Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 281344 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 944 AM EDT TUE JUL 28 2015 .SYNOPSIS... WEAK HIGH PRESSURE COVERS THE NORTHEAST UNITED STATES THROUGH WEDNESDAY. A WEAK COOL FRONT PASSES THROUGH THE MID ATLANTIC STATES THURSDAY NIGHT. ANOTHER COOL FRONT MAY APPROACH FROM THE NORTHWEST NEXT MONDAY. MEANWHILE, LOW PRESSURE CENTERS ALONG THE SOUTHEAST COAST OF THE UNITED STATES THIS WEEK WILL BE MONITORED FOR POSSIBLE NORTHWARD DEVELOPMENT NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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THE LAST OF THE LOW CLOUDS WERE LIFTING AND DISSIPATING AROUND 930 AM. THE REMNANTS OF THE FRONTAL BOUNDARY THAT ARRIVED ON SUNDAY NIGHT EXTENDED ACROSS SOUTHERN NEW JERSEY AND THE UPPER DELMARVA PENINSULA THIS MORNING. THE BOUNDARY IS FORECAST TO DRIFT NORTHWESTWARD INTO NORTHERN NEW JERSEY AND SOUTHEASTERN PENNSYLVANIA TODAY. MEANWHILE, WEAK AREAS HIGH PRESSURE SHOULD REMAIN CENTERED OVER THE EASTERN GREAT LAKES AND OFF THE MIDDLE ATLANTIC COAST. AS THE BOUNDARY CONTINUES TO DISSIPATE, WE ARE NOT EXPECTING MUCH OF A CHANCE OF SHOWERS AND THUNDERSTORMS IN ITS VICINITY. HOWEVER, WE WILL CONTINUE TO CARRY A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS FOR THIS AFTERNOON IN PARTS OF SOUTHERN NEW JERSEY, DELAWARE AND NORTHEASTERN MARYLAND. DEVELOPING SEA AND BAY BREEZE BOUNDARIES MAY PROVIDE ENOUGH LIFT TO RESULT IN ISOLATED CONVECTION. MIXED LAYER CAPE VALUES ARE ANTICIPATED TO INCREASE TO ABOUT 700 TO 1100 J/KG IN THOSE AREAS DURING THE AFTERNOON. MAXIMUM TEMPERATURES ARE EXPECTED TO BE AROUND 90 AT MOST LOCATIONS IN OUR FORECAST AREA. READINGS SHOULD BE A BIT LOWER THAN THAT IN THE ELEVATED TERRAIN AND ALONG THE COAST. DEW POINT READINGS SHOULD FAVOR THE UPPER 60S AND LOWER 70S. THE RESULTING MAXIMUM HEAT INDEX VALUES ARE IN THE LOWER AND MIDDLE 90S. TODAY MAY BE THE FIRST OF AT LEAST SEVEN CONSECUTIVE DAYS OF 90 PLUS TEMPERATURE READINGS IN MUCH OF OUR REGION. THE MAXIMUM NUMBER OF CONSECUTIVE 90 PLUS DAYS AT PHILADELPHIA IS 18 SET FROM JULY 29 THROUGH AUGUST 15, 1988. THE 8 TO 14-DAY OUTLOOK FOR THE PERIOD FROM AUGUST 4-10 SUGGESTS A COOLING TREND AT THAT TIME, SO WE DO NOT ANTICIPATE APPROACHING THE RECORD.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
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A WEAK SURFACE HIGH IS FORECAST TO BE OVER OUR AREA TONIGHT AS AN UPPER-LEVEL RIDGE AXIS SLIDES ACROSS THE EASTERN GREAT LAKES AND OHIO VALLEY. THIS STILL MAINTAINS NORTHWESTERLY FLOW ALOFT, BUT LIGHT AND VARIABLE FLOW AT THE SURFACE. DUE TO A LACK OF ORGANIZED SHORT WAVES TO PROVIDE ENOUGH LIFT, AN ISOLATED SHOWER OR THUNDERSTORM INITIATED PROBABLY BY ANY LOW-LEVEL CONVERGENCE /I.E. SEA AND BAY BREEZES/ ARE EXPECTED TO DISSIPATE EARLY IN THE EVENING. IN ADDITION, ANY CUMULUS FIELD IS EXPECTED TO FLATTEN AND DISSIPATE WITH PERHAPS SOME HIGH CLOUDINESS OCCURRING AT TIMES. IT WILL BE A WARM AND MUGGY NIGHT FOR MUCH OF THE CWA AS THE SURFACE DEW POINTS SHOULD RECOVER FROM ANY DAYTIME HEATING INFLUENCE. THE COMBINATION OF LIGHT TO CALM WINDS, A MOIST BOUNDARY LAYER AND NOT A LOT OF CLOUDINESS COULD RESULT IN PATCHY LOW CLOUDS/FOG DEVELOPMENT LATE. AS FOR THE LOW TEMPERATURES, A MOS BLEND WAS GENERALLY USED.