Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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136
FXUS61 KPHI 232000
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
400 PM EDT Tue May 23 2017

.SYNOPSIS...
A couple of areas of low pressure will pass to our south this
evening then east of our area overnight into Wednesday as they
combine and move along a frontal boundary. As an area of low
pressure moves into the Ohio Valley Wednesday night into Thursday,
an occluded front and warm front will lift toward our region. A
triple point low will develop and take over as the dominant low as
it moves across our area Thursday night. This low will move away
from the area Friday, with a weak frontal boundary or surface trough
crossing the area during the day. Weak high pressure may briefly
move across the area Friday night into early Saturday. Another
frontal system is expected to affect the area Saturday night into
Sunday, followed by another on Monday and Tuesday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
An email briefing with a coastal flood graphic will post by 315 PM
this afternoon. It highlights tidal inundation flood potential
for the Wed-Thu evening high tide cycles on the Atlantic coasts
of DE and NJ. The next briefing of either a full scale package
or email will post around 3 PM Wednesday, incorporating not
only the minor to possibly moderate coastal flood threat and
associated products but also a possible QLCS event for se PA/
the Delmarva/s NJ late Thursday.

Isolated showers may be drying into sprinkles as this is written
near and sw of PHL. Otherwise sprinkles were flirting with s DE
At 345PM. HRRR was too emphatic about this northern extension
of the showers this aftn into PHL.

Tonight: Low pressure off the mid Atlantic coast will continue
to slide northeast, with showers along the coasts but chancey
for e PA/nNJ late tonight. northeast wind. Confidence on the
extent of showers is below average, since models are offering a
wide variety of solutions.

This forecast was based on a 50 50 blend of the 12z/23 GFS/NAM.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Wednesday...scattered leftover showers possible in the morning
but it should dry out and be a decent afternoon everywhere.
Northeast wind becomes southeast in the afternoon.

This forecast was based on a 50 50 blend of the 12z/23 GFS/NAM.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
An unsettled weather pattern continues for much of the extended
forecast with several periods of rain possible.

On Wednesday night, an area of low pressure will be lifting
through the Ohio Valley and toward the southern Great Lakes region.
Meanwhile, an occluded front and warm front will be lifting toward
our area. A triple point low is forecast to develop to our
southwest overnight, which will likely slow down the northward
progression of the frontal boundaries. This will lead to an area
of rainfall overrunning the frontal boundary and lifting across
out area overnight Wednesday into Thursday morning. As the
short wave/vorticity impulse that helps create this area of
rainfall lifts north of the area, this area of rainfall will
move north as well early in the day. Then the question for the
afternoon becomes how far north the warm front progresses as
the triple point low approaches from the west. Another period of
rainfall is expected during the afternoon and evening, but
depending on how far north the front lifts, there could be a
chance of thunderstorms to develop later in the day for a
portion of the area. The best chance for this to happen would be
for portions of Delaware and the eastern shore of Maryland, as
well as far southern New Jersey. The rest of the area would
likely be stable enough to prevent thunderstorms, and just
receive rain.

By Thursday night, the triple point low will begin moving across the
area, pulling the occluded frontal system across the area as well.
This will lead to continuing scattered showers during the night
Thursday. On Friday, the low will continue to move to our northeast
and offshore of New England. A weak frontal boundary or surface
trough New England is forecast to move across the area during the
day. This could lead to another chance of scattered showers during
the afternoon.

Friday night through most of Saturday is expected to be dry as weak
high pressure quickly moves across the area. However, a warm front
will begin approaching the area from the south late in the day and
into the overnight hours as an area of low pressure lifts into the
Great Lakes region. As the low continues to lift through the Great
Lakes region Sunday, the warm front may lift across the area before
a triple point low forms and moves across the area as well. The
exact timing of these features is still a little uncertain, but
Saturday night through Sunday looks like there should be several
periods of showers, and possible thunderstorms if enough instability
builds on Sunday.

