Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 040130 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 930 PM EDT FRI JUL 3 2015 .SYNOPSIS... A WEAK HIGH PRESSURE SYSTEM WILL REMAIN OVER NEW ENGLAND TONIGHT, BEFORE MOVING OFFSHORE ON SATURDAY. MEANWHILE, LOW PRESSURE OVER THE OHIO VALLEY WILL MOVE ALONG A STALLED FRONTAL BOUNDARY TO OUR SOUTH AND PASS EAST OF THE DELMARVA PENINSULA ON INDEPENDENCE DAY. ANOTHER AREA OF HIGH PRESSURE WILL THEN MOVE INTO THE REGION FOR THE END OF THE HOLIDAY WEEKEND AND MONDAY. A WEAK LOW PRESSURE SYSTEM MIGHT EASE NORTH INTO THE AREA ON TUESDAY AS ANOTHER COLD FRONT APPROACHES THE FORECAST AREA BY MIDWEEK. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... THE EVENING WATER VAPOR SATELLITE IMAGERY SHOWS A POSITIVELY- TILTED UPPER TROUGH OVER THE MIDWEST. MOISTURE IS STREAMING AHEAD OF THE TROUGH FROM THE WESTERN GULF OF MEXICO NORTHEASTWARD TOWARD THE CENTRAL APPALACHIANS AND MID-ATLANTIC COAST. AT THE SURFACE, A STATIONARY FRONTAL BOUNDARY WAS POSITIONED TO OUR SOUTH NEAR THE VA-NC BORDER. REGIONAL RADAR MOSAIC THIS EVENING SHOWED A BAND OF LIGHT SHOWERS TO OUR SOUTH AND WEST OVER WESTERN PA/VA/CENTRAL MD THAT WAS ASSOCIATED WITH DPVA FROM A LEADING MID-LEVEL SHORTWAVE TROUGH AND ISENTROPIC LIFT. POPS THRU TONIGHT CLOSELY FOLLOW THE LATEST HRRR, RAP AND NCEP WRF-NMM, WHICH SEEM TO HAVE HAD A GOOD HANDLE ON THE PROGRESSION OF THESE SHOWERS THUS FAR. PRECIP IS GENERALLY EXPECTED TO ADVANCE NORTHEASTWARD INTO THE EASTERN SHORE OF MD THIS EVE, DELAWARE CLOSE TO MIDNIGHT AND EASTERN PA/NJ LATE TONIGHT INTO THE EARLY MORNING. THE BEST LIFT WITH THE FRONT AND THE UPPER TROUGH WILL REMAIN UPSTREAM OF THE AREA TONIGHT. THE CWA WILL BE LOCATED ON THE COOL/STABLE SIDE OF THE BOUNDARY. THERE IS SOME RESIDUAL DRY AIR IN THE MID AND LOW-LEVELS. THEREFORE, DO NOT EXPECT THE PRECIP TO BE STEADY OR HEAVY TONIGHT IN THIS SETUP. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... STILL LOTS OF UNCERTAINTY IN THIS PERIOD. THERE IS CONSIDERABLE DISAGREEMENT BETWEEN MODELS AND RUN-TO-RUN ON INDIVIDUAL MODEL RUNS. FOR THE MOST PART, THE MAIN DETERMINISTIC MODELS HAD A SLIGHTLY DRIER TREND WITH THE 12Z/18Z RUNS. HOWEVER, THIS HAS BEEN THE CASE THE LAST FEW DAYS, WITH THE 00Z RUNS TENDING TO BE WETTER SOLUTIONS. AT THIS POINT, THINK THE HIGHEST CHANCES WILL STILL COME BEFORE 21Z. THINK THAT IT WILL MOSTLY BE A STEADY RAIN GIVEN A RATHER STABLE ATMOSPHERE IN PLACE. AS FAR AS RAIN AMOUNTS, HAVE FAVORED LIGHTER AMOUNTS GIVEN THE UNCERTAINTY OF HOW MUCH MOISTURE ADVECTION WE WILL HAVE. THE THREAT OF THUNDERSTORMS, HEAVY RAINFALL AND FLOODING LOOKS TO BE DWINDLING GIVEN THESE RECENT TRENDS. MOST MODEL SOLUTIONS CONTINUE TO SHOW THE PRECIP LIFTING OUT QUICKLY FROM MID TO LATE AFTERNOON. THIS TIMING MAY ALLOW FOR SOME OUTDOOR 4TH OF JULY FESTIVITIES TO TAKE PLACE LATE IN THE DAY. THE GROUND MAY BE DAMP THOUGH IN PARTS OF THE AREA THAT RECEIVE THE STEADIER/HEAVIER RAINFALL (MOST LIKELY DELMARVA AND SOUTHERN NJ). WITH ALL THE CLOUD COVER IN PLACE, IT LOOKS TO BE A RATHER COOL DAY (HIGHS IN THE 60S IN THE MOUNTAINS AND 70S ELSEWHERE). && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... ANY LINGERING PRECIP SHUD BE ENDING ERLY SAT EVE WHICH SHUD HAVE A POSITIVE IMPACT ON ANY FIREWORKS DISPLAYS AND OTHER HOLIDAY FESTIVITIES. HIGH PRES WILL THEN BUILD IN FOR SAT NIGHT THRU MON KEEPING THIS PD DRY OVER MOST, IF NOT ALL OF THE AREA. THE ONLY LOCATION THAT GUID IMPLIES CUD SEE SOME PRECIP WUD BE OVER THE DELMARVA COME MON. BY MON NIGHT INTO TUE, ANOTHER QUICK WV MOVES THRU, THEN THE GFS IS MUCH