557  
FXUS61 KPHI 151309  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
909 AM EDT WED AUG 15 2018  
   
SYNOPSIS
 
 
A SURFACE TROUGH WILL REMAIN IN PLACE ACROSS THE EAST COAST  
THROUGH FRIDAY, WHILE A BACK DOOR COLD FRONT APPROACHES THE AREA  
THURSDAY INTO THURSDAY NIGHT. A COLD FRONT WILL MOVE ACROSS THE  
EAST COAST ON SATURDAY AND STALLS TO OUR SOUTH SUNDAY INTO  
MONDAY AS HIGH PRESSURE BUILDS ACROSS NEW ENGLAND. THIS FRONT  
WILL RETURN NORTH AS A WARM FRONT TUESDAY INTO TUESDAY NIGHT,  
BEFORE ANOTHER COLD FRONT MOVES ACROSS THE AREA WEDNESDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
NO CHANGES MADE FOR THE 9:30 AM FORECAST UPDATE. FORECAST  
MATCHES CURRENT TRENDS. HIGH RESOLUTION MODELS CONTINUE TO BACK  
OFF ON POTENTIAL SHOWERS AND STORMS THIS AFTERNOON, BUT I DON'T  
HAVE ENOUGH CONFIDENCE TO COMPLETELY REMOVE MENTION OF  
PRECIPITATION THIS AFTERNOON.  
 
A MID LEVEL TROUGH EXTENDED FROM NEW ENGLAND TO THE WATERS OFF  
NEW JERSEY AND DELAWARE EARLY THIS MORNING. THE FEATURE WILL  
CONTINUE TO PROGRESS EASTWARD TODAY, ALLOWING SOME RIDGING TO  
BUILD OVERHEAD FROM THE WEST.  
 
A WESTERLY SURFACE FLOW SHOULD RESULT IN DECREASING HUMIDITY  
LEVELS FOR TODAY, ALTHOUGH TEMPERATURES WILL BECOME RATHER WARM.  
HIGHS ARE FORECAST TO BE AROUND 90 DEGREES IN MUCH OF OUR  
REGION, WITH READINGS NOT GETTING ABOVE THE 80S AT THE SHORE AND  
IN THE ELEVATED TERRAIN OF THE POCONOS AND FAR NORTHERN NEW  
JERSEY.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/
 
 
THE MID LEVEL RIDGE SHOULD CONTINUE TO INFLUENCE OUR WEATHER  
FOR TONIGHT WITH WEAK SURFACE HIGH PRESSURE NUDGING INTO OUR  
REGION FROM THE WEST.  
 
THE WIND SHOULD BECOME LIGHT AND VARIABLE FOR TONIGHT WITH LOWS  
RANGING FROM THE MIDDLE 60S TO THE LOWER 70S. WE HAVE INCLUDED  
PATCHY FOG AFTER MIDNIGHT.  
 

 
   
LONG TERM /THURSDAY THROUGH TUESDAY/
 
 
AN ACTIVE WEATHER PATTERN WILL CONTINUE FOR THE END OF THIS  
WEEK, THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK, ALTHOUGH IT  
WILL NOT RAIN THE ENTIRE TIME.  
 
ON THURSDAY, A SURFACE TROUGH WILL BE IN PLACE ACROSS THE EAST  
COAST, WHILE A BACK DOOR FRONT APPROACHES THE AREA FROM THE  
NORTH LATER THURSDAY INTO THURSDAY NIGHT. THE BACK DOOR FRONT IS  
NOT EXPECTED TO FULLY MAKE IT INTO OUR AREA. THIS WILL ALLOW  
FOR THICKNESSES AND 925MB TEMPERATURES TO REMAIN ELEVATED ACROSS  
THE AREA. TEMPERATURES ARE EXPECTED TO REMAIN WELL ABOVE NORMAL  
ACROSS THE AREA. DEWPOINTS ARE LOW ENOUGH THAT HEAT INDEX  
VALUES ARE EXPECTED TO REMAIN BELOW ADVISORY LEVELS. THERE WILL  
BE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS DURING THE DAY  
AND OVERNIGHT THURSDAY AS SEVERAL SHORT WAVE/VORTICITY IMPULSES  
WILL MOVE ACROSS THE AREA AND CREATE ISOLATED TO SCATTERED  
SHOWERS AND THUNDERSTORMS.  
 
