687  
FXUS61 KPHI 290845  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
445 AM EDT MON MAY 29 2017  
   
SYNOPSIS
 
 
LOW PRESSURE LOCATED OFF THE MIDDLE ATLANTIC COAST EARLY THIS  
MORNING WILL MOVE FARTHER OUT TO SEA TODAY. ANOTHER WEAK LOW IS  
EXPECTED TO FOLLOW ALONG A TRAILING FRONTAL BOUNDARY AND IT  
SHOULD PASS OFF THE MIDDLE ATLANTIC COAST ON TUESDAY NIGHT. A  
COLD FRONT IS FORECAST TO APPROACH FROM THE NORTHWEST ON  
WEDNESDAY AND IT SHOULD PASS THROUGH OUR REGION ON WEDNESDAY  
NIGHT. ANOTHER COLD FRONT IS ANTICIPATED TO ARRIVE ON FRIDAY  
NIGHT OR SATURDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
CLOUDY, SHOWERY, AND COOL CONDITIONS TO START OFF THE DAY  
ACROSS THE AREA, WITH A PARTIAL IMPROVEMENT POSSIBLE LATER TODAY  
FOR SOME AREAS.  
 
AN AREA OF LOW PRESSURE LOCATED OFFSHORE OF THE MID-ATLANTIC  
THIS MORNING WILL CONTINUE TO MOVE EASTWARD AND AWAY FROM THE  
AREA THROUGH TODAY. THE ASSOCIATED STATIONARY BOUNDARY TO OUR  
SOUTH IS FORECAST TO REMAIN TO OUR SOUTH, WHILE AN APPROACHING  
OCCLUDED FRONT WILL LIKELY WASH OUT AND DISSIPATE AS IT  
APPROACHES THE AREA FROM THE WEST THIS AFTERNOON. HIGH PRESSURE  
ACROSS THE CANADIAN MARITIMES WILL NOSE ITS WAY DOWN THE EASTERN  
SEABOARD AND KEEP A COOL AND MOIST EASTERLY FLOW ACROSS THE  
AREA.  
 
SHOWERS WILL CONTINUE TO SPREAD ACROSS THE AREA THROUGH THE  
MORNING HOURS AS A SHORT WAVE/VORTICITY IMPULSE MOVES ACROSS THE  
AREA AND INTERACTS WITH THE ABUNDANT MID-LOW LEVEL MOISTURE. AS  
THIS SHORT WAVE PASSES TO OUR EAST, THE SHOWERS WILL BEGIN TO  
DISSIPATE LATER THIS MORNING INTO THE AFTERNOON. THE CLOUD COVER  
WILL HAVE A CHANCE TO DISSIPATE AND BREAK SOME BY THIS  
AFTERNOON AS WELL FOR A PORTION OF THE AREA, ESPECIALLY FOR  
PORTIONS OF THE DELMARVA AND SOUTHERN NEW JERSEY.  
 
WHERE CLOUDS REMAIN THROUGH THE DAY, TEMPERATURES WILL LIKELY  
HAVE A HARD TIME RISING, BUT IF/WHERE ANY BREAKS OF SUN OCCUR  
ACROSS THE SOUTHERN AREAS, TEMPERATURES WILL RISE MORE. WE USED  
A BLEND OF AVAILABLE MOS AND MOSGUIDE FOR DAYTIME HIGHS.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/
 
 
THE AFOREMENTIONED OCCLUDED FRONT IS EXPECTED TO HAVE  
DISSIPATED BY THIS EVENING, WHILE HIGH PRESSURE FROM EASTERN  
CANADA CONTINUES NOSING DOWN THE EASTERN SEABOARD. WITH AN  
EASTERLY FLOW CONTINUING ACROSS THE AREA, THIS WILL KEEP COOL  
AND MOIST CONDITIONS ACROSS THE AREA THROUGH THE NIGHT. IT IS  
POSSIBLE SOME ISOLATED SHOWERS MAY DEVELOP OVERNIGHT, BUT PATCHY  
AREAS OF FOG AND DRIZZLE MAY ALSO OCCUR. UNCERTAIN AS HOW DENSE  
FOG WILL GET BECAUSE NOT MUCH OF THE GUIDANCE GETS VISIBILITIES  
BELOW 1-2 MILES. SO WE WILL KEEP PATCHY FOG AND DRIZZLE IN THE  
FORECAST FOR NOW, BUT WE ARE NOT EXPECTING WIDESPREAD DENSE FOG  
AT THIS TIME.  
 

