National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 280801
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
401 AM EDT Sun May 28 2017

.SYNOPSIS...
-- Changed Discussion --
A weak area of high pressure will shift east of the New England
coast this morning, keeping a warm front to our south and west today
into tonight. A stronger low pressure system will move into
southeastern Canada Monday, bringing a cold front through our area.
A couple of cold fronts will then move through our region through
about midweek, before high pressure builds toward our area Thursday
and Friday. A weak cold front however may settle across our area
Friday night and Saturday.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
High pressure located off the New England coast early this morning
will progress northeastward today. Meanwhile, a frontal boundary
will extend from the Ohio River Valley and the Great Lakes
southeastward to the waters off Virginia and North Carolina.

The sky was mostly cloudy over the Poconos and far northern New
Jersey, and over northeastern Maryland, Delaware and southern New
Jersey around 3:30 AM. The sky was mainly clear over areas between
the two. Where there is little cloud cover, we continue to
anticipate the development of some stratus and fog early this
morning.

An onshore flow is expected to develop for today. Additional clouds
will overspread our region from the west. It appears as though the
daylight hours will be mainly rain-free with conditions remaining
fairly stable. We may see some showers begin to spread into eastern
Pennsylvania and the upper Delmarva from the west early this evening.

High temperatures are expected to range from the upper 60s to the
middle 70s. Readings should get no higher than the middle 60s right
along the coast due to the onshore flow.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
-- Changed Discussion --
A mid level trough over the central part of the country early this
morning will work its way eastward. Showers and thunderstorms will
develop ahead of the feature and they should move into our region
from the west tonight. As a result, we will carry categorical or
likely probabilities of precipitation for much of our forecast area.
Generally, rainfall amounts should favor the quarter to half inch
range.

The continued onshore flow and the precipitation are anticipated to
result in the development of low clouds over much of our region for
tonight.

Low temperatures should favor the upper 50s and lower 60s.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
-- Changed Discussion --
Summary...Remaining shower/thunder chances through the first half of
this upcoming week. Temperatures overall on the mild/warm side.

Synoptic Setup...A closed low initially centered near the upper
Great Lakes will slowly shift eastward through much of this upcoming
week. While the core of this feature is forecast to remain well to
our northwest and north, spokes of energy will rotate around the
parent closed low. A potentially stronger short wave is forecast to
shift eastward Wednesday, which is tied to a cold front. This short
wave may sharpen the southern extent of the long wave trough some,
potentially enhancing a ribbon of lift. As we go toward the end of
the week and to start next weekend, the closed low shifts closer to
the Canadian Maritimes and perhaps weakens some. Additional short
waves on the western and southern side may amplify the trough across
the Northeast Friday into Saturday before the entire system shifts
more eastward. This all results in a few episodes of possible
showers/thunder, although exact timing and coverage is less certain.
We used a model/continuity blend for Monday through Tuesday night,
then blended in the 00z WPC Guidance thereafter. Some adjustments
were then made following additional collaboration with our
neighboring offices.

For Monday and Tuesday...The center of a closed low is forecast to
move to a position between the Great Lakes and James Bay Canada. A
stronger short wave is forecast to be lifting across the Northeast
Monday, with a narrow trough axis possibly taking on some negative
tilt. This will produce a ribbon of enhanced forcing, resulting in a
band of showers and perhaps thunder. This looks to quickly lift to
our north and east during the morning. A weakening cold front then
moves through during Monday, however there may not be much in the
way of forcing once the earlier morning band of showers clears the
area. The forecast soundings overall indicate the column dries out
in the afternoon especially for the central and southern areas. As a
result, PoPs were lowered faster but still kept in some low PoPs in
through the day. Another cold front or surface trough arrives during
Tuesday, and with short wave energy accompanying it a band or two of
showers will be possible. There could be just enough instability to
allow for some thunder Tuesday afternoon. Daytime temperatures are
expected to be mild/warm, however the far north and northeast areas
on Monday may be cooler depending on the amount of clearing.

For Wednesday and Thursday...As the center of the closed low slowly
shifts across southeastern Canada, a stronger embedded short wave
allows for the southern part of the long wave trough to amplify
across the Northeast Wednesday. This should be reflected by another
cold front at the surface. While some instability is forecast to
develop during Wednesday, soundings generally show it being meager
with any convection being low-topped. If the boundary layer warms
more, low-level lapse rates would steepen and result in a bit more
instability. Therefore, a thunder mention was expanded south and
eastward some in the afternoon. The challenge is how much coverage
occurs with showers/thunder Wednesday. Some guidance suggest
coverage could be fairly widespread in the afternoon. For now, kept
mostly chance PoPs with the idea there will be at least scattered
activity around. The flow aloft may start to turn more zonal
Thursday allowing for a dry day, however more short wave energy
diving into the base of the closed low looks to start another
eastbound amplification.