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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**POTENTIAL SEVEN DAY OR LONGER HEAT WAVE FOR PHL BEGINNING TODAY AND PROBABLY CONTINUING THROUGH NEXT MONDAY OR TUESDAY** 500 MB: HIGH PRESSURE IN THE SOUTHERN PLAINS WILL BE THE DOMINANT INFLUENCE HERE THROUGH THURSDAY. OTHERWISE A TROUGH TRIES TO EVOLVE OVER THE EASTERN STATES NEXT WEEKEND. TEMPERATURES: THE MONTH OF JULY SO FAR HAS BEEN NEAR NORMAL (TEMPS). THIS EXTENDED PERIOD WILL SEE CALENDAR DAY AVERAGES ABOVE NORMAL EVERY DAY. TEMPS SHOULD AVERAGE 5 TO 7 DEGREES ABOVE NORMAL WEDNESDAY AND THURSDAY AND 3 TO 5 DEGREES ABOVE NORMAL FRIDAY THROUGH SUNDAY AND THEN MORE THAN 5 DEGREES ABOVE NEXT MONDAY AUGUST 3. FORECAST BASIS: UNLESS OTHERWISE NOTED, A 50 50 BLEND 00Z/28 GFS/NAM MOS GUIDANCE WEDNESDAY-THURSDAY, 00Z/28 MEX MOS THURSDAY NIGHT AND FRIDAY, THEN THE 0521Z/28 WPC GRIDDED ELEMENTS OF MAX/MIN TEMP, 12 HOUR POP, 6 HOUR DEW POINT-SKY-WIND FROM FRIDAY NIGHT THROUGH NEXT MONDAY. THE DAILIES... WHILE NOT IN THE SYNOPSIS DUE TO ITS POTENTIAL TO CAUSE CONFUSION... AND ITS LACK OF SIGNIFICANT WEATHER IMPACT, IT LOOKS LIKE THERE WILL BE A LEFTOVER WIND SHIFT BOUNDARY SOMEWHERE NEAR I-95 THROUGH THURSDAY BEFORE A MORE STRUCTURED WEAK COOL FRONTAL PASSAGE OCCURS THURSDAY NIGHT. WEDNESDAY...RELATIVELY DRY HEAT. PWAT ~1.35 INCHES. HEAT INDEX BELOW 100F. SOUTHWEST WIND GUST 15 MPH DURING THE AFTERNOON EXCEPT WEAK SEA BREEZES COASTAL LOCATIONS BEGINNING AROUND NOON. USED THE WARMER MAV TEMPS FOR THE DAYTIME FCST. FCST MAX TEMPS MAY BE A DEGREE TOO LOW. OVERALL CONFIDENCE: ABOVE AVERAGE. THURSDAY...APPROACHING WET BULB FRONT WITH THE 850 MB HOT PROD OF 18-20C AHEAD OF THE CF AND A QUICK START TO 90F THURSDAY MORNING. AFTERNOON DEW POINTS ARE EXPECTED TO BE MUCH HIGHER THAN WEDNESDAY (BY ALMOST 10F). RAISED THE 00Z/28 NCEP GUIDANCE USING THE 00Z/28 ECMWF BUT DID SO WITH LESS THAN IDEAL CONFIDENCE. MLCAPE BUILDS IN CENTRAL PA TO 1400J BY 18Z THU AND 600J NJ. APPEARS UNLIKELY TO HAVE ANY SHOWERS OR TSTMS GOING IN OUR AREA BEFORE 16Z AND PROBABLY NOT TO THE I-95 CORRIDOR TIL NEAR 22Z. THAT SHOULD ALLOW MORE WARMING THAN MODELED AND HI NEARING 100F BY 18Z. MAX TEMPS SHOULD REMAIN BELOW RECORDS WHICH ARE 97-99F EXCEPT KMPO 90. SSW WIND GUST 15-20 MPH DURING THE AFTN. WHAT WOULD PREVENT THE HEAT INDEX REACHING 100F? THURSDAY MORNING SHOWERS AND TSTMS VCNTY KPHL SOUTH AND EAST WOULD LESSEN SUNSHINE AND MAKE IT MUCH MORE DIFFICULT FOR THE AIR TEMPERATURE TO EXCEED 90F. THERE ARE 00Z/28 EC/GFS MODEL HINTS OF A WEAK INSTABILITY BURST TRYING TO SHOVE NEWD INTO THE DELMARVA AND SNJ THURSDAY MORNING AND PRODUCE MORNING SHOWERS. A SCT-BKN BAND OF SHOWERS AND TSTMS SHOULD DEVELOP AND PASS ACROSS THE AREA THU AFTN/NIGHT. PWAT INCREASES TO 1.9 INCHES ALONG THE I- 95 CORRIDOR DURING THURSDAY EVENING SO HEAVY RAINERS AND LOCAL POOR DRAINAGE FLOODING ANTICIPATED AND CANT RULE OUT ISOLATED FF. WHILE TIMING IS EXCELLENT FOR STRONG TSTM DEVELOPMENT, SVR UNLIKELY SINCE 0-6KM BULK SHEAR IS PRETTY WEAK AND LAPSE RATES VIA TT INDEX LOOK PRETTY POOR. SREF MODELED PWAT BACK EDGE OF 1.5 INCHES DOWN TO A KDOV- KBLM LINE BY 12Z FRIDAY. FRIDAY...DEW POINTS LOWER BY 10 TO 12F ON LIGHT NLY FLOW AND AIR TEMPS DOWN 2-3F. BLUE MOON AND POTENTIALLY NICE HOT SUMMER DAY FOR THE END OF JULY. ABOVE AVERAGE CONFIDENCE. SATURDAY AND SUNDAY...HEATS UP MAYBE A BIT MORE EACH DAY ON WSW AFTERNOON WIND GUSTS 10-15 MPH. A NICE WEEKEND SINCE AFTERNOON DEW POINTS STILL REMAIN PRETTY MODEST...LOW TO MID 60S. SMALL CHC OF A TSTM NE PA SAT EVE IN WAA - THIS PER 1400J NEAR KHZL MIDDAY REACHING KBLM BY 00Z/SUNDAY. AVERAGE CONFIDENCE. NEXT MONDAY...MORE HUMID AND CONTD HOT. 2000J MLCAPE I95 SEWD. AVERAGE CONFIDENCE ON THE FCST DETAILS.
