713  
FXUS61 KPHI 310748  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
348 AM EDT SUN MAY 31 2020  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL BUILD INTO THE AREA THROUGH MONDAY BEFORE SLIDING  
TO THE SOUTH AND OFFSHORE ON TUESDAY. A WEAK TROUGH MAY APPROACH THE  
REGION LATE IN THE DAY ON TUESDAY. A COLD FRONT WILL DROP DOWN INTO  
THE REGION WEDNESDAY AND THEN STALL OVER THE MID-ATLANTIC THROUGH  
THE END OF THE WEEK.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
HIGH PRESSURE WILL MOVE FROM MICHIGAN THIS MORNING TOWARDS THE  
UPPER OHIO VALLEY BY TONIGHT. THIS WILL KEEP FAIR WEATHER  
ACROSS THE REGION TODAY. AFTER SOME SEASONABLY CHILLY MORNING  
LOWS, TEMPERATURES WILL RISE INTO THE MID/UPPER 60S N/W AND LOW  
70S ELSEWHERE. THESE TEMPS WILL BE ABOUT 5 DEGREE BELOW NORMAL.  
WINDS WILL BE NORTH TO NORTHWEST AROUND 10 MPH WITH SOME GUSTS  
NEAR 20 MPH.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/
 
 
HIGH PRESSURE WILL CONTINUE TO MOVE SLOWLY ACROSS THE UPPER OHIO  
VALLEY INTO THE MIDDLE ATLANTIC REGION. A CONTINUATION OF FAIR  
WEATHER WITH MOSTLY CLEAR SKIES IS EXPECTED ACROSS OUR REGION. LOWS  
TONIGHT WILL BE ABOUT 5 DEGREES COOLER THAN SAT NIGHT, SO MERCURY  
READINGS WILL FALL INTO THE UPPER 30S/LOW 40S N/W AND CLOSE TO 50  
FOR DELMARVA AND SRN NJ. WINDS WILL BE MOSTLY N AT 5 MPH OR  
LESS.  
 

 
   
LONG TERM /MONDAY THROUGH SATURDAY/
 
 
OVERVIEW: THE LONG TERM WILL START COOL AND DRY AS A LARGE AREA OF  
HIGH PRESSURE BUILDS OVER OUR REGION BEFORE SHIFTING OFF SHORE.  
HOWEVER, BY TUESDAY, WE'LL SEE A BIG SHIFT IN THE OVERALL PATTERN AS  
THE MID AND UPPER LEVEL RIDGE WHICH HAS BEEN OVER THE CENTRAL U.S.  
WILL START BUILDING EAST BEFORE WEAKENING AND FLATTENING. THAT WILL  
LEAVE THE MID ATLANTIC WITH A MOSTLY ZONAL PATTERN UNTIL NEXT  
WEEKEND, WHEN A TROUGH MAY TRY TO DIG SOUTH OVER THE NORTHEASTERN  
U.S. ONCE AGAIN. AT THE SURFACE, A FRONT IS EXPECTED TO APPROACH THE  
REGION MID WEEK, THEN STALL OVER THE MID ATLANTIC THROUGH THE  
REMAINDER OF THE WEEK.  
 
DETAILS:  
 
MONDAY...MONDAY WILL BE THE MOST COMFORTABLE DAY OF THE WEEK TO BE  
OUTSIDE. WE WILL STILL HAVE THE LOW HUMIDITY LIKE WHAT WE WILL SEE  
TODAY, AND TEMPERATURES SHOULD BE 5 TO 10 DEGREES BELOW NORMAL, WITH  
HIGHS MOSTLY IN THE LOWER 70S. SOME MODELS DO SHOW A WEAK LOW LEVEL  
TROUGH IMPENDING ON THE LARGE AREA OF HIGH PRESSURE WHICH COULD LEAD  
TO SHOWERS ESPECIALLY OVER NORTHERN NJ AND E CENTRAL PA. HOWEVER, I  
KEPT THE FORECAST DRY AS DEWPOINTS SHOULD STILL BE IN THE 30S AND  
40S, AND WE SHOULD GENERALLY SEE NORTHWESTERLY LOW AND MID LEVEL  
FLOW, WHICH MEANS THERE WILL BE VERY LIMITED MOISTURE EVEN IF THE  
TROUGH DOES DEVELOP.  
 
