Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KPHI 270751
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
351 AM EDT Sat May 27 2017

.SYNOPSIS...
As a front remains draped to our south today and tonight, weak low
pressure will track along it and exit off the Mid Atlantic coast
tonight into Sunday. Another low pressure system is forecast to
consolidate just north of the Great Lakes Monday and then gradually
shift eastward through Wednesday. An associated cold front moves
through our area later Monday, then a secondary cold front arrives
during Tuesday. High pressure builds from the Midwest to the
Carolinas Wednesday and Thursday, then closer to our area
Friday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A mid level short wave located over Lake Erie and vicinity early
this morning will progress east southeastward and it is forecast to
pass over our region during the late afternoon and early evening
hours. We are anticipating an increase in cloud cover this morning
in advance of the system.

The short wave was producing a fair amount of shower activity in
Ohio early this morning along with isolated thunder. The
precipitation is expected to diminish a bit this morning as it moves
to the east southeast. The showers may become reinvigorated this
afternoon as they encounter marginal instability to the southwest of
our forecast area.

We are anticipating only isolated to scattered rain showers in
eastern Pennsylvania and New Jersey for this afternoon. There
appears to be a better chance for scattered showers and
thunderstorms in northeastern Maryland and Delaware.

A light west wind is expected for this morning. The direction should
become variable in the afternoon. Highs should be within a couple
degrees of normal for today, ranging from the upper 60s in the
elevated terrain to the middle 70s on the coastal plain. Maximum
temperatures are forecast to be in the middle and upper 60s right
along the coast.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
Lingering showers and thunderstorms are possible on the upper
Delmarva this evening, then we are not expecting any additional
precipitation overnight. Partial clearing is anticipated, mainly
over eastern Pennsylvania, and northern and central New Jersey.

Another mid level short wave trough is expected to move from the
Ozarks vicinity this morning to North Carolina late tonight. A weak
surface low associated with the mid level trough is forecast to pass
off the coast between the Virginia Capes and Cape Hatteras late
tonight. It is not anticipated to have much impact on our region.

The wind should be light tonight, with its direction favoring
southeast to northeast. Lows are expected to be mainly in the 50s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Summary...Unsettled at times through early next week. After a cooler
Sunday especially closer to the coast, warmer temperatures (close to
where they should be this time of year) are expected next week.

Synoptic Setup...While a weak ridge slides across the Northeast
Sunday, a closed low in south-central Canada is forecast to amplify
south and eastward through the middle of next week before weakening
some Thursday and Friday. It is forecast to remain centered well to
our north, however cyclonic flow will be in place along with several
short waves revolving around it. This will drive a couple of fronts
eastward. The exact timing of the embedded features are less certain
given an amplified pattern with a closed low involved, however a
model consensus now indicates that Sunday is drier than Monday. We
used a model/continuity blend for Sunday through Monday night, then
blended in the 00z WPC Guidance thereafter. Some adjustments were
then made following additional collaboration with our neighboring
offices.

For Sunday...A weak ridge is forecast to slide across the East,
however it should quickly move off the coast in the afternoon. This
will take weak surface high pressure to off the coast of New England
through the afternoon, meanwhile a front remains draped to our south
with weak low pressure slowly moving offshore of the Mid Atlantic
coast. A closed low centered just north of the Great Lakes is
forecast to expand south and east some through Sunday. This will
drive weak surface low pressure up across the eastern Great Lakes,
then it should consolidate eventually north of the Great Lakes at
night. The frontal zone to our south should lift northward some,
however weak surface high pressure wedged southwestward will keep an
onshore flow in place and probably hold back the surface front. What
appeared to be an unsettled day may end up being dry, at least for
the daylight hours. A cold front or occluded front looks to arrive
later at night, and enough lift and moisture should result in some
showers and perhaps thunderstorms mainly at night as we wait for
convection to our west to arrive. The onshore flow should result in
a fair amount of clouds (perhaps low clouds/drizzle to start
Sunday), and therefore temperatures are anticipated to be held down
at least some especially closer to the coast.

For Monday and Tuesday...The center of a closed low is forecast to
slowly move across southeastern Canada, mostly near James Bay. A
short wave trough with an embedded stronger short wave lifts up
across the Northeast Monday. This will be accompanied by a weakening
front, however enough lift and instability should be present to
result in some showers and thunderstorms Monday. The greatest deep-
layer shear is forecast to be to our south Monday, however if enough
instability can develop then an isolated strong/severe thunderstorm
is possible across our southern zones. The initial front may
dissipate as it shifts east Monday night into Tuesday, however a
secondary front is forecast to arrive during Tuesday. The forcing
looks weaker for Tuesday with the incoming secondary front, however
cyclonic flow combined with some height falls may allow for limited
convective development in the afternoon especially near the higher
terrain. We therefore have the highest PoPs on Monday, then lower on
Tuesday when isolated to perhaps scattered convection is possible.
We are anticipating warmer temperatures ahead of the weak fronts.

