Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 030947
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
547 AM EDT TUE MAY 3 2016

.SYNOPSIS...
BROAD LOW PRESSURE CENTERED OVER DELAWARE THIS MORNING WILL
RELOCATE ALONG THE MID ATLANTIC COAST LATER TODAY. A PIECE OF THE
LOW MAY MOVE NORTHEAST TOWARD CAPE COD LATE WEDNESDAY WHILE THE
PRIMARY LOW PRESSURE SYSTEM DEVELOPS OFF THE NEW JERSEY COAST LATER
THIS WEEK. THE LOW MOVES OUT TO SEA SATURDAY WITH A WEAK COLD
FRONTAL PASSAGE FOLLOWING SUNDAY MORNING. HIGH PRESSURE SHOULD
BECOME DOMINANT HERE EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AN UPPER-LEVEL TROUGH REMAINS WELL TO OUR WEST TODAY. THIS RESULTS
IN THE MAINTENANCE OF SOUTHWESTERLY FLOW ALOFT. A SHORT WAVE
EMBEDDED IN THE FLOW IS FORECAST TO TRANSLATE TO OUR NORTHEAST THIS
MORNING, TAKING MUCH OF THE FORCING FOR ASCENT WITH IT. AS A RESULT,
PERIODS OF RAIN WILL MOSTLY TAPER OFF LATER THIS MORNING FROM WEST
TO EAST WITH SOME SHOWERS STILL POSSIBLE THEREAFTER.

AS OF 0940Z, RADAR TRENDS HAVE THE STEADIEST RAIN ALONG AND
SOUTH/EAST OF I-95. A WEAK SURFACE LOW HOWEVER REMAINS VERY NEAR THE
AREA, KEEPING A FRONTAL ZONE TO OUR SOUTH. THIS WILL ENHANCE A LOW-
LEVEL NORTHEASTERLY FLOW KEEPING A MARINE INFLUENCE GOING. OUR AREA
REMAINS IN THE RIGHT REAR QUADRANT OF A 250 MB JET DURING MUCH OF
TODAY, THEREFORE SOME ADDITIONAL SHOWERS CANNOT BE RULED OUT THIS
AFTERNOON AS WELL. SOME THUNDER THIS AFTERNOON COULD BE CLOSE TO OUR
FAR SOUTHERN ZONES, HOWEVER THIS LOOKS TO BE MAINLY REMOVED FROM OUR
AREA AND THEREFORE DID NOT ADD IN THUNDER ATTM.

THE PRESENCE OF A LOW-LEVEL NORTHEAST FLOW OFF THE COOL OCEAN WILL
KEEP LOWER CLOUDS IN PLACE. THE FORECAST SOUNDINGS HOWEVER INDICATE
THAT DRYING ALOFT OCCURS THIS AFTERNOON. WHILE THERE IS AN INVERSION
IN PLACE, SOME BREAKS IN THE CLOUDS ARE POSSIBLE. GIVEN A RATHER
MOIST LOW-LEVEL PROFILE IN THE SOUNDINGS, OPTED TO KEEP TEMPERATURES
ON THE COOLER SIDE AND WE USED A MOS/CONTINUITY BLEND FOR THE HIGH
TEMPERATURES.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
THE AFOREMENTIONED UPPER-LEVEL TROUGH IS FORECAST TO SHARPEN SOME TO
OUR WEST DURING THE COURSE OF TONIGHT. THERE DOES NOT APPEAR TO BE A
MORE FOCUSED SHORT WAVE WITHIN THE SOUTHWESTERLY FLOW ALOFT UNTIL
TOWARD MORNING. THE 250 MB JET IS FORECAST TO MOVE RIGHT OVER OUR
AREA TONIGHT, REMOVING THE REGION FROM THE MORE FAVORABLE AREA OF
LIFT. AS A RESULT, WE KEPT POPS IN THE SLIGHT CHC TO LOW CHC RANGE
AS SOME SHOWERS CANNOT BE RULED OUT. THE IDEA OF LOW CLOUDS
CONTINUES ACROSS THE AREA GIVEN THE MARINE INFLUENCE, AND THEREFORE
SOME DRIZZLE IS POSSIBLE AS THE FORECAST SOUNDINGS INDICATE SOME MID
LEVEL DRYING IN PLACE.