The low pressure system that moves across the Great Lakes over the
weekend is forecast to remain nearly stationary across south-central
Canada Monday into Tuesday. This may send a couple of frontal
boundaries across the area Monday and Tuesday, leading to additional
showers or thunderstorms early next week.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Through tonight...VFR lowering CIGS with potential MVFR Conds
in showers KACY/KMIV late at night while any period of showers
elsewhere should not lower conditions to MVFR. Northeast wind,
may gust 20 kt ACY.

Wednesday...VFR cigs inn the morning and then sct-bkn aoa 4000
ft in the aftn. MVFR/IFR conditions possible early in the day,
mainly at KMIV/KACY. northeast wind become southeast in the
afternoon. max gusts 15 kt.

Outlook...

Wednesday night-Thursday...Conditions lowering to IFR overnight and
continuing into Thursday as periods of rain affect the area late
Wednesday night into Thursday. Improvement to VFR possible for
southern areas later in the day.

Thursday night...MVFR to IFR conditions possible with low clouds and
fog/drizzle possible.

Friday-Friday night...Improving to VFR during the day and into the
night, scattered showers possible during the daytime. Gusty
northwest winds 20-25 knots.

Saturday...Generally VFR. Showers moving into the area later in the
day, which will lead to lowering ceilings.

Saturday night-Sunday...MVFR to IFR conditions possible with periods
of low clouds and rain. Thunderstorms possible Sunday. An
improvement to VFR possible Sunday outside of
showers/thunderstorms.

&&

.MARINE...
SCA continues DE Atlc waters late tonight and now extended
through the day tomorrow.

SCA added for the NJ waters, primarily there for hazardous 5 ft
seas. There is a chance the guidance might be a foot too high
but felt I had to issue since our fcst is for 4 to 6 ft.

Rip Risk for tomorrow-Wednesday. Preliminary... LOW but on the
cusp of moderate and so please refer to the 830PM forecast for
tomorrows rip risk. The reason we dont issue the tomorrow
forecast sooner... most of our rip current fatalities occur
between 6PM and 8PM. Therefore, we want todays forecast available
to any potential victims so they have more information for decision
making.

The safest way to swim the surf zone...is in sight of life guards!!!


Outlook...

Wednesday night-Friday...Small Craft Advisory conditions
possible. Varies between wind and waves criteria each period.

Friday night-Sunday...Conditions expected to remain below advisory
levels.

&&

.TIDES/COASTAL FLOODING...
CFW for minor coastal flooding issued for the Wednesday evening
high tide cycle. A CF Watch may be needed for the Thursday evening
high tide cycle for Monmouth/Ocean and Middlesex counties but
that wont be issued, if at all, until sometime Wednesday.

This afternoons issuance is also appended to a blast email for
EM`s including an image with a followup Wednesday around or
shortly after 3 Pm.

Some of the highest astronomical tides of the year are occuring
late this week. The new moon cycle on Thursday, combined with a
possible prolonged easterly flow, we will probably see some of
our coastal sites exceed minor tidal flooding levels during the
Wednesday and Thursday evening tide cycles. There is also a
small chance that we could reach moderate levels in a few spots.

&&

.CLIMATE...
ACY is #6 wettest May on record with its 6.07. The record there for
May is 8.80 set in 1948....POR back to 1874.

Monthly avg temps should end up within .7 degrees of where they
are now, possibly edging on the warmer side of the current departures
as seen in our climate data ending the 22nd.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Advisory from 6 PM Wednesday to midnight EDT
     Wednesday night for NJZ012>014-020>027.
DE...Coastal Flood Advisory from 6 PM Wednesday to midnight EDT
     Wednesday night for DEZ002>004.
MD...None.
MARINE...Small Craft Advisory from 8 AM to 4 PM EDT Wednesday for
     ANZ450>453.
     Small Craft Advisory from midnight tonight to 4 PM EDT
     Wednesday for ANZ454-455.

&&

$$
Synopsis...Robertson
Near Term...Drag 359P
Short Term...Drag
Long Term...Robertson
Aviation...Drag/Robertson
Marine...Drag/Robertson 359P
Tides/Coastal Flooding...
Climate...



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