Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 040905
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
505 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/...
EARLY TODAY...SHOWERS AS PER 455 AM RADAR...MOSTLY ALONG AND NW
OF I95 WITH A LOBE SWD ALONG THE S NJ AND DE COASTS.

AFTER SUNRISE...PERIODS OF SHOWERY RAINS AND DRIZZLE, ESPECIALLY
I-95 CORRIDOR WESTWARD. (THERE MAY BE A SEVERAL HOUR BREAK IN THE
SHOWERS THIS MORNING BUT NOT MAKING A MOVE ON THAT TIL 6 AM AT THE
EARLIEST...ALREADY MORE SHOWERS DEVELOPING NEWD FROM E VA INTO THE
DELMARVA).

ISOLATED THUNDER POSSIBLE DELMARVA OR EVEN SE PA OR S NJ IN
RESPONSE TO A POCKET OF INSTABILITY ALOFT ASSOCIATED WITH A KI
POOL 30+ AND TT NEAR 52 AS WELL AS A WEAK 850MB TROUGH. QPF IS
THAT FROM WPC. SHOULD BE SMALL POCKETS OF EMBEDDED .25 TO .5
INCHES TODAY, SINCE PWAT INCREASES TO ABOUT 1 INCH.

MAY ADD "HEAVY" WORDING TO NNJ IN THE 630 AM UPDATE? MAY ALSO ADD
THUNDER TO THE FCST IN THE 630 AM ISSUANCE.. S NJ AND DE AS WELL
AS COASTS. STILL UNCERTAIN ON WHETHER TO ADD.

NE WIND GUSTY 15-20 MPH THIS AFTERNOON I-95 CORRIDOR EASTWARD IN
CYCLONIC FLOW WITH A GRADUALLY INCREASING PRESSURE GRADIENT.

FOG...MAINLY IN THE HIGH TERRAIN...POCONOS/KITTATINNYS.

50 50 BLENDED 00Z/4 GFS/NAM MOS...FAVORING THE COLDER SIDE AS WE
DRAW FROM THE COOLER WET BULB RESERVOIR OVER SOUTHERN NEW ENGLAND.

&&

.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 /09Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

EARLY TODAY...GENERALLY IFR CIGS WITH PATCHY 2 TO 5 MI FOG. SHOWERS
AND DRIZZLE, ESPECIALLY KRDG/KABE/KILG/KPNE/KTTN WHICH WILL
RESULT IN PATCHY LIFR CONDITIONS. LIGHT NE WIND.

TODAY AFTER 12Z...GENERALLY IFR CIGS WITH PATCHY 2-5 MI IN NUMEROUS
SHOWERS/ PATCHY DRIZZLE-FOG. TIMING OF THE RAIN/DRIZZLE LESS THAN
CERTAIN.  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. MAY NEED TO ADD SCA FOR THE DE
COAST PER RECENT UPTICK IN SEAS TO NEAR 5 FT.

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.

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.

&&

.RIP CURRENTS...
WE WILL BE TESTING THE SRF THIS MORNING FOR AN HOUR AROUND 630A
TO ENSURE CORRECT POSTING OF THE SRF PRODUCT FOR ITS MAY 20 530 AM
START UP.

HERE`S A SHORT USEFUL REVIEW OF RIP CURRENT SCIENCE PRODUCED BY A
PARTNERSHIP OF NWS AND OCEANS TODAY.

HTTP://OCEANTODAY.NOAA.GOV/RIPCURRENTSCIENCE/

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...COASTAL FLOOD ADVISORY FROM 6 PM TO 11 PM EDT THIS EVENING FOR
     NJZ012>014-020>027.
DE...COASTAL FLOOD ADVISORY FROM 6 PM TO 11 PM EDT THIS EVENING FOR
     DEZ002>004.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 9 AM THIS MORNING
     TO 6 PM EDT THURSDAY FOR ANZ452-453.
     SMALL CRAFT ADVISORY FROM 9 AM THIS MORNING TO 6 PM EDT
     THURSDAY FOR ANZ450-451.

&&

$$
SYNOPSIS...GORSE
NEAR TERM...DRAG  505
SHORT TERM...DRAG 505
LONG TERM...GORSE
AVIATION...DRAG/GORSE 505
MARINE...DRAG/GORSE 505
TIDES/COASTAL FLOODING...505


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