Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 010137 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 937 PM EDT SAT APR 30 2016 .SYNOPSIS... WEAK HIGH PRESSURE WILL BE ACROSS THE REGION EARLY TONIGHT. THE HIGH WILL THEN MOVE OFFSHORE AS LOW PRESSURE ADVANCES UP THE OHIO VALLEY. THIS LOW WILL AFFECT OUR WEATHER FOR SUNDAY AND INTO MONDAY. HIGH PRESSURE WILL EXTEND ACROSS THE AREA LATER MONDAY INTO TUESDAY. MORE LOW PRESSURE WILL MOVE TOWARDS THE AREA FOR THE MIDDLE AND END OF THE UPCOMING WEEK BRINGING UNSETTLED WEATHER TO THE REGION. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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NO BIG CHANGES TO THE OVERALL FORECAST THIS EVENING. WE MADE SOME ADJUSTMENTS TO THE HOURLY SKY GRIDS EARLY THIS EVENING WITH SOME CLEARING ACROSS THE EASTERN THIRD OF THE AREA. ALTHOUGH THIS WILL FILL BACK IN WITH CLOUD COVER OVER THE THE NEXT FEW HOURS. ALSO MADE SOME ADJUSTMENTS TO THE DEWPOINTS THE NEXT FEW HOURS AS THERE REMAINS SOME DRIER AIR ALONG THE EASTERN THIRD OF THE AREA, BUT AGAIN, THESE SHOULD NOT DROP MUCH MORE. OTHERWISE, THE FORECAST LOOKS ON TRACK WITH RAINFALL SPREADING ACROSS THE AREA OVERNIGHT. LOW PRESSURE WILL TRACK NORTHEAST ALONG A FRONTAL BOUNDARY FROM THE OHIO VALLEY INTO THE GREAT LAKES KEEPING MOSTLY CLOUDY SKIES IN PLACE TONIGHT. MOISTURE WILL LIFT ALONG AND OVERRUN THE BOUNDARY RESULTING IN RAIN DEVELOPING TO OUR WEST OVERNIGHT. IT LOOKS TO BE MAINLY DRY FOR THE OVERNIGHT WITH LIGHT RAIN SPREADING INTO EASTERN PENNSYLVANIA AND THE DELMARVA BY SUNRISE. ANY QPF LOOKS TO BE UNDER 1/10TH OF AN INCH. LOWS WILL LIKELY FALL INTO THE 40`S WITH MOST OF THE DROP IN TEMPERATURES DURING THE EVENING HOURS. DID NOT DEVIATE MUCH FROM MET/MAV/LAV GUIDANCES IN THIS PERIOD. WINDS WILL BE UNDER 10 MPH FROM THE EAST AND SOUTHEAST.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
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AN AREA OF LOW PRESSURE WILL CONTINUE TO TRACK EASTWARD TOWARD THE REGION ALONG A WARM FRONTAL BOUNDARY IN THE SOUTHERN DELMARVA. MOISTURE OVERRUNNING THE BOUNDARY WILL LEAD TO CONTINUED PERIODS OF LIGHT TO MODERATE RAIN ACROSS MOST OF THE REGION THROUGHOUT THE DAY ON SUNDAY. ENOUGH INSTABILITY MAY ADVECT IN JUST SOUTH OF THE WARM FRONT FOR AN ISOLATED THUNDERSTORM AS WELL. A GRADIENT IN TEMPERATURES IS EXPECTED AS WELL WITH THE FRONT IN THE REGION. MANY LOCALES NORTH OF PHILADELPHIA ARE LIKELY TO BE SEVERAL DEGREES COOLER THAN MAV/MET GUIDANCE IN THE 40`S TO LOW 50`S. ON THE OTHER HAND, SOUTH OF THE FRONT HIGHS SHOULD GET INTO THE 60`S. CONTINUED WINDS FROM THE EAST AND SOUTHEAST UNDER 10 MPH. THE SREF PLUMES ARE FOR THE MOST PART TIGHTLY CLUSTERED AROUND 1/2 INCH TO 3/4 OF AN INCH OF NEEDED RAINFALL, COMPONENTS OF WPC QPF ALONG WITH THE WRF- ARW AND NMM WERE ADDED FOR THE QPF FORECAST.
