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000
FXUS61 KPHI 171628
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1228 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 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 PM THIS EVENING/...
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The areas of stratus are finally thinning and lifting as heating
continues. The visible satellite imagery shows the cloud pattern
now becoming more convective looking. The extensive cloud cover
though has slowed the temperature increase for much of the area
thus far, therefore adjustments were needed. In addition, the
high temperatures were lowered a little for much of the area.

Not much difference in the synoptic setup compared to yesterday,
with a weak trough aloft sitting across the region. While the
forcing is weak, local convergence combined with enough
instability this afternoon will allow for isolated to perhaps
scattered showers once again. These should be primarily inland
from the coast, although the start of this is delayed some due
to the slow erosion of the stratus. The 12z Sterling, VA raob
indicates a strong inversion once again near 700 mb, while the
12z Upton, NY raob has less of an inversion. Some of the high-
res guidance hinting at the most shower development near the
I-95 corridor, although the main focus may be near remaining
differential heating boundaries. Overall, we are anticipating
low-topped activity therefore will continue with no thunder
mention. Despite this, precipitable water values from the two
nearby raobs are 1.2 to 1.4 inches, therefore any slower moving
shower that is able to develop will be capable of producing
localized heavy rainfall.

The hourly temperature, dew point and wind grids were adjusted based
on the latest observations, then the LAMP guidance was blended in
for a few hours. The cloud cover was adjusted upward for awhile
longer given trends.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
The showers that develop during the day are expected to dissipate
around or after sunset as daytime heating wanes. Once the sun goes
down and the surface temperatures cool, areas of fog and/or stratus
should begin to develop and spread across the area from east to
west. Overall fog is not expected to be widespread dense, but a some
locally patchy dense fog will be possible.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
What is stated here in the long term sections that follow is
preliminary.

As has been the case the last several days, 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. Note that with
the 11 am advisory the probabilities for sustained 34 knot
(tropical) winds has increased considerably. Those probabilities
will be incorporated into the forecast wording at the 1230 PM
issuance.


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...of at least 10 feet,
possibly 16 feet in the Atlantic coastal waters. We have high
confidence of at least 10 feet.

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.

3. Tropical Storm force winds (sustained of 34 KT or higher):
Recent guidance trends suggest the potential continues for a
period of sustained 34 kt winds along the immediate coasts
Tuesday and Tuesday night but no TSa at this time for the land.
There is a better chance for sustained 34 knot winds on portions
of our Atlantic Coastal waters and a tropical storm watch may be
issued for the marine zones late this afternoon, pending receipt
of and in-house WFO-NHC collaborating multiple model guidance.
For now...gusts 30-40 MPH in parts of NJ and DE are possible
Tuesday, stronger gusts of 40 kt possible on the Atlantic waters
but still plenty...of uncertainty.


4. Heavy Rain: Current track keeps the heavy rain just off shore
on Tuesday, but WPC does have us with a marginal 2-5% chance of
excessive rain from Ocean and Monmouth counties northeastward.
Any excessive rain at the shore near or shortly before a high
tide could exacerbate coastal flooding, especially Tuesday
evening north of Atlantic City.

Post Jose---

Thursday through Saturday...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 that a northeast gradient
of moist marine air may tend to linger. This would temper the
potential of the warming trend due to the building high to our
north and some marine influence.

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 /18Z SUNDAY THROUGH FRIDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

This afternoon...MVFR ceilings are expected to improve to VFR
ceilings. Isolated to scattered showers are expected later this
afternoon, especially inland from the coast. Light and variable
winds, favoring a northeast to east direction of 10 knots or less.

Tonight...Any showers end early, then areas of stratus and fog are
expected to redevelop especially overnight. This will result in
areas of IFR or lower conditions. Light and variable winds
overall.

Monday...MVFR/IFR or lower conditions due to low clouds and
fog, then improving to VFR after 14z. Northeast winds 10 knots
or less, however increasing to 10-15 knots in the afternoon at
KACY.

Outlook...
Monday night...Widespread MVFR cigs likely. northeast wind,
increasingly gusty PHL to ACY, MIV and ILG during the night...near
20 kt late. 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 with showers likely vcnty KACY.  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.
-- End Changed Discussion --

&&

.MARINE...
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The seas are running about a foot lower than forecast, therefore
delayed the increase some through the afternoon. Overall, seas
on the ocean build to 4-6 feet toward the end of the day then
remain tonight. We will continue with the Small Craft Advisory
for Hazardous Seas. The conditions will remain below advisory
criteria on Delaware Bay. An onshore flow is expected through
tonight with winds mainly at and below 15 knots.

Outlook...
A tropical storm marine hazard may be issued at 5 PM...dependent
on internal assessment of the wind fields.

Monday through Wednesday...Tropical storm conditions will be possible
Tuesday. However, even Monday, northeast wind gusts may increase
above 25 KT late in the day and at night in advance of Hurricane
Jose approaching from the south. Although winds will begin to diminish
Wednesday, it will take time for seas to subside.

Wednesday night and Thursday...once seas subside below 5 ft
Wednesday night, winds and seas should stay below SCA criteria
for the remainder of the period.

Rip Currents...
With swells of 12-13 seconds forecast to build to 5-6 feet later
today, along with an easterly wind of 5-10 knots, we will continue
with a high risk for the development of dangerous rip currents
today.

The high risk will continue through mid week. 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 gradual increasing
and dangerous surf. ANKLE DEEP only. Please follow the advice
of local officials.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
Widespread minor to possibly moderate tidal inundation coastal
flooding is expected with the Atlantic coast high tide cycles
Monday evening 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. We may be
issuing a coastal flood watch of some sort at 5 PM. So we dont
know for sure if we see areas of moderate coastal flooding but
the potential for exceeding the moderate threshold exists.


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. All of this with very little easterly inflow and
relatively high surface pressure.

&&

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None.
NJ...High Rip Current Risk until 11 PM EDT this evening for NJZ014-
     024>026.
DE...High Rip Current Risk until 11 PM EDT this evening for DEZ004.
MD...None.
MARINE...Small Craft Advisory for hazardous seas until 6 AM EDT Monday
     for ANZ450>455.
-- End Changed Discussion --

&&

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