Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 250144 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 944 PM EDT FRI JUL 24 2015 .SYNOPSIS... A WEAK AREA OF HIGH PRESSURE WILL SLOWLY SHIFT OFF THE MID ATLANTIC COAST THROUGH LATE SATURDAY. A COLD FRONT APPROACHES LATE SUNDAY, THEN DISSIPATES AS IT REACHES OUR AREA ON MONDAY. HIGH PRESSURE SHOULD BUILD BACK OVER OUR REGION LATER MONDAY THROUGH WEDNESDAY. THE NEXT COLD FRONT IS FORECAST TO ARRIVE LATER THURSDAY, THEN POTENTIALLY STALL IN OUR AREA FRIDAY. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 9 PM SURFACE ANALYSIS REVEALED A 1016 MB SURFACE HIGH CENTERED OVER THE CENTRAL/NORTHERN APPALACHIANS. HIGH PRESSURE AND SHORTWAVE RIDGING ALOFT WILL YIELD ANOTHER QUIET NIGHT ON THE WEATHER FRONT WITH CALM WINDS AND MAINLY CLEAR SKIES. HIGH CLOUDS OVER THE GREAT LAKES THAT WERE CAPTURED ON THE LATEST IR AND 11-3.9U SATELLITE IMAGERY MAY SPILL INTO THE AREA LATER TONIGHT, BUT IT SHOULD NOT HAVE MUCH OF AN IMPACT ON RADIATIONAL COOLING. THE PREVIOUS FORECASTER WENT A FEW DEGREES BELOW GUIDANCE FOR MIN TEMPS TONIGHT, WHICH SEEM REASONABLE GIVEN THE ABOVE SETUP. TEMPS OVERNIGHT SHOULD BOTTOM OUT IN THE LOW TO MID 60S ALONG AND EAST OF THE I-95 CORRIDOR; MID TO UPPER 50S FARTHER NORTH AND WEST. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... SFC HIGH PRES WILL MOVE OFFSHORE AS THE FLOW ALOFT BECOMES MORE ZONAL. THIS WILL ALLOW MID-LVL MOISTURE TO BEGIN STREAMING IN FROM THE WEST...BUT NOT UNTIL LATER IN THE DAY. CONVECTIVE TEMPS REMAIN OUT OF REACH UNTIL THE LATE AFTERNOON...SO CU DEVELOP SHOULD HOLD OFF UNTIL THEN. AFOREMENTIONED MID-LVL MOISTURE WILL ALSO LEAD TO INCREASING CLOUDINESS AFTER 18Z...MAINLY TO THE WEST OF THE I-95 CORRIDOR. WITH REGARD TO POPS...DEEPER MOISTURE AND BETTER LIFT OCCUR WELL AFTER 00Z SUN...SO IT IS EXPECTED TO BY A DRY DAY. PRES GRAD WILL CONTINUE TO BE VERY WEAK...WITH A SRLY SYNOPTIC WIND...WHILE A SEA-BREEZE DEVELOPS ALONG THE COAST. H85 TEMPS A COUPLE DEGREES WARMER WILL SUPPORT MAX TEMPS MAINLY IN THE 80S W/ SLIGHTLY COOLER TEMPS NEAR THE SHORE. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... THE SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH THAT AMPLIFIES ACROSS THE PACIFIC NORTHWEST THROUGH SUNDAY. THIS ALONG WITH A RIDGE ACROSS THE SOUTHERN STATES HELPS MAINTAIN A NORTHWEST FLOW ALOFT WITHIN SOME TROUGHING ACROSS THE NORTHEAST AND MID ATLANTIC. THIS TROUGH REMAINS IN PLACE MONDAY, THEN THE RIDGE ACROSS THE CENTRAL AND SOUTHERN PLAINS LOOKS TO START EXPANDING EAST- NORTHEAST TUESDAY AND WEDNESDAY. THE RIDGE THEN SHIFTS TO OUR EAST THURSDAY AS AN UPPER-LEVEL TROUGH AMPLIFIES ACROSS THE GREAT LAKES AND SLIDES TOWARD THE NORTHEAST THURSDAY AND FRIDAY. WE USED A MODEL BLEND FOR SATURDAY NIGHT THROUGH MONDAY, THEN WENT WITH WPC GUIDANCE/CONTINUITY. SOME ADJUSTMENTS WERE THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH OUR NEIGHBORING OFFICES. FOR SATURDAY NIGHT AND SUNDAY...LOW PRESSURE IS FORECAST TO TRACK WELL TO OUR NORTH LATE SATURDAY AND SUNDAY, WITH AN ASSOCIATED COLD FRONT MOVING OUR WAY LATE SUNDAY. THE FRONT ITSELF LOOKS TO START WEAKENING, HOWEVER A POSSIBLE PRE-FRONTAL TROUGH MAY HELP FOCUS SOME CONVECTION SUNDAY IN CONJUCTION WITH SOME MOISTURE RETURN AND A WEAK LOW-LEVEL JET. THERE IS NORTHWEST FLOW ALOFT CONTINUING, SO PERHAPS A LOCALIZED GUSTY THUNDERSTORM LATER SUNDAY WITH MORE OF A PULSE MODE AS SHEAR IS NOT FORECAST TO BE ALL THAT STRONG. THERE COULD BE SOME SHOWERS/THUNDER ARRIVING FROM THE NORTHWEST LATE SATURDAY NIGHT, WHICH MAY BE TIED TO THE LOW-LEVEL JET ARRIVAL AND LEFTOVER UPSTREAM CONVECTION. GIVEN LOWER CONFIDENCE, JUST MAINTAINED SOME SLIGHT CHC TO LOW CHC POPS ACROSS THE NORTHWEST LATER SATURDAY NIGHT. THE POPS THEN INCREASE TO CHC FROM WEST TO EAST SUNDAY. SOME RISE IN THE DEW POINTS ARE EXPECTED SUNDAY, AS THE LOW-LEVEL MOISTURE INCREASES, AND THEREFORE IT WILL FEEL MORE HUMID. SOME CONVECTION COULD LINGER FOR AWHILE SUNDAY NIGHT, BUT THE BETTER CHC LOOKS TO BE IN THE EVENING. FOR MONDAY THROUGH WEDNESDAY...A COLD FRONT LOOKS TO DISSIPATE MONDAY AS IT ARRIVES DUE TO IT BECOMING WELL REMOVED FROM THE PARENT SURFACE LOW. HOWEVER A POSSIBLE LEE SIDE TROUGH MIGHT BE ABLE TO FORCE SOME CONVECTION ESPECIALLY ACROSS THE SOUTHERN ZONES AS SOME DRIER AIR MAY ARRIVE ACROSS THE NORTHERN AREAS. DESPITE WEAK SURFACE HIGH PRESSURE ARRIVING FROM THE WEST DURING MONDAY, OUR AREA REMAINS INFLUENCED BY AN UPPER-LEVEL TROUGH MIGRATING ACROSS THE NORTHEAST WITH THE TAIL END OF THE TROUGH BACK INTO THE MID ATLANTIC. THE UPPER-LEVEL TROUGH HOWEVER LOOKS TO BE SHIFTING TO OUR EAST TUESDAY WITH SURFACE HIGH PRESSURE SETTLING OVERHEAD THROUGH WEDNESDAY. AS AN UPPER-LEVEL RIDGE ACROSS THE SOUTHERN STATES EXPANDS EAST AND NORTHEAST SOME, AN INCREASE IN HEAT AND HUMIDITY OCCURS ESPECIALLY AS WE GET TO WEDNESDAY. AS OF NOW, THE HIGHEST HEAT INDICES ARE FORECAST TO START ARRIVING WEDNESDAY, HOWEVER THIS WILL DEPEND ON HOW MUCH THE SURFACE DEW POINTS RISE. FOR THURSDAY AND FRIDAY...HEAT AND HUMIDITY FOR MUCH OF THE AREA, WITH HEAT INDICES POTENTIALLY NEAR 100 DEGREES FOR SOME AREAS ESPECIALLY THURSDAY AFTERNOON. AS ENERGY ROLLS ACROSS SOUTHERN CANADA, AN UPPER-LEVEL TROUGH AMPLIFIES FROM THE MIDWEST AND GREAT LAKES TOWARD THE NORTHEAST. AS THIS OCCURS, A RIDGE EXTENDS INTO THE MID ATLANTIC AND A POOL OF WARMER AIR ALOFT LOOKS TO ARRIVE FOR THURSDAY. LOW PRESSURE IS FORECAST TO TRACK WELL TO OUR NORTH, WITH ITS TRAILING COLD FRONT ARRIVING LATER THURSDAY. A PRE-FRONTAL TROUGH MAY BE PRESENT WHICH COULD HELP TRIGGER SOME CONVECTION BY LATE DAY. AS A RESULT, WE WENT WITH SLIGHT CHC TO LOW CHC POPS. THE FRONT MAY THEN SLOW OR EVEN STALL IN OUR AREA FRIDAY, AND THEREFORE CHC POPS ARE INCLUDED ATTM. THIS WILL PROBABLY TEMPER THE HEAT SOME DEPENDING ON THE EXTENT OF CLOUD COVER AND CONVECTION. