Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 060717 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 317 AM EDT MON JUL 6 2015 .SYNOPSIS... A WARM FRONT IN NORTH CAROLINA IS FORECAST TO LIFT NORTHWARD AND THROUGH OUR REGION LATE TONIGHT AND TUESDAY MORNING. ANOTHER FRONTAL BOUNDARY IS EXPECTED TO ARRIVE ON WEDNESDAY, THEN THE FRONT IS ANTICIPATED TO MEANDER IN OR NEAR OUR REGION WEDNESDAY NIGHT INTO FRIDAY AS LOW PRESSURE MOVES ALONG IT. WEAK HIGH PRESSURE MAY TRY TO BUILD DOWN FROM THE NORTHWEST NEXT WEEKEND AS THE FRONT REMAINS NEARBY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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EARLY THIS MORNING: MID LVL SHOWERS DELMARVA MOVING INTO S NJ AND SE PA PRIOR TO 12Z. THIS ASSTD WITH INSTABILITY BURST AND PWAT POOL OF 2+ INCHES SHIFTING NWD INTO THE DELMARVA EARLY TODAY. AFTER 12Z TODAY...IT APPEARS TO ME THAT THIS IS GOING TO BE A RELATIVELY SOUR-DOUR DAY. MOCLOUDY AND HUMID WITH A PERIOD OF SHOWERS DRYING OUT TO THE SW OF A KABE-KACY LINE DURING THE 12Z TO 15Z TIME FRAME. THEN HEATING UP A BIT UNDER THE CANOPY OF VARIABLE CLOUD COVER. HEAVY SHOWERS AND SCT TSTMS DEVELOPING THIS AFTN OVER THE DELMARVA AND SPREADING NNEWD, ESPECIALLY INTO E PA. THIS SUPPORTED IN PART BY MODELED 1200J MLCAPE ON THE DELMARVA THIS AFTN. QUITE A BIT OF UNCERTAINTY ON SHOWER TIMING TODAY LEAVING ME WITH LOW CONFIDENCE ON THE RAIN DETAILS EXCEPT TO SAY THE LARGE PWAT OF 1.75 TO 2 INCHES SUGGESTS BRIEF TORRENTS OF POOR DRAINAGE FLOODING RAIN POTENTIAL DELMARVA AND E PA TODAY, ESPECIALLY MID AFTN. NOT IMPOSSIBLE FOR ISOLATED SVR ON THE DELMARVA THIS AFTN DESPITE LACK OF CRITERIA 0-6KM 30KT BULK SHEAR. THE LOW LVL SHEAR IS SIGNIFICANT INDICATING TO ME THAT TSTMS MIGHT DEVELOP SHALLOW MESOCYCLONE SIGNATURES OVER THE DELMARVA THIS AFTN WITH STILL POTENTIAL FOR ISOLATED 45 KT GUSTS. PLS SEE NC SVR REPORTS FROM YDY. ALSO TODAYS SWODY1 FROM SPC. WORDED TSTM HEAVY RAIN E PA AND DELMARVA AND ON THE DELMARVA ADDED GUSTY WINDS. TEMPS WERE A 50 50 BLEND OF THE 00Z/6 GFS/NAM MOS BLENDED WITH THE NAM 2M TEMPS. THIS IS COOLER THAN WHAT WE HAD INDICATED FOR THE PAST SVRL DAYS BUT THEN TOO WE TOO WE DIDNT THINK CLOUD AND SHOWERS. SO THIS MONDAYS FCST IS GLOOMIER THAN PREVIOUSLY EXPECTED. WINDS...MAX GRADIENT WIND GUSTS SHOULD BE AROUND 15-18 MPH THIS AFTERNOON.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
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WAA CONTINUES TONIGHT WITH THE WARM FRONTAL BOUNDARY LIFTING NORTHWARD THROUGH OUR FCST AREA, POSSIBLY ACCOMPANIED BY CLUSTERS OF SHOWERS AND ISOLATED HEAVY TSTMS, ESPECIALLY I95 WESTWARD. CONFIDENCE ON WHERE IT RAINS AND WHEN IS BELOW AVG. HOWEVER WE DO NOTE MODELED 25 KT 700 AND 850 MB SPEED MAX`D OVER CHES BAY AROUND 06Z WHICH SHOULD SUPPORT BANDS OF SHOWERS IN E PA. OUR FCST POPS TONIGHT APPEAR TOO LOW AND MAY RAISE THESE IN THE 630 AM UPDATE. PATCHES OF STRATUS/FOG ARE LIKELY LATE TONIGHT AND ITS CONCEIVABLE A FEW LOCATIONS WILL DROP TO 1/2MI IN FOG AFTER MIDNIGHT, ESPECIALLY I-78 NORTHWARD. TEMPS WERE MOSTLY THE WARMER 00Z/6 GFS MAV MOS AND ABOVE NORMAL...BY 5 TO 10 DEGREES!