TUESDAY...AS THE SURFACE HIGH SHIFTS OFF SHORE, LOW LEVEL  
SOUTHWESTERLY RETURN FLOW DEVELOPS LEADING TO MOISTURE ADVECTION,  
AND SETTING THE STAGE FOR RAIN CHANCES LATER IN THE WEEK. THE  
SOUTHWESTERLY FLOW WILL ALSO HELP START A WARMING TREND, ALTHOUGH  
THE MID AND UPPER LEVEL TROUGH WHICH WILL BE STUBBORNLY STICKING  
AROUND FOR ONE MORE DAY, WILL KEEP TEMPERATURES NEAR NORMAL. A  
SHORTWAVE TROUGH DIGGING ON THE BACK SIDE OF THE MAIN MID/UPPER  
LEVEL TROUGH COULD BE ENOUGH TO RESULT IN SHOWERS, THOUGH IT REMAINS  
TO BE SEEN IF THIS SHORTWAVE TROUGH WILL TRACK CLOSE ENOUGH TO OUR  
REGION TO RESULT IN RAIN FOR US. THEREFORE, KEPT THE RAIN CHANCES  
LIMITED TO 20 TO 40 PERCENT WITH THIS PERIOD.  
 
WEDNESDAY...AT THIS POINT, WEDNESDAY LOOKS LIKE THE MOST  
UNCOMFORTABLE DAY OF THE WEEK. THE COLD FRONT IS NOT EXPECTED TO  
ARRIVE UNTIL WEDNESDAY NIGHT, KEEPING OUR REGION IN THE PRIME  
LOCATION FOR MOISTURE ADVECTION (WITH DEW POINTS POSSIBLY GETTING IN  
TO THE 60S) AND WARM AIR ADVECTION FOR ONE MORE DAY. IN FACT, A LOT  
OF GUIDANCE HAS THE COASTAL PLAINS IN THE UPPER 80S TO NEAR 90  
(SIGNIFICANT AS WE HAVE YET TO HAVE ANY 90 DEGREE DAYS AT ANY OF THE  
CLIMATE SITES IN OUR AREA THIS YEAR). WE MAY NOT SEE MUCH IN THE WAY  
OF RAIN DURING THE DAY ON WEDNESDAY AS WE LIKELY WON'T HAVE MUCH IN  
THE WAY OF LIFT UNTIL THE FRONT GETS CLOSER TO OUR AREA.  
 
THURSDAY THROUGH SATURDAY...THE FRONT THAT APPROACHES OUR REGION  
WEDENSDAY NIGHT IS EXPECTED TO STALL AS THE MID AND UPPER LEVEL  
PATTERN TRANSITIONS TO A ZONAL FLOW PATTERN. THE EXTENT AND TIMING  
OF SHOWERS AND THUNDERSTORMS THROUGH THIS PERIOD WILL DEPEND ON  
EXACTLY WHERE THE FRONT STALLS. FOR NOW, I HAVE STAYED CLOSE TO THE  
PREVIOUS FORECAST, WITH A BROAD BRUSH OF SLIGHT CHANCE TO CHANCES OF  
SHOWERS AND STORMS THROUGH OUT THE PERIOD. HOWEVER, IT IS VERY  
UNLIKELY THAT THIS WILL BE A WASHOUT, AND IF THE FRONT STALLS FAR  
ENOUGH SOUTH, NORTHERN PORTIONS OF OUR REGION, MAY NOT SEE MUCH RAIN  
AT ALL (WITH THE EXCEPTION OF WHEN THE FRONT INITIALLY ARRIVES).  
 

