Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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584
FXUS61 KPHI 041354
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
954 AM EDT WED MAY 4 2016

.SYNOPSIS...
LOW PRESSURE WILL CONSOLIDATE OFFSHORE THROUGH THURSDAY BEFORE
MOVING NORTHEASTWARD. MEANWHILE, ANOTHER LOW PRESSURE SYSTEM
DEVELOPS OFF THE MID ATLANTIC COAST THURSDAY NIGHT AND FRIDAY AND
THEN MOVES NORTHEASTWARD THROUGH SATURDAY. A COLD FRONT IS
FORECAST TO MOVE THROUGH SUNDAY MORNING FOLLOWED BY HIGH PRESSURE
BUILDING IN FOR MONDAY AND TUESDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WE HAVE MADE SOME MINOR ADJUSTMENTS TO THE PREVIOUS FORECAST. AN
AREA OF SHOWERS DEVELOPING OVER OUR SOUTHERN COUNTIES AT MID
MORNING WILL INCREASE IN COVERAGE AS IT ADVECTS TO THE NORTH. IT
SHOULD IMPACT THE REMAINDER OF OUR FORECAST AREA DURING THE
BALANCE OF THE MORNING AND INTO THE EARLY TO MID AFTERNOON. THE
LATEST HRRR SEEMS TO BE HANDLING THE OVERALL TREND WELL.

OTHERWISE, LOW CLOUDS WILL PERSIST THROUGH THE DAY ALONG WITH FOG
IN THE ELEVATED TERRAIN. TEMPERATURES WILL REMAIN BELOW NORMAL IN
THE NORTHEASTERLY FLOW.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
PWAT DRIES TO 0.75 INCHES AND INSTABILITY ALOFT DECREASES BUT A
CONTD MOIST CYCLONIC CIRCULATION WITH PROBABLY PERIODS OF
MEASURABLE DRIZZLE AND MAYBE A FEW POCKETS OF SHOWERS.

50 50 BLENDED 00Z/4 GFS NAM GUIDANCE. WE SEE THE SPC WRF DRIES US
OUT CONSIDERABLY TONIGHT SO POPS ARE GENERALLY 60 PCT N AND 30-40
PCT SOUTH. BEST CHANCE FOR MEASURABLE MAY BE PRIOR TO MIDNIGHT.

NE WIND GUSTY NEAR 15 MPH... EXPECT 20-25 MPH MONMOUTH COUNTY
COAST.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
THE SYNOPTIC SETUP IS COMPRISED OF AN OMEGA BLOCK, THEN THIS
PATTERN IS FORECAST TO BREAK DOWN SOME DURING THE SECOND HALF OF
THE WEEKEND AND ESPECIALLY EARLY NEXT WEEK. A FEW WEEKS AGO THERE
WAS AN OMEGA BLOCK IN PLACE, HOWEVER AT THAT TIME WE WERE UNDER
THE RIDGE. THIS GO AROUND WE ARE UNDER THE TROUGH PART OF THE
BLOCK, KEEPING OUR WEATHER COOLER AND UNSETTLED. THE REST OF THE
WEEK WILL THEREFORE BE UNSETTLED WITH SOME IMPROVEMENT DURING THE
WEEKEND, THEN A MORE NOTABLE IMPROVEMENT ANTICIPATED FOR EARLY
NEXT WEEK. WE USED A MODEL BLEND APPROACH FOR THURSDAY INTO
SATURDAY, THEN BLENDED IN THE 00Z WPC GUIDANCE THEREAFTER. SOME
ADJUSTMENTS WERE THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH
OUR NEIGHBORING OFFICES.