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&& .LONG TERM /TUESDAY THROUGH SUNDAY/... THE MID LEVEL RIDGE THAT WAS OVER THE WESTERN STATES IS FORECAST TO DISAPPEAR FOR THE NEW WEEK AS LOW PRESSURE MEANDERS OFF THE CALIFORNIA COAST, MOVES INLAND AND FILLS. THE MID LEVEL FLOW EAST OF THE ROCKIES IS EXPECTED TO BECOME SOMEWHAT ZONAL, RESULTING IN ANOTHER POTENTIALLY ACTIVE WEEK FOR OUR REGION. THE WESTERN RIDGE IS ANTICIPATED TO RETURN NEXT WEEKEND. THE TIMING OF ADDITIONAL IMPULSES IN THE NEARLY ZONAL MID LEVEL FLOW DURING THE MID AND LATE WEEK PERIOD BECOMES A BIT OF A CHALLENGE AFTER THE INITIAL MID LEVEL TROUGH PASSES ON TUESDAY AFTERNOON. WHILE IT SEEMS THAT CONVECTION WILL OCCUR IN PARTS OF OUR AREA ON WEDNESDAY, AND PERHAPS ON THURSDAY AND FRIDAY, AS WELL, THE EXACT LOCATION OF THE GREATEST POTENTIAL REMAINS A LOW CONFIDENCE FORECAST. PRESENTLY, IT LOOKS AS THOUGH OUR HIGHEST CHANCE FOR SEVERE THUNDERSTORMS MAY BE ON WEDNESDAY AFTERNOON AND EVENING WITH THE ARRIVAL OF THE FRONT FROM THE NORTHWEST. THE FORECAST WIND PROFILES FOR THAT TIME PERIOD SUGGEST THAT IF CONVECTION DEVELOPS IT COULD BECOME ORGANIZED. CAPE VALUES IN EXCESS OF 1000 J/KG ARE ANTICIPATED. THE LATEST GENERAL TIMING OF THE MAIN SURFACE LOW RIDING ALONG THE FRONTAL BOUNDARY BRINGS IT ACROSS OUR REGION ON THURSDAY NIGHT. AS IS THE CASE WITH THE MID LEVEL FEATURES, THE TIMING OF THE SURFACE WAVE REMAINS IN QUESTION. WE WILL KEEP A CHANCE OF SHOWERS AND THUNDERSTORMS FOR THURSDAY INTO THURSDAY NIGHT, WITH MAINLY A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS FOR FRIDAY. PRECIPITABLE WATER VALUES ARE FORECAST TO RISE NEAR OR ABOVE 2 INCHES DURING THE MID AND LATE WEEK PERIOD. ANY THUNDERSTORMS COULD BRING HEAVY DOWNPOURS ALONG WITH LOCALIZED FLOODING OF ROADWAYS AND AREAS OF POOR DRAINAGE. ALSO, WE WILL KEEP AN EYE ON THE FLASH FLOODING POTENTIAL ESPECIALLY IF CERTAIN AREAS ARE AFFECTED BY HEAVY RAINFALL ON MORE THAN ONE DAY. THE GUIDANCE DIFFERS WITH THE FORECAST FOR NEXT WEEKEND. THE MAIN QUESTION CONCERNS WHETHER THE FRONTAL BOUNDARY WILL BE PUSHED FAR ENOUGH SOUTH TO ALLOW WEAK HIGH PRESSURE TO BUILD INTO OUR REGION FROM THE NORTHWEST AND NORTH. AS A RESULT, WE WILL CONTINUE TO CARRY EITHER A LOW OR SLIGHT CHANCE FOR