Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 311416 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1016 AM EDT SUN AUG 31 2014 .SYNOPSIS... HIGH PRESSURE WELL OFF THE EAST COAST WILL MAINTAIN A SOUTHWESTERLY FLOW OVER THE AREA THROUGH THE FIRST PART OF THE WEEK. A WEAK COLD FRONT IS THEN EXPECTED TO MOVE ACROSS OUR AREA TUESDAY NIGHT AND EARLY WEDNESDAY. HIGH PRESSURE WILL BUILD IN BEHIND THIS FRONT FOR THE SECOND HALF OF THE WEEK. ANOTHER COLD FRONT MAY APPROACH FROM THE WEST NEXT WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... NOT MUCH CHANGE NEEDED TO THE GRIDS AT THIS TIME. THE TIMING OF THE POPS, BASED ON CURRENT REGIONAL RADAR AND DECENT HANDLING BY THE 10Z HRRR, LOOK GOOD. DID DECREASE SKY COVER ACROSS THE SOUTHERN HALF OF THE CWA THROUGH THE REMAINDER OF THE MORNING BEFORE ANOTHER INCREASE IS EXPECTED UNDER A SELF DESTRUCTING SKY...LOTS OF LOW-LEVEL MOISTURE AND EXCEEDING CONVECTIVE TEMPERATURES. LATEST 12Z REGIONAL SOUNDINGS SHOW VERY WEAK MID- LEVEL LAPSE RATES WITH SOME MID-LEVEL CAPPING IN PLACE...LESS OF CAP TO OUR SOUTHWEST BUT SURPRISINGLY ALSO A LITTLE LESS MOISTURE. ORIGINALLY OUR REGION WAS UNDER A SLIGHT RISK FOR SEVERE THUNDERSTORMS, 15 PERCENT PROBABILITY, BUT AFTER COORDINATION WITH SPC, BASED ON HOW BENIGN THE LAPSE RATES AND LESS CAPE THAN EXPECTED, WE ARE IN SEE TEXT NOW. THIS MEANS THE PROBABILITY OF SEVERE THUNDERSTORMS, MOSTLY IN THE FORM OF WET DOWNBURSTS FROM PRECIPITATION LOADING, ARE LESS THAN BEFORE BUT NOT ENTIRELY OUT OF THE QUESTION. OTHERWISE, OUR REGION WILL MAINLY BE CAUGHT BETWEEN SYSTEMS TODAY, AS AN UPPER-LEVEL RIDGE REMAINS SITUATED TO OUR SOUTH AND SOUTHEAST WITH SURFACE HIGH PRESSURE TO THE EAST. MEANWHILE, AN UPPER-LEVEL TROUGH WILL CONTINUE TO TRACK ACROSS THE GREAT LAKES THEN ACROSS SOUTHERN ONTARIO CANADA. THIS WILL RESULT IN A DEEP SOUTHWESTERLY FLOW, WHICH WILL PULL AN ABUNDANCE OF MOISTURE INTO OUR REGION. AS A RESULT, A MORE HUMID DAY IS EXPECTED. AS WE STEP FORWARD THROUGH THE DAY, ENOUGH HEATING COMBINED WITH CLIMBING SURFACE DEW POINTS SHOULD RESULT IN ENOUGH INSTABILITY /MLCAPE UP TO 1500 J/KG/ TO PRODUCE SHOWERS AND THUNDERSTORMS. THE BULK OF THIS ACTIVITY IS EXPECTED TO DEVELOP TO OUR WEST NEAR A WEAK FRONTAL BOUNDARY WITH ADDITIONAL DEVELOPMENT POSSIBLY NEAR A DIFFERENTIAL HEATING ZONE. THE HEIGHT FALLS ARE WEAK THIS FAR EAST AS THE SHORT WAVE TROUGH TRACKS TO OUR NORTH LATE IN THE DAY. HOWEVER, AN INCREASE IN THE MID LEVEL FLOW TO NEAR 40 KNOTS WILL INCREASE THE SHEAR WITH TIME. THIS SHOULD BE ENOUGH TO PROMOTE SOME STORM ORGANIZATION WITH THE MAIN MODE BEING LINE SEGMENTS, IF WE GET BETTER UPDRAFT GROWTH TO OCCUR. IN ADDITION, THE PW VALUES ARE FORECAST TO INCREASE TO AROUND 2 INCHES WHICH WILL LEAD TO DOWNPOURS. THESE DOWNPOURS MAY RESULT IN BRIEF POOR DRAINAGE FLOODING, HOWEVER THE FLASH FLOOD THREAT GENERALLY LOOKS LOW AS THERE SHOULD BE ENOUGH OF A STORM MOTION. THE MOIST