FOR THURSDAY AND FRIDAY...THE OMEGA BLOCK CONTINUES WITH A STRONG
SHORT WAVE CLOSING OFF THE TROUGH AS IT TRACKS FROM THE OHIO
VALLEY AND ACROSS THE SOUTHEASTERN STATES THURSDAY. SOME SHORT
WAVE ENERGY TRACKING NORTHWARD ON THE EAST SIDE OF THE LARGE
TROUGH WILL TEAM UP WITH ISENTROPIC LIFT ABOVE A MARINE LAYER AND
PRODUCE SOME SHOWERS. THURSDAY MORNING HOWEVER COULD ALSO START
WITH SOME DRIZZLE. THE ENTIRE TROUGH AND CLOSED LOW ARE FORECAST
TO BECOME CENTERED ALONG THE EAST COAST FRIDAY WITH THE CLOSED LOW
ITSELF MOVING OVER OUR CWA DURING FRIDAY. THIS WILL DRIVE LOW
PRESSURE OFF THE MID ATLANTIC COAST NORTHWARD ALTHOUGH IT LOOKS TO
NOT DEEPEN CONSIDERABLY. AS THIS OCCURS, THE 500 MB TEMPERATURES
ARE FORECAST TO COOL TO NEAR -24C ON FRIDAY. THIS WOULD PROMOTE
SOME INSTABILITY AND PERHAPS SOME LOW-TOPPED CONVECTION, HOWEVER
CLOUD COVER AND NUMEROUS SHOWERS MAY TEMPER THIS POTENTIAL.

OTHERWISE, AN EASTERLY LOW-LEVEL JET DEVELOPS FRIDAY ACROSS OUR
NORTHEASTERN ZONES THEN THIS PIVOTS NORTH-NORTHWESTWARD DURING THE
AFTERNOON. SOME GUIDANCE IS STRONGER WITH THIS FEATURE WHICH ALSO
DRIVES A BAND OF STRONGER 700-800 MB FRONTOGENETIC FORCING.
OVERALL, THERE LOOKS LIKE DECENT LIFT ON THE NOSE OF THE EASTERLY
JET TO PROMOTE AN AREA OF SHOWERS/RAIN THAT PIVOTS INLAND DURING
FRIDAY. WE MAY NOT SEE ANY BREAKS IN THE CLOUDS, BUT IF THERE ARE
THEN ANY LOW- TOPPED CONVECTION COULD PRODUCE SMALL HAIL GIVEN THE
VERY COLD 500 MB TEMPERATURES. AS OF NOW HOWEVER, ANY INSTABILITY
LOOKS MEAGER. THE SYSTEM THEM MEANDERS OVER OUR AREA FRIDAY NIGHT
AND WHILE THERE SHOULD BE A DECREASE IN THE SHOWER COVERAGE SOME
SHOULD LINGER THROUGH THE NIGHT.

FOR SATURDAY AND SUNDAY...THERE HAS BEEN A GENERAL SLOWING TREND
IN THE GUIDANCE WHEN COMPARING THE MANY MODELS AND ENSEMBLES. THIS
TENDS TO HAPPEN WITH BLOCKING PATTERNS AS IT TAKES LONGER FOR THE
CLOSED LOW TO OPEN UP AND LIFT OUT. THERE ARE CONSIDERABLE
DIFFERENCES AT THE SURFACE ON SATURDAY WHICH LEADS TO PLENTY OF
DETAIL UNCERTAINTIES INCLUDING THE AMOUNT OF RAIN. WE THEREFORE
LEANED CLOSER TO THE WPC GUIDANCE BUT ALSO INCORPORATING SOME
CONTINUITY. THIS MEANS THAT SATURDAY LOOKS TO BE STILL UNSETTLED
WITH SOME SHOWERS STILL HANGING AROUND. THE AMOUNT OF SHOWER
ACTIVITY WILL DEPEND ON THE SHORT WAVE FORCING AROUND THE CLOSED
LOW, HOWEVER PLENTY OF COLD AIR REMAINS ALOFT WHICH WILL HELP WITH
SOME INSTABILITY. THIS SYSTEM SHOULD OPEN UP AND START SHIFTING
EAST SATURDAY NIGHT AS UPSTREAM ENERGY IN THE FORM OF A TROUGH
SLIDES SOUTHEASTWARD FROM THE GREAT LAKES. THIS DRIVES A COLD
FRONT ACROSS OUR AREA MOSTLY SUNDAY MORNING WITH PERHAPS SOME
SHOWERS. THE AIR ALOFT MODIFIES SOME THROUGH THE WEEKEND,
THEREFORE MODERATING DAYTIME TEMPERATURES SHOULD RESULT ESPECIALLY
ON SUNDAY.

