Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 010439
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1239 AM EDT SUN MAY 1 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 THIS MORNING/...
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.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 AM MONDAY/...
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.

&&

.LONG TERM /MONDAY THROUGH SUNDAY/...
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 /06Z SUNDAY THROUGH THURSDAY/...
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.

&&

.MARINE...
SEAS HAVE FALLEN BELOW 5 FEET ACROSS THE AREAS WATERS AND WE HAVE
CANCELLED THE SMALL CRAFT ADVISORY. WINDS WILL REMAIN AROUND 10
KNOTS OVERNIGHT OUT OF THE SOUTHEAST CONTINUING THROUGH MUCH OF
TODAY. THERE MAY BE A FEW GUSTS NEAR 20 KNOTS THIS AFTERNOON.

OUTLOOK...
SUN NIGHT THRU MON NIGHT...SCA CONDITIONS EXPECTED ON THE
OCEAN WATERS DUE TO SEAS.

TUE THRU THU...MOSTLY SUB SCA.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...SZATKOWSKI
NEAR TERM...GAINES/ROBERTSON
SHORT TERM...GAINES
LONG TERM...SZATKOWSKI
AVIATION...GAINES/ROBERTSON
MARINE...SZATKOWSKI/MEOLA



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