Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 270728 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 328 AM EDT MON JUL 27 2015 .SYNOPSIS... A COLD FRONT IS FORECAST TO WEAKEN AND DISSIPATE INTO OUR AREA TODAY. HIGH PRESSURE WILL THEN BUILD EASTWARD INTO THE REGION FOR THE MIDDLE OF THE WEEK BEFORE ANOTHER COLD FRONT COMES THROUGH THURSDAY NIGHT. HIGH PRESSURE WILL BUILD EASTWARD FOR THE END OF THE WEEK WITH A FRONTAL BOUNDARY LOCATED TO OUR SOUTH. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE SYNOPTIC SETUP IS COMPRISED OF NORTHWEST FLOW ALOFT WITH AN EMBEDDED SHORT WAVE TROUGH. THIS FEATURE WILL CROSS OUR AREA DURING THE COURSE OF TODAY. THE CONTINUATION OF PVA WITH LINGERING INSTABILITY AND VEERING FLOW WITH HEIGHT IN THE LOWER TO MID LEVELS IS MAINTAINING CONVECTION EARLY THIS MORNING. THE FLOW/SHEAR IS ON THE LIGHTER SIDE, HOWEVER ORGANIZATION IS BEING MAINTAINED PROBABLY DUE TO COLD POOLS AND NEW UPDRAFT CORES ALONG THE LEADING EDGE. THE MODEL GUIDANCE IN GENERAL SUGGESTS THAT A GRADUAL WEAKENING TREND OCCURS WITH AN EASTERN EXTENT FOR AWHILE THIS MORNING BEFORE ADDITIONAL ACTIVITY DEVELOPS WITH RENEWED HEATING WITHIN INCREASING INSTABILITY. THEREFORE WE BUMPED UP POPS QUITE A BIT FOR A TIME THIS MORNING THEN TRENDED BACK TOWARD THE CHC RANGE FOR MOST OF THE AREA. THE PW VALUES ARE AROUND 1.5 INCHES, AND THIS COMBINED WITH CLUSTERING OF THE CONVECTIVE UPDRAFTS /EVEN SOME BACK BUILDING/ EARLY THIS MORNING IS LEADING TO VERY HEAVY RAINFALL IN SOME AREAS. THIS WILL PRODUCE SOME LOCALIZED FLOODING. IT DOES NOT APPEAR A LOT OF LIFT IS NEEDED WITHIN THE AIRMASS TO PROMOTE NEW DEVELOPMENT AS A WEAKENING COLD FRONT GENERALLY DISSIPATES INTO OUR AREA. A WEAK SURFACE TROUGH MAY PERSIST THOUGH AND HELP FOCUS SOME NEW DEVELOPMENT THROUGH THE DAY. AS FOR THE HIGH TEMPERATURES, WE MOSTLY WENT WITH A NAM/GFS MOS BLEND WITH THE ANTICIPATION OF ENOUGH CLOUDS AND CONVECTION AROUND. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... THE SHORT WAVE TROUGH IS FORECAST TO SHIFT TO OUR EAST THIS EVENING, AND THEN SOME SUBTLE HEIGHT RISES OCCUR AS SLIGHT RIDGING STARTS TO ARRIVE FROM THE WEST. AS A RESULT, THE PVA WITHIN THE NORTHWESTERLY FLOW ALOFT IS FORECAST TO WANE AND THIS SHOULD ALLOW ANY CONVECTION TO DISSIPATE BY LATE EVENING FOR MUCH OF THE AREA. THEREFORE, WE TRENDED THE POPS DOWNWARD THROUGH THE EVENING WITH THE LAST MENTIONABLE CONVECTION IN PORTIONS OF THE DELMARVA OVERNIGHT. OTHERWISE, SOME PARTIAL CLEARING SHOULD TAKE PLACE FROM THE NORTHWEST