PRECIPITATION. DAYTIME TEMPERATURES ARE ANTICIPATED TO BE WITHIN A FEW DEGREES OF NORMAL FOR THE PERIOD FROM MONDAY NIGHT THROUGH SUNDAY. NIGHTTIME TEMPERATURES ARE FORECAST TO BE SOLIDLY ABOVE NORMAL. && .AVIATION /07Z MONDAY THROUGH FRIDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. PRIOR TO 12Z...VFR CIGS MAINLY AOA 7000 FT. VISIBILITIES DROP TO SPOTTY 3-5 MI IN FOG OVER THE COUNTRYSIDE NEAR KABE/KRDG AND KMIV. LIGHT WIND. SOME MID DECK SHOWERS ARE POSSIBLE CLOSER TO DAYBREAK NEARING KILG. TODAY AFTER 12Z...ANY VSBY LIMITATIONS SHOULD DISSIPATE BY 14Z OTHERWISE MAINLY VFR CIGS AOA 5000 FT. SHOWERS MOVING INTO THE TAF VCNTY EXCEPT PROBABLY NOT AT KTTN AND KABE THIS MORNING. PLS SEE TAFS FOR DETAILS. THIS AFTERNOON SHOULD SEE HEAVIER SHOWERS AND THUNDERSTORMS DEVELOP OVER THE DELMARVA AND MOVE NNE INTO THE KILG-KPHL-KRDG AREA BY MID OR LATE AFTN. THOSE COULD EASILY GENERATE BRIEF IFR CONDITIONS IN HEAVY RAIN WITH WIND GUSTS 30-35 KT. ISOLATED SVR STORM POSSIBLE DELMARVA. OTHERWISE NON TSTM WINDS WILL TEND SOUTHEAST TODAY WITH AFTERNOON GUSTS AROUND 15 KT. TONIGHT...CONDITIONS POSSIBLY LOWERING TO MVFR OR IFR IN LOW CLOUDS, HAZE AND FOG ESPECIALLY DURING THE LATE NIGHT AND EARLY MORNING HOURS. SCATTERED SHOWERS AND THUNDERSTORMS, ESPECIALLY EASTERN PA. OUTLOOK... TUESDAY MORNING...LEFTOVER IFR CONDS IN ST/FOG AT 12Z WILL DISSIPATE TO 6SM OR GREATER HAZE BY 15Z. S-SW WIND. TUESDAY AFTERNOON AND TUESDAY EVENING...MAINLY VFR WITH A CHANCE OF SHOWERS AND THUNDERSTORMS. TUESDAY NIGHT AND WEDNESDAY MORNING...CONDITIONS POSSIBLY LOWERING TO MVFR OR IFR IN LOW CLOUDS, HAZE AND FOG ESPECIALLY DURING THE LATE NIGHT AND EARLY MORNING HOURS. WEDNESDAY AFTERNOON THROUGH THURSDAY NIGHT...A CHANCE OF SHOWERS AND THUNDERSTORMS WHICH MAY CAUSE CONDITIONS TO LOWER TO MVFR OR IFR AT TIMES. FRIDAY...MAINLY VFR.
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&& .MARINE... NO MARINE HEADLINES THROUGH TONIGHT. OUTLOOK... TUESDAY THROUGH FRIDAY...NO MARINE HEADLINES ARE ANTICIPATED. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...DRAG/GORSE/IOVINO NEAR TERM...DRAG 318 SHORT TERM...DRAG/NIERENBERG 318 LONG TERM...IOVINO AVIATION...DRAG/IOVINO 318 MARINE...DRAG/IOVINO 318

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