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR TNGT. NOT EXPECTED MUCH IN THE WAY OF FOG AT THE TERMINALS, EXCEPT MAYBE AT MIV, WITH SUCH A DRY AIRMASS IN PLACE, ESPECIALLY GIVEN THE RELATIVELY SHORT NIGHTS THIS TIME OF YEAR. HIGHER DEWPOINTS ON THE EAST SIDE OF A SEA-BREEZE FRONT WERE PRESENT AT MIV AND ACY. FOR THE 00Z TAFS, KEPT IN A FEW HOURS OF MVFR VSBYS AT MIV, WHICH IS A FOG-PRONE SITE. AS HIGH PRESSURE MOVES OFFSHORE ON SATURDAY...WINDS WILL GRADUALLY VEER FROM THE NORTH-NORTHWEST IN THE MORNING TO SOUTH-SOUTHEAST IN THE AFTN...GENERALLY AOB 10 KNOTS. SOME DIURNAL CU MAY FORM AGAIN BUT MOST LIKELY LATER IN AFTN W/ LESS COVERAGE COMPARED TO FRIDAY. MORE EXTENSIVE MID-LEVEL CLOUDS WILL WORK INTO THE TERMINALS ALONG AND WEST OF I-95 DURING THE LATE AFTN AND EVE. OUTLOOK... SATURDAY NIGHT...GENERALLY VFR. A FEW SHOWERS OR A THUNDERSTORM ARE POSSIBLE LATE ESPECIALLY AROUND THE KABE AND KRDG AREAS. SUNDAY AND MONDAY...VFR OVERALL. SOME SHOWERS AND THUNDERSTORMS ARE POSSIBLE WITH LOCALLY REDUCED CEILINGS/VISIBILITIES. AS OF NOW, ANY THUNDERSTORMS LOOK TO BE ISOLATED TO SCATTERED. TUESDAY AND WEDNESDAY...MAINLY VFR WITH WEAK HIGH PRESSURE IN PLACE. && .MARINE... SUB-SCA CONDITIONS EXPECTED TONIGHT AND SATURDAY AS HIGH PRESSURE MOVES OVER THE COASTAL WATERS. TONIGHT AND SATURDAY...THE WIND DIRECTION WILL BE VARIABLE...AND AOB 10 KNOTS. A SEA-BREEZE IS ALSO LIKELY AGAIN ON SATURDAY AFTN. OUTLOOK... SATURDAY NIGHT THROUGH MONDAY...A WEAKENING FRONT IS FORECAST TO MOVE INTO OUR AREA MONDAY BEFORE DISSIPATING. AS A RESULT, THERE IS A CHANCE OF SOME SHOWERS AND THUNDERSTORMS /PERHAPS LOCALLY GUSTY WINDS/ LATE SUNDAY AND MONDAY. WHILE A SOUTHERLY WIND MAY INCREASE SOME SUNDAY INTO MONDAY AHEAD OF A WEAKENING COLD FRONT, THE CONDITIONS ARE EXPECTED TO BE BELOW SMALL CRAFT ADVISORY CRITERIA. TUESDAY AND WEDNESDAY...AS WEAK HIGH PRESSURE BUILDS INTO THE REGION, THE CONDITIONS ARE ANTICIPATED TO BE BELOW SMALL CRAFT ADVISORY CRITERIA. BUOY 44009... WATER TEMPERATURE HAS NOT BEEN REPORTED BY BUOY 44009 SINCE JULY 22ND. WE`VE BEEN INFORMED BY THE NDBC THAT THE FAILED SENSOR WILL UNFORTUNATELY REMAIN OUT OF SERVICE UNTIL IT IS REPAIRED OR REPLACED SOMETIME NEXT YEAR. && .RIP CURRENTS... WAVEWATCH GUIDANCE STILL INDICATING A PRIMARY 12 SECOND SELY SWELL FOR SATURDAY. IN-HOUSE GUIDANCE SUGGESTS A BORDERLINE LOW/MODERATE RIP CURRENT RISK. ATTM, WENT WITH LOW RISK FOR SATURDAY AS WAVE HEIGHTS IN THE SURF ZONE WILL BE SMALL THOUGH, GENERALLY 2 FT OR LESS AND SLY WINDS WILL INCREASE LATE IN THE DAY BUT BE AROUND 10 KT OR LESS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GIGI/GORSE NEAR TERM...KLEIN SHORT TERM...FRANCK LONG TERM...GORSE AVIATION...GORSE/KLEIN MARINE...FRANCK/GORSE/KLEIN RIP CURRENTS...KLEIN

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