ENVIRONMENT COMBINED WITH ENOUGH INSTABILITY COULD ALSO RESULT IN SOME STORMS PRODUCING FREQUENT LIGHTNING. GIVEN THE FORECAST THERMODYNAMIC SETUP, SOME STORMS WILL BE CAPABLE OF PRODUCING GUSTY TO PERHAPS LOCALLY DAMAGING WINDS. THIS GENERALLY LOOKS TO BE FROM ABOUT THE INTERSTATE 95 CORRIDOR ON NORTH AND WEST BY LATE AFTERNOON. WE THEREFORE MAINTAINED INCREASING POPS FROM WEST TO EAST WITH THE WESTERN ZONES GOING TO LIKELY IN THE AFTERNOON, AND WE ALSO ADDED SOME ENHANCED WORDING. MUCH OF THE EASTERN AND SOUTHEASTERN ZONES MAY REMAIN DRY FOR THE BULK OF THE DAY. AS FOR HIGH TEMPERATURES, WE USED AN EVEN BLEND OF THE NAM/GFS MOS THEN ADJUSTED DOWN A LITTLE BIT FOR SOME AREAS WITH THE IDEA OF LOTS OF CLOUDS PREVAILING. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... THE AFOREMENTIONED SHORT WAVE TROUGH IS FORECAST TO DAMPEN OUT AS IT TRACKS WELL TO OUR NORTH TONIGHT. THERE IS STILL A TRAIL OF SHORT WAVES ROLLING UP THE BACKSIDE OF THE UPPER-LEVEL RIDGE WITH ALSO A WEAKENING FRONTAL BOUNDARY NEARING THE AREA. THE FORECAST SOUNDINGS INDICATE THAT ENOUGH INSTABILITY IS MAINTAINED FOR AWHILE FOR SOME SHOWERS AND THUNDERSTORMS TO CONTINUE THROUGH THE EVENING, ESPECIALLY FROM THE INTERSTATE 95 CORRIDOR ON NORTH AND WEST. A SOMEWHAT MORE PRONOUNCED SHORT WAVE MAY HELP TO FOCUS A CONVECTIVE CLUSTER OVERNIGHT, HOWEVER WHERE THIS IS FOCUSED HAS LESS CERTAINTY WITH IT ATTM. AS THE PW VALUES REMAIN RATHER HIGH, LOCAL DOWNPOURS COULD PUT DOWN A DECENT AMOUNT OF RAIN HOWEVER ANY FLOOD THREAT LOOKS BRIEF AND LOCALIZED. AS MENTIONED ABOVE, SOME STRONG CONVECTION MAY OCCUR IN THE EVENING WITH LOCALLY GUSTY WINDS POSSIBLE. THIS WOULD BE MORE TIED TO ANY LINE SEGMENTS THAT ARE ABLE TO MAINTAIN THEMSELVES WITH PERHAPS SOME ENHANCEMENT FROM WATER LOADED DOWNDRAFTS. OTHERWISE, A WEALTH OF CLOUDS SHOULD BE AROUND THROUGH THE NIGHT FOR MUCH OF THE AREA ALONG WITH MUGGY CONDITIONS. AS FOR LOW TEMPERATURES, AN EVEN BLEND OF THE NAM/GFS MOS WAS GENERALLY USED. && .LONG TERM /MONDAY THROUGH SATURDAY/... UNSETTLED WEATHER IS EXPECTED ON MONDAY WITH CONVECTION STILL POSSIBLE MOST AREAS THROUGH MOST OF THE DAY. LOCALLY HEAVY RAIN IS POSSIBLE JUST ABOUT ANYWHERE...BUT LATEST GUIDANCE SUGGESTS NEAR AND SOUTH AND EAST OF THE I-95 CORRIDOR MIGHT BE FAVORED. ANY FLOODING SHOULD BE MORE URBAN AND POOR DRAINAGE FLOODING. WITH A CONTINUED SOUTHWESTERLY FLOW, TEMPERATURES WILL PEAK 5 TO 10 DEGREES ABOVE NORMAL FOR THE BEGINNING OF SEPTEMBER. MONDAY NIGHT AND TUESDAY...A LULL IN THE PRECIPITATION IS EXPECTED LATE MONDAY NIGHT THROUGH TUESDAY AFTERNOON. IF THERE`S ENOUGH SUNSHINE...TEMPERATURES COULD PEAK OUT IN THE LOW 90S. TUESDAY NIGHT...SHOWERS AND THUNDERSTORMS...SOME WITH LOCALLY HEAVY RAIN...CAN BE EXPECTED AS A COLD FRONT SWINGS THROUGH THE AREA FROM WEST TO EAST. WEDNESDAY THROUGH FRIDAY...THE AIR MASS BEHIND THE COLD FRONT REALLY WON`T BE TOO MUCH COOLER COURTESY OF A MID-LEVEL ZONAL FLOW, BUT