647  
FXUS61 KPHI 181950  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
350 PM EDT WED SEP 18 2019  
   
SYNOPSIS
 
 
A RIDGE OF HIGH PRESSURE WILL GRADUALLY BUILD SOUTHWARD INTO THE MID-  
ATLANTIC THROUGH THE END OF THE WORKWEEK AS HURRICANE HUMBERTO  
CONTINUES TO MOVE TO THE NORTHEAST, AWAY FROM OUR REGION. THE HIGH  
WILL PUSH OFFSHORE THIS WEEKEND AS AN AREA OF LOW PRESSURE AND  
ATTENDANT COLD FRONT APPROACH THE REGION.  
 

 
   
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
 
 
A GOOD AMOUNT OF SHALLOW CUMULUS IS DOTTING OUR AREA THIS AFTERNOON,  
AS PEAK HEATING COMBINES WITH WEAK LIFT FROM A SHORTWAVE SLIDING  
EAST OF OUR AREA. THIS CLOUD COVER SHOULD PIVOT SOUTH AND THIN OUT  
TONIGHT IN THE WAKE OF THE AFOREMENTIONED WAVE. CONSEQUENTLY EXPECT  
MOSTLY CLEAR SKIES (PARTICULARLY OVER THE NORTHERN 2/3RDS OF THE  
AREA) OVERNIGHT AND THIS COMBINED WITH DIMINISHING WINDS SHOULD  
PROVIDE A GOOD SETUP FOR RADIATIONAL COOLING. LOWS WILL LIKELY  
REMAIN IN THE LOWER 50S IN THE URBAN CORRIDOR, DELMARVA, AND THE  
IMMEDIATE COAST, WHILE MOST OTHER AREAS WILL BOTTOM OUT IN THE 40S  
(SOME 30S WILL EVEN BE POSSIBLE IN THE POCONOS/NW NJ).  
 

 
   
SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/
 
 
THE SURFACE HIGH PRESSURE THAT HAS BEEN CENTERED TO OUR NORTH WILL  
MOVE OVERHEAD BY THURSDAY AFTERNOON. LARGE-SCALE SUBSIDENCE  
ASSOCIATED WITH THE HIGH & THE UPSTREAM H5 RIDGE SHOULD MAKE FOR A  
VERY DRY DAY TOMORROW (FORECAST PWATS ARE ONLY AROUND 0.3 INCHES).  
THINK THAT EVEN SHALLOW CUMULUS WILL HAVE A HARD TIME DEVELOPING IN  
THIS ENVIRONMENT (EXCEPT MAYBE OVER THE IMMEDIATE COAST) SO WOULD  
EXPECT MOSTLY SUNNY SKIES. LOW-LVL FLOW WILL REMAIN FROM THE  
NORTHEAST FOR MUCH OF THE DAY SO HIGHS SHOULD REMAIN SEASONABLE  
(GENERALLY IN THE LOW 70S).  
 

 
   
LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/
 
 
TRANQUIL WEATHER IS EXPECTED THROUGH THE REMAINDER OF THE WEEK WITH  
ONLY A FEW MARINE CONCERNS EARLY INTO THE FORECAST. HIGH PRESSURE  
WILL LARGELY DOMINATE OUR WEATHER PATTERN AS HURRICANE HUMBERTO  
MOVES TO THE NORTH AND EAST ACROSS THE OPEN ATLANTIC, FURTHER  
OFFSHORE. UPPER LEVEL RIDGING WILL KEEP THE HIGH OVERHEAD FOR THE  
MOST PART UNTIL A SHORTWAVE TROUGH PROGRESSES EASTWARD ACROSS THE  
GREAT LAKES AND INTO THE NORTHEAST BY MONDAY.  
 
SURFACE HIGH PRESSURE WILL DOMINATE OUR WEATHER FRIDAY THROUGH  
SUNDAY WITH GRADUAL WARMING ALL THREE DAYS WITH A SHIFT FROM ONSHORE  
NORTHEASTERLY WINDS TO MORE OF A SOUTHWESTERLY FLOW. THIS, COMBINED  
WITH ADIABATIC COMPRESSION WILL LEAD TO SIGNIFICANT WARMING. BY  
SATURDAY, HIGHS WILL LIKELY SIT SOME 5 TO 15 DEGREES ABOVE AVERAGE  
ACROSS THE REGION. SUNDAY WILL LIKELY BE THE WARMEST OF THE TWO, AND  
THE WARMEST OF THE NEXT WEEK AT THAT WITH UPPER 80S MOST EVERYWHERE  
EXPECT THE HIGHER ELEVATIONS OF THE SOUTHERN POCONOS. A FEW 90S ARE  
NOT OUT OF THE QUESTION AT THIS POINT EITHER.  
 
