Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 300757 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 357 AM EDT THU JUL 30 2015 .SYNOPSIS... A WEAK COLD FRONT WILL MOVE THROUGH OUR REGION TONIGHT, THEN STALLS TO OUR SOUTH AND EAST. THE NEXT WEAK COLD FRONT SHOULD CROSS OUR AREA LATE SATURDAY BEFORE STALLING OFFSHORE SUNDAY. A FEW WEAK WAVES OF LOW PRESSURE MAY TRACK ALONG THE FRONT AND POSSIBLY MOVE CLOSER TO OUR COAST MONDAY AS HIGH PRESSURE TRIES TO ARRIVE. A STRONGER COLD FRONT IS THEN FORECAST TO ARRIVE DURING TUESDAY, BEFORE ALSO STALLING NEARBY ON WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... EXCESSIVE HEAT WARNING REMAINS IN EFFECT FOR TODAY FOR THE PHILADELPHIA METRO AND SURROUNDING AREAS. SOME SCATTERED SHOWERS HAVE STARTED TO POP UP ACROSS THE REGION THIS MORNING AND ARE MOVING FAIRLY QUICKLY TO THE NORTHEAST. CLOUDS WILL FILTER INTO THE REGION AS A COLD FRONT APPROACHES FROM THE WEST. HOWEVER, THERE WILL STILL BE PLENTY OF SUNSHINE TO BE HAD FOR MUCH OF THE REGION THROUGH TODAY. THE COLD FRONT WILL TRACK FROM WESTERN PENNSYLVANIA TO OUR AREA TODAY, REACHING OUR WESTERN ZONES AROUND LATE MORNING/EARLY AFTERNOON. AS THE FRONT CROSSES THE REGION, THERE WILL SHOWERS AND THUNDERSTORMS ASSOCIATED WITH IT AS IT PUSHES TOWARDS THE COAST. STORMS LOOK MOST LIKELY TO ARRIVE TO THE REGION AFTER NOON, WITH A GRADUAL SHIFT TO THE SOUTH AND EAST. WITH A RIPE ATMOSPHERE AND PLENTY OF MOISTURE AROUND HEAVY RAIN WILL BE POSSIBLE WITH ANY STORM THAT DEVELOPS. IN ADDITION, THE STORM PREDICTION CENTER HAS MUCH OF OUR AREA IN A MARGINAL RISK FOR SEVERE STORMS. THE GREATEST THREAT FROM STRONGER STORMS WILL BE GUSTY TO POTENTIALLY DAMAGING WINDS. ANOTHER HUMID DAY ON TAP AS WE SEE TEMPERATURES CONTINUE TO RISE NEAR 90 ACROSS MUCH OF THE AREA. HEAT INDEX VALUES WILL BE IN THE MIDDLE TO UPPER 90S, APPROACHING 100. THEREFORE, WE HAVE CONTINUED THE EXCESSIVE HEAT WARNING FOR THE URBAN AREAS IN AND AROUND PHILADELPHIA. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... THE AFOREMENTIONED COLD FRONT WILL CONTINUE ITS TREK TOWARD THE COAST AND SHOULD MOVE OFFSHORE TONIGHT. THE SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO TONIGHT AND WILL END FROM NORTHWEST TO SOUTHEAST AS THE FRONT PUSHES OFF THE COAST AND THEN FURTHER OFFSHORE. AS THE FRONT PUSHES AWAY, WE WILL ALSO SEE SOME CLEARING BEHIND IT AND AREAS TO THE NORTH AND WEST OF PHILLY WILL BE ABLE TO COOL OFF A BIT AND DROP DOWN INTO THE LOWER TO MID 60S OVERNIGHT. AREAS TO THE SOUTH AND EAST OF PHILLY WILL HOLD ONTO THE CLOUD COVER A BIT LONGER AND WILL LIKELY REMAIN IN THE UPPER 60S TO LOWER 70S FOR OVERNIGHT LOWS. EVEN WITH THE CLEARING, LOW LEVEL MOISTURE MAY HANG AROUND FOR A BIT AND PATCHY FOG WILL REMAIN POSSIBLE. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... THE SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH FROM THE GREAT LAKES TO THE NORTHEAST FRIDAY WITH SOME AMPLIFICATION INTO THE WEEKEND. DESPITE A WARM TO HOT AIRMASS IN PLACE, A SUBSTANTIAL REDUCTION IN THE DEW POINTS IS EXPECTED FRIDAY AND EVEN FOR THE WEEKEND OVERALL FOR THE CWA. A WEAK FRONT MOVES THROUGH LATE SATURDAY WITH SOME POTENTIALLY TRICKY CONVECTIVE CHCS, THEN THE NEXT ONE ARRIVES DURING TUESDAY BEFORE STALLING NEARBY WEDNESDAY. THERE IS MORE UNCERTAINTY IN THE DETAILS ESPECIALLY NEXT WEEK AS THE AMPLITUDE OF THE TROUGH AND THE POSITIONING OF FRONTAL BOUNDARIES WILL IMPACT OUR SENSIBLE WEATHER. WE USED A MODEL BLEND FRIDAY THROUGH SUNDAY, THEN WENT WITH MOSTLY A WPC/CONTINUITY BLEND THEREAFTER. FOR FRIDAY...AN INITIAL FRONT IS STALLED OFFSHORE AS IT BECOMES TRAPPED BETWEEN A RIDGE IN THE WESTERN ATLANTIC AND A TROUGH FROM THE GREAT LAKES TO THE NORTHEAST. ANY REMAINING FRONTAL FORCING AND ASSOCIATED CONVECTION SHOULD REMAIN WELL OFFSHORE, MEANWHILE A NOTICEABLE DRIER AIRMASS SETTLES INTO OUR AREA. DESPITE IT STILL BEING WARM TO HOT ACROSS THE CWA, THE LOWER DEW POINTS WILL RESULT IN A MUCH LESS HUMID FEEL /EVEN COOLER AT NIGHT/. THE AFOREMENTIONED UPPER-LEVEL TROUGH AMPLIFIES SOME ESPECIALLY TO OUR NORTHWEST THROUGH NORTHEAST, AND SOME UPSTREAM CONVECTION MAY TRY TO MAKE A RUN AT OUR NORTHWEST ZONES VERY LATE AT NIGHT. OVERALL, THIS LOOKS LIKE A VERY SMALL CHC PLUS WITH THE INITIAL DRIER AIRMASS IN PLACE AND THEREFORE WE OPTED TO LEAVE THE NIGHT TIME FRAME DRY. FOR SATURDAY AND SUNDAY...AN UPPER-LEVEL TROUGH REMAINS ACROSS THE NORTHEAST ALTHOUGH IT MAY WEAKEN SOME SUNDAY AS A RIDGE IN THE WESTERN ATLANTIC TRIES TO EXPAND NORTHWESTWARD. THIS KEEPS A STALLED FRONTAL BOUNDARY OFFSHORE HOWEVER IT APPEARS THAT WEAK RIPPLES OF ENERGY ALONG IT REMAINS TO OUR EAST. A SECONDARY FRONTAL ZONE IS FORECAST TO MOVE THROUGH LATE SATURDAY INTO SUNDAY, AND THE GREATEST LIFT AND SHEAR IS MOSTLY FROM NEAR OUR NORTHERN ZONES ON NORTHWARD INTO NEW ENGLAND. THE DEW POINTS SHOULD START TO INCH BACK UPWARD AGAIN LATER SATURDAY, HOWEVER ENOUGH DRYING MAY LIMIT MUCH CONVECTIVE DEVELOPMENT. SOME GUIDANCE DOES INITIATE MORE CONVECTION BY LATE SATURDAY FROM NORTHEASTERN PENNSYLVANIA TO NORTHERN NEW JERSEY THEN SLIDES IT SOUTHEASTWARD. THERE MAY BE ENOUGH SHEAR WITH INCREASING INSTABILITY TO ALLOW FOR A GUSTY THUNDERSTORM, HOWEVER THIS IS DEPENDENT ON THE AIRMASS MOISTENING UP SUFFICIENTLY AS THE UPPER-LEVEL TROUGH REMAINS IN PLACE. FOR NOW, WE CONTINUED SOME LOW END CHC POPS ACROSS THE FAR NORTH SATURDAY AFTERNOON. THE FRONT LOOKS TO STALL JUST OFFSHORE GIVEN WEAKER FLOW WITH A SOUTHEASTERN EXTENT, HOWEVER SOME WEAK IMPULSES MAY TRACK ALONG IT. IT APPEARS THAT ANY CONVECTION LEFTOVER WITH THE FRONT IS OFFSHORE, THEREFORE WE HAVE A DRY SUNDAY. IT WILL CONTINUE TO BE WARM GIVEN A SIMILAR PATTERN AND THE DEW POINTS WILL PROBABLY INCREASE A BIT MAINLY SUNDAY NIGHT ACROSS THE SOUTHERN AND EASTERN AREAS. FOR MONDAY AND TUESDAY...AS THE UPPER-LEVEL TROUGH RELOADS FROM THE WEST, IT MAY SUPPORT WEAK IMPULSES TRAVERSING THE OFFSHORE FRONT. IF THIS OCCURS AND WITH THE UPPER-LEVEL FLOW TURNING MORE SOUTHWESTERLY FOR A TIME, THE FRONT MAY INCH BACK INTO OUR AREA TO HELP FOCUS SOME CONVECTION MONDAY. THIS LOOKS WEAK OVERALL WITH THE MAIN FORCING REMAINING MOSTLY ACROSS THE GREAT LAKES REGION MONDAY. TIED TO THIS FORCING, ANOTHER COLD FRONT ARRIVES DURING TUESDAY WITH THE POTENTIAL FOR SOME CONVECTION ALTHOUGH THE STRONGER SHEAR MAY AGAIN SLIDE TO OUR NORTH. WE OPTED TO GO CLOSE TO THE 00Z WPC GUIDANCE WHICH CARRIES