For Wednesday and Thursday...As the center of the closed low
gradually shifts east more across eastern Canada, it amplifies
across the Northeast and northern Mid Atlantic for at least a time.
At least some guidance shows a pronounced short wave rotating around
the closed low late Wednesday into Thursday as it crosses the
eastern Great Lakes then slides across interior New England. This
may be accompanied by a surface trough especially during Wednesday
with potentially some convection with it. There is still some
resemblance of a surface trough on Thursday, however much of the
forcing is forecast to shift into New England. Meanwhile, surface
high pressure is forecast to build from the Midwest to the Carolinas
during this time frame. Due to the cyclonic flow, daytime
temperatures will be in the 70s to about 80 degrees each day. The
Pops were kept at low chance or less.

For Friday...As the closed low gradually weakens and heads toward
the Canadian Maritimes, a lobe of vorticity may sharpen the western
part of the upper-level trough as is swings across the Great Lakes
and Northeast. Weak high pressure is forecast to be building much
closer to our area from the west and south, however another weak
front or surface trough slides across our area. Depending on the
moisture available along with the sharpness of the trough, some
convection cannot be ruled out especially in the afternoon and early
evening. As of now, kept slight chance PoPs.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

VFR conditions are expected to prevail through the TAF period. We
are anticipating an increase in cloud cover for today and partial
clearing for tonight.

There is a chance of showers from this afternoon into the early
evening. The showers are expected to be isolated to scattered around
KRDG, KABE, KTTN, KPHL, KPNE and KACY. There is a slightly better
chance for showers around KILG and KMIV along with a small potential
for thunder. The impact of the showers is anticipated to be limited.

A light west wind this morning is forecast to become variable for
this afternoon. The wind should favor the southeast to northeast
tonight at 8 knots or less.

OUTLOOK...
Sunday...MVFR/IFR possible to start due to low clouds and/or some
fog, otherwise mainly VFR during the remainder of the day. Lower
confidence regarding low clouds/fog in the morning. Ceilings should
then lower to MVFR or IFR at night as some showers and perhaps a
thunderstorm moves through.

Monday...MVFR/IFR conditions with some showers and thunderstorms.
Some improvement may occur in the afternoon and at night as a cold
front moves through. Some fog is possible later at night. Lower
confidence regarding timing of improving conditions and
timing/coverage of showers/thunder.

Tuesday and Wednesday...Some fog possible to start Tuesday,
otherwise generally VFR through Wednesday. Some showers and
thunderstorms still possible mainly Tuesday afternoon and
evening.

&&

.MARINE...
The wind is forecast to back from the northwest and west to the
south and southeast today at speeds of 5 to 10 knots. The wind
should become east to northeast tonight around 10 knots.

Wave heights on our ocean waters will be mainly in the 2 to 3 foot
range. Waves on Delaware Bay will be 2 feet or less.

RIP CURRENTS...
A light northwest to west wind this morning is expected to become
south to southeast this afternoon. Wave heights off the coast should
be 2 to 3 feet. As a result, we are anticipating a low risk for the
development of dangerous rip currents for today.

For Sunday, an onshore flow is forecast to strengthen some and
this may result in the rip current risk approaching moderate
especially for the coast of New Jersey.

OUTLOOK...
Sunday through Wednesday...The conditions are anticipated to be
below Small Craft Advisory criteria. East to southeast winds however
should increase Sunday with some gusts to around 20 knots at times.
The seas are currently expected to be 4 feet or less.

Some showers and thunderstorms are expected, especially later Sunday
night and Monday.

&&

.TIDES/COASTAL FLOODING...
No coastal flooding is anticipated with this morning`s high tide.
However, we will issue another Coastal Flood Advisory for tonight`s
high tide. It will be in effect for the coastal counties of New
Jersey and Delaware, and for the counties along Delaware Bay and the
lower Delaware River up to near the Commodore Barry Bridge.

The guidance is suggesting the tonight`s coastal flooding will be
greater than that on Friday evening and a bit less than what
occurred on Thursday evening. The loss of the offshore wind should
allow some water to return back toward the coast, so the guidance
seems reasonable.

We will continue to keep an eye on Sunday evening`s high tide as
well since the surface wind is expected to be onshore at that time
and the astronomical tides will remain high.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Advisory from 8 PM this evening to 2 AM EDT
     Sunday for NJZ012>014-020>027.
     Coastal Flood Advisory from 11 PM this evening to 3 AM EDT
     Sunday for NJZ016.
DE...Coastal Flood Advisory from 8 PM this evening to 2 AM EDT
     Sunday for DEZ002>004.
     Coastal Flood Advisory from 11 PM this evening to 3 AM EDT
     Sunday for DEZ001.
MD...None.
MARINE...None.

&&

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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.