BY MONDAY, A SHORTWAVE TROUGH PROGRESSES TOWARD THE EASTERN U.S.,  
THOUGH THERE REMAINS SOME UNCERTAINTY IN ITS TIMING AND  
ORGANIZATION. THE GFS TENDS TO KEEP THE TROUGH MORE NEUTRALLY  
TILTED, WHILE THE ECMWF PORTRAYS A POSITIVE TILT WITH A SOUTHERN  
DETACHMENT OFF THE MAIN TROUGH OVER CANADA INTO THE CENTRAL U.S.  
THIS SIGNIFICANTLY SLOWS THE PROGRESSION OF THE SURFACE LOW AND COLD  
FRONT WITH THIS SIMULATION, THUS THE TIMING OF PRECIPITATION REMAINS  
SOMEWHAT UNRESOLVED. THE VARIANCE RIDES INTO THE MIDDLE OF NEXT WEEK  
WITH THE PLACEMENT OF A DEEP TROUGH AND "FOUR CORNER'S" LOW BY  
WEDNESDAY, WITH THE ECMWF RETAINING ITS SLOWER APPROACH.  
 

 
   
AVIATION /20Z WEDNESDAY THROUGH MONDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
REST OF TODAY/TONIGHT...VFR CONDITIONS WITH 4-6K FT. CLOUDS THINNING  
AFTER SUNSET. WINDS GENERALLY NORTHEASTERLY AROUND 10 KTS THIS  
AFTERNOON DECREASING TO AROUND 5 KTS OVERNIGHT.  
 
THURSDAY...VFR CONDITIONS WITH NORTHEASTERLY WINDS 5-10 KTS  
INITIALLY, EVENTUALLY BECOMING LIGHT AND VARIABLE IN THE  
AFTERNOON.  
 
OUTLOOK...  
 
FRIDAY THROUGH SUNDAY...MOSTLY VFR CONDITIONS ARE EXPECTED THROUGH  
THIS TIME WITH LIGHT WINDS FROM A PREVAILING WESTERLY DIRECTION.  
 
MONDAY...GENERALLY VFR, THOUGH RESTRICTION MAY ENSUE AS SHOWERS AND  
THUNDERSTORMS WILL BEGIN TO WORK THEIR WAY INTO THE MID-ATLANTIC  
AHEAD OF A COLD FRONT. THE TIMING REMAINS SOMEWHAT UNCERTAIN,  
HOWEVER. SOUTHWESTERLY WINDS FROM 5 TO 10 KNOTS WITH GUSTS TO 15  
KNOTS.  
 

 
   
MARINE
 
 
SEAS ABOVE SCA CRITERIA (GENERALLY 6-8 FT) ON THE OCEAN WATERS ARE  
EXPECTED TO PERSIST THROUGH THE DAY ON THURSDAY. WIND GUSTS IN THE  
25KT RANGE ARE EXPECTED TO PEAK TONIGHT AND THEN DECREASE THROUGH  
THE DAY ON THURSDAY. CONDITIONS SHOULD REMAIN SUB-SCA FOR DELAWARE  
BAY ALTHOUGH WINDS COULD GUST UP TO 20 KTS THROUGH THE OVERNIGHT  
PERIOD.  
 
OUTLOOK...  
 
FRIDAY...SCA CONDITIONS LIKELY WITH ELEVATED SEAS  
FROM 5 TO 8 FEET. WESTERLY WINDS FROM 10 TO 15 KNOTS WITH GUSTS  
UP TO 20 KNOTS POSSIBLE IN THE MORNING HOURS.  
 
SATURDAY...SCA CONDITIONS AS SEAS REMAIN ABOVE 5 FEET. WESTERLY  
WINDS CONTINUE FROM 10 TO 15 KNOTS WITH GUSTS TO 20 KNOTS AT  
TIMES DURING THE MORNING HOURS. WINDS SLACKEN DURING THE  
AFTERNOON TO BELOW 10 KNOTS.  
 
SUNDAY...SUB-SCA CONDITIONS EXPECTED WITH SOUTHERLY WINDS FROM 10 TO  
15 KNOTS AND GUSTS TO 20 KNOTS. SEAS FROM 1 TO 3 FEET.  
 
MONDAY...SUB-SCA CONDITIONS EXPECTED WITH SOUTHWESTERLY WINDS FROM  
10 TO 15 KNOTS AND GUSTS TO 20 KNOTS. SEAS FROM 2 TO 4 FEET.  
 
RIP CURRENTS...  
 
A HIGH RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS IS  
EXPECTED TODAY. ENHANCED CONDITIONS (EITHER MODERATE OR HIGH  
RISK) WILL LIKELY REMAIN AROUND FOR SEVERAL DAYS WITH HURRICANE  
HUMBERTO WELL OFFSHORE SENDING SWELLS BACK ACROSS OUR WATERS.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...HIGH RIP CURRENT RISK UNTIL 11 PM EDT THIS EVENING FOR NJZ014-  
024>026.  
DE...HIGH RIP CURRENT RISK UNTIL 11 PM EDT THIS EVENING FOR DEZ004.  
MD...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT SATURDAY FOR ANZ450>455.  
 

 
 

 
SYNOPSIS...DAVIS  
NEAR TERM...CARR  
SHORT TERM...CARR  
LONG TERM...DAVIS  
AVIATION...CARR/DAVIS  
MARINE...CARR/DAVIS  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab PA Page
The Nexlab NJ Page
The Nexlab DE Page
The Nexlab MD Page Main Text Page