Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 060754 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 354 AM EDT MON JUL 6 2015 .SYNOPSIS...
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LOW PRESSURE ACROSS NORTH CAROLINA WILL CONTINUE MOVING NORTHWARD TODAY INTO THE DELMARVA ALONG A WARM FRONT. BY TUESDAY NIGHT, THESE FEATURES WILL GIVE WAY TO HIGH PRESSURE LOCATED TO OUR SOUTH. A COLD FRONTAL BOUNDARY THEN WILL PASS THROUGH THE REGION LATER THIS WEEK WITH SEVERAL WAVES OF LOW PRESSURE POTENTIALLY TRAVELING EASTWARD ALONG THE BOUNDARY. THE FRONTAL BOUNDARY WILL STALL AND WEAKEN TO OUR SOUTH BY NEXT WEEKEND BEFORE ANOTHER WARM FRONT COMES NORTHWARD INTO THE REGION EARLY NEXT WEEK
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... 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. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... 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! && .LONG TERM /TUESDAY THROUGH SUNDAY/...
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TUESDAY AND TUESDAY NIGHT: A SHORTWAVE IS LIKELY TO BE THE FOCUS OF SOME SCATTERED SHOWERS EARLY IN THE DAY ACROSS EASTERN PA, DEPARTING THE REGION BY AFTERNOON. ANY FOG ON LAND SHOULD BURN OFF BY MID-MORNING GIVEN INCREASING WINDS. THE GFS AND NAM SOUNDINGS ARE BOTH SHOWING ENOUGH MOMENTUM TRANSFER TO SUGGEST 15-20 MPH AFTERNOON SOUTHWESTERLY WIND GUSTS. WE SHOULD SEE SOUTHWESTERLY FLOW ON THE BACKSIDE OF THE HIGH PRESSURE SYSTEM AS WELL. THIS WILL LEAD TO CONTINUED WARM AND HUMID AIR BEING ADVECTED INTO THE REGION. AN ABSENCE OF ANY TRIGGER FOR SHOWERS AND STORMS IS LIKELY TO BE PRESENT BUT THE PRESENCE OF HEAT/HUMIDITY WILL LEAD TO A UPTICK IN INSTABILITY. THIS MAY BE ENOUGH TO DEVELOP A ISOLATED AFTERNOON SHOWER OR STORM. 925 MB TEMPERATURES ARE LIKELY TO BE AROUND 20C EQUATING TO SURFACE HIGH TEMPERATURES PUSHING 90. MUGGIER/WARMER OVERNIGHT TEMPERATURES ARE ALSO LIKELY DUE TO THE AIRMASS ADVECTING IN. WEDNESDAY AND WEDNESDAY NIGHT: A COLD FRONTAL BOUNDARY BEGINS TO ENTER THE PICTURE WEDNESDAY AFTERNOON AND EVENING GIVING US THE TRIGGER MISSING ON TUESDAY FOR A MORE WIDESPREAD SHOWER AND THUNDERSTORM CHANCE. WITH THE HIGHER CHANCES OF RAIN, HIGH TEMPERATURES MAY NOT REACH THE FULL POTENTIAL DUE TO THE PRESENCE OF MORE CLOUDS, MODELED 925 MB TEMPS AROUND 25C WITH THE ABUNDANT ADVECTION WOULD GIVE US MID 90`S FOR HIGHS. SLOWER TIMING OF THE FRONT WOULD LEAD TO A HOTTER DAY AND A FASTER FRONTAL PASSAGE OR MORE IN THE WAY OF DEBRIS CLOUDS WOULD KEEP WELL UNDER THOSE VALUES. WENT WARMER THAN MET/MAV AND ECMWF MOS GIVEN THEY MAY SLOW TO SHOW THE ADVECTION POTENTIAL BUT DIDN`T WANT TO DEVIATE TO MUCH GIVEN SOME UNCERTAINTY WITH WEDNESDAY`S HIGHS. INSTABILITY IS CURRENTLY MODELED AT OVER 1000 J/KG IN TERMS OF SURFACE AND MIXED LAYER ON THE NAM AND GFS WITH STEEP LOW AND MID- LEVEL LAPSE RATES. HOWEVER 0-6 KM BULK SHEAR IS VERY SMALL LESS THAN 20 