THE SURFACE TROUGH REMAINS IN PLACE THROUGH FRIDAY, AND THE  
WARM TEMPERATURES CONTINUE AS WELL. DEWPOINTS MAY INCREASE SOME  
AS THE SOUTHWESTERLY FLOW INCREASES, SO HEAT INDEX VALUES ON  
FRIDAY MAY APPROACH ADVISORY LEVELS FOR SOME AREAS, MAINLY ALONG  
THE I-95 URBAN CORRIDOR. SHOWER/THUNDERSTORM CHANCES INCREASE  
ON FRIDAY AS A STRONGER SHORT WAVE/VORTICITY IMPULSE MOVES  
ACROSS THE AREA. THERE IS NOT MUCH IN THE WAY OF SHEAR, BUT  
THERE WILL BE A FAIR AMOUNT OF INSTABILITY WITH CAPE VALUES  
1,500-2,000 J/KG. EVEN WITHOUT STRONG SHEAR, IF ANY STORMS BUILD  
TALL ENOUGH, SOME SMALL HAIL AND LOCALLY GUSTY WINDS WILL BE  
POSSIBLE IN ADDITION TO HEAVY RAINFALL. PW VALUES INCREASE TO 2+  
INCHES, SO THERE WILL BE HEAVY RAINFALL, ALTHOUGH THE STORMS  
SHOULD HAVE A STEADY ENOUGH FORWARD MOTION TO LIMIT A  
SIGNIFICANT FLOODING THREATS. THE SHOWERS AND THUNDERSTORMS  
SHOULD CONTINUE INTO THE EVENING, BEFORE DIMINISHING OVERNIGHT  
AS DAYTIME INSTABILITY WANES AND THE STRONGER SHORT WAVE PASSES  
TO OUR EAST.  
 
ON SATURDAY, AN AREA OF LOW PRESSURE WILL MOVE OUT OF THE GREAT  
LAKES REGION AND TOWARD NEW ENGLAND, PULLING A COLD FRONT  
ACROSS THE AREA, THEN THE FRONT WILL SLOWLY PUSH TO OUR SOUTH  
OVERNIGHT SATURDAY. THERE WILL CONTINUE TO BE A CHANCE OF  
SHOWERS AND THUNDERSTORMS SATURDAY INTO SATURDAY NIGHT AS  
ADDITIONAL SHORT WAVES/VORTICITY IMPULSES MOVE ACROSS THE AREA.  
 
THE FRONT WILL STALL TO OUR SOUTH SUNDAY INTO MONDAY AS HIGH  
PRESSURE BUILDS ACROSS NEW ENGLAND. HOWEVER, A COUPLE OF SHORT  
WAVES/VORTICITY IMPULSES ARE EXPECTED TO PASS ACROSS THE AREA  
NORTH OF THE FRONTAL BOUNDARY SUNDAY, WHICH MAY CREATE SOME  
SHOWERS OR THUNDERSTORMS, ESPECIALLY ACROSS THE SOUTHERN HALF OF  
THE AREA.  
 
SUNDAY NIGHT THROUGH MONDAY NIGHT, THE HIGH IS FORECAST TO  
BUILD A LITTLE FARTHER SOUTH ACROSS OUR AREA, WHICH WILL ALLOW  
PW VALUES TO DROP BELOW ONE INCH AND PROVIDE DRY WEATHER.  
 
HOWEVER, THIS DRY WEATHER WILL BE TEMPORARY AS SHOWERS AND  
THUNDERSTORMS RETURN TO THE FORECAST TUESDAY AND TUESDAY NIGHT.  
THE FRONTAL BOUNDARY TO OUR SOUTH IS FORECAST TO LIFT NORTHWARD  
AS A WARM FRONT LATE TUESDAY INTO TUESDAY NIGHT, BEFORE A COLD  
FRONT MOVES ACROSS THE AREA NEXT WEDNESDAY. SHOWERS AND  
THUNDERSTORM RETURN TO THE FORECAST LATE TUESDAY INTO WEDNESDAY,  
AND AS PW VALUES INCREASE, THE POTENTIAL FOR HEAVY RAINFALL  
RETURNS.  
 

