Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 072003 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 403 PM EDT TUE JUL 7 2015 .SYNOPSIS...
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A TROUGH OF LOW PRESSURE TO OUR SOUTH WILL MOVE EASTWARD VERY SLOWLY THIS EVENING, AS A COLD FRONTAL BOUNDARY SLOWLY MAKES ITS WAY TOWARDS OUR REGION. THE TROUGH TO OUR SOUTH WILL MERGE WITH THIS FRONTAL BOUNDARY ON THURSDAY, STALLING THE FRONT OVER OUR AREA. SEVERAL AREAS OF LOW PRESSURE WILL MOVE ALONG THE FRONTAL BOUNDARY ON THURSDAY AND FRIDAY. HIGH PRESSURE WILL BRIEFLY MOVE INTO THE REGION FOR THE WEEKEND, BEFORE A WARM FRONTAL BOUNDARY MOVES TO OUR NORTH ON MONDAY. A TROUGH LOOKS TO PERSIST OVER OUR AREA THROUGH MOST OF NEXT WEEK, AS A RESULT OF A DOMINANT RIDGE OVER THE MIDWEST.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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A SHORT WAVE TROUGH WAS PASSING OVERHEAD IN THE MID LEVEL FLOW THIS AFTERNOON. THE FEATURE WAS HELPING TO ENHANCE THE SCATTERED SHOWER ACTIVITY IN OUR REGION. MIXED LEVEL CAPE VALUES WERE PEAKING IN THE 1000 TO 1500 J/KG RANGE AT MID AFTERNOON IN EASTERN PENNSYLVANIA AND IN NORTHERN AND CENTRAL NEW JERSEY. A BIT OF DRYING ALOFT IN THE SOUTHWESTERLY FLOW ALONG WITH THE GRADUAL LOSS OF DAYTIME HEATING SHOULD CAUSE THE CAPE VALUES TO DECREASE SLOWLY DURING THE LATE AFTERNOON AND EARLY EVENING HOURS. THE MID LEVEL TROUGH SHOULD PASS TO OUR NORTHEAST AND EAST EARLY THIS EVENING AND IT WILL LIKELY TAKE THE LAST OF THE SHOWERS AND ISOLATED THUNDERSTORMS WITH IT AT THAT TIME. WE ARE ANTICIPATING A MOSTLY CLEAR SKY FROM ABOUT SUNSET UNTIL SHORTLY AFTER MIDNIGHT, THEN CLOUDS AHEAD OF AN APPROACHING FRONTAL BOUNDARY SHOULD BEGIN TO SPREAD OVER OUR REGION FROM THE NORTHWEST LATE TONIGHT. IT WILL REMAIN HUMID TONIGHT WITH MINIMUM TEMPERATURES FORECAST TO RANGE FROM THE UPPER 60S TO THE MIDDLE 70S.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
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A FRONTAL BOUNDARY IS FORECAST TO EXTEND FROM THE CATSKILLS ACROSS NORTHEASTERN PENNSYLVANIA TO AROUND PITTSBURGH EARLY ON WEDNESDAY MORNING. THE BOUNDARY IS EXPECTED TO SINK SLOWLY INTO OUR NORTHWESTERN COUNTIES AS THE DAY PROGRESSES. MEANWHILE, A SURFACE TROUGH IS ANTICIPATED TO DEVELOP TO THE LEE OF THE APPALACHIANS IN THE SOUTHWESTERLY FLOW. THE CONVECTION THAT WAS OVER THE EASTERN GREAT LAKES AND THE LOWER OHIO RIVER VALLEY THIS AFTERNOON SHOULD REACH OUR REGION ON WEDNESDAY. AS A RESULT, WE WILL INDICATE AN INCREASING CHANCE OF SHOWERS AND THUNDERSTORMS FROM NORTHWEST TO SOUTHEAST. THE MODEL GUIDANCE IS SUGGESTING ONLY MARGINAL INSTABILITY FOR WEDNESDAY. HOWEVER, PRECIPITABLE WATER VALUES WILL LIKELY INCREASE TO 2 INCHES OR MORE. AS A RESULT, WE WILL CONTINUE TO MENTION THE POSSIBILITY OF LOCALLY HEAVY RAINFALL. MAXIMUM TEMPERATURES ON WEDNESDAY ARE ANTICIPATED TO BE MAINLY IN THE 80S WITH SOME UPPER 70S IN THE FAR NORTH AND SOME LOWER 90S IN THE FAR SOUTH.