KNOTS. THIS WOULD IMPLY ENOUGH INSTABILITY IS PRESENT TO DEVELOP THUNDERSTORMS IN ASSOCIATION WITH THE COLD FRONT BUT THE OVERALL PROBABILITIES FOR STORM ORGAINIZATION AND DEVELOPMENT INTO MORE THAN ISOLATED STRONG TO SEVERE STORMS ARE LOW. PW VALUES ARE ELEVATED THOUGH ABOVE 2 INCHES, SO THE POTENTIAL EXISTS FOR HEAVY DOWNPOURS RESULTING IN POOR DRAINAGE FLOODING. HIGHEST CHANCES AFTERNOON AND EVENING FOR STORMS ON WEDNESDAY.ONCE AGAIN MODELED SOUNDINGS FROM THE NAM AND GFS SHOW THE POTENTIAL FOR SOME 15 MPH WIND GUSTS FROM THE WEST-SOUTHWEST IN THE AFTERNOON HOURS. THURSDAY THROUGH FRIDAY NIGHT: THE FRONTAL BOUNDARY WILL LIKELY STALL JUST TO OUR SOUTH IN RESPONSE TO A MID-LEVEL RIDGE OVER THE SOUTHEAST UNITED STATES. COOLER TEMPERATURES ARE LIKELY WITH A MORE NORTHERLY WIND. THE HIGHEST CHANCE OF LINGERING SHOWERS/STORMS WITH ANY WAVE OF LOW PRESSURE IS FORECASTED FOR THURSDAY, GIVEN MORE UNCERTAINTY IN THE FRONTAL LOCATION ON FRIDAY. EXTENSIVE CLOUDS EITHER DAY COULD KEEP TEMPERATURES LOWER THAN FORECASTED EACH DAY. TIGHT CLUSTER WITH ENSEMBLE GUIDANCE IN THIS PERIOD AND WAS LEANED ON QUITE A BIT IN THIS PERIOD FOR THE FORECAST. SATURDAY THROUGH SUNDAY NIGHT: THE FRONT LOOKS TO WEAKEN TO OUR SOUTH, ENOUGH FOR THIS PERIOD TO LEAN DRIER ON SATURDAY. HIGH PRESSURE SYSTEMS TRAVERSING NORTH OF OUR REGION MAY ALLOW FOR A WIND DIRECTION CHANGE TO MORE SOUTHERLY BY THE EMD OF NEXT WEEKEND POSSIBLY YIELDING A RETURN OF WARMER AND MORE HUMID CONDITIONS WITH LOW CHANCES OF SHOWERS AND STORMS BY LATE SUNDAY. TIGHT CLUSTER WITH ENSEMBLE GUIDANCE IN THIS PERIOD AND WAS LEANED ON QUITE A BIT IN THIS PERIOD FOR THE FORECAST.
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&& .AVIATION /08Z 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 AND TUESDAY NIGHT: VFR. SOUTHERLY WINDS UNDER 10 KNOTS AND GUSTS AT OR UNDER 15 KNOTS. ANY THUNDERSTORM RESTRICTION TO MVFR OR IFR LOOKS ISOLATED. WEDNESDAY AND WEDNESDAY NIGHT: POTENTIAL MVFR AND IFR RESTRICTIONS IN SHOWERS AND THUNDERSTORMS WEDNESDAY AFTERNOON AND EVENING. WEST- SOUTHWEST WIND GUSTS AT OR UNDER 15 KNOTS. THURSDAY THROUGH FRIDAY NIGHT: MAINLY VFR, A FEW LOWER MVFR OR IFR RESTRICTIONS POSSIBLE IN ISOLATED TO SCATTERED SHOWERS AND STORMS. NORTHERLY WINDS UNDER 10 KNOTS.
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&& .MARINE...
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NO MARINE HEADLINES THROUGH TONIGHT. OUTLOOK... SUB-SCA WINDS AND SEAS EXPECTED. ANY WIND GUSTS LOOK TO REMAIN BELOW 20 KNOTS, MORE SOUTHWESTERLY THROUGH WEDNESDAY THEN MORE NORTHERLY THURSDAY AND FRIDAY. SEAS MAY REACH FOUR FEET ON WEDNESDAY. THE HIGHEST CHANCE OF THUNDERSTORMS IS WEDNESDAY AFTERNOON AND EVENING.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GAINES NEAR TERM...DRAG SHORT TERM...DRAG/NIERENBERG LONG TERM...GAINES AVIATION...DRAG/GAINES MARINE...DRAG/GAINES

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