 
   
AVIATION /13Z WEDNESDAY THROUGH SUNDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
TODAY...VFR WITH SCATTERED CLOUDS. WEST WIND 6 TO 10 KNOTS WITH  
GUSTS OF 14 TO 18 KNOTS.  
 
TONIGHT...MAINLY VFR WITH SCATTERED CLOUDS. LOCAL VISIBILITY  
RESTRICTIONS IN FOG AFTER 06Z. LIGHT AND VARIABLE WIND.  
 
OUTLOOK...  
 
THURSDAY-THURSDAY NIGHT..GENERALLY VFR. SLIGHT CHANCE OF  
SHOWERS AND THUNDERSTORMS WHICH MAY TEMPORARILY LEAD TO LOWER  
CONDITIONS.  
 
FRIDAY-FRIDAY NIGHT....GENERALLY VFR. SHOWERS AND THUNDERSTORMS  
LIKELY DURING THE AFTERNOON AND EVENING WHICH MAY LEAD TO LOWER  
CONDITIONS. SOUTHWEST WINDS GUSTING TO 20-25 KNOTS, BECOMING  
WESTERLY OVERNIGHT WITH LESS GUSTINESS OVERNIGHT.  
 
SATURDAY-SATURDAY NIGHT...MVFR CIGS POSSIBLE ACROSS THE AREA,  
ALONG WITH A CHANCE OF SHOWERS AND THUNDERSTORMS WHICH MAY LEAD  
TO LOWER CONDITIONS. WESTERLY WINDS EARLY SHIFTING TO  
NORTHWESTERLY DURING THE DAY, THEN NORTHEAST OVERNIGHT. WINDS  
GUSTING 15-20 KNOTS AT TIMES.  
 
SUNDAY...MVFR CIGS POSSIBLE TO CONTINUE INTO SUNDAY. SLIGHT  
CHANCE OF SHOWERS AND THUNDERSTORMS. WINDS SHIFT FROM NORTHEAST  
EARLY TO EAST DURING THE DAY.  
 

 
   
MARINE
 
 
WEAK HIGH PRESSURE IS FORECAST TO BUILD GRADUALLY OVER THE  
COASTAL WATERS OF NEW JERSEY AND DELAWARE FROM THE WEST DURING  
TODAY AND TONIGHT. WIND SPEEDS ARE EXPECTED TO REMAIN GENERALLY  
LESS THAN 15 KNOTS WITH SOME GUST INTO THE UPPER TEENS.  
 
WAVES ON THE COASTAL WATERS OFF NEW JERSEY AND DELAWARE ARE  
ANTICIPATED TO BE 2 TO 3 FEET. WAVES ON DELAWARE BAY SHOULD BE 2  
FEET OR LESS.  
 
OUTLOOK...  
 
THURSDAY-THURSDAY NIGHT..CONDITION EXPECTED TO REMAIN BELOW  
ADVISORY LEVELS.  
 
FRIDAY-FRIDAY NIGHT....WINDS MAY APPROACH SMALL CRAFT ADVISORY  
LEVELS FRIDAY AFTERNOON AND EVENING AS SOUTHWEST FLOW INCREASES  
ACROSS THE AREA. SEAS MAY APPROACH 5 FEET AS WELL LATE FRIDAY  
INTO FRIDAY EVENING.  
 
SATURDAY...CONDITIONS EXPECTED TO BE BELOW ADVISORY LEVELS ON  
SATURDAY.  
 
SATURDAY NIGHT-SUNDAY...WINDS AND SEAS INCREASE LATE SATURDAY  
AND SUNDAY AND MAY APPROACH SMALL CRAFT ADVISORY LEVELS.  
 
RIP CURRENTS...  
 
THERE IS A LOW RISK FOR THE DEVELOPMENT OF DANGEROUS RIP  
CURRENTS FOR TODAY. THE WIND SHOULD BLOW OFFSHORE FOR MUCH OF  
THE DAY. BREAKING WAVES IN THE SURF ZONE WILL LIKELY BE 2 FEET  
OR LESS WITH A MEDIUM PERIOD SOUTHERLY SWELL.  
 

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

 
 

 
SYNOPSIS...ROBERTSON  
NEAR TERM...IOVINO/JOHNSON  
SHORT TERM...IOVINO  
LONG TERM...ROBERTSON  
AVIATION...IOVINO/ROBERTSON  
MARINE...IOVINO/ROBERTSON  
 
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