 
   
LONG TERM /TUESDAY THROUGH SUNDAY/
 
 
A MID LEVEL LOW IS FORECAST TO MEANDER OVER UPPER ONTARIO AND  
VICINITY DURING THE MID WEEK PERIOD BEFORE SHIFTING EASTWARD  
OVER QUEBEC AND EVENTUALLY ATLANTIC CANADA DURING THE WEEKEND.  
AN INITIAL MID LEVEL TROUGH AXIS IS EXPECTED TO PASS OVER OUR  
REGION AROUND WEDNESDAY NIGHT WITH A SECONDARY AXIS ANTICIPATED  
AROUND SATURDAY NIGHT. THE PATTERN SHOULD BE RATHER UNSETTLED  
WITH THE BEST CHANCE FOR DRY WEATHER EXTENDING FROM WEDNESDAY  
NIGHT INTO EARLY FRIDAY.  
 
WE ARE EXPECTING TUESDAY TO BEGIN WITH A LOW OVERCAST IN MUCH  
OF EASTERN PENNSYLVANIA, NEW JERSEY AND THE UPPER DELMARVA. SOME  
FOG IS ANTICIPATED AT THAT TIME, AS WELL. A SOUTHEASTERLY  
SURFACE FLOW ON TUESDAY SHOULD KEEP THE CLOUDS FROM LIFTING AND  
BREAKING QUICKLY. AS A RESULT, WE ARE FORECASTING A MOSTLY  
CLOUDY DAY ALONG WITH A CHANCE OF SHOWERS AND PERHAPS SOME  
THUNDER. HIGH TEMPERATURES SHOULD BE IN THE 60S UP NORTH AND  
RIGHT ALONG THE COAST. MAXIMUM READINGS ARE EXPECTED TO BE IN  
THE LOWER 70S FROM THE PHILADELPHIA METROPOLITAN AREA SOUTHWARD.  
THE MOST LIKELY AREA FOR A SUBSTANTIAL BREAK IN THE CLOUD COVER  
IS SOUTHERN DELAWARE AND THE ADJACENT COUNTIES OF NORTHEASTERN  
MARYLAND. THERE THE HIGHS COULD REACH THE UPPER 70S.  
 
A WEAK SURFACE LOW IS FORECAST TO PASS OFF THE MIDDLE ATLANTIC  
COAST ON TUESDAY NIGHT WITH PARTIAL CLEARING POSSIBLE IN ITS  
WAKE FOR WEDNESDAY. HOWEVER, A COLD FRONT APPROACHING FROM THE  
NORTHWEST ALONG WITH SOME MARGINAL INSTABILITY MAY RESULT IN THE  
DEVELOPMENT OF SHOWERS AND THUNDERSTORMS MAINLY DURING THE  
AFTERNOON AND EVENING HOURS. THE BEST CHANCE FOR PRECIPITATION  
AT THAT TIME WILL BE IN EASTERN PENNSYLVANIA AND NORTHERN NEW  
JERSEY.  
 
THE COLD FRONT IS EXPECTED TO PASS THROUGH OUR REGION ON  
WEDNESDAY NIGHT FOLLOWED BY DRY WEATHER AND SEASONABLE  
TEMPERATURES FOR THURSDAY AND THURSDAY NIGHT.  
 
ANOTHER COLD FRONT IS ANTICIPATED TO APPROACH FROM THE  
NORTHWEST ON FRIDAY AND IT SHOULD PASS SLOWLY THROUGH OUR REGION  
ON FRIDAY NIGHT AND SATURDAY. WE WILL MENTION ANOTHER CHANCE  
FOR SHOWERS AND THUNDERSTORMS IN ADVANCE OF THE FRONT.  
 
THE SOUTHWARD PROGRESS OF THE FRONT OVER THE WEEKEND IS A LOW  
CONFIDENCE FORECAST. THE MODELS DIFFER ON HOW PROGRESSIVE THE  
BOUNDARY WILL BE. AS A RESULT, WE WILL KEEP A CHANCE OR SLIGHT  
CHANCE OF SHOWERS INTO SUNDAY.  
 