For Friday and Saturday...The details of the forecast during this
time frame mostly depend on the speed of the closed low to our
north. While it will gradually shift eastward and probably
eventually weaken, some guidance shows more amplification as strong
short wave energy slides across the southern portion of the trough.
This sends another cold front our way, which may be mostly just to
our north. The evolution of the energy and therefore chances for
convection is less certain. The entire system eventually shifts
closer to the Canadian Maritimes with less influence on our region.
As of now, kept slight chance PoPs for Friday and dry on
Saturday.
-- End Changed Discussion --

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Variable conditions are expected through 1300Z. Ceiling and
visibility values should favor VFR. However, areas of MVFR and
possibly IFR conditions are possible, especially around KRDG, KABE
and KTTN.

VFR conditions are anticipated from about 1300Z until 0000Z although
there should be a fair amount of cloud cover for much of the day.

Ceilings are expected to lower into the IFR range for tonight with
the arrival of showers and scattered thunderstorms from the west,
along with an onshore wind flow. The timing and coverage of
thunderstorms for tonight remains a bit uncertain so we have
mentioned only showers in the TAF at this time.

A light and variable wind early this morning should settle into the
southeast today at 5 to 10 knots. The wind direction is forecast to
back toward the east tonight.

OUTLOOK...
Monday...MVFR/IFR conditions with some showers and thunderstorms
mainly in the morning, then improving in the afternoon and at night
as a cold front moves through. Some fog or low clouds are possible
late at night.

Tuesday and Wednesday...Some possible fog or low clouds to start
Tuesday, otherwise generally VFR through Wednesday. Some showers and
thunderstorms possible mainly each afternoon and evening, however
timing and coverage is less certain.

Thursday...VFR is anticipated with dry conditions.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
As high pressure moves away to our northeast today, a southeast to
east wind is forecast to increase to 10 to 15 knots. Wind speeds may
rise into the 15 to 20 knot range for tonight, especially on the
waters off New Jersey.

Wave heights of 2 to 3 feet on our ocean waters today should build
to 3 to 4 feet tonight. It appears as though they may reach 5 feet
on our coastal waters from north of Atlantic City to Sandy Hook. We
have placed those areas under a Small Craft Advisory beginning at
midnight.

RIP CURRENTS...
Waves off the coast are forecast to be in the 2 to 3 foot range for
today. An southeast to east wind is expected around 10 knots or so.
It appears as though the risk for the development of dangerous rip
current will be low for much of the day. However, it may begin to
approach moderate toward evening as wind speeds increase
gradually.

The outlook for Monday is a low risk for the development of
dangerous rip currents, as winds should become about 10 knots or
less mainly from the southeast and south and waves lower some.

OUTLOOK...
Monday through Thursday...East to southeast winds are forecast to be
strongest (gusts near 25 knots) Monday morning across the northern
ocean zones before diminishing. This should maintain seas to about 5
feet at least in the morning before subsiding. Therefore, a Small
Craft Advisory has been issued for our three northern ocean zones
through 16z Monday. Otherwise, generally sub-advisory conditions are
expected through Thursday.

Some showers and thunderstorms are expected, mainly Monday morning
and again Tuesday and Wednesday afternoons.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
-- Changed Discussion --
The development of an onshore flow for today into tonight and the
continued high astronomical tides should result in another round of
minor coastal flooding tonight. As a result, we will issue another
Coastal Flood Advisory for tonight`s high tide. It will cover the
coastal counties of New Jersey and Delaware, as well as the counties
along Delaware Bay and the lower Delaware River up to the area just
below the Commodore Barry Bridge.

Based on the guidance and on the fact that the astronomical tides
are decreasing as we move away from the new moon, tonight`s Coastal
Flood Advisory should be the last one for a while.
-- End Changed Discussion --

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
PA...None.
NJ...Coastal Flood Advisory from 9 PM this evening to 3 AM EDT
     Monday for NJZ012>014-020>027.
     Coastal Flood Advisory from midnight tonight to 4 AM EDT
     Monday for NJZ016.
DE...Coastal Flood Advisory from 9 PM this evening to 3 AM EDT
     Monday for DEZ002>004.
     Coastal Flood Advisory from midnight tonight to 4 AM EDT
     Monday for DEZ001.
MD...None.
MARINE...Small Craft Advisory from midnight tonight to noon EDT Monday
     for ANZ450>452.
-- End Changed Discussion --

&&

$$
Synopsis...Gorse
Near Term...Iovino
Short Term...Iovino
Long Term...Gorse
Aviation...Gorse/Iovino
Marine...Gorse/Iovino
Tides/Coastal Flooding...Iovino