Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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036
FXUS61 KPHI 180156
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
956 PM EDT Sun Sep 17 2017

.SYNOPSIS...
High pressure from New England to the Maritimes dominates our
weather into Monday. All interests in coastal areas of New Jersey
and Delaware should continue to closely follow the forecast of
Hurricane Jose as it moves northward off the mid-Atlantic coast,
probably passing well east of New Jersey Tuesday into Wednesday.
High pressure is expected to settle back down into our area
late in the week, behind the weakening remains of Jose.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
930 pm update: Made minor adjustments to temperatures, dew
points, and winds based on latest observations and statistical
guidance. Main change was to lower the temperatures a little bit
north of I-80 and increase them a little along and east of the
urban corridor.

Main question tonight is the redevelopment of stratus and fog.
Agree with previous shift`s thinking that stratus will win the
match tonight east of I-95. Though progress of the low-cloud
deck has been slow (basically near the NJ coast so far), subtly
stronger onshore flow will permit the spread of these clouds
westward readily overnight. Farther west is more of a question
mark, and fog may become more prevalent here (especially with
the frequent-fogger valley locations). Already seeing lower
visibilities at some sites (KFWN, K22N, and KPTW), and this will
likely worsen through the early morning before low clouds set
in (and if they set in). Will keep an eye on it and make
adjustments as necessary.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
As we start the day Monday, ongoing stratus and some fog is expected
to improve through the day. This may take the entire morning and
even into the early afternoon for most places (especially the
stratus), however we do think there should be some improvement for a
time.

As we look to the synoptic scale, some resemblance of the weak
trough aloft remains on Monday. All the focus turns to Hurricane
Jose moving northward as it parallels the East Coast. The tropical
system is not anticipated to really have an influence on our weather
during the day Monday, although some increase in the northeasterly
wind is expected in the afternoon mainly closer to the coast. There
may still be a zone of weak convergence within some instability to
pop a few showers once again Monday afternoon. This looks to be near
and north/west of the I-95 corridor especially with any ongoing
morning showers pivoting to the west. We therefore continued with
some slight chance PoPs with the idea of isolated showers.

As the onshore flow starts to increase especially later in the day,
temperatures should be a bit cooler. The high temperatures will also
be dependent on how quickly the stratus breaks. High temperatures
are mainly a MOS/continuity blend.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Tropical products have started with the marine. TRA will post
shortly and include the now cancelled RP.s, in lieu of the TRA.
Key message will be in the NHC product.

Earlier internal communication issue has been resolved, and the HLS
has been sent.

The focus in the long term is on Hurricane Jose and the size of
its 34 knot sustained wind field, as the center of Hurricane
Jose probably passes 200 to 250 miles east of NJ later Tuesday
or early Wednesday. Please see the forecast discussion from the
National Hurricane Center for the latest details on the forecast.

1. High Surf resulting in beach erosion and a high risk of rip
currents: Though guidance has been running a foot or two on the
high side since late yesterday, we expect reality to catch up
to the guidance, though possibly not until late Monday. Highest
wave heights will probably occur Tuesday...at least 10 feet,
possibly 16 feet in the Atlantic coastal waters. We have high
confidence of at least 10 feet. Note: we see that decent swell
of 5 to 6 feet has made it into our northern waters but not
into DE. We are perplexed.

2. Tidal flooding: We have very high confidence that tidal coastal
flooding will occur, though there is still some uncertainty with
the severity of the coastal flooding. See the coastal flooding
section below for more details. All of this will be in the TRA.


3. Tropical Storm force winds (sustained of 34 KT or higher):
Recent guidance trends suggests the potential continues for a
period of sustained 34 kt winds along the immediate coasts
Tuesday and Tuesday night. TRA posts shortly. There is a better
chance for sustained 34 knot winds on portions of our Atlantic
Coastal waters and a tropical storm watch was issued for the
marine zones late this afternoon and for the immediate 10-15
miles of the adjacent land.

4. Heavy Rain: 2-4" of rain possible NJ coast, much much less e
PA and e MD, maybe none and we`re not sure how much rain will
develop back to the DE coast. Think of this as deformation zone
winterlike nor`easter. WPC does have us with a marginal 2-5%
chance of excessive rain over most of NJ now. Any excessive rain
at the shore near or shortly before a high tide could worsen
coastal flooding, especially Tuesday evening north of Atlantic
City.

Post Jose---

Thursday through Sunday...A high amplitude ridge should begin
to build over our region. The pressure pattern may not allow a
quick demise and departure of Jose so much so that it loops
south and then west and draws marine moisture back into our area
late this coming week. This will temper the potential of the
warming trend and we`ve not accepted the GFS MOS for Wednesday.

Also, we have spent very little time on the Thu-Sunday portion
of the forecast.

