936  
FXUS61 KPHI 012219  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
619 PM EDT FRI JUL 1 2016  
   
SYNOPSIS
 
 
A COLD FRONT WILL APPROACH FROM THE WEST THIS AFTERNOON BEFORE  
MOVING THROUGH THE AREA THIS EVENING AND OFFSHORE LATE TONIGHT. THE  
FRONT WILL STALL TO OUR SOUTH THIS WEEKEND WHILE HIGH PRESSURE  
BUILDS INTO OUR REGION. THE FRONT WILL START TO LIFT BACK NORTHWARD  
WITH SEVERAL WAVES OF LOW PRESSURE TRACKING ALONG IT MONDAY AND  
TUESDAY. HIGH PRESSURE BRIEFLY RETURNS WEDNESDAY BEFORE SHIFTING OFF  
THE COAST LATE IN THE WEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM SATURDAY MORNING/
 
 
610 PM: WATCH CONTINUES FOR A LITTLE WHILE LONGER, BUT WE'RE NOT  
OPTIMISTIC ABOUT RESURGENCE TO NEAR SVR LEVELS ACROSS EASTERN PA  
AND NW NJ. DRIER AIR APPEARS TO MAKING ITS WAY INTO EASTERN PA  
INDICATING A GRADUAL STABILIZATION. SO WHILE MODELED MASS FIELDS  
ARE MORE UNSTABLE AT 00Z/2, THE LACK OF MUCH QPF FROM 00Z ONWARD  
FITS THE IDEA THAT THE WORST HAS OCCURRED ALONG AND NW OF I95. SO  
THE WATCH CONTINUES BUT NOT WITH HIGH CONFIDENCE FOR RESURGENCE TO  
NEAR SVR LEVELS.  
 
TONIGHT AFTER 9 PM...AFTER LINE SEGMENTS MULTI CELLULAR STORM  
GROUPS DIE OUT AND ADVANCE OFF THE COAST, MODELS HAVE BEEN  
CONSISTENT ON CLEARING CONDITIONS QUICKLY BEHIND THE COLD FRONT  
WHICH SHOULD BE OFFSHORE BY 09Z. DEPENDING HOW QUICKLY THE CLOUDS  
CLEAR AND IF THE WINDS DECOUPLE, PATCHY DENSE FOG MAY FORM. MORE  
DETAILS AT 3 PM.  
 
FCST BASIS IS A 50 50 BLEND OF THE 12Z/1 GFS/NAM MOS.  
 

 
   
SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/
 
 
SUNNY START WITH SOME AFTERNOON CIRRUS. A BEAUTIFUL DAY WITH A  
NORTHWEST WIND OF 15-20 MPH. PWAT DOWN TO .65 INCHES.  
 
FCST ELEMENT BASIS WAS A 50 50 BLEND OF THE 12Z/1 GFS/NAM MOS.  
 

 
   
LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/
 
 
A VERTICALLY-STACKED LOW WILL DRIFT NORTHEASTWARD ACROSS EASTERN  
CANADA WHILE THE COLD FRONT THAT MOVES THROUGH OUR AREA TONIGHT  
STALLS TO OUR SOUTH THROUGH THE REMAINDER OF THE WEEKEND. IN BETWEEN  
THESE TWO SYSTEMS, WEAK HIGH PRESSURE WILL BE POSITIONED OVER THE  
MIDWEST AND NORTHERN MID-ATLANTIC REGIONS. WE ARE EXPECTING A DRY  
STRETCH OF WEATHER SATURDAY NIGHT AND SUNDAY WITH TEMPERATURES NEAR  
NORMAL.  
 
