  
NORTHWESTERN ZONES MAY PULSE UP THROUGH THE EVENING BUT THE AMOUNT  
OF CLOUD COVER TODAY REALLY HAVE KEPT THE INSTABILITY AT BAY.  
ACROSS SOUTHERN DELMARVA, CLOSER TO THE LINGERING/WASHED OUT  
FRONTAL BOUNDARY, IS THE BEST PLACE TO SEE A PROLONGED PERIOD OF  
SHOWERY ACTIVITY. THE ATMOSPHERE IS PRIME IN A LOT OF PLACES  
OUTSIDE OF OUR WESTERN ZONES SO ANY LITTLE IMPULSE OR LOCALIZED  
CONVERGENCE WILL BE ENOUGH TO GET THINGS GOING. ONCE THEY GET  
GOING, WITH THE INCREASE IN PWATS AND RELATIVE LOW-TOPPINESS THESE  
STORMS HAVE THEY WILL BE VERY EFFICIENT RAIN PRODUCERS...LOCALIZED  
POOR DRAINAGE WILL CONTINUE TO BE AN ISSUE.  
 
LATE TONIGHT ONCE THINGS BEGIN TO SETTLE DOWN OR SHIFT FARTHER TO  
OUR SOUTH, PATCHY FOG FORMATION LOOKS PROBABLE. NOT SURE HOW DENSE  
IT WILL BECOME, BUT ANY CLEARING TONIGHT WILL HELP TO AID IN ITS  
DEVELOPMENT WITH LIGHT OR CALM WINDS. OVERNIGHT LOWS WERE A BLEND  
OF THE MET/MAV.  
 

 
   
SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/
 
 
ONCE WE BURN OFF ANY FOG AND STRATUS THAT MAY FORM DURING THE  
EARLY MORNING HOURS WE SHOULD BE LEFT WITH CLEARING SKIES, ALBEIT  
SELF DESTRUCTING. A RAPID CU-FIELD SHOULD DEVELOP BY EARLY  
AFTERNOON AS CONVECTIVE TEMPERATURES ARE REACHED WITH TEMPERATURES  
CLIMBING INTO THE LOW-90S. WINDS WILL REMAIN RELATIVELY LIGHT SO  
NO RELIEF IN TERMS OF THE HUMIDITY. SEA AND BAY BREEZES SHOULD  
DEVELOP BY EARLY AFTERNOON AND GIVEN THE SOUPINESS OF THE AIR MASSTHEY  
MIGHT BE ENOUGH TO GET ISOLATED SHOWERS STARTED.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH MONDAY/
 
 
A MID LEVEL RIDGE AXIS IS FORECAST TO EXTEND ACROSS THE GREAT  
LAKES ON TUESDAY NIGHT. THE RIDGE IS EXPECTED TO PROGRESS EASTWARD  
AND ITS AXIS SHOULD PASS OVER OUR REGION ON WEDNESDAY NIGHT. A MID  
LEVEL LOW IS ANTICIPATED TO MOVE FROM SOUTHERN MANITOBA ON TUESDAY  
NIGHT TO HUDSON BAY ON WEDNESDAY NIGHT. THE LOW IS FORECAST TO  
MEANDER OVER THE HUDSON BAY REGION FROM WEDNESDAY NIGHT THROUGH  
MONDAY. MID LEVEL TROUGHING IS EXPECTED OVER THE NORTHEASTERN  
STATES FOR THURSDAY NIGHT THROUGH MONDAY WITH A RIDGE BUILDING  
OVER THE WESTERN STATES.  
 
THE HEAT IS FORECAST TO BE ON THE INCREASE FOR WEDNESDAY AND  
THURSDAY. WE ARE ANTICIPATING MAXIMUM TEMPERATURES MAINLY IN THE  
LOWER AND MIDDLE 90S ON BOTH DAYS WITH HEAT INDEX VALUES  
APPROACHING 100 EXCEPT IN THE ELEVATED TERRAIN AND IN THE  
COMMUNITIES ALONG THE COAST. DEW POINT READINGS ARE EXPECTED TO BE  
MAINLY IN THE MID TO UPPER 60S ON WEDNESDAY AFTERNOON AND IN THE  
UPPER 60S AND LOWER 70S ON THURSDAY AFTERNOON.  
 
THE MAXIMUM HEAT INDEX VALUES IN OUR HIGHLY URBANIZED AREAS ALONG  
THE INTERSTATE 95 CORRIDOR ARE EXPECTED TO BE IN THE UPPER 90S ON  
WEDNESDAY AND THURSDAY BASED ON THE LATEST GUIDANCE. AS A RESULT,  
WE WILL NOT ISSUE AN EXCESSIVE HEAT WATCH AT THIS TIME. THE  
GUIDELINE CRITERION IS 100. HOWEVER, WE WILL KEEP A CLOSE WATCH TO  
SEE IF THE GUIDANCE BEGINS TO CREEP UPWARD WITH EITHER THE  
TEMPERATURE OR DEW POINT FORECAST.  
 