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&& .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... TEMPERATURES WILL RUN 2 TO 4 DEGREES BELOW NORMAL DURING THIS TIME PERIOD. ONE STORM SYSTEM WILL BE IMPACTING THE REGION AT THE START OF THIS TIME PERIOD WITH ANOTHER STORM SYSTEM EXPECTED TO AFFECT THE REGION LATE NEXT WEEK. BETWEEN THIS TWO STORM EVENTS, A FRONTAL BOUNDARY WILL LINGER CLOSE TO THE AREA, RESULTING IN GENERALLY UNSETTLED CONDITIONS THROUGH THIS TIME PERIOD. 12Z SUPERBLEND WAS USED AS PRIMARY GUIDANCE DURING THIS TIME PERIOD. SOME ADJUSTMENTS WERE MADE TO THE COASTAL WATERS FORECAST FOR SUNDAY NIGHT FOR BETTER CONSISTENCY WITH ADJACENT OFFICES AND CONTINUITY. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/...
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THE EVENING WILL START OUT WITH VFR CEILINGS. HOWEVER, WITH THE APPROACH OF A LOW PRESSURE SYSTEM RAIN WILL DEVELOP FROM WEST TO EAST OVERNIGHT THROUGH SUNRISE. CEILINGS AND VSBYS WILL GRADUALLY LOWER AS WELL, REACHING IFR AROUND OR SHORTLY AFTER 12Z SUNDAY. SOME UNCERTAINTY IS STILL PRESENT IN HOW QUICK THE CEILINGS WILL LOWER. A HIGHER DEGREE OF CONFIDENCE IS PRESENT FOR A WINDOW OF IFR CEILINGS CENTERED AROUND THE HEAVIEST RAINFALL IN THE MORNING AND EARLY AFTERNOON HOURS ON SUNDAY. WE`VE INTRODUCED -DZ WITH IFR CEILINGS/VISIBILITIES FOR SUNDAY EVENING AT PHL AS WE LOSE DEEP MOISTURE, BUT KEEP LOW LEVEL MOISTURE WHICH WOULD BE MORE INDICATIVE OF DRIZZLE. OUTLOOK... SUNDAY NIGHT THRU MONDAY...WIDESPREAD IFR/MVFR WITH FREQUENT RAINS AND AREAS OF FOG. MONDAY NIGHT THRU WED...VFR MOSTLY. LOWER CONDITIONS WITH OVERNIGHT FOG POSSIBLE. THU...INCREASING RISK OF MVFR AS RAIN MOVES BACK INTO THE AREA.
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&& .MARINE...
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WITH A PERSISTENT ONSHORE SWELL, SEAS HAVE BEEN VERY SLOW TO FALL THIS AFTERNOON. BUOY 44009 REMAINS AROUND 5 FEET, WHILE THE OTHER BUOYS HAVE FALLEN BELOW. WE WILL LEAVE THE SMALL CRAFT ADVISORY IN PLACE THROUGH THE OVERNIGHT HOURS AS THERE COULD STILL BE SOME ELEVATED SEAS FOR A COUPLE OF MORE HOURS. WINDS WILL BE OUT OF THE SOUTHEAST AROUND 10 KNOTS BOTH TONIGHT AND SUNDAY, WITH SOME HIGHER GUSTS UP TO 20 KNOTS IN THE AFTERNOON. OUTLOOK... SUN NIGHT THRU MON NIGHT...SCA CONDITIONS EXPECTED ON THE OCEAN WATERS DUE TO SEAS. TUE THRU THU...MOSTLY SUB SCA.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 AM EDT SUNDAY FOR ANZ450>455. && $$ SYNOPSIS...SZATKOWSKI NEAR TERM...GAINES/ROBERTSON SHORT TERM...GAINES LONG TERM...SZATKOWSKI AVIATION...GAINES/ROBERTSON MARINE...GAINES/ROBERTSON/SZATKOWSKI

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