 
   
AVIATION /08Z SUNDAY THROUGH THURSDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
TODAY...VFR EXPECTED WITH A MINIMAL AMOUNT OF DIURNAL CU. THE WINDS  
WILL BE MOSTLY NW AROUND 10 KNOTS WITH SOME GUSTS CLOSER TO 20 KNOTS  
FROM LATE MORNING INTO THE AFTERNOON.  
 
TONIGHT...VFR. SKC. LIGHT N TO NW WINDS, LOCALLY CALM.  
 
OUTLOOK...  
 
MONDAY...VFR CONDITIONS EXPECTED. NORTHWEST WINDS AROUND 5 TO 10  
KNOTS WITH GUSTS TO 20 KNOTS POSSIBLE. HIGH CONFIDENCE.  
 
MONDAY NIGHT AND TUESDAY...MOSTLY VFR CONDITIONS EXPECTED. HOWEVER,  
THERE IS A CHANCE FOR BRIEF REDUCTIONS IN CEILING OR VISIBILITY WITH  
SHOWERS AND THUNDERSTORMS DURING TUESDAY AND TUESDAY NIGHT. LIGHT  
WINDS MONDAY NIGHT WILL BECOME SOUTHWESTERLY AROUND 5 TO 10 KNOTS.  
MODERATE CONFIDENCE ON MOST ASPECTS OF THE FORECAST, BUT LOW  
CONFIDENCE ON THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS.  
 
WEDNESDAY THROUGH THURSDAY...PREDOMINANTLY VFR CONDITIONS ARE  
LIKELY. HOWEVER, THERE IS A CHANCE FOR SHOWERS AND THUNDERSTORMS  
THROUGH OUT THE PERIOD. WESTERLY WINDS AROUND 5 TO 10 KNOTS. LOW  
CONFIDENCE, ESPECIALLY WITH THE TIMING OF SHOWERS AND  
THUNDERSTORMS.  
 

 
   
MARINE
 
 
FAIR WEATHER IS EXPECTED TODAY AND TONIGHT WITH HIGH PRESSURE ACROSS  
THE WATERS. A FEW SCA GUSTS ARE POSSIBLE THIS MORNING, BUT OVERALL  
CONDITIONS WILL BE SUB-SCA BOTH TODAY AND TONIGHT. WINDS WILL BE  
FROM THE NORTH/NORTHWEST TODAY AND NORTH/NORTHEAST TONIGHT. SEAS ON  
THE OCEAN MOSTLY 3 TO 4 FT WHILE ACROSS DEL BAY SEAS WILL BE 1-2 FT  
NORTH AND 2 TO 3 FT SOUTH.  
 
OUTLOOK...  
 
MONDAY THROUGH THURSDAY...WINDS AND SEAS SHOULD STAY BELOW SCA  
CRITERIA.  
 
RIP CURRENTS...  
 
A NORTHWEST WIND IS EXPECTED FOR SUNDAY WITH BREAKING WAVES  
AROUND 2 FEET. AS A RESULT, THERE IS A LOW RISK FOR THE  
DEVELOPMENT OF DANGEROUS RIP CURRENTS.  
 
THE WIND IS FORECAST TO BACK TOWARD THE SOUTHWEST ON MONDAY.  
BREAKING WAVES SHOULD AGAIN BE AROUND 2 FEET. THE LOW RISK IS  
EXPECTED TO CONTINUE INTO MONDAY.  
 

 
   
FIRE WEATHER
 
 
RELATIVE HUMIDITY VALUES COULD DROP TO 30 PERCENT BY THIS  
AFTERNOON (ESPECIALLY ACROSS THE COASTAL PLAINS OF NJ AND DE),  
AND WIND GUSTS UP TO AND IN EXCESS OF 20 MPH ARE EXPECTED TODAY.  
THIS COULD LEAD TO ELEVATED FIRE WEATHER CONCERNS.  
 

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

 
 

 
SYNOPSIS...JOHNSON/MEOLA  
NEAR TERM...O'HARA  
SHORT TERM...O'HARA  
LONG TERM...JOHNSON  
AVIATION...JOHNSON/O'HARA  
MARINE...JOHNSON/O'HARA  
FIRE WEATHER...  
 
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