FOR MONDAY AND TUESDAY...WE TRANSITION OUT OF AN OMEGA BLOCK
DURING THIS TIME FRAME, RESULTING IN WARMER TEMPERATURES. SOME
GUIDANCE HOWEVER HAS A SHORT WAVE AMPLIFYING A TROUGH ACROSS THE
NORTHEAST MONDAY BEFORE SHIFTING EAST TUESDAY AS A RIDGE
APPROACHES FROM THE WEST. IT APPEARS THAT HIGH PRESSURE BUILDS IN
WITH TIME, HOWEVER ENERGY IN THE PLAINS WILL SEND A DEVELOPING
WARM FRONT TO OUR SOUTH TOWARD OUR AREA TUESDAY. WE KEPT THE
FORECAST DRY ATTM WITH MUCH WARMER AIR BUILDING INTO THE AREA.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

TODAY...GENERALLY IFR CIGS WITH PATCHY 2-5 MI IN PERIODS OF
SHOWERS. TIMING OF THE RAIN MAINLY LATE MORNING TO MID AFTERNOON.
ISOLATED THUNDER NOT IMPOSSIBLE PER NAM/GFS INSTABILITY ALOFT,
MAINLY DELMARVA OR SE PA/S NJ. NE WIND WITH A FEW GUSTS 15-20 KT
VCNTY KPHL/KACY.

TONIGHT...GENERALLY IFR CIGS WITH PATCHY 2-5 MI IN SCT SHOWERS
DIMINISHING OR ENDING-EXITING NEWD EARLY/PATCHY DRIZZLE-FOG IN THE
WAKE OF THE NEWD SHOWER DEPARTURE. POSSIBLE LIFR CIGS. NE WIND G
15-20 KT POSSIBLE KPHL- KTTN- KACY.

OUTLOOK...
THURSDAY AND FRIDAY...MVFR/IFR CEILINGS PERSIST WITH AN ONSHORE
FLOW AND WEAK LOW PRESSURE NEAR THE COAST. TIMES OF SHOWERS ARE
EXPECTED AS WELL WITH THE MOST WIDESPREAD ACTIVITY OCCURRING ON
FRIDAY. NORTHEAST WINDS MAINLY IN THE 10-15 KNOT RANGE /LESS AT
NIGHT/ WITH THE HIGHER SPEEDS MAINLY CLOSER TO THE COAST.

SATURDAY AND SUNDAY...MVFR/IFR CEILINGS POSSIBLE TO START
SATURDAY, THEN IMPROVEMENTS TO VFR SHOULD OCCUR. SOME SHOWERS ARE
POSSIBLE AS ONE SYSTEM DEPARTS ON SATURDAY, THEN A COLD FRONT
MOVES THROUGH MAINLY SUNDAY MORNING. THE WINDS SHIFT TO THE
NORTHWEST SATURDAY THEN LIGHT SOUTHWEST AT NIGHT, BEFORE SHIFTING
TO THE NORTHWEST AND INCREASING TO 10-15 KNOTS DURING SUNDAY.

&&

.MARINE...
SCA WITH WIND NNJ AND SCA SNJ.

DID NOT ATTM ADD SCA FOR DE COAST SINCE 44009 ON THE OUTER EDGE
OF 455 IS MARGINALLY 5 FT. HOWEVER, AM NOW ANTICIPATING WE`LL NEED
AN SCA IN THE DE ATLC WATERS FOR LATER TONIGHT.

SST`S ARE NEAR OR SLIGHTLY ABOVE NORMAL.