ALTHOUGH SOME HIGH LEVEL CLOUDS MAY CONTINUE TO MOVE ACROSS. THE PRESENCE OF LIGHT WINDS AND AREAS OF LESSENING CLOUD COVER MAY RESULT IN LOCAL FOG DEVELOPMENT OVERNIGHT, ESPECIALLY IN AREAS WHERE HEAVY RAIN HAS FALLEN WHICH WILL ASSIST IN LOW-LEVEL MOISTURE POOLING. THIS MAY BE LOCALIZED ENOUGH THEREFORE IT WAS NOT INCLUDED ATTM. AS FOR THE LOW TEMPERATURES, WE SIDED WITH A GFS/NAM MOS BLEND WITH SOME MINOR LOCAL TWEAKS. && .LONG TERM /TUESDAY THROUGH SUNDAY/... TUESDAY THROUGH WEDNESDAY NIGHT: A GRADUAL CONTINUED UPTICK IN HEAT AND HUMIDITY WITH A STRONG RIDGE ACROSS THE SOUTHERN PLAINS MAKING ANOTHER CHARGE INTO THE REGION WITH RISING HEIGHTS. THIS WILL RESULT IN A MAINLY DRY PERIOD (POSSIBLE EXCEPTION OF AN ISOLATED THUNDERSTORM SOUTH TUESDAY AFTERNOON). FOR ACTUAL HIGH TEMPERATURES, MODELED 925 MB TEMPERATURES RISE FROM AROUND 23C ON TUESDAY TO 25C FOR WEDNESDAY. THIS EQUATES TO HIGH TEMPERATURES STARTING OFF AROUND 90 ON TUESDAY THEN RISING INTO THE MID 90`S FOR WEDNESDAY, STARTING ANOTHER POTENTIAL MODELED HEAT WAVE FOR MOST OF THE REGION. LESS SPREAD IN PRESENT IN THE OPERATIONAL MODELS AND THE ENSEMBLES IN THIS PERIOD COMPARED TO YESTERDAY AS THE GFS HAS TRENDED COOLER WITH TEMPERATURES. FORTUNATELY MODELED DEW POINTS ARE IN THE LOW/MID 60`S DURING THE PEAK HEATING HOURS BOTH TUESDAY AND WEDNESDAY. THIS WOULD LIMIT THE MAXIMUM HEAT INDEX TO BETWEEN 95 AND 100 DEGREES. THURSDAY THROUGH SUNDAY: THE COLD FRONTAL BOUNDARY APPROACHING THE REGION TO START THIS PERIOD WILL LIKELY BE THE TRIGGER FOR AN INCREASE IN CLOUDS AND SOME SCATTERED AFTERNOON/EVENING SHOWERS AND STORMS ON THURSDAY. ONCE AGAIN, THE LACK OF SHEAR LOOKS TO BE A LIMITATION IN THE WAY OF ANY SEVERE WEATHER. HOWEVER, AN ISOLATED STRONG WIND GUST CAN NOT BE RULED OUT. THE 12Z (DAYTIME) RUNS OF THE GFS CONTINUE TO RUN WARMER AND DRIER ON THURSDAY THAN OTHER MODELS AND GFS RUNS, CURRENT THINKING IS THIS AN ANOMALY RATHER THAN THE RULE AND THE FORECAST WILL GO MORE TOWARD THE ECMWF WITH TEMPERATURES ON THURSDAY. HIGHER HUMIDITY THOUGH GIVES THE REGION A HIGHER CHANCE FOR THE HEAT INDEX TO REACH 100 DEGREES IN PARTS OF THE REGION. SOME DRIER AND PERHAPS SLIGHTLY COOLER AIR IS LIKELY TO END THE POTENTIAL HEAT WAVE BEHIND THE FRONT ON FRIDAY. COMPARED TO JUST YESTERDAY, THE OPERATIONAL MODELS AND THE RESPECTIVE ENSEMBLES ARE FARTHER OFFSHORE WITH THE FRONT AND ARE SHOWING A MUCH LOWER THREAT FOR WAVES OF LOW PRESSURE DEVELOP ALONG THE BOUNDARY. THE FORECAST REFLECTS A DRY BUT STILL HOT CONDITIONS NEXT WEEKEND WITH EVEN WARM AIR ADVECTION AGAIN BY NEXT SUNDAY WITH A FRONTAL PASSAGE TO OUR NORTH. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAY...SHOWERS AND SOME THUNDERSTORMS EARLY THIS MORNING SETTLING EASTWARD ACROSS MUCH OF THE AREA. THIS WILL RESULT IN A TIME OF MVFR/IFR CONDITIONS ESPECIALLY VISIBILITIES. OUTSIDE OF ANY SHOWERS AND THUNDERSTORMS, VFR IS ANTICIPATED /LOCAL LIGHT FOG POSSIBLE EARLY THIS MORNING/. SOME SHOWERS AND THUNDERSTORMS ARE EXPECTED THROUGH THE DAY, HOWEVER CARRIED A TEMPO FOR SHOWERS AS THUNDERSTORM PLACEMENT AFTER THE EARLY MORNING ACTIVITY IS A BIT UNCERTAIN. SOUTH- SOUTHWEST WINDS GENERALLY 5-10 KNOTS. TONIGHT...SOME SHOWERS AND THUNDERSTORMS WITH BRIEFLY REDUCED VISIBILITIES AND/OR CEILINGS IN THE EVENING ARE EXPECTED TO DIMINISH. THERE IS THE CHANCE FOR LOCAL FOG TO DEVELOP LATE. SOUTHERLY WINDS 5 KNOTS OR LESS. OUTLOOK... TUESDAY THROUGH WEDNESDAY NIGHT: VFR. WINDS AT OR UNDER 10 KNOTS THROUGH MOST OF THE PERIOD, WITH SOME SOUTHWESTERLY WIND GUSTS AROUND 15 KNOTS WEDNESDAY AFTERNOON. THURSDAY AND THURSDAY NIGHT: VFR, ISOLATED TO SCATTERED SHOWERS THUNDERSTORMS, MAY BRIEFLY REDUCE VISIBILITIES AND CEILINGS. WEST- SOUTHWEST WIND GUSTS AROUND 15 KNOTS POSSIBLE THURSDAY AND EVENING, LOCALLY HIGHER GUSTS IN THUNDERSTORMS. FRIDAY AND FRIDAY NIGHT: VFR. WINDS AT OR UNDER 10 KNOTS. && .MARINE... THE CONDITIONS ARE ANTICIPATED TO REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA TODAY AND TONIGHT. A SOUTHERLY FLOW IS EXPECTED TO CONTINUE AS A DISSIPATING COLD FRONT ARRIVES TODAY. SOME GUSTS TO 20 KNOTS ARE ANTICIPATED AT TIMES HOWEVER, WITH POTENTIALLY HIGHER GUSTS IN AND NEAR ANY STRONGER THUNDERSTORM. OUTLOOK... SEAS AND WINDS LOOK TO REMAIN BELOW SCA CRITERIA THROUGH FRIDAY. ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE THURSDAY AFTERNOON/EVENING WITH THE POTENTIAL FOR A STRONG WIND GUST OR TWO. SEAS OVERALL FOUR FEET OR LESS WITH WIND GUSTS 20 KNOTS OR LESS THROUGH THURSDAY. SEAS BUILDING TO AROUND FIVE FEET WITH SOME ISOLATED 25 KNOT FOR A PERIOD THURSDAY NIGHT BEFORE DECREASING ON FRIDAY. && .RIP CURRENTS... A LONG PERIOD /10-12 SECOND/ EAST-SOUTHEAST SWELL LOOKS TO CONTINUE, RESULTING IN A MODERATE RISK OF DANGEROUS RIP CURRENTS THROUGH TONIGHT FOR THE NEW JERSEY AND DELAWARE COASTS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GAINES/GORSE NEAR TERM...GORSE SHORT TERM...GORSE LONG TERM...GAINES AVIATION...GAINES/GORSE MARINE...GAINES/GORSE RIP CURRENTS...GORSE

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