Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 010136
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
936 PM EDT TUE MAY 31 2016

.SYNOPSIS...
A cold front has weakened and pushed offshore today, and a secondary
backdoor front will push southward across the area tonight into
Wednesday morning. Our area will be on the southern edge of high
pressure located across eastern Canada through early Thursday. A
cold front will move across the area Friday. An area of low pressure
and associated frontal boundaries will move across the Great Lakes
region Saturday into Sunday, and across the Northeast Monday into
Tuesday, bringing unsettled weather to our area early next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
The sea breeze has slid as far west as the Delaware Valley, but
should be dissipating soon. Exactly how far west it goes will
have impacts for fog potential tonight, as east of the sea breeze,
dew points are generally in the mid to upper 60s, while west of
the see breeze, dewpoints range anywhere from the upper 50s to
lower 60s. With limited moisture advection (may even see dew
point values drop behind the back door cold front) tonight do not
expect fog to develop west of the sea breeze. Patchy fog should
develop east of the sea breeze where dewpoint depressions as of 9
PM are already less than 5 degrees in some locations. One
possible caveat is for locations, even west of the sea breeze, that
have had heavy rain over the past 3 days, if the ground remains
very wet, patchy fog could develop. Thus adjusted the grids to
have a mention of patchy fog generally along and east of the fall
line.

Lows tonight should generally be in the 60s for much of the
region, with the exception of the higher terrain of the Poconos
and NW NJ, where 50s will be possible.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
The high pressure to the north of the area Wednesday morning will
move into eastern Canada. The will place our region in the erly
flow on the south side of the high. This should provide some fair
weather for Wednesday with cooler temperatures (compared to
Tuesday). Highs will be in the upper 70s to low 80s in most areas.
Sky cover will be mostly sunny early with some clouds developing
late across the srn/wrn areas. We have included a small chc for a
shower across the Delmarva and se PA areas. Some of the
operational models show some qpf output.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Our area will continue to be on the far southern edge of an area of
high pressure that will be residing across central and eastern
Canada Wednesday night through Thursday. Mostly dry conditions are
expected, although an isolated shower could be possible overnight
Wednesday into early Thursday as a weak vorticity impulse slides
across the area and could interact with some increased moisture
within the return flow at the surface. Another vorticity impulse is
forecast to approach the area late in the day and overnight, which
could bring additional isolated showers by the afternoon. However,
there will be a greater potential for showers overnight as this
short wave/vorticity impulse moves across the area.

On Friday, we expect a cold front to move across the area from west
to east as an area of low pressure moves across eastern Canada.
there will be an increase in instability, along with PW values
reaching 1.75 inches. Therefore, we can expect scattered showers and
thunderstorms to develop ahead of and along the frontal boundary
during the day. The flow is not very strong, so any slow moving
storms could produce some high amounts. But the front should still
be fairly progressive, so no widespread flooding is expected at this
time. The front will slowly make its way offshore Friday night, so
there could still be some lingering showers and thunderstorms during
the evening and early in the night Friday. All showers should be
ending overnight.

There could be a dry period Saturday as high pressure across central
Canada tries to nose its way down across the area. It would not be
surprising if an isolated shower were to occur, but we`ll keep this
out of the forecast for now as the chances are small at this time.

Unsettled weather returns for Sunday through Monday as an area of
low pressure will be moving through the Great Lakes region and into
the northeast. A warm front should be lifting across the area late
Sunday into Sunday night, then a cold front will move across the
area late Sunday night into early Monday. A period of showers and
isolated thunderstorms should move across the area through this time
period. PW values approach 2 inches during this time, so there could
be some periods of heavy rainfall possible.

There will continue to be a chance of showers Monday night into
Tuesday as the low slowly pinwheels to our north through New
England, especially during the afternoon Tuesday as a secondary
surface trough/frontal boundary crosses the area.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

For KPHL, KPNE, KTTN, and KILG...The sea breeze has made it to
KPHL, KTTN, and KPNE, though KILG still remains west of the sea
breeze. Will continue to monitor the dew points through 06z, but
will continue with the forecast of patchy fog reducing
visibilities to generally the MVFR range, with the highest risk
between 08 and 11Z. Tomorrow, winds will be shifting out of the
East and East Southeast by late morning, but VFR conditions are
expected through the day.

For KABE and KRDG...VFR conditions should continue through the TAF
period. Earlier concerns about fog development have decreased as
dew point temperatures are in the 50s and are not expected to
recover much overnight. Winds will be light and variable
overnight, but eventually settling in out of the east and
southeast by late tomorrow morning.

For KMIV and KACY...VFR conditions will continue through at least
03z. After that, expect fog to begin to develop on the coastal
plains. Visibilities are expected to drop into the IFR range
before 12Z, but confidence is low as to when this will happen or
how long it will last. Visibilities should begin to improve after
sunrise. Winds will be light and variable overnight, but should
settle out of the east and southeast by 18Z.

OUTLOOK...

Wednesday night-Thursday...Generally VFR inland. Lower clouds
and/or fog possible near the coast may push inland. Mostly light
east to southeast flow.

Thursday night...MVFR ceilings may develop across the area, with
showers possibly developing from west to east.

Friday-Friday night...MVFR and/or IFR ceilings possible. Showers
and thunderstorms possible, especially later in the day. Improving
conditions later in the evening and overnight.

Saturday...Generally VFR.

Saturday night-Sunday...Diminishing conditions, possible becoming
IFR by Sunday morning. Rainfall becoming more widespread Sunday.
Gusty southeast winds possible Sunday.

&&

.MARINE...
Patchy fog is expected to develop later tonight, but confidence is
low on how low the visibilities will be. So for now, will continue
to monitor, but have not issued a dense fog advisory.

Winds and seas are expected to remain below small craft advisory
conditions tonight and tomorrow.

OUTLOOK...

Wednesday-Sunday...Conditions forecast to be below Small Craft
Advisory levels through the period. Winds could gust around 20
knots at times. Generally east to southeasterly winds, except
west to northwest briefly behind frontal boundary passage Friday
night.

&&

.TIDES/COASTAL FLOODING...
Onshore flow is expected to develop on Wednesday and continue
into Friday. We will need to monitor the possibility of minor
tidal flooding at times of high tide along the coast late this
week owing to the persistent onshore flow and the approaching new
moon this Saturday.

&&

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

&&

$$
Synopsis...Robertson
Near Term...Johnson
Short Term...O`Hara
Long Term...Robertson
Aviation...Johnson/Robertson
Marine...Johnson/Robertson/O`Hara
Tides/Coastal Flooding...



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