THE NEXT SYSTEM WE ARE WATCHING IS A SHORTWAVE TROUGH CURRENTLY OVER  
THE FOUR CORNERS REGION. THIS DISTURBANCE IS FORECAST TO GET STEERED  
BY THE STRONGER WESTERLIES ALOFT RESIDING SOUTH OF THE BROAD  
LONGWAVE TROUGH. IT IS FORECAST TO MOVE EASTWARD ALONG A STATIONARY  
FRONT THAT RESIDES ACROSS THE EASTERN TWO-THIRDS CONUS THIS WEEKEND  
AND EARLY NEXT WEEK. SOME OF THE EARLIER MODEL GUIDANCE HAD THIS  
DISTURBANCE TRACKING FAR ENOUGH TO OUR SOUTH TO KEEP US DRY FOR  
MONDAY AND TUESDAY. THE LATEST MODEL RUNS TODAY HAVE TRENDED  
SLIGHTLY FARTHER NORTH WITH THE DISTURBANCE AND FRONTAL BOUNDARY.  
ACCORDINGLY, A DRY INDEPENDENCE DAY IS LOOKING LESS LIKELY AS EVEN A  
SLIGHT NORTHWARD SHIFT COULD BRING THE THREAT OF SHOWERS AND STORMS  
TO OUR AREA. THERE IS ALSO A POSSIBILITY THAT A MORE ORGANIZED MCS  
MOVES THROUGH OUR AREA (ESPECIALLY FOR THE SOUTHERN HALF OF THE  
CWA), WHICH COULD POTENTIALLY IMPACT OUTDOOR HOLIDAY PLANS,INCLUDING  
FIREWORKS. HIGHEST POPS ON MONDAY RESIDE ACROSS THE DELMARVA AND  
SOUTHERN NJ DURING THE AFTERNOON AND EVENING, WHEN DIURNAL  
INSTABILITY PEAKS. POPS ARE STILL HIGHEST ACROSS OUR SOUTHERN ZONES  
TUESDAY BUT DECREASE LATE IN THE DAY WITH THE FRONT EVENTUALLY  
MOVING BACK TO OUR SOUTH AND SUBSIDENCE BUILDING OVERHEAD IN WAKE  
OF THIS SHORTWAVE TROUGH. TIMING OF PRECIP WILL NEED TO BE  
REFINDED AS WE GET CLOSER TO THE EVENT AND DETAILS ON THE  
MESOSCALE BECOMING CLEARER. THERE IS ALSO A POTENTIAL FOR HEAVY  
RAINFALL AND FLOODING IN VICINITY OF WHERE THE FRONTAL BOUNDARY  
SETS UP. PWATS COULD EXCEED 2" NEAR THE FRONT. THE LATEST WPC QPF  
SHOWS A MAX OF2.5 INCHES IN THE DELMARVA.  
 
A DRY WEATHER PATTERN RETURNS TUESDAY NIGHT AND WEDNESDAY WITH HIGH  
PRESSURE BRIEFLY IN CONTROL. SOUTH TO SOUTHWESTERLY RETURN FLOW  
LOOKS TO DEVELOP EITHER WEDNESDAY NIGHT OR THURSDAY ONCE THE HIGH  
MOVES OFFSHORE. THE HEAT THEN BUILDS ACROSS THE AREA AS THE UPPER  
RIDGE SHIFTS TO THE SOUTHEAST STATES AND POSSIBLY BUILDS NORTHWARD.  
WE COULD SEE OUR FIRST 90 DEGREE DAY IN PHILADELPHIA FOR THE FIRST  
TIME SINCE JUNE 20TH AS EARLY AS WEDNESDAY BUT MORE LIKELY BY  
THURSDAY (LOW 90S ARE FAVORED FARTHER INLAND TOWARD ABE/RDG  
WEDNESDAY AND THURSDAY). WE WILL LIKELY NEED TO MENTION IN THE  
UPCOMING DAYS THE POTENTIAL FOR HEAT HAZARDS LATE NEXT WEEK (HEAT  
INDICES NEAR 100F ARE FORECAST FOR FRIDAY). THERE IS ALSO A CHANCE  
FOR SHOWERS AND STORMS THURSDAY AND FRIDAY WITH THE LATEST GUIDANCE  
SHOWING OUR AREA POSITIONED JUST DOWNSTREAM OF THE CONVECTIVE RING  
OF FIRE. IN THIS REGION, SEVERAL FAST-MOVING MCCS MAY TRACK AROUND  
THE NORTHERN PERIPHERY OF THE UPPER RIDGE WHERE A BELT OF STRONGER  
WESTERLIES RESIDE.  
 

 
   
AVIATION /22Z FRIDAY THROUGH WEDNESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
REST OF TODAY THROUGH 01Z/2...SCT-BKN CLOUDS AOA 4000 FT WITH SOUTH  
OR SOUTHWEST...GUSTY 15-20 KT. SHORT LINE SEGMENTS OR GROUPS OF  
IFR TSTMS PRODUCING WIND GUSTS 35-45 KT, HAIL OF VARIOUS SIZES  
AND DANGEROUS LIGHTNING, TORRENTIAL RAINS, MAINLY SOUTHERN NJ AND  
DELMARVA.  
 
TONIGHT AFTER 01Z/2...VFR WITH SCT THUNDERSTORMS ENDING/MOVING  
OFF THE COAST BY 04Z/2. PATCHY IFR STRATUS/FOG CAN DEVELOP TOWARD  
09Z/2. LIGHT SOUTH TO SOUTHWEST WIND SHIFT TO NORTHWEST.  
 
SATURDAY...VFR. CIRRUS IN THE AFTERNOON. NORTHWEST WIND GUST 15-20  
KT.  
 
OUTLOOK...  
 
SATURDAY NIGHT THROUGH SUNDAY NIGHT...PREDOMINATELY VFR CONDITIONS  
EXPECTED. W TO NW WINDS 5 TO 10 KT SATURDAY NIGHT, BECOMING W TO SW  
SUNDAY.  
 
MONDAY AND TUESDAY...MVFR TO IFR POSSIBLE WITH MULTIPLE ROUNDS OF  
SHOWERS AND STORMS POSSIBLE. BETTER CHANCES FROM PHL SOUTHWARD.  
 