WHILE SOME FOG MAY BE AROUND IT IS NOT ANTICIPATED TO BE SIGNIFICANT
AS THE STRATUS MAY LIMIT THE ACTUAL DEVELOPMENT OVERALL. THEREFORE,
OPTED TO NOT INCLUDE FOG ATTM BUT THIS WILL BE REVISITED LATER. AS
FOR THE LOW TEMPERATURES, WE USED A MOS BLEND OVERALL. TEMPERATURES
SHOULD NOT FALL A LOT GIVEN THE CLOUD COVER AND DEW POINTS GENERALLY
REMAINING UP DUE TO NEAR LOW-LEVEL SATURATION.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
CONFIDENCE IN ANY DETAILS OF THIS FORECAST FROM WEDNESDAY THROUGH
EARLY NEXT WEEK IS AVERAGE TO BELOW AVERAGE.

A VERTICALLY DEEP CLOSED LOW WILL FORM ALONG THE MID ATLANTIC COAST
LATER THIS WEEK THEN WEAKEN EASTWARD THIS COMING WEEKEND IN RESPONSE
TO INTERACTION WITH A CLOSED LOW SHORT WAVE OVER HUDSON BAY.

CALENDAR DAY AVERAGE TEMPS: ABOUT 5 DEGREES BELOW NORMAL WED-FRI,
NEAR NORMAL SAT-MON.

CONSIDERABLE CLOUDINESS WILL DOMINATE WEDNESDAY THROUGH AT LEAST
FRIDAY EVENING WITH SEVERAL PERIODS OF SHOWERS AFFECTING THE
REGION.

SHOWER/RAIN GENERATION IS BLAMED IN PART ON INSTABILITY AS THE
COLD POOL EVOLVES OVERHEAD WITH THE 500MB TEMP AT PHL -14C THIS
MORNING COOLING TO -23C FRIDAY, AND SOME OF IT ATLANTIC INFLOW AS
THE 850-700MB LOW MAY HUG THE MID ATLANTIC COAST WITH DEEP
MOISTURE JUST TO THE LEFT OF THE TRACK.

MUCH OF THE TIME FROM WEDNESDAY THROUGH FRIDAY NIGHT MAY BE RAINFREE
BUT TIMING THE PERIODIC LULLS IN RAINFALL WAS NOT CONFIDENTLY
ASSESSED THIS MORNING.

IF IT CLEARS A BIT FOR A FEW HOURS AT NIGHT, THEN FOG COULD
DEVELOP.

OVERALL, DAYTIME TEMPERATURES WILL BE COOLER THAN NORMAL AND
NIGHTTIME MINS NEAR NORMAL (NARROW DIURNALS DUE TO MOISTURE)

NEXT WEEKEND INTO EARLY NEXT WEEK...IT SHOULD BRIGHTEN AND WARM
UP TO NEAR NORMAL AS THE LOW PRESSURE SYSTEM HEADS EAST. A WEAK
COLD FRONT COULD BRING A FEW SHOWERS WITH ITS PASSAGE SUNDAY MORNING
BUT AT THIS TIME ANY RAIN OCCURRENCE DOES NOT LOOK TO BE AS PROLONGED
AS WHAT MAY OCCUR LATER THIS WORK WEEK.

&&

.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

TODAY...MVFR/IFR CEILINGS, WITH SOME IMPROVEMENT POSSIBLE THIS
AFTERNOON. THE VISIBILITY WILL TEND TO VARY BETWEEN VFR AND MVFR
MOSTLY TIED TO RAIN INTENSITY. OUR CONFIDENCE HOWEVER ON THE EXTENT
OF THE CEILING IMPROVEMENTS BY LATE THIS AFTERNOON IS ON THE LOWER
SIDE. PERIODS OF RAIN THIS MORNING, WILL THEN TAPER TO A FEW
SHOWERS. EAST TO NORTHEAST WINDS MAINLY 10 KNOTS OR LESS.

TONIGHT...MVFR TO IFR CEILINGS WITH A CONTINUED ONSHORE FLOW. A
COUPLE OF SHOWERS OR SOME DRIZZLE POSSIBLE, WITH LOCAL MVFR
VISIBILITY AT TIMES. NORTHEAST WINDS 3-6 KNOTS OVERALL.

