Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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663
FXUS61 KPHI 220248
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1048 PM EDT SAT MAY 21 2016

.SYNOPSIS...
Low pressure off the Virginia coast will lift northeast of our
region through the day Sunday. However, a second offshore low is
expected to develop by Monday, before lifting away from the region
on Tuesday. A ridge will build over our region mid week. By Friday,
the ridge is expected to shift east as another low begins to slide
over the Great Plains.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Surface low pressure located off the Delmarva coast this evening
will continue to move northeastward through tonight. A mid/upper
trough to our west will continue to send several vorticity
impulses across the area tonight as well. One is moving through
early this evening which has led to an increase in some moderate
to at times heavy rainfall from the I-95/295 corridor
north and westward. We`ve increased pops significantly in this
area through the evening hours, then lower them through the night
as precipitation may become more showery overnight. Also added
drizzle and fog across southern portions of New Jersey, as well as
the Delmarva.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
The upper level low pressure system that will be to our northwest
will drop southward on Sunday. The 12z GFS/CMC/UKMET are a bit
further west than the 12Z ECMWF with this feature. With this
forecast package, we opted to go with a slightly more west track of
the low. This could potentially keep the highest coverage of showers
across Eastern Pennsylvania throughout the day. The areal coverage of
showers looks to be of a diurnal nature as low level lapse rates
steepen (instability mechanism) to increase the coverage by the
afternoon. Rainfall amounts are going to be light but a continued
low freezing level around 10,000 feet may result in a few showers
containing pea size hail in the afternoon hours. Coverage of
hail looks to low to place in forecast attm.

The track of the low will also effect the high temperatures. A
further east and cloudier ECMWF keeps highs down in the low and mid
60`s for most. On the other hand, A further west low track would
allow for breaks of sunshine and a chance at 70 degrees for Delaware
and New Jersey.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Monday through Tuesday...As the upper level short wave trough digs
and intensifies over the Mid Atlantic, a surface low will
subsequently develop off the coast of VA/NC. As a result, expect the
work week to begin with much of the same weather pattern we`re
seeing this weekend. Northeasterly flow will temper max temperatures
a bit, staying slightly below normal. However, thanks to air mass
modification, we should see a modest warming trend into Tuesday and
highs may be near normals. The moisture advection, thanks to
persistent onshore flow, and synoptic scale lift thanks to the upper
level low will result in continued rain chances. How quickly we dry
out will be dependent on how quickly the low lifts out of the
region. On this point, there are some slight differences between the
models with the GFS being a bit slower to clear everything out.
Would expect the bulk of the precipitation to be done by mid day
Tuesday as the flow turns more northwesterly, but a few showers
could linger into Tuesday evening.

Wednesday and Thursday...Upper level ridge shifts east, with the
ridge axis over our region by Thursday morning, bringing a lull in
rain chances and a very noticeable warming trend, with 80s expected
across much of the region both days.

Friday and Saturday...ridge shifts further east offshore through
this time, leaving our region on the periphery of the ridge. As
such, could see primarily afternoon and evening showers and
thunderstorms as shortwave troughs embedded in the upper level SW
flow slide over the region.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Tonight: Conditions vary from VFR across the north at ABE and RDG,
to IFR at ILG/MIV/PHL, and MVFR at ACY/PNE/TTN. We expect IFR
conditions to develop for all sites through this evening and
overnight, except for ABE/RDG where we expect MVFR conditions to
develop. An area of moderate to heavy rain is moving across
eastern Pennsylvania and northern New Jersey this evening, then
we expect more showery conditions through the night. Generally
north to northeast winds 5-10 knots, with some gusts 15-20 knots
possible from PHL south and eastward.

Sunday: Ceilings will start off IFR/MVFR in the morning, and begin
lifting from north to south, and may eventually lift to VFR by
the afternoon. Scattered showers could continue occur through the
day. North to northeast winds will start the day, becoming
northwest for ILG/PHL and points westward. Winds are expected to
become southeast for TTN and points south and east.

Outlook...

Monday and Tuesday...Occasional MVFR conditions possible with
showers and fog especially Monday night.

Wednesday and Thursday...VFR conditions likely. Small chance of MVFR
conditions with showers and thunderstorms Thursday afternoon and
evening.

&&

.MARINE...
We`ve extended the Small Craft Advisory on the Delaware Bay
through 2 am as winds look to remain gusty around 25 knots for
a few more hours. The Small Craft Advisory will continue for the
Atlantic coastal waters with no change with building seas expected
and gusts around 25-30 knots, especially across the southern half
of the waters.

Sunday: Winds will be more northerly and lighter. However wave
heights will still run from five to eight feet. SCA in effect.

RIP CURRENTS...Moderate risk for rip currents is expected for
Sunday. Northeast winds will be lighter than Saturday, but a
higher swell height will likely lead to moderate risk for the
formation of dangerous rip currents.

Outlook...

Sunday night into Monday...Seas are expected through this
period and could be at or above 5 feet as early as Monday morning
(especially on the southern coastal waters).

Monday night...SCA conditions are likely on the coastal waters,
primarily for seas above 5 feet, though gusts near or above 20 kt
are possible.

Tuesday...seas should slowly subside, though SCA conditions may
linger through much of the day.

Tuesday night through Thursday...winds and seas should stay below
SCA criteria.

&&

.TIDES/COASTAL FLOODING...
With the full moon today (Saturday), and on shore flow developing
later today and persisting through at least Sunday morning, tide
levels should be higher than normal on the Atlantic oceanfront and
the Delaware Bay. However, we expect water levels to fall short of
minor flooding thresholds at this point. The highest water levels
are expected with the high tide cycles on Sunday and Monday evening.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ452>455.
     Small Craft Advisory until 6 AM EDT Monday for ANZ450-451.
     Small Craft Advisory until 2 AM EDT Sunday for ANZ430-431.

&&

$$
Synopsis...Johnson
Near Term...Gaines/Robertson
Short Term...Gaines
Long Term...Johnson
Aviation...Gaines/Johnson/Robertson
Marine...Drag/Gaines/Johnson/Robertson
Tides/Coastal Flooding...



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