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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HEMISPHERIC WAVE GUIDANCE SHOWS DEEP SOUTHWESTERLY FLOW ACROSS THE EASTERN HALF OF THE U.S. AT THE START OF THE LONGTERM PERIOD. BY THE WEEKEND THE WAVELENGTH ACROSS THE CONTIGUOUS U.S. BECOMES LONGER ALLOWING THE SOUTHEAST RIDGING TO RETROGRADE TOWARDS THE CENTRAL U.S. THIS SETS UP A PSEUDO-HIGH LATITUDE OMEGA BLOCK, WITH OUR REGION ON THE PERIPHERY OF AN EAST COAST TROUGH. THIS PATTERN LOOKS TO REMAIN IN PLACE, WHILE LIFTING AND WEAKENING A BIT, GOING INTO NEXT WORK WEEK, ADDING TO OUR DAILY CHANCES FOR SHOWERS AND THUNDERSTORMS. THURSDAY - FRIDAY NIGHT...THE SLOW SAGGING COLD FRONT THAT BEGINS TO CROSS THE REGION ON WEDNESDAY LOOKS TO MAKE IT AS FAR SOUTH AS DELMARVA ON THURSDAY AND REMAIN NEARLY IN PLACE THROUGH FRIDAY. MULTIPLE WAVES MOVE ALONG THIS BOUNDARY AS IT PRESSES SOUTHWARD ADDING TO THE INCREASED CHANCES FOR SCATTERED SHOWERS AND EMBEDDED THUNDER. GUIDANCE TRIES TO ADVECT IN MORE INSTABILITY FROM THE SOUTH ON THURSDAY AHEAD OF THE FRONT BUT THE TIMING DOESN`T LOOK LIKE IT OVERLAPS THE FRONTAL PASSAGE. THAT BEING SAID PWATS WILL STILL BE WELL ABOVE NORMAL, POSSIBLY 2+ INCHES GIVING US MORE LOCALIZED FLOODING ISSUES...SAME AS IT EVER WAS. WE CONTINUE WITH THE HEAVY RAIN WORDING IN THE FORECAST THURSDAY NIGHT INTO FRIDAY MORNING, BUT CONFINE IT TO OUR NORTHERN HALF...BETTER LIFT/DYNAMICS AND SOME ELEVATED INSTABILITY TO WORK WITH. AFTER WHAT COULD BE A GREAT LAKES MCS PASSAGE FRIDAY MORNING ACROSS OUR NORTH, THE FRONT CONTINUES TO SAG SOUTHWARD DURING THE DAY WITH ISOLATED SHOWERS AND THUNDERSTORMS POSSIBLE ACROSS DELMARVA...DRYING OUT BEHIND THE FRONT ACROSS THE NORTH. IT SHOULD BE NOTED THAT FFG ACROSS THE NORTHERN ZONES IS RUNNING QUITE LOW WITH A LOT OF AREAS ONLY NEEDING 1.5 INCHES IN AN HOUR TO CAUSE ISSUES...SOMETHING TO WATCH. SATURDAY...THE AFOREMENTIONED FRONT SHOULD BE FARTHER TO OUR SOUTH THIS WEEKEND WHILE LARGE SCALE SUBSIDENCE TAKES OVER...THE LONGWAVE RIDGING RETROGRADING ALL THE WHILE. WE STILL EXPECT SATURDAY TO BE RAIN FREE BUT THERE COULD BE LINGERING MID-LEVEL ENERGY MOVING BY TO OUR SOUTHWEST THAT MAY TOUCH OFF A FEW ISOLATED TO SCATTERED SHOWERS IN OUR EXTREME SOUTHWEST ZONES...HAVE TIME TO BETTER DEFINE THESE CHANCES IF ANY. SUNDAY - TUESDAY...WARM FRONT PASSAGE, FROM WHAT WAS ONCE THE COLD FRONT EARLIER IN THE PERIOD, MOVES BACK TOWARDS THE NORTH ON SUNDAY NIGHT INTO MONDAY. COLD FRONT THEN NEARS FROM THE NORTHWEST LATE ON MONDAY INTO TUESDAY AS TROUGHING TAKES BACK OVER AGAIN. NORTHWEST FLOW ALOFT LOOKS TO PREVAIL AS CENTRAL U.S. RIDGING AMPLIFIES. THIS MAY SEND SEVERAL SHORTWAVES THROUGH THE REGION FROM LATE MONDAY ONWARD...NORTHERN PLAINS MCS SEASON.