OUTLOOK...
WEDNESDAY THROUGH FRIDAY...VARYING BETWEEN VFR CIGS AND MVFR
CONDITIONS WITH THE POTENTIAL FOR RAIN SHOWERS DURING THE PERIOD.
CONDITIONS MAY DROP TO IFR AT TIMES IN THE RAIN SHOWERS. IN A
GENERAL A NORTHEAST WIND, WHICH MAY BECOME GUSTY 15 TO 20 KT AT
TIMES,  ESPECIALLY FRIDAY.

SATURDAY...MAINLY VFR.

&&

.MARINE...
A WEAK LOW PRESSURE SYSTEM OVER THE AREA TODAY INTO TONIGHT WILL
KEEP AN ONSHORE FLOW IN PLACE. WHILE THIS MAY SOME INCREASE FOR A
TIME ESPECIALLY LATER TODAY AND TONIGHT ACROSS THE NORTHERN ATLANTIC
COASTAL WATERS, IT SHOULD REMAIN BELOW 25 KNOTS. SINCE THE FLOW IS
FORECAST TO BE WEAK ENOUGH, SEAS ARE ANTICIPATED TO BE 4 FEET OR
LESS. THEREFORE, THE CONDITIONS ARE EXPECTED TO BE BELOW SMALL CRAFT
ADVISORY CRITERIA THROUGH TONIGHT.

OUTLOOK...
WEDNESDAY THROUGH THURSDAY...WAVE HEIGHTS ON OUR OCEAN WATERS MAY
BUILD AROUND 5 FEET IN THE NORTHEASTERLY FLOW.

THURSDAY NIGHT AND FRIDAY...SCA PROBABLE IN RESPONSE TO LOW PRESSURE
ORGANIZING OFF THE NJ COAST. ATLANTIC SEAS WERE CAPPED AT 6 FEET,
1-2 FT BELOW GUIDANCE, DUE TO LOW CONFIDENCE REGARDING THE WIND
FIELDS ASSOCIATED WITH THE MID ATLANTIC COASTAL LOW.

SATURDAY...NO MARINE HEADLINES ANTICIPATED AT THIS TIME.

&&

.HYDROLOGY...
WE WILL APPRECIATE ANY UNUSUAL FLOODING REPORT FROM MARYLANDS EASTERN
SHORE AND CENTRAL-SOUTHERN DELAWARE LAST NIGHT, AS WELL AS ANY DAMAGING
WIND OR LARGE HAIL REPORTS. YOU SAW THE 50 KT AT BRANDYWINE IN
OUR LSR.

&&

.TIDES/COASTAL FLOODING...
A LONG DURATION NORTHEASTERLY FETCH IS EXPECTED TO DEVELOP OFF
OUR MID ATLANTIC COAST WEDNESDAY THROUGH FRIDAY. ASTRONOMICAL
TIDES WILL BE ON THE INCREASE AS WE APPROACH THE NEW MOON ON
FRIDAY. AS A RESULT, THERE COULD BE SOME MINOR TIDAL FLOODING
AROUND THE TIMES OF HIGH TIDE (6-7 PM EDT) ON WEDNESDAY EVENING,
THURSDAY EVENING AND MORE LIKELY FRIDAY EVENING (WITHIN 1 HOUR OF
THE HIGH TIDE NEAR 8PM), PENDING MODELS CONTINUING TO FOCUS LOW
PRESSURE DEVELOPMENT SOUTH OF LONG ISLAND LATER THIS WEEK. THE
FRIDAY EVENING HIGH TIDE CYCLE WILL ONLY NEED A SURGE OF .7 FEET
TO RAISE THE WATER LEVEL TO MINOR THRESHOLD. THERE IS EVEN A
SLIGHT CHANCE OF REACHING A MODERATE THRESHOLD FRIDAY EVENING BUT
WE CANT SAY THIS WITH CONFIDENCE SINCE ITS ALL DEPENDENT ON THE
POSITION AND STRENGTH OF THE LOW FORMING ALONG THE MID ATLANTIC
COAST.

AS A SIDE NOTE: IT IS OUR UNDERSTANDING THAT EVENTUALLY WE WILL
BEGIN REFERENCING COASTAL FLOODING WITH RESPECT TO MHHW WHICH
WILL EQUATE TO INUNDATION DEPTH WITH RESPECT TO NORMALLY DRY
GROUND. THERE WILL LIKELY BE TRAINING REFERENCES DURING THE
TRANSITION.

&&

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

&&

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



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