POPS OF LOW END CHC OR LESS. FOR WEDNESDAY...AS THE UPPER-LEVEL TROUGH STARTS TO WEAKEN IN THE NORTHEAST, THE FRONTAL BOUNDARY FROM TUESDAY SHOULD SLOW OR EVEN STALL IN OUR VICINITY. THIS COULD HELP FOCUS SOME CONVECTIVE DEVELOPMENT ESPECIALLY DURING PEAK HEATING, WITH POSSIBLE CONVECTIVELY INDUCED IMPULSES ARRIVING FROM THE WEST. THERE IS MUCH MORE UNCERTAINTY THIS FAR OUT AS THE POSITIONING OF THE UPPER-LEVEL TROUGH WILL GOVERN THE FRONTAL ZONE PLACEMENT AND SUBSEQUENT CONVECTIVE CHCS. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. A COUPLE OF LIGHT SHOWERS HAVE DEVELOPED NEAR KRDG THIS MORNING. THESE SHOWERS ARE FAIRLY LIGHT AND ARE MOVING QUICKLY OFF TO THE NORTHEAST. SOME ADDITIONAL SHOWERS MAY DEVELOP THROUGH THE EARLY MORNING, FULLY EXITING THE REGION BY LATE MORNING. MAJORITY OF THE REGION REMAINS DRY WITH SHOWERS HAVING LITTLE TO NO IMPACT TO THE TERMINALS THIS MORNING. MAINLY MID LEVEL CLOUDINESS IS EXPECTED AT THE TERMINALS THROUGH THIS MORNING WITH SOME MVFR DECKS IMPACTING KRDG AND POSSIBLY KABE THROUGH AROUND 12-13Z. SHOWERS AND THUNDERSTORMS, ASSOCIATED WITH AN APPROACHING COLD FRONT, ARE EXPECTED TO REACH THE AREA BETWEEN 16-18Z. THE FRONT WILL PUSH TO THROUGH THE TERMINALS FROM THE NORTHWEST TO THE SOUTHEAST, EXITING OFFSHORE LATE TONIGHT. TIMING IS STILL AN ISSUE BUT EXPECT THE FRONT TO PUSH THROUGH KACY BETWEEN 22-01Z. CLEARING IS EXPECTED TO OCCUR BEHIND THE FRONTAL PASSAGE. SOUTH TO SOUTHWEST WINDS AROUND 5 TO 10 ARE EXPECTED THROUGH TODAY, BECOMING NORTHWEST BEHIND THE FRONTAL PASSAGE. OUTLOOK... FRIDAY...A CHANCE OF SOME FOG EARLY MAINLY AT KMIV AND KACY, OTHERWISE VFR. NORTHWEST WINDS AROUND 10 KNOTS, THEN DIMINISHING TO NEAR 5 KNOTS AT NIGHT AND BECOMING SOUTHWESTERLY. SATURDAY...VFR OVERALL. A SHOWER OR THUNDERSTORM POSSIBLE IN THE AFTERNOON AND EVENING MAINLY NORTH AND WEST OF KPHL. SOUTHWEST WINDS 5-10 KNOTS. SUNDAY AND MONDAY...VFR IS ANTICIPATED. && .MARINE... A SOUTH TO SOUTHWEST FLOW OF AROUND 10 TO 15 KNOTS WITH GUSTS UP TO 20 KNOTS IS EXPECTED ON THE AREA WATERS THROUGH TONIGHT. SEAS WILL REMAIN AROUND 2 TO 4 FEET. A COLD FRONT WILL APPROACH FROM THE WEST AND REACH THE AREA WATERS LATE TONIGHT. SHOWERS AND THUNDERSTORMS ARE EXPECTED TO ACCOMPANY THE FRONTAL PASSAGE. OUTLOOK... FRIDAY THROUGH MONDAY...THE CONDITIONS ARE ANTICIPATED TO BE BELOW SMALL CRAFT ADVISORY CRITERIA OVERALL. A LINGERING FRONT OFFSHORE FRIDAY INTO SATURDAY, THEN ANOTHER FRONT MOVES THROUGH LATE SATURDAY AND POSSIBLY STALLS NEARBY INTO MONDAY. && .RIP CURRENTS... A MODERATE RISK OF DANGEROUS RIP CURRENTS IS FORECAST FOR TODAY, WITH INCREASING SOUTH TO SOUTHWEST FLOW AHEAD OF A COLD FRONT AND THE FULL MOON ON FRIDAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...EXCESSIVE HEAT WARNING UNTIL 6 PM EDT THIS EVENING FOR PAZ070- 071-102-104-106. NJ...EXCESSIVE HEAT WARNING UNTIL 6 PM EDT THIS EVENING FOR NJZ015- 017>019. DE...EXCESSIVE HEAT WARNING UNTIL 6 PM EDT THIS EVENING FOR DEZ001. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GORSE NEAR TERM...MEOLA SHORT TERM...MEOLA LONG TERM...GORSE AVIATION...GORSE/MEOLA MARINE...GORSE/MEOLA RIP CURRENTS...

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