Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 290752 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 352 AM EDT WED JUL 29 2015 .SYNOPSIS... A WEAK AREA OF HIGH PRESSURE WILL SHIFT TO OUR EAST TODAY. A WEAKENING COLD FRONT MOVES THROUGH OUR REGION THURSDAY NIGHT, HOWEVER IT THEN SLOWS OFFSHORE ON FRIDAY. THE NEXT WEAK COLD FRONT SHOULD CROSS OUR AREA LATE SATURDAY INTO SUNDAY FOLLOWED BY HIGH PRESSURE. A POTENTIALLY STRONGER COLD FRONT IS THEN SCHEDULED TO ARRIVE FROM THE NORTHWEST DURING TUESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE WEAK BOUNDARY HAS TEMPORARILY WASHED OUT AS LESS DEFINED AND NORTHWARD TO NEAR I-78 EARLY THIS MORNING. A LITTLE FOG WILL FORM DURING THE PREDAWN HOURS BUT NOT AS EXTENSIVE AS SEEN IN YDYS 9Z- 10Z OBS. THE AREAS WHERE IT RAINED LATE YDY MAY BE MORE PREDISPOSED TO FOG FORMATION. AFTER SUNRISE...THE BOUNDARY DRYING BECOMES EVIDENT BY FORENOON WITH HIGHEST DEWPOINTS AND MLCAPE THIS AFTN (400J) CONFINED TO THE SOUTHERN PORTION OF OUR DELMARVA FCST AREA WHERE AM CARRYING A SLIGHT CHC FOR A THUNDERSTORM WITH HEAVY RAIN. PWAT INCREASES TO 1.7 INCHES THERE LATE TODAY. ELSEWHERE...HOT HOT HOT AND USED THE GFS MAVMOS STRAIGHT UP. SEA BREEZES WILL EVENTUALLY MITIGATE SOME OF THE PURE HEAT IN DE AND NJ BUT THIS WILL BE A TOASTY DAY WITH 18C AT 850 AND NEAR RECORD IN SOME PLACES. PLS SEE THE CLIMATE SECTION FOR THE VULNERABLE RECORDS. MAX HI TODAY 98-99F...BASICALLY JUST BELOW URBAN CORRIDOR CRITERIA OF 100...BUT SINCE DITTO THURSDAY AND WARM NIGHT WE ISSUED A TWO DAY WARNING. SW WINDS THIS AFTN MAY GUST 15 MPH IN A FEW SPOTS WITH SEABREEZES DEVELOPING ALONG THE COASTS BETWEEN NOON AND 2 PM. CONFIDENCE: ABOVE AVERAGE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... ANY SHOWERS ON THE DELMARVA SHOULD DISSIPATE BY 00Z. THEREAFTER...SLY FLOW AND MORE HUMID WITH PATCHY FOG AND STRATUS FORMING. PWAT INCREASES TO 1.9 INCHES BY MORNING ALONG THE I-95 CORRIDOR. MODELS HAVE A WEAK IB THRUST ACROSS DE AND S NJ OVERNIGHT WHERE SCT OR ISOLATED HEAVY SHOWERS AND TSTMS MIGHT DEVELOP. TEMPS WELL ABOVE NORMAL AND USED A BLEND OF 00Z/29 NAM/GFS MOS WITH A FAVORING OF THE WARMER AVBL GUIDANCE. CONFIDENCE: ABOVE AVERAGE EXCEPT BELOW AVG ON CONVECTION FORMING OVERNIGHT. && .LONG TERM /THURSDAY THROUGH TUESDAY/... THE SYNOPTIC SETUP IS COMPRISED OF A NARROWING UPPER-LEVEL RIDGE THURSDAY THAT SHIFTS TO OUR EAST AS AN UPPER-LEVEL TROUGH SLIDES ACROSS THE MIDWEST AND GREAT LAKES REGIONS. THIS TROUGH IS FORECAST TO OVERSPREAD THE NORTHEAST AND INTO THE MID ATLANTIC THURSDAY NIGHT THROUGH THE WEEKEND. DESPITE THIS TROUGH IN PLACE, WE ARE MAINLY ON THE SOUTHERN EXTENT OF IT THEREFORE A RATHER WARM TO HOT AIRMASS WILL BE IN PLACE. A WEAKENING COLD FRONT THURSDAY LOOKS TO BRING THE GREATEST CHC FOR CONVECTION, THEN WE AWAIT FOR THE NEXT POTENTIALLY STRONGER FRONT TO ARRIVE DURING TUESDAY. WE USED A MODEL BLEND THURSDAY THROUGH SATURDAY, THEN WENT WITH A WPC/CONTINUITY BLEND THEREAFTER. FOR THURSDAY AND FRIDAY...AS A NARROWING UPPER-LEVEL RIDGE SHIFTS OFFSHORE, WE START TO BECOME INFLUENCED BY AN UPPER-LEVEL TROUGH TRAVERSING THE GREAT LAKES REGION AND SOUTHERN CANADA. A SOUTHWESTERLY LOW-LEVEL