FASTER WITH A CDFNT FROM THE W, BRINGING IT THRU BY WED MRNG AND THE ASSOCD PRECIP. THE CMC AND ECMWF ARE MUCH SLOWER BRING THE FRONT THRU LATER WED INTO WED NIGHT. IF THE EC IS TO BE BELIEVED, WITH THE SLOWER FRONTAL TIMING, TUE NIGHT INTO ERLY WED, CUD BE DRY AND WED CUD BE ON THE HOT SIDE AHEAD OF THE FRONT. THEN THE ECMWF DEVELOPS WHAT APPEARS TO BE A VERY STRONG WAVE FOR FRI THAT THE GFS DOESN`T HAVE, AND IS SUBSEQUENTLY DRY. ONCE AGAIN, CONFIDENCE IS LOWER THAN AVERAGE. THERE WILL BE A CFP. HAVE SHADED THIS FCST TWD THE MDL CONSENSUS AND THE SLOWER TIMING, BUT, NOT SURE ON THE MOST LIKELY PDS OF PRECIP AS A RESULT OF THE UNCERTAINTY. FOR NOW, AM JUST CARRYING LOW POPS FOR FRI, AS WE HAVE A WEEK TO SEE WHAT, IF ANYTHING, DEVELOPS. TEMPS WILL START OFF NR NRML AND RISE TO ABV NRML VALUES BY THE MIDDLE AND END OF THE WEEK. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS EXPECTED THROUGH THE OVERNIGHT WITH CEILINGS AOA 5,000 FEET. SOME LIGHT RAIN SHOWERS MAY BEGIN TO MOVE INTO THE REGION BY 05Z WITH CHANCES INCREASING FROM SOUTH TO NORTH OVERNIGHT. THE STEADIEST AND HEAVIEST SHOWERS LOOK TO BE FROM 13-18Z SATURDAY, WHICH WILL CORRESPOND TO THE HIGHEST CHANCE FOR MVFR CEILINGS/VSBYS FROM PHL/PNE TO THE SOUTHEAST. RDG AND ABE COULD ESCAPE THE PROSPECTS FOR ANY MVFR RESTRICTIONS. ACY HAS HIGHEST LIKELIHOOD TO SEE MVFR CONDITIONS WITH THE SLOWEST RISE IN CEILINGS LATE IN THE DAY. CEILINGS WILL LIKELY LIFT TO VFR AND BECOME BROKEN BY 19Z OUTSIDE OF ACY WHERE AN ONSHORE FLOW WILL TEND TO KEEP THEM LOWER. WINDS WILL BE AT OR UNDER 10 KNOTS FROM THE SOUTH LATE THIS EVENING THEN SHIFTING TO EASTERLY FOR MOST OF SATURDAY. A WIND SHIFT TO A MORE WESTERLY DIRECTION IS LIKELY TO START BY SATURDAY EVENING. OUTLOOK... SAT NIGHT...SOME MVFR FOG PSBL AT THE MORE RURAL ARPTS, OTHERWISE VFR. HIGH CONFIDENCE. SUN THRU TUE NIGHT...VFR SUN AND SUN NIGHT. HIGH CONFIDENCE. VFR MON AND TUE OUTSIDE OF ANY SHRA/TSRA MAINLY IN THE AFTNS. WED...PREDOMINATELY VFR, BUT DECREASING TO MVFR/IFR WITH INCREASING CHCS OF SHRA/TSRA, ESPECIALLY W AS CDFNT APPROACHES. MDT CONFIDENCE. && .MARINE... WINDS AND SEAS SHOULD STAY BELOW SCA CRITERIA TONIGHT INTO TOMORROW MORNING. BY TOMORROW AFTERNOON, WINDS AND SEAS COULD BUILD TO NEAR 25 KT/5 FT, PRIMARILY ON THE NORTHERN ATLANTIC WATERS. HOWEVER, THERE IS CONSIDERABLE UNCERTAINTY AND HAVE CAPPED WINDS/SEAS JUST BELOW SCA THRESHOLD. OUTLOOK... SAT NIGHT AND SUN...THERE IS STILL SOME UNCERTAINTY WITH THE STRENGTH AND TRACK OF THE LOW, BUT IT APPEARS THE BEST CHC OF SEAS ABOVE SCA CONDS WILL BE EARLY SAT NIGHT AND PSBLY SOME MRGNL WIND. HOWEVER, CONFIDENCE IS LOW ENOUGH AT THE MOMENT TO HOLD OFF ISSUING ANY FLAGS ATTM. THE BEST CHCS APPEAR TO BE ON THE NRN WATERS. AFTER ANY SCA LINGERING INTO THE MRNG, THE CONDS SHUD DECREASE BELOW SCA LATER INTO SUN. SUN NIGHT THRU WED...NO MARINE FLAGS ARE ANTICIPATED. && .TIDES/COASTAL FLOODING... WITH CONTINUED WEAK ON SHORE FLOW, HIGH TIDES THIS EVENING AND SATURDAY EVENING COULD APPROACH THE MINOR FLOODING LEVEL, BUT RIGHT NOW NO SITES ARE FORECAST TO REACH LEVELS NEEDED FOR A COASTAL FLOOD ADVISORY. SAT NIGHT AND SUN LOOK TO BE THE SAME WAY. WHILE SOME SITES MAY APPROACH MINOR TIDAL FLOODING LEVELS, CURRENT DATA INDICATES THEY WILL REMAIN BELOW CRITERIA. && .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...NIERENBERG NEAR TERM...KLEIN SHORT TERM...JOHNSON/KLEIN LONG TERM...NIERENBERG AVIATION...GAINES/JOHNSON/NIERENBERG MARINE...JOHNSON/NIERENBERG TIDES/COASTAL FLOODING...JOHNSON RIP CURRENTS...KLEIN

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