IT WILL BE DRIER AND MORE COMFORTABLE. HIGHS ALL THREE DAYS WILL BE PRIMARILY IN THE LOW TO MID 80S, WHICH IS STILL ABOVE NORMAL. BEAUTIFUL EARLY SEPTEMBER WEATHER. SATURDAY...INCREASING CLOUDINESS AS THE DAY WEARS ON AS A COLD FRONT APPROACHES FROM THE WEST. SHOWERS AND THUNDERSTORMS ARE POSSIBLE WITH TEMPERATURES STILL ABOVE NORMAL. && .AVIATION /14Z SUNDAY THROUGH THURSDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAY...AREAS OF MVFR TO LOCAL IFR CEILINGS WILL IMPROVE TO VFR CEILINGS BY MIDDAY. SOME SHOWERS AND THUNDERSTORMS ARE EXPECTED TO CONTINUE TO DEVELOP TO OUR WEST AND OVERSPREAD OUR AREA THIS AFTERNOON. SOME TIMING WAS INDICATED IN THE TAFS, WITH THUNDER ONLY MENTIONED AT KABE TO KRDG DUE TO HIGHER CONFIDENCE AS OF NOW. THERE WILL BE BRIEF TIMES OF MVFR/IFR VISIBILITIES ESPECIALLY WITHIN SHOWERS AND THUNDERSTORMS AS DOWNPOURS ARE ANTICIPATED. SOUTH-SOUTHEAST WINDS INCREASING TO GENERALLY 10-15 KNOTS AND BECOMING SOUTH-SOUTHWEST. TONIGHT...SHOWERS AND THUNDERSTORMS SHOULD CONTINUE EASTWARD WITH MUCH OF THE ACTIVITY IN THE EVENING HOURS. AS A RESULT, THERE WILL BE TIMES OF MVFR/IFR DUE TO DOWNPOURS. IN ADDITION, SOME LIGHT FOG COULD DEVELOP LATE IF SOME CLEARING OCCURS COMBINED WITH LIGHT WINDS. OUTLOOK... MONDAY INTO MONDAY NIGHT...IFR CONDITIONS EXPECTED WITH SHOWERS AND THUNDERSTORMS. COVERAGE OF PRECIPITATION DECREASING DURING THE OVERNIGHT HOURS. TUESDAY...GENERALLY VFR CONDITIONS EXPECTED DURING THE DAY. TUESDAY NIGHT...IFR CONDITIONS POSSIBLE AS A COLD FRONT MOVES THROUGH THE AREA. WEDNESDAY THROUGH FRIDAY...GENERALLY VFR CONDITIONS EXPECTED. && .MARINE... A SOUTHERLY FLOW IS EXPECTED THROUGH TONIGHT AHEAD OF A WEAKENING FRONTAL BOUNDARY AS A DISTURBANCE TRACKS WELL TO OUR NORTH. AS THIS OCCURS, THE FLOW IS FORECAST TO INCREASE AND THIS OPENS THE DOOR TO SOME MIXING. IT APPEARS THAT THE WARM AIR ADVECTING ACROSS THE AREA WILL KEEP THE STRONGER WINDS ABOVE THE SURFACE. WHILE THERE CAN BE SOME GUSTINESS ESPECIALLY NEARSHORE, IT GENERALLY LOOKS MARGINAL. THE SOUTHERLY FLOW WILL ALSO ALLOW THE SEAS TO BUILD THROUGH TONIGHT, HOWEVER GIVEN THE SOUTHERLY FLOW DIRECTION AND FETCH, WE KEPT SEAS UP TO 4 FEET. THEREFORE, NO SMALL CRAFT ADVISORY HAS BEEN ISSUED AT THIS TIME. SOME SHOWERS AND THUNDERSTORMS WILL ARRIVE LATE THIS AFTERNOON AND TONIGHT, AND SOME STORMS COULD PRODUCE LOCALLY GUSTY WINDS. OUTLOOK... MONDAY AND MONDAY NIGHT...WINDS AND SEAS SHOULD REMAIN JUST BELOW SMALL CRAFT ADVISORY CRITERIA. GUSTIER WINDS POSSIBLE IN THE VICINITY OF THUNDERSTORMS. TUESDAY THROUGH THURSDAY...WINDS AND SEAS EXPECTED TO REMAIN BELOW SCA CRITERIA. HOWEVER, SOME GUSTY WINDS ARE POSSIBLE WITH THUNDERSTORMS TUESDAY NIGHT AND EARLY WEDNESDAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...MIKETTA NEAR TERM...GORSE/HEAVENER SHORT TERM...GORSE LONG TERM...MIKETTA AVIATION...GORSE/MIKETTA MARINE...GORSE/MIKETTA

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