As far as the week as a whole goes for temperatures: Daily
calendar day averages for the week should average close to 10
degrees above normal...possibly only 7 degrees above normal next
weekend. Still there is no end in sight for the persistent late
summer warmth with above normal temps expected to continue
through week two (the end of September).

&&

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

Low-confidence TAFs tonight as onset of stratus/fog remains in
question. Conditions are slowly deteriorating along the coast
and have briefly occurred at ACY. Expect conditions to worsen
rather quickly after midnight, with MVFR/IFR conditions at
most/all sites thereafter. Conditions may not improve readily in
the morning, especially the low CIGs. VFR conditions may occur
by early afternoon, but timing of this is uncertain. Winds
generally easterly (generally around/under 5 kts tonight; up to
10 kts or so tomorrow). Stronger gusts may develop at ACY by
late afternoon.

Outlook...
Monday night...Widespread MVFR cigs likely. northeast wind, increasingly
gusty PHL to ACY, MIV and ILG during the night...near 20 kt late
at night. A good chance of showers developing vcnty KACY.

Tuesday...VFR conditions are expected to develop at KRDG and KABE.
For the Delaware Valley TAF sites (KPHL, KILG, KPNE, and KTTN) and
coastal sites (KMIV and KACY) MVFR ceilings are likely...possibly
lower in showers. Northeasterly winds 10 to 20 KT with gusts to
possibly past 30 KT except gusts only 20-25 kt vcnty KABE/KRDG.

Wednesday...Becoming VFR with decreasing northwest winds...gusting
15 to 20 KT.

Thursday...Mostly VFR conditions are expected. Light winds shifting
from northerly to northeasterly.

Friday...Probably VFR sct-bkn aoa 4000 ft.

&&

.MARINE...
The swell energy from Hurricane Jose will continue to arrive through
Monday. The winds are on the lighter side, however it will increase
during the day Monday from a northeasterly direction. It is possible
that wind gusts near 25 knots across the southern ocean zones toward
later Monday afternoon. The seas/swells have been slower to
build across our waters, therefore slowed this down a bit more
through tonight as we await the increase in winds. The
conditions will remain below advisory criteria on Delaware Bay.

Outlook...
A tropical storm watch is in effect. Details in the MWW.

Late Monday night through Wednesday...Tropical storm conditions
will be possible. Although winds will begin to diminish Wednesday,
it will take time for seas to subside.

Wednesday night through Friday...Northeast to east swells of 5
feet may continue hazardous seas advisory because of the
meandering and slowly decaying remains of Jose.

Rip Currents...
Swells of 4-5 feet (11-14 second period) combined with an onshore
wind is resulting in dangerous rip currents. Therefore, we continue
the high risk through tonight. As the swell energy builds on Monday
and the winds gradually increase from south to north, the rip
current risk is expected to remain at high.

The high risk will continue through mid week and will be embedded
in the TRA. Despite comfortable water temps in the lower to mid
70s, swimming at the beaches is not recommended the next few
days due to rough and gradually increasing and dangerous surf.
ANKLE DEEP only. Please follow the advice of local officials.

&&

.TIDES/COASTAL FLOODING...
Widespread minor to possibly moderate tidal inundation coastal
flooding is expected with the Atlantic coast high tide cycles
Tuesday through Tuesday night due to the passage of Hurricane
Jose. Whether it is moderate is debatable but we have several
model guidances suggesting 2 to possibly 3 consecutive high tide
cycles of moderate coastal flooding are possible. The high tide
cycle of greatest concern at this point is the Tuesday evening
high tide, especially Sandy Hook to Cape May. The tropical HLS
will contain information on coastal flooding.

We dont know for sure if we will see areas of moderate coastal
flooding but the potential for exceeding the moderate threshold
exists for one or more high tide cycles centered on Tuesday.

A prolonged period of east to northeast winds will force water
to build along the shores. In addition, there is a new moon on
Wednesday, September 20th, so astronomical tide levels will be
running high.

Positive departures along the Atlantic coast compared to the
astronomical prediction yesterday (24 hours ago) were about .4
feet higher, today the departure has increased slightly to about
.6 FT and at about 645Pm we were just .6 ft below minor flood
threshold. All of this with very little easterly inflow and
relatively high surface pressure.

So you can see what probably lies ahead with better inflow
Monday evening through Tuesday evening.

&&

.EQUIPMENT...
KSMQ transmission of data continues ots.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Tropical Storm Watch for NJZ013-014-020-022>027.
DE...Tropical Storm Watch for DEZ003-004.
MD...None.
MARINE...Tropical Storm Watch for ANZ431-450>455.
&&

$$
Synopsis...Drag
Near Term...CMS
Short Term...Gorse
Long Term...Drag
Aviation...CMS/Drag
Marine...Drag/Gorse
Tides/Coastal Flooding...Staff
Equipment...Staff



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