OUTLOOK...
THURSDAY AND FRIDAY...A PERSISTENT ONSHORE FLOW WILL INCREASE FOR
A TIME THURSDAY AS ONE LOW PRESSURE SYSTEM TO OUR SOUTH TRACKS
NORTHEASTWARD. THIS SHOULD RESULT IN WIND GUSTS TO AROUND 25 KNOTS
MAINLY ACROSS THE NORTHERN ATLANTIC COASTAL WATERS THURSDAY. A
SECONDARY LOW PRESSURE SYSTEM ARRIVES DURING FRIDAY WITH A
POSSIBLE 25-30 KNOT NORTHEASTERLY SURGE ACROSS OUR NORTHERN
ATLANTIC COASTAL WATERS. THIS WILL DEPEND ON THE STRENGTH OF AN
EASTERLY LOW-LEVEL JET THAT LIFTS NORTHWARD FRIDAY. THE SEAS ARE
FORECAST TO BE 4-6 FEET MOSTLY FOR THE NEW JERSEY ATLANTIC COASTAL
WATERS, AND THE SMALL CRAFT ADVISORY WAS EXTENDED THROUGH 22Z
THURSDAY. THIS WILL LIKELY NEED TO BE EXTENDED AGAIN, AND SEAS MAY
BUILD TO 5 FEET FARTHER SOUTH THROUGH FRIDAY AND THEREFORE THE
ADVISORY MAY NEED TO BE EXPANDED SOUTHWARD.

SATURDAY AND SUNDAY...A COLD FRONT ARRIVES SUNDAY MORNING WITH
THE WINDS TURNING SOUTHWEST AHEAD OF IT LATE SATURDAY THEN
SHIFTING TO THE NORTHWEST ON SUNDAY. THE WINDS ARE FORECAST TO
INCREASE SUNDAY BEHIND THE FRONTAL PASSAGE, HOWEVER IT APPEARS
THAT SPEEDS ARE BELOW ADVISORY CRITERIA. THE SEAS SHOULD ALSO BE
DROPPING BELOW 5 FEET WITH SOME HELP ON SUNDAY DUE TO THE FLOW
INCREASING FROM OFFSHORE.

&&

.TIDES/COASTAL FLOODING...
CF ADVISORY ISSUED. GUIDANCE SUGGESTIONS OF INCREASED POSITIVE
DEPARTURES COMBINED WITH INCREASING ASTRONOMICAL EVENING TIDES,
LOWERING PRESSURE AND AN INCREASING ONSHORE WIND FAVORED AN
ADVISORY ISSUANCE. IT WILL BE MARGINAL...PROBABLY PLUS OR MINUS .2
FT FROM THRESHOLD.

THIS MORNINGS HIGH TIDE, ESPECIALLY NEAR LEWES WAS .3FT HIGHER
THAN LAST EVENINGS. THAT UPWARD DEPARTURE TREND SHOULD CONTINUE
THE NEXT SEVERAL CYCLES.

THE LONG DURATION NORTHEASTERLY FETCH COMBINED WITH A DAILY
INCREASE IN ASTRONOMICAL TIDES AS WE APPROACH THE NEW MOON FRIDAY
WILL RESULT IN PERIODS OF MINOR EVENING COASTAL FLOODING.

ALL AVAILABLE GUIDANCE SUGGESTS THERE COULD/SHOULD BE SOME MINOR
TIDAL FLOODING AROUND THE TIMES OF HIGH TIDE THIS EVENING,
THURSDAY EVENING, AND MORE LIKELY FRIDAY EVENING.

FOR NOW, ISSUED A COASTAL FLOOD ADVISORY FOR THE NJ/DE COASTS AND
DELAWARE BAY FOR THIS EVENINGS HIGH TIDE.

THERE IS ALSO A SLIGHT CHANCE OF REACHING A MODERATE THRESHOLD
FRIDAY EVENING, BUT CONFIDENCE IS LOW.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...COASTAL FLOOD ADVISORY FROM 5 PM THIS AFTERNOON TO 11 PM EDT
     THIS EVENING FOR NJZ012>014-020>027.
DE...COASTAL FLOOD ADVISORY FROM 5 PM THIS AFTERNOON TO 11 PM EDT
     THIS EVENING FOR DEZ002>004.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 PM EDT
     THURSDAY FOR ANZ452-453.
     SMALL CRAFT ADVISORY UNTIL 6 PM EDT THURSDAY FOR ANZ450-451.

&&

$$

SYNOPSIS...GORSE
NEAR TERM...DRAG/IOVINO
SHORT TERM...DRAG
LONG TERM...GORSE
AVIATION...DRAG/GORSE
MARINE...DRAG/GORSE
TIDES/COASTAL FLOODING...STAFF



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