157  
FXUS61 KPHI 250141  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
941 PM EDT FRI SEP 24 2021  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH  
SATURDAY. A COLD FRONT APPROACHING FROM THE NORTHWEST IS  
FORECAST TO ARRIVE ON SATURDAY NIGHT. HIGH PRESSURE IS EXPECTED  
TO FOLLOW FOR SUNDAY INTO MONDAY. A SLOW MOVING COLD FRONT IS  
ANTICIPATED TO DROP THROUGH OUR REGION ON MONDAY NIGHT AND  
TUESDAY, WITH ANOTHER AREA OF HIGH PRESSURE EXPECTED IN ITS  
WAKE.  
 

 
   
NEAR TERM /THROUGH SATURDAY/
 
 
NO SIGNIFICANT CHANGES WITH THE LATE EVENING UPDATE. HIGH  
PRESSURE CONTINUES TO BUILD OVER THE REGION IN THE WAKE OF  
YESTERDAY'S COLD FRONT. THE SURFACE HIGH WILL BE THE DOMINANT  
FEATURE FOR OUR REGION THROUGH TOMORROW, SO THERE IS NOT MUCH TO  
SPEAK OF WITH THE WEATHER THROUGH THIS TIME. A CHILLY NIGHT  
EXPECTED TONIGHT WITH CLEAR SKIES AND LIGHT WINDS. THE COOLEST  
NIGHT OF THE SEASON SO FAR OVERALL, WITH MAINLY UPPER 40S AND  
LOW 50S, WITH SOME MID 40S TO THE NORTHWEST.  
 
WE ALREADY HAVE SOME SITES THAT ARE NEAR OR AT SATURATION AT THE  
SURFACE. THEREFORE, KEPT A MENTION OF PATCHY FOG GENERALLY IN  
THE PRE DAWN HOURS. HOWEVER, WILL HAVE TO KEEP A CLOSE EYE ON  
THIS IF IT DEVELOPS ANY FASTER.  
 
SATURDAY LOOKS TO BE ANOTHER BEAUTIFUL DAY. WE GET SOME SUBTLE  
WARM ADVECTION AHEAD OF A WEAK COLD FRONT OVER THE GREAT LAKES.  
THIS WILL LEAD TO HIGH TEMPERATURES A LITTLE WARMER THAN ON  
FRIDAY, A COUPLE DEGREES ON EITHER SIDE OF 75 IN MOST AREAS.  
WE'LL ALSO SEE A FEW MORE HIGH CLOUDS BY AFTERNOON AHEAD OF THAT  
FRONT. BUT OVERALL, LOOKS LIKE A GREAT DAY.  
 

 
   
SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/
 
 
A MID LEVEL TROUGH IS FORECAST TO SETTLE OVER THE NORTHEASTERN  
STATES FOR THE PERIOD FROM SATURDAY NIGHT THROUGH MONDAY.  
 
A SURFACE LOW MAY DEVELOP ALONG THE OLD FRONTAL BOUNDARY WELL  
OFF OUR COAST. IT MAY SPREAD SOME CLOUDS TOWARD NEW JERSEY AND  
DELAWARE ON SATURDAY NIGHT, BUT WE ARE NOT EXPECTING THEM TO  
MAKE MUCH PROGRESS INLAND.  
 
A SHORT WAVE TROUGH IS EXPECTED TO PASS OVERHEAD LATE ON  
SATURDAY NIGHT WITH AN ASSOCIATED SURFACE COLD FRONT MOVING  
THROUGH OUR REGION AT THAT TIME. THE SYSTEM WILL BE MOISTURE  
STARVED AND WE ARE ANTICIPATING ONLY SOME CIRRUS AND PERHAPS  
SCATTERED MID LEVEL CLOUDS AHEAD OF IT.  
 
SURFACE HIGH PRESSURE IS FORECAST TO NOSE INTO OUR AREA FROM  
THE SOUTHWEST AND SOUTH FOR SUNDAY AND MONDAY. WARM ADVECTION  
ALOFT COULD BRING SOME MID LEVEL CLOUDS OR HIGH BASED  
STRATOCUMULUS ON SUNDAY NIGHT INTO MONDAY MORNING.  
 
TEMPERATURES WILL LIKELY BE SEASONABLE WITH HIGHS MOSTLY IN THE  
70S AND LOWS MAINLY IN THE 50S.  
 

 
   
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
 
 
DURING THE PERIOD FROM MONDAY NIGHT THROUGH THURSDAY, AN OMEGA  
PATTERN IS EXPECTED TO DEVELOP IN THE MID LEVEL FLOW. WE WILL BE  
ON ITS FORWARD SIDE, WITH A TROUGH DIGGING DOWN THE EAST COAST.  
THE TROUGH IS ANTICIPATED TO TRANSITION TO A CUT-OFF LOW OVER  
OR NEAR THE MIDDLE ATLANTIC STATES ON FRIDAY.  
 
