Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 041327 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 927 AM EDT SAT JUL 4 2015 .SYNOPSIS... LOW PRESSURE OFF THE DELMARVA COAST WILL MOVE OUT TO SEA SOUTH OF CAPE COD BY THIS EVENING. WEAK HIGH PRESSURE FOLLOWS LATE TONIGHT AND SUNDAY, THEN SHIFTS OFFSHORE MONDAY. A WARM FRONT MOVES SLOWLY NORTHEAST THROUGH THE MID ATLANTIC STATES TUESDAY WITH A COLD FRONT TO FOLLOW LATE WEDNESDAY OR THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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THE UPPER LEVEL TROF IS PROGRESSING SLOWLY EASTWARD ACROSS THE GRTLKS AND OH VLY. EXTENSIVE MID CLOUDS AND AREAS OF SHOWERS HAVE SPREAD ACROSS THE FCST AREA AHEAD OF THE TROF AND NORTH OF THE QUASI- STNRY FRONTAL BOUNDARY EXTENDING W TO E ACROSS VA. BASED ON THE LTST RADAR, HAVE INCREASED POPS N AND W IN THE NEAR TERM AND DECREASED S AND E. THE MOST CURRENT HRRR INDICATES PRECIP MAY DECREASE IN COVERAGE LATER IN THE DAY AS IT MOVES SEWD AND IF THAT IS THE CASE, THEN POPS WILL BE OVERDONE. WE`LL REASSESS FOR THE NEXT UPDATE. OTHERWISE, MADE A FEW MINOR ADJUSTMENTS (UPWARD) TO TEMPS BASED ON CURRENT OBS. CLOUDS AND SHOWERS TODAY WILL LIMIT MAX TEMPS TO THE UPPER 60S N/W AND MID 70S S/E. CHANCE FOR PRECIP SHOULD DECREASE FROM W TO E FROM MID AFTERNOON ONWARD AS FORCING FOR UVV MOVES AWAY FROM THE AREA. HWVR CLOUDINESS WILL LINGER AS DRIER AIR WILL BE SMWHT SLOW TO FILTER IN BEHIND THE LOW.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... FOR TONIGHT...THE UPPER TROF AXIS WILL CONT MOVING EWD AND OFFSHORE BY SUNDAY MORNING WITH DRIER AIR FILTERING IN BEHIND IT. WEAK HIGH PRES WILL BUILD IN AT THE SFC. ANY LINGERING SHOWERS NEAR THE COAST SHOULD MOVE OUT BEFORE DARK ALLOWING FOR FIREWORKS TO PROCEED. EVENING CLOUDS SHOULD CLEAR FROM THE NW OVER NIGHT WITH THE DRIER AIR COMING IN. WIND WILL BE RATHER LIGHT ALLOWING FOR MIN TEMPS GENLY IN THE 50S EXCEPT 60S IN DELMARVA. && .LONG TERM /SUNDAY THROUGH FRIDAY/... 500MB: A TROUGH CENTERED NEAR THE TENNESSEE VALLEY SUNDAY WILL WEAKEN NORTHEASTWARD ACROSS THE MID ATLANTIC STATES TUESDAY. A WEAK WEST SOUTHWEST FLOW PREVAILS THEREAFTER WITH WEAK EMBEDDED DISTURBANCES. TEMPERATURES: CALENDAR DAY TEMPERATURES NEAR OR SLIGHTLY BELOW NORMAL ON SUNDAY WARM TO ALMOST 5 DEGREES ABOVE NORMAL TUESDAY AND WEDNESDAY AND POSSIBLY REMAIN ABOVE NORMAL THURSDAY AND FRIDAY. FORECAST BASIS: UNLESS OTHERWISE NOTED, THIS 330 AM SATURDAY JULY 4TH FORECAST WAS GENERALLY A 50 50 BLEND OF THE 00Z/4 GFS/NAM MOS GUIDANCE SUNDAY-MONDAY, 00Z/4 MEX MOS MONDAY NIGHT AND TUESDAY, THEN THE 0521Z/4 WPC GRIDDED ELEMENTS OF MAX/MIN TEMP, 12 HOUR POP, 6 HOUR DEW POINT- SKY-WIND FROM TUESDAY NIGHT THROUGH NEXT FRIDAY WITH THE EXCEPTION OF MAX TEMPS TUESDAY AND WEDNESDAY WHEN THE 00Z/4 GFS MEX BLENDED WITH THE EVEN WARMER 00Z/4 ECMWF 2M TEMPS PREVAILED. THE DAILIES... SUNDAY...AFTER ANY EARLY MORNING PATCHY FOG DISSIPATES...SCT-BKN AOA 5000 FT. WEST WIND GUST 15 MPH. CONFIDENCE: ABOVE AVERAGE. MONDAY....INCREASING CLOUDS. ST/FOG POSSIBLE LATE MONDAY NIGHT? SOUTH WIND GUST 15 MPH MONDAY AFTERNOON. CONFIDENCE: ABOVE AVERAGE. TUESDAY...AREAS OF SHOWERS AND EMBEDDED TSTMS WITH PWAT OF 1.75 TO TO 2 INCHES, MLCAPE 1200J, AND WEAK STEERING WHICH COULD MEAN SEVERAL INTENSE TSTMS WITH EXCESSIVE SHORT DURATION RAINFALL (POOR DRAINAGE FLOODING FOR STARTERS). SOUTHERLY WIND GUST 20 MPH. NEAR 90F PHILLY AREA. CONFIDENCE: ABOVE AVERAGE. WEDNESDAY...LIKELY A HOT DAY. TSTMS LATE IN THE DAY AHEAD OF THE APPROACHING AND EVENTUALLY SLOWING COLD FRONT. 