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THE SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS IN OUR REGION THIS AFTERNOON SHOULD PULL AWAY TO OUR NORTHEAST THIS EVENING. WE HAVE THE MENTION OF PRECIPITATION IN THE TAFS FOR KABE AND KTTN UNTIL 2100Z. MAINLY VFR CONDITIONS ARE EXPECTED FOR TONIGHT. THE SKY IS FORECAST TO BE MAINLY CLEAR BEFORE MIDNIGHT WITH AN INCREASE IN VFR CLOUDS FROM THE NORTHWEST LATE TONIGHT. A SLOW MOVING FRONTAL BOUNDARY WILL APPROACH FROM THE NORTHWEST ON WEDNESDAY. MVFR CEILINGS ALONG WITH SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO REACH KRDG AND KABE IN THE MORNING. THE LOWERING CONDITIONS AND PRECIPITATION SHOULD REACH OUR REMAINING SIX TAF SITES IN THE AFTERNOON. A SOUTHWESTERLY WIND AROUND 10 KNOTS THIS AFTERNOON SHOULD DROP TO 4 TO 8 KNOTS FOR TONIGHT. A WEST SOUTHWEST WIND AROUND 5 TO 10 KNOTS IS EXPECTED FOR WEDNESDAY. OUTLOOK... THURSDAY...POTENTIAL MVFR AND IFR RESTRICTIONS IN SHOWERS AND THUNDERSTORMS, HIGHEST CHANCES EACH AFTERNOON AND EVENING. WEST- SOUTHWEST WIND GUSTS AT OR UNDER 20 KNOTS. FRIDAY - SATURDAY NIGHT...VFR. WINDS AT OR UNDER 10 KNOTS, MAINLY NORTHERLY. SUNDAY...MOSTLY VFR. SOME SCATTERED SHOWERS AND EMBEDDED THUNDER POSSIBLE.
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&& .MARINE...
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WEAK HIGH PRESSURE WILL INFLUENCE THE COASTAL WATERS OF NEW JERSEY AND DELAWARE FOR TONIGHT AND EARLY WEDNESDAY. A SLOW MOVING FRONTAL BOUNDARY IS FORECAST TO APPROACH FROM THE NORTHWEST ON WEDNESDAY AFTERNOON. A SOUTH TO SOUTHWEST WIND AROUND 10 TO 15 KNOTS IS ANTICIPATED. SPEEDS MAY INCREASE TO 15 TO 20 KNOTS FOR A TIME TONIGHT ON OUR OCEAN WATERS. WAVE HEIGHTS ON OUR OCEAN WATERS SHOULD FAVOR THE 2 TO 4 FOOT RANGE FOR TONIGHT AND WEDNESDAY. WAVES ARE EXPECTED TO BE 2 FEET OR LESS ON DELAWARE BAY. OUTLOOK... SUB-SCA WINDS AND SEAS EXPECTED. ANY WIND GUSTS LOOK TO REMAIN BELOW 20 KNOTS, MORE NORTHERLY THROUGH SATURDAY NIGHT. SEAS AROUND FOUR FEET ON WEDNESDAY AND THURSDAY. THE HIGHEST CHANCE OF THUNDERSTORMS IS WEDNESDAY AFTERNOON AND EVENING THEN AGAIN LATER THURSDAY.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...SPIVEY NEAR TERM...IOVINO SHORT TERM...IOVINO LONG TERM...HEAVENER AVIATION...IOVINO/HEAVENER/GAINES MARINE...IOVINO/HEAVENER/GAINES

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