WE ARE NOT ANTICIPATING ANY PRECIPITATION FOR TUESDAY NIGHT,  
WEDNESDAY AND WEDNESDAY NIGHT DUE TO THE LACK OF ANY SUBSTANTIAL  
TRIGGERING MECHANISMS. WE WILL MENTION A CHANCE OF SHOWERS AND  
THUNDERSTORMS FOR THURSDAY AFTERNOON INTO THURSDAY NIGHT AS A  
FRONTAL BOUNDARY IS EXPECTED TO APPROACH AND PASS THROUGH OUR  
REGION DURING THAT PERIOD OF TIME. A WEAK WAVE OF LOW PRESSURE MAY  
DEVELOP ALONG THE FRONT CAUSING PRECIPITATION TO LINGER INTO EARLY  
FRIDAY MORNING IN OUR SOUTHEASTERN COUNTIES.  
 
HIGH PRESSURE IS EXPECTED TO FOLLOW THURSDAY NIGHT'S FRONTAL  
PASSAGE. THE HIGH IS ANTICIPATED TO INFLUENCE OUR WEATHER FOR  
FRIDAY AND THE WEEKEND. WE WILL CARRY A PRECIPITATION-FREE  
FORECAST ALONG WITH SLIGHTLY ABOVE NORMAL DAYTIME TEMPERATURES.  
EVEN WITH THE MID LEVEL TROUGHING, IT APPEARS AS THOUGH OUR  
WEATHER WILL REMAIN QUITE WARM. HOWEVER, HUMIDITY LEVEL SHOULD  
DROP A BIT FROM THOSE EXPECTED DURING THE MID WEEK PERIOD.  
 
ANOTHER FRONTAL BOUNDARY MAY APPROACH FROM THE NORTHWEST ON  
MONDAY AND WE WILL MENTION A CHANCE OF SHOWERS AND THUNDERSTORMS  
FOR THAT PERIOD OF TIME.  
 

 
   
AVIATION /20Z MONDAY THROUGH SATURDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
TONIGHT...VFR TRENDING TO MVFR/IFR. ISOLATED TO SCATTERED  
MVFR/IFR SHOWERS WITH EMBEDDED THUNDER STILL POSSIBLE THROUGH THE  
EVENING HOURS BEFORE DISSIPATING. OTHERWISE WINDS DROP OFF LATE  
TONIGHT AND THE CEILINGS MAY LOWER TO MVFR...IFR FOG IS ALSO  
POSSIBLE DEPENDING ON ADDED RAIN FROM SHOWERS. OVERALL A LOW TO  
MEDIUM CONFIDENCE FORECAST.  
 
TUESDAY...MOSTLY VFR. WE SHOULD LOSE ANY LOWER CLOUDS AND FOG BY  
LATE MORNING LEAVING US WITH A SCATTERED CU FIELD. SHOWER CHANCES  
WILL BE LOWER THAN THE PAST COUPLE OF DAYS WITH MIV/ACY HAVING  
BETTER CHANCES. LOCAL SEA/BAY BREEZES MAY OCCUR AT ACY/MIV/ILG BY  
THE EARLY AFTERNOON WITH WINDS BACKING MORE TOWARDS THE SOUTHEAST.  
 
OUTLOOK...  
TUESDAY NIGHT THROUGH THURSDAY MORNING...MAINLY VFR. HOWEVER, THE  
HIGH HUMIDITY LEVELS MAY RESULT IN SOME LATE NIGHT AND EARLY  
MORNING LOW CLOUDS, HAZE AND FOG.  
 
THURSDAY AFTERNOON AND THURSDAY NIGHT...A CHANCE OF SHOWERS AND  
THUNDERSTORMS THAT MAY RESULT IN MVFR OR IFR CONDITIONS AT TIMES.  
 
FRIDAY THROUGH SATURDAY...MAINLY VFR.  
 

 
   
MARINE
 
 
SUB-SCA CONDITIONS EXPECTED TONIGHT AND TOMORROW UNDER PROLONGED  
SOUTHERLY FLOW. WINDS WILL CONTINUE TO DECREASE TONIGHT AND  
TOMORROW AS THE PRESSURE GRADIENT SLACKENS. SEAS WILL ALSO BE ON  
THE DOWNWARD TREND RUNNING CLOSER TO 2-3 FEET THROUGH TUESDAY.  
 
OUTLOOK...  
TUESDAY NIGHT THROUGH SATURDAY...NO MARINE HEADLINES ARE  
ANTICIPATED.  
 

 
   
RIP CURRENTS
 
 
A LONG PERIOD /10-12 SECOND/ EAST-SOUTHEAST SWELL LOOKS TO  
CONTINUE, RESULTING IN A MODERATE RISK OF DANGEROUS RIP CURRENTS  
THROUGH TONIGHT FOR THE NEW JERSEY AND DELAWARE COASTS.  
 

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

 
 

 
 
SYNOPSIS...IOVINO  
NEAR TERM...HEAVENER  
SHORT TERM...HEAVENER  
LONG TERM...IOVINO  
AVIATION...IOVINO/HEAVENER  
MARINE...IOVINO/HEAVENER  
RIP CURRENTS...HEAVENER  
 
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