A WEAK COLD FRONT IS EXPECTED TO DROP THROUGH OUR REGION ON  
MONDAY NIGHT AND TUESDAY. IT SHOULD HAVE LIMITED MOISTURE  
ASSOCIATED WITH IT, SO WE WILL MENTION ONLY A SLIGHT CHANCE OF  
SHOWERS. SURFACE HIGH PRESSURE IS FORECAST TO SETTLE IN QUEBEC  
FOR THE BALANCE OF THE WEEK. THE CIRCULATION AROUND THE HIGH AND  
A DEVELOPING INVERTED TROUGH OR WEAK LOW OFF THE MIDDLE  
ATLANTIC AND SOUTHEAST COASTS WILL LIKELY PUT OUR REGION IN A  
PERSISTENT NORTHEAST FLOW. DRY WEATHER IS EXPECTED FOR MUCH OF  
THE PERIOD. HOWEVER, DEPENDING UPON THE ACTUAL EVOLUTION OF THE  
SURFACE TROUGH/LOW OFF THE COAST, WE COULD SEE SOME  
PRECIPITATION ON THURSDAY NIGHT AND FRIDAY. HOWEVER, THE  
POTENTIAL APPEARS LOW AT THIS TIME BUT THAT COULD CHANGE.  
 
TEMPERATURES ARE FORECAST TO REMAIN TYPICAL FOR LATE SEPTEMBER.  
 

 
   
AVIATION /02Z SATURDAY THROUGH WEDNESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
THROUGH TONIGHT... MAINLY VFR. WEST-NORTHWEST WIND 5 TO 10 KT  
DECREASING AND GENERALLY BECOMING LIGHT AND VARIABLE OVERNIGHT.  
PATCHY FOG WITH LOCALIZED VSBY RESTRICTIONS POSSIBLE AFTER 08Z,  
MAINLY NORTHWEST OF PHL, AND IT SHOULD NOT BE WIDESPREAD. HIGH  
CONFIDENCE ON MOST ASPECTS OF THE FORECAST, BUT MODERATE  
CONFIDENCE ON THE POTENTIAL FOR FOG.  
 
SATURDAY... VFR. LIGHT WINDS, MAINLY FROM THE WEST BUT COULD BE  
LIGHT AND VARIABLE AT TIMES. ONSHORE FLOW WILL LIKELY DEVELOP  
NEAR THE COAST INCLUDING ACY. HIGH CONFIDENCE.  
 
OUTLOOK...  
 
SUNDAY...MAINLY VFR. NORTHWEST WIND 10 TO 15 KNOTS. HIGH  
CONFIDENCE.  
 
MONDAY...MAINLY VFR. WEST TO SOUTHWEST WIND AROUND 10 KNOTS.  
HIGH CONFIDENCE.  
 
TUESDAY...MAINLY VFR. WEST TO NORTHWEST WIND AROUND 10 KNOTS.  
HIGH CONFIDENCE.  
 
WEDNESDAY...MAINLY VFR. NORTH WIND AROUND 10 KNOTS. HIGH  
CONFIDENCE.  
 

 
   
MARINE
 
 
THROUGH SATURDAY... SUB-SCA CONDITIONS ARE EXPECTED. THE  
PREVIOUS SCA WAS CANCELLED IN RESPONSE TO A DECREASE IN SEAS.  
SEAS WILL REMAIN 3 TO 4 FT THROUGH SATURDAY. NORTHWEST WIND 5 TO  
10 KT THROUGH MOST OF TONIGHT, SHIFTING TO NORTH THEN NORTHEAST  
LATE TONIGHT INTO SATURDAY AT AROUND 10 KT.  
 
OUTLOOK...  
 
SATURDAY NIGHT THROUGH WEDNESDAY...NO MARINE HEADLINES ARE  
ANTICIPATED.  
 
RIP CURRENTS...  
 
LOW LEVEL FLOW WILL REMAIN OFF SHORE THROUGH THE WEEKEND. THIS  
SHOULD HELP TO KEEP THE RIP CURRENT RISK SLIGHTLY LOWER THAN  
WHAT WE HAVE SEEN THE LAST FEW DAYS. HOWEVER, WE STILL EXPECT TO  
SEE A MODERATE RISK THROUGH THE WEEKEND.  
 

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

 
 

 
SYNOPSIS...IOVINO  
NEAR TERM...JOHNSON/O'BRIEN  
SHORT TERM...IOVINO  
LONG TERM...IOVINO  
AVIATION...IOVINO/JOHNSON/O'BRIEN  
MARINE...IOVINO/JOHNSON/O'BRIEN  
 
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