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&& .AVIATION /14Z TUESDAY THROUGH SATURDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAY...SOME LOW CLOUDS WILL DISSIPATE BY LATE MORNING, OTHERWISE VFR WITH A CLOUD BASE MOSTLY BETWEEN 3500-5000 FEET. AN ISOLATED SHOWER OR THUNDERSTORM MAY DEVELOP THROUGH THE DAY ESPECIALLY SOUTH AND EAST OF KPHL. SEA/BAY BREEZES ARE EXPECTED TO DEVELOP BY MID AFTERNOON AND AFFECT KACY, KMIV AND KILG WITH WINDS TURNING MORE FROM THE SOUTHEAST. TONIGHT...MAINLY VFR. HOWEVER DUE TO THE MOIST AIR MASS IN PLACE, SOME LATE NIGHT LOW CLOUDS/FOG MAY DEVELOP, AND OUR CONFIDENCE IS ON THE LOWER SIDE AT THIS TIME. LIGHT SOUTHERLY TO CALM WINDS. OUTLOOK... WEDNESDAY THROUGH THURSDAY MORNING...MAINLY VFR. HOWEVER, THE HIGH HUMIDITY LEVELS MAY RESULT IN SOME LATE NIGHT AND EARLY THURSDAY MORNING MVFR OR IFR LOW CLOUDS, HAZE AND FOG. LIGHT SW WIND. THURSDAY AFTERNOON AND THURSDAY NIGHT...A CHANCE OF SHOWERS AND THUNDERSTORMS THAT MAY RESULT IN MVFR OR IFR CONDITIONS AT TIMES. GRADIENT SW WIND GUSTS 15-20 KT THU AFTN. FRIDAY THROUGH SATURDAY...MAINLY VFR. LIGHT WIND, MAINLY NORTH FRIDAY MORNING WITH SEA BREEZES BOTH FRIDAY AND SATURDAY.
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&& .MARINE...
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THE CONDITIONS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA THROUGH TONIGHT. A SOUTHERLY FLOW WILL CONTINUE WITH SOME ENHANCEMENT OCCURRING THIS AFTERNOON AND EARLY EVENING AS A SEA AND BAY BREEZE DEVELOPS. THE SEAS SHOULD RUN IN THE 1-3 FEET RANGE THROUGH TONIGHT. OUTLOOK... WEDNESDAY THROUGH SATURDAY...NO MARINE HEADLINES ARE ANTICIPATED.
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&& .RIP CURRENTS...
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A LONG PERIOD /AROUND 10 SECONDS/ SWELL FROM THE EAST-SOUTHEAST WILL CONTINUE TODAY. A SOUTHERLY WIND AT 10-15 MPH WITH SOME AFTERNOON SEA BREEZE ENHANCEMENT ALONG WITH WAVES OF AROUND 2 FEET IN THE SURF ZONE ARE FORECAST TODAY. THE SETUP IS SIMILAR TO YESTERDAY AND THEREFORE WE WILL MAINTAIN A MODERATE RISK OF DANGEROUS RIP CURRENTS FOR BOTH THE NEW JERSEY AND DELAWARE COASTS.
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&& .CLIMATE... KACY RAINFALL 6.33 RANKED 15TH WETTEST WITH THE POR DATING BACK THROUGH 1874. WETTEST 13.09 IN 1959. KABE MAY EXPERIENCE NEAR RECORD WARMTH ON WEDNESDAY JULY 29. THE RECORD THERE IS IS 96 SET IN 1954. RIGHT NOW WE`RE FCSTG 94. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...DRAG NEAR TERM...IOVINO SHORT TERM...GORSE LONG TERM...DRAG AVIATION...DRAG/GORSE MARINE...DRAG/GORSE RIP CURRENTS...GORSE CLIMATE...DRAG

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