 
   
AVIATION /09Z MONDAY THROUGH FRIDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
AN EASTERLY FLOW WILL CONTINUE THROUGH TODAY ACROSS THE AREA AS  
LOW PRESSURE MOVES OUT TO SEA, AND HIGH PRESSURE NOSES DOWN THE  
EASTERN SEABOARD ACROSS THE AREA. THIS WILL KEEP PLENTY OF  
MOISTURE LOW LEVEL MOISTURE ACROSS THE AREA THROUGH TODAY. IFR  
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MUCH OF THE DAY,  
WITH SHOWERS THROUGH THIS MORNING AS WELL. HOWEVER, THERE IS A  
CHANCE FOR SOME IMPROVEMENT LATE THIS AFTERNOON INTO THIS  
EVENING. EVEN IF THIS IMPROVEMENT DOES OCCUR, CLOUDS ARE  
EXPECTED TO FILL BACK IN OVERNIGHT WITH LOW CLOUDS AND FOG  
DEVELOPING AGAIN, LEADING TO IFR CONDITIONS OVERNIGHT. THERE IS  
ALSO THE POSSIBILITY FOR PATCHY DRIZZLE TO DEVELOP OVERNIGHT AS  
WELL.  
 
OUTLOOK...  
TUESDAY...IFR CONDITIONS IN THE MORNING IMPROVING TO MVFR AND  
VFR DURING THE COURSE OF THE DAY. A CHANCE OF SHOWERS AND  
THUNDERSTORMS DEVELOPING.  
 
TUESDAY NIGHT AND WEDNESDAY MORNING...CONDITIONS MAY LOWER BACK  
TO MVFR AND IFR FOR A TIME.  
 
WEDNESDAY AFTERNOON AND EVENING...MAINLY VFR WITH A CHANCE OF  
SHOWERS AND THUNDERSTORMS.  
 
WEDNESDAY NIGHT THROUGH FRIDAY MORNING...MAINLY VFR.  
 
FRIDAY AFTERNOON...MAINLY VFR WITH A CHANCE OF SHOWERS AND  
THUNDERSTORMS.  
 

 
   
MARINE
 
 
SMALL CRAFT ADVISORY CONTINUES ACROSS THE NORTHERN HALF OF THE  
ATLANTIC COASTAL WATERS THROUGH THIS MORNING AS SEAS ARE  
EXPECTED TO BUILD TO AROUND 5 FEET AND WINDS COULD GUST AROUND  
25 KNOTS. CONDITIONS ARE EXPECTED TO FALL BACK BELOW ADVISORY  
LEVELS THIS AFTERNOON. THE REST OF THE WATERS ARE EXPECTED TO  
REMAIN BELOW ADVISORY LEVELS THROUGH TONIGHT.  
 
OUTLOOK...  
TUESDAY THROUGH WEDNESDAY...WIND SPEEDS AND WAVE HEIGHTS ARE  
FORECAST TO REMAIN BELOW THE SMALL CRAFT ADVISORY CRITERIA.  
HOWEVER, SOME FOG IS POSSIBLE ON THE WATERS.  
 
WEDNESDAY NIGHT THROUGH FRIDAY...NO MARINE HEADLINES ARE  
ANTICIPATED.  
 
RIP CURRENTS...  
THE POTENTIAL FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS IS  
LOW FOR TODAY.  
 

 
   
TIDES/COASTAL FLOODING
 
 
TIDAL DEPARTURES OF AROUND 1 FOOT ARE EXPECTED AGAIN TONIGHT FOR  
COASTAL AREAS OF NEW JERSEY AND DELAWARE AND AREAS ALONG  
DELAWARE BAY. THESE TIDAL DEPARTURES WOULD LEAD TO ANOTHER  
ROUND OF MINOR COASTAL FLOODING FOR TONIGHT'S HIGH TIDE.  
THEREFORE WE'VE ISSUED A COASTAL FLOOD ADVISORY FOR TONIGHT.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...COASTAL FLOOD ADVISORY FROM 10 PM THIS EVENING TO 4 AM EDT  
TUESDAY FOR NJZ012>014-020>027.  
DE...COASTAL FLOOD ADVISORY FROM 10 PM THIS EVENING TO 4 AM EDT  
TUESDAY FOR DEZ002>004.  
MD...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ450>452.  
 

 
 

 
SYNOPSIS...IOVINO  
NEAR TERM...ROBERTSON  
SHORT TERM...ROBERTSON  
LONG TERM...IOVINO  
AVIATION...IOVINO/ROBERTSON  
MARINE...IOVINO/ROBERTSON  
TIDES/COASTAL FLOODING...ROBERTSON  
 
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