TUESDAY NIGHT AND WEDNESDAY...MAINLY VFR.  
 

 
   
MARINE
 
 
535PM UPDATE FOR SHORT FUSE SCA ALL OF OUR WATERS EXPIRING 01Z. A  
NUMBER OF REPORTS OF 25-30 KT GUSTS ON THE WATER LATE THIS AFTERNOON.  
 
OTHERWISE WINDS AND SEAS SHOULD GENERALLY REMAIN BELOW SCA CRITERIA  
AFTER 9 PM THIS EVENING THROUGH SATURDAY.  
 
AN ESE SWELL OF 2.5 FT MAY BE SURPASSED BY A SOUTHERLY SWELL OF 3 FEET  
TONIGHT, THEN TOMORROW WE DROP BACK TO THE SEASONALLY PERSISTENT  
AND NORMAL SE SWELL OF 2.5 FEET.  
 
MWS FOR FOG CONTINUES NNJ WATERS TIL ABOUT 02Z.  
 
THUNDERSTORMS LATE TODAY OR THIS EVENING WILL PROBABLY BE ASSOCIATED  
WITH 30-45 KT WESTERLY WIND GUSTS AND HAIL.  
 
SATURDAY IS A NICE DAY TO BE OUT ON THE WATER ALTHOUGH WITH SOME  
LEFTOVER SOUTHERLY SWELL.  
 
OUTLOOK...  
SATURDAY NIGHT THROUGH WEDNESDAY...WINDS AND SEAS (3 FT OR LESS  
THRU TUESDAY, 3-4 FT WEDNESDAY IN OUR COASTAL ATLANTIC ZONES) ARE  
EXPECTED TO REMAIN BELOW SCA CRITERIA. HOWEVER, LOCALLY STRONGER  
WIND GUSTS POSSIBLE IN THUNDERSTORMS MONDAY AND TUESDAY. GREATEST  
RISK TO SEE STORMS WILL ACROSS OUR SOUTHERN ZONES.  
 
RIP CURRENTS...PROJECTING A SOLID LOW FOR SATURDAY WITH A 3 FT 7SEC  
SE SWELL BUT AN OFFSHORE WIND. SUNDAY-MONDAY-TUESDAY PROJECTING A  
LOW ENHANCED OR POSSIBLY LOW END OF A MODERATE RISK WHERE THE NEW  
MOON TENDS TO ACCENTUATE TIDAL FLUCTUATIONS AND THEREBY INCREASES  
CURRENT STRENGTH. THE SUNDAY-TUESDAY CONFIDENCE PROJECTION IS AVERAGE.  
IN OTHER WORDS, CAUTION IS ADVISED WHEN USING A PROJECTION THIS  
FAR IN ADVANCE, SINCE A 1 FOOT DIFFERENCE IN WAVE HEIGHT EXPECTATION  
AND/OR A SIGNIFICANT CHANGE IN ONSHORE WIND CAN EASILY CHANGE THE  
POTENTIAL FOR DANGEROUS RIP CURRENT FORMATION.  
 
THE ATLANTIC BASIN CONTINUES QUIET FOR AT LEAST THE NEXT 5 DAYS SO  
THAT BODES WELL FOR CONTINUING THE LOW RISK, OR AT WORST, MODERATE  
RISK FOR THE FORMATION OF DANGEROUS RIP CURRENTS.  
 
MOST FATALITIES FROM RIP CURRENTS OCCUR AT UNGUARDED BEACHES. THE  
VAST MAJORITY OF FATALITIES ARE ON LOW-MODERATE RISK DAYS WHICH  
MEANS THERE IS A LACK OF AWARENESS OF THE DANGERS OF SWIMMING AT  
UNGUARDED AREAS, OR NEAR JETTIES AND PIERS. ADDITIONALLY,  
BYPASSING THE SAFETY NET OF LIFEGUARD PATROLS HAS NETTED A  
PRONOUNCED INCREASE IN FATALITIES WITH OUR NWS STORM DATA  
STATISTICS SHOWING THE PREPONDERANCE OF RIP CURRENT RELATED  
DROWNINGS FROM NEAR THE DINNER HOUR TO SUNSET.  
 

 
   
CLIMATE
 
 
ALLENTOWN'S 1.87 INCHES FOR THE MONTH OF JUNE MADE THIS THE 10TH  
DRIEST JUNE IN THE ALLENTOWN PERIOD OF RECORD DATING BACK TO 1922.  
THE DRIEST JUNE ON RECORD WAS .34 INCHES IN JUNE 1949.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...NONE.  
DE...NONE.  
MD...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR ANZ430-  
431-450>455.  
 

 
 

 
SYNOPSIS...KLEIN  
NEAR TERM...DRAG/JOHNSON 619A  
SHORT TERM...DRAG/JOHNSON  
LONG TERM...KLEIN  
AVIATION...DRAG/JOHNSON/KLEIN 619  
MARINE...DRAG/JOHNSON/KLEIN  
CLIMATE...  
 
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