1000J MLCAPE. COULD BE STRONG TSTMS E PA. HEAT INDEX RIGHT NOW MODELED 99 PHL AND NEAR 100 DELMARVA. WILL BE REEVALUATED NEXT SEVERAL DAYS. NO HEAT INDEX ACTION ATTM IN THE MORNING HWO. CONFIDENCE: ABOVE AVERAGE. THURSDAY...UNCERTAINTY ON TIMING BUT TSTMS ARE IN THE FCST WITH ANOTHER SHORT WAVE PASSAGE. ALSO UNCERTAINTY ON TEMPS, DEPENDENT ON TIMING CONVECTIVE RELATED SKY COVER. CONFIDENCE: AVERAGE OR BELOW AVERAGE. FRIDAY...PROBABLY DRYING OUT AFTER THURSDAY`S ANTICIPATED SHORT WAVE PASSAGE. CONFIDENCE: AVERAGE OR BELOW AVERAGE. && .AVIATION /13Z SATURDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDS THIS MORNING WILL WORSEN SOMEWHAT AS AREAS OF SHOWERS DEVELOP/SPREAD ACROSS THE REGION. SHOWERS ARE AHEAD OF A SHRTWV TROF MOVING EAST FROM THE OHIO VLY. THERE WILL BE PERIODS OF MVFR CIGS/VSBYS WITH SOME OF THE HEAVIER SHOWERS. CONDS SHOULD IMPROVE FROM MID/LATE AFTN ON INTO THE EVENING. CURRENT LIGHT SE WINDS WILL INCREASE SOME AND BACK TO THE NE AS LOW PRES DEVELOPS LATER THIS MORNING S OF DELMARVA AND THEN MOVES OFFSHORE. OUTLOOK... SUNDAY...VFR SCT-BKN AOA 5000 FT. WEST WIND MAX GUST 15 KT DURING THE AFTERNOON. PATCHY MVFR FOG POSSIBLE TO START THE DAY AND AGAIN LATE SUNDAY NIGHT. HIGH CONFIDENCE. MONDAY...VFR SCT-BKN AOA 5000 FT DURING THE DAY WITH A CHANCE OF IFR ST/FOG LATE MONDAY NIGHT AHEAD OF A WARM FRONT. SOUTHERLY WIND MAX GUST 15 KT DURING MONDAY AFTERNOON. HIGH CONFIDENCE. TUESDAY...VFR SCT-BKN AOA 5000 FT WITH SCT TSTMS AND ASSTD BRIEF IFR CONDS IN HEAVY RAIN, ESPECIALLY E PA DURING THE AFTN-EVENING. HIGH CONFIDENCE. WED...VFR SCT-BKN WITH A PRETTY GOOD CHANCE OF AFTN OR NIGHTTIME TSTMS. IFR CONDS POSSIBLE IN TSTMS. CONFIDENCE: AVERAGE OR ABOVE AVERAGE. && .MARINE... SE WINDS EARLY THIS MORNING WILL BACK TO THE E AND NE LATER THIS MORNING AND AFTN AS LOW PRES DEVELOPS EAST OF DELMARVA. WIND SPEED AND WAVES WILL INCREASE SOME TODAY BUT ARE EXPECTED TO REMAIN BELOW SCA LEVELS. WINDS SHOULD DECREASE AND BECOME NLY TONIGHT AS THE LOW PRES MOVES AWAY AND WEAK HIGH PRES BUILDS IN. OUTLOOK... SUNDAY NIGHT THRU WEDNESDAY...NO MARINE FLAGS ARE ANTICIPATED AS OF THIS WRITING. CONFIDENCE: AVERAGE && .TIDES/COASTAL FLOODING... TONIGHT (THIS EVENING). WHILE SOME TIDAL LOCATIONS MAY APPROACH MINOR TIDAL FLOODING LEVELS, CURRENT DATA INDICATES THEY WILL REMAIN BELOW ADVISORY THRESHOLD. && .RIP CURRENTS... THERE IS A MODERATE RISK OF RIP CURRENTS ON SATURDAY ALONG THE NEW JERSEY SHORE GIVEN THE CONTINUED ONSHORE FLOW AND MODERATE PERIOD SWELLS. THE RISK IS LOW FOR DELAWARE. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...DRAG NEAR TERM...AMC/NIERENBERG SHORT TERM...AMC LONG TERM...DRAG AVIATION...AMC/DRAG MARINE...AMC/DRAG TIDES/COASTAL FLOODING... RIP CURRENTS...

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