FLOW WILL PULL ADDITIONAL MOISTURE INTO THE CWA WHICH WILL BE REFLECTED IN HIGHER SURFACE DEW POINTS COMPARED TO WEDNESDAY. THE AIRMASS AT 850 MB IS FORECAST TO BE SIMILAR TO WEDNESDAY THEREFORE ANOTHER HOT DAY IS EXPECTED. HOWEVER THE FORECAST CHALLENGE IS CLOUD COVER AND THE TIMING OF CONVECTION ESPECIALLY DURING THE AFTERNOON AND EVENING THURSDAY. IF THIS IS DELAYED LATE ENOUGH WITH MORE SUNSHINE, THEN HEAT INDICES WILL BE A BIT HIGHER. THE INFLUENCE OF THE INCOMING UPPER-LEVEL TROUGH WILL OFFER SOME HEIGHT FALLS, HOWEVER A RATHER TOASTY BOUNDARY LAYER LOOKS TO BE MAINTAINED. WHILE THERE MAY BE SOME CLOUDS TO START THURSDAY WITH MAYBE A SHOWER OR THUNDERSTORM, WE THINK THERE WILL BE ENOUGH SUNSHINE TO GET TEMPERATURES INTO THE LOWER 90S FOR MANY AREAS ESPECIALLY THE DELAWARE VALLEY. THIS PUTS HEAT INDICES VERY CLOSE TO 100 DEGREES FOR A FEW HOURS IN THE AFTERNOON. THIS IS OF MOST CONCERN FOR THE URBAN CENTERS WHERE HEAT REMAINS TRAPPED DURING THE NIGHT AS WELL. AS A RESULT, FOR THE URBAN CORRIDOR FROM WILMINGTON TO PHILADELPHIA TO TRENTON AND THE IMMEDIATE NEARBY LOCATIONS WE OPTED TO CARRY AN EXCESSIVE HEAT WARNING THROUGH 6 PM THURSDAY. REGARDING CONVECTION, A WEAKENING COLD FRONT ARRIVES LATER IN THE DAY HOWEVER THERE SHOULD BE ENOUGH LIFT WITHIN THE HOT AND HUMID AIRMASS TO PROMOTE STORM INITIATION TO OUR WEST. IT IS NOT QUITE CLEAR IF WE CAN GET SOME ISOLATED ACTIVITY IN THE MORNING AS THE MOISTURE POOLS, OTHERWISE WE FOCUS ON THE AFTERNOON AND EVENING HOURS AS PLENTY OF INSTABILITY WILL BE PRESENT. THE GREATEST SHEAR THOUGH IS FORECAST TO PASS JUST TO OUR NORTH WHERE A MID LEVEL SPEED MAX MOVES THROUGH. THE SIGNALS IN THE MODEL GUIDANCE INDICATE A LINE/BROKEN LINE OR CLUSTERS OF CONVECTION ARRIVING FROM THE WEST. IF ENOUGH ORGANIZATION CAN OCCUR AND ALSO FACTORING IN PRECIPITATION LOADING OF THE DOWNDRAFTS, LOCALLY DAMAGING WINDS COULD RESULT. IN ADDITION, PW VALUES ABOUT 2 INCHES WILL PROMOTE TORRENTIAL RAIN WITHIN CONVECTIVE CORES AND THIS COULD LEAD TO LOCALIZED FLOODING. THE CONVECTION SHOULD WANE DURING THURSDAY NIGHT AS THE FRONT WEAKENS BUT THEN SLOWS AS IT MOVES OFF THE COAST. THEREFORE WE KEPT THE HIGHEST POPS IN THE EVENING ACROSS THE EASTERN ZONES. THE FRONT LOOKS TO STALL OFFSHORE FRIDAY WITH A POSSIBLE WEAK WAVE OF LOW PRESSURE TRACKING ALONG IT. AS OF NOW, IT LOOKS LIKE THE PRECIPITATION SHOULD BE OFFSHORE WITH DRYING OCCURRING ACROSS OUR AREA. ANOTHER WARM TO EVEN HOT DAY ON FRIDAY, HOWEVER THE DEW POINTS ARE EXPECTED TO BE NOTICEABLY LOWER FOR MUCH OF THE AREA. 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 RIPPLES OF ENERGY ALONG IT REMAIN TO OUR EAST. SINCE THE TRUE COOLING AFFECTS FROM THE UPPER-LEVEL TROUGH ARE RELEGATED WELL TO OUR NORTH, THE VERY WARM TO HOT CONDITIONS PERSIST ALTHOUGH DEW POINTS MAY REMAIN ON THE LOWER SIDE. A WEAK FRONT OR SURFACE TROUGH LOOKS TO MOVE THROUGH LATER SATURDAY, HOWEVER MUCH OF THE LIFT MAY REMAIN TO OUR NORTH. FOR MONDAY AND TUESDAY...THE OFFSHORE FRONT SHOULD DISSIPATE AS THE UPPER-LEVEL TROUGH RELOADS SOME ACROSS THE GREAT LAKES AND INTO NEW ENGLAND. THIS WILL SEND ANOTHER COLD FRONT OUR WAY DURING TUESDAY WITH THE POTENTIAL FOR SOME CONVECTION MAINLY DURING THAT TIME. IT APPEARS THAT MANY AREAS SHOULD ADD TO THE STRETCH OF 90+ DEGREE DAYTIME TEMPERATURES. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THROUGH 12Z...VFR WITH POSSIBLE MVFR FOG IN THE 6Z-12Z TIME FRAME. LIGHT MOSTLY SW WIND. AFTER 12Z...VFR WITH CLOUDS AOA 6000 FT THIS AFTN. ISOLATED TSTMS POSSIBLE VCNTY KGED AND KESN MID OR LATE THIS AFTN. SW WIND GUST NEAR 15 KT THIS AFTN EXCEPT SOUTH SOUTHEAST SEABREEZES DEVELOPING COASTAL LOCATIONS 16Z-18Z. TONIGHT....VFR TO START THEN PATCHY MVFR OR IFR CONDS IN FOG/STRATUS/ HAZE LATE, ESPECIALLY NW NJ AND PTNS E PA. OUTLOOK... THURSDAY...SOME FOG/HAZE POSSIBLE EARLY, THEN MOSTLY VFR. SOME SHOWERS AND THUNDERSTORMS ARE EXPECTED FROM WEST TO EAST MAINLY IN THE AFTERNOON AND EVENING, POSSIBLY IN THE FORM OF A LINE. SOME CEILING AND ESPECIALLY VISIBILITY RESTRICTIONS ARE ANTICIPATED FOR A TIME AS A RESULT. SOUTHWEST WINDS INCREASING TO 10-15 KNOTS, THEN DIMINISHING TO AROUND 5 KNOTS AT NIGHT AND BECOMING WEST-NORTHWEST. FRIDAY THROUGH SUNDAY...MAINLY VFR AS A FRONT LINGERS OFFSHORE. WEST- NORTHWEST WINDS NEAR 10 KNOTS FRIDAY, BECOMING SOUTHWESTERLY NEAR 5 KNOTS SATURDAY AND SUNDAY. && .MARINE... BUOY 44009 SEA SURFACE TEMPERATURE DATA HAS RETURNED. NO HEADLINES THROUGH TONIGHT. A DISTANT OCEAN LOW PRESSURE SYSTEM SOUTHEAST OF NEW ENGLAND IS PRODUCING A LITTLE MORE SWELL THAN ANTICIPATED. STILL ATLC SEAS AOB 4 FT THROUGH TONIGHT. SW WINDS LESS 18KT EARLY THIS MORNING BECOMING SSE THIS AFTN AND SLY TONIGHT... ALL GUST SPEEDS AOB 22 KT. OUTLOOK... THURSDAY THROUGH SUNDAY...THE CONDITIONS ARE EXPECTED TO BE BELOW SMALL CRAFT ADVISORY CRITERIA. A SOUTHERLY FLOW SHOULD INCREASE THOUGH THURSDAY AHEAD OF A WEAKENING COLD FRONT, HOWEVER GUSTS SHOULD BE BELOW 25 KNOTS. THE SEAS WILL RESPOND FOR A TIME, HOWEVER THEY SHOULD BE BELOW 5 FEET. SOME THUNDERSTORMS ARE EXPECTED LATE THURSDAY WITH THE APPROACH OF A WEAKENING COLD FRONT, WITH LOCALLY GUSTY WINDS POSSIBLE. THE FRONT THEN LINGERS OFFSHORE FRIDAY THROUGH SUNDAY. && .RIP CURRENTS... THERE IS A MODERATE RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS ALONG THE NEW JERSEY AND DELAWARE COAST TODAY DUE TO A LONG PERIOD SOUTHEASTERLY SWELL. THE WAVE PERIOD WILL CONTINUE TO BE AROUND 10 SECONDS. && .CLIMATE... KACY RAINFALL 6.58 RANKED 14TH WETTEST NOW WITH THE POR DATING BACK THROUGH 1874. WETTEST 13.09 IN 1959. KABE WILL PROBABLY EXPERIENCE NEAR RECORD WARMTH THIS AFTERNOON-JULY 29. THE RECORD THERE IS 96 SET IN 1954. RIGHT NOW WE`RE FCSTG 95. KRDG AND KMPO MAY BE THE OTHER LOCATIONS WITHIN 2F OF THE RECORD FOR THIS DATE KRDG - 97 SET BACK IN 2002. KMPO - 90 SET BACK IN 1949. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...EXCESSIVE HEAT WARNING FROM NOON TODAY TO 6 PM EDT THURSDAY FOR PAZ070-071-102-104-106. NJ...EXCESSIVE HEAT WARNING FROM NOON TODAY TO 6 PM EDT THURSDAY FOR NJZ015-017>019. DE...EXCESSIVE HEAT WARNING FROM NOON TODAY TO 6 PM EDT THURSDAY FOR DEZ001. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GORSE NEAR TERM...DRAG SHORT TERM...DRAG LONG TERM...GORSE AVIATION...DRAG/GORSE MARINE...DRAG/GORSE RIP CURRENTS... CLIMATE...

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