Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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325
FXUS61 KPHI 200137
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
937 PM EDT Tue Sep 19 2017

.SYNOPSIS...
Hurricane Jose will move northeastward through Wednesday and then
stall well offshore of the mid-Atlantic coast through the weekend.
Meanwhile, high pressure will build southward from eastern Canada
during the second half of the week and then remain anchored over the
region into early next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Dangerous surf and rip currents along with coastal flooding are the
main impacts from Hurricane Jose.

Hurricane Jose continues to move northward well offshore this
evening. Its effects are very noticeable at the shore areas and
they diminish as you proceed n/w. Showers that were across most
of NJ/DE earlier have decreased to just a few patches with more
spinning well offshore. Pops have been lowered for the overnight
periods and cloud cover mostly unchanged with fewer clods across
the W areas attm.

Low temperatures were not changed, but some edits to the hourly
temps/dew points were made.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
An upper-level ridge is forecast to build across the Ohio Valley and
eastern Great Lakes then north of Hurricane Jose. This will weaken
the steering flow and allow Jose to slow down and meander southeast
of Cape Cod during Wednesday. While the pressure gradient remains on
the tightened side and there will be a northwest breeze, it is not
expected to be all that strong. There should be enough subsidence to
the west of Jose to result in more sunshine although at least some
cloud cover is expected especially across the northern half of the
area.

Some guidance hinting at a few showers possible across the northern
zones especially in the afternoon, however the chance looks to small
given a lack of overall forcing and therefore we continued with a
dry forecast. High temperatures are closer to the warmer GFS MOS as
some subsidence should allow a bit more warming especially for
the southern and western areas.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Jose is expected to become a post-tropical storm Wednesday night or
Thursday and meander about 400-500 miles east of the NJ coast
through the end of the week and possibly all the way into early next
week. The large-scale pattern through the duration of the long term
looks to be amplified, featuring persistent troughing over the
western CONUS, downstream ridging over the eastern CONUS and
tropical activity over the western Atlantic.

Owing to upper ridging and surface high pressure over our area, a
clear signal for warm and dry conditions exists for the next 7 days.
No mention of rain through the entire period. Northerly flow regime
is typically indicative of cold air advection. In this upcoming
pattern, persistent northerly flow around the backside of Jose and
away from the center of the surface high will actually yield warm
air advection as the core of the heat (owing to a maximum of
subsidence) will be located underneath the anticyclone that will be
anchored just to our north and west throughout the period. High
temperatures in the 80s will be common across the area (except
cooler in the 70s at higher elevations in NE PA/NW NJ and along the
coast), which are 5-10F above normal for late September. Sunday and
Monday should be the warmest days of the period (temps 10-15F above
normal) with the center of the anticyclone expanding toward the
northern mid-Atlantic region. There is a potential that a few spots
could reach 90F (particularly the urban centers) on one or both of
these days.

&&

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

Tonight...VFR overall, although some MVFR ceilings can occur for a
time mainly at KMIV and KACY. Scattered showers for the next few
hours, but no sig vsby restrictions expected. Winds have
increased quite a bit the past hour, but a trend back to lower
winds expected after midnight.

Wednesday...VFR with cloud bases at or above 4000 feet.
Northwest winds around 10 knots, with some gusts up to 20 knots
possible.

Outlook...

Wednesday night through Sunday...VFR. However, patchy radiational
fog cannot be ruled out early Thursday morning at the typical fog-
prone terminals (RDG, ABE, MIV) but setup for fog becomes less
favorable each successive night as drier air works into the area.
Light N winds.

&&

.MARINE...
Tropical Storm Warning remains in effect for the ocean zones. We
decided to continue overnight in collab with AKQ/OKX. Winds have
been somewhat slower to decrease this evening. Strong gusts are
still psbl with showers. A Gale Warning remains in effect through
this evening for Lower Delaware Bay, and a Small Craft Advisory
continues for Upper Delaware Bay.

Wednesday, the strongest winds should be over our northern
coastal waters however these will diminish through the day. The
seas will take some time to subside.

Outlook...

Wednesday night through Sunday...Seas in our coastal waters will
slowly subside in wake of Jose Wednesday night and Thursday. Seas
may briefly drop below SCA levels of 5 ft on Thursday. Thereafter,
seas should start to increase again to 5-7 ft Friday into the
weekend with Jose meandering offshore and then with long-period
swells from Hurricane Maria gradually propagating up the
eastern seaboard this weekend. Winds vary between N-NW and N-NE
and remain below 25 kt thru the outlook period.

Rip Currents...
Hurricane Jose continues to push powerful swells into the coasts
of Delaware and New Jersey through tonight. As a result, there
is a High Risk of dangerous rip currents and heavy surf tonight.
Significant beach erosion, localized dune overwash and minor
damage to piers have been reported today.

It will take some time for these large waves/swells to subside
and despite the surface wind more northwesterly on Wednesday.
A High Risk for Rip currents is expected for Wednesday. The
High Surf Advisory has been extended through 600 a.m. Wednesday
with 8-10 foot breaking waves reach the coast.

Jose is expected to stall well offshore through the end of the
week and into the weekend. Long-period swells will enhance the
risk for the development of dangerous rip currents during this
time. The risk may drop to moderate for Thursday-Friday with
waves subsiding a bit and winds becoming light. However, long-
period swells from Hurricane Maria may arrive this weekend,
which could raise the risk to high again.

&&

.TIDES/COASTAL FLOODING...
The Coastal Flood Warning continues with the present high tide
cycle this evening along the NJ and DE coast and along the DE
Bay. A Coastal Flood Advisory remains in effect tonight for New
Castle County and Salem County.

The ETSS has had the best performance thus far with this morning`s
high tide and with the current low tide this afternoon. This model
brings Philadelphia close to minor threshold for tidal flooding,
close to moderate for Reedy Point. Lewes is cresting presently
at Moderate levels.

Minor tidal flooding will likely linger into Wednesday and
perhaps into Thursday.

&&

.EQUIPMENT...
KSMQ observations are not being sent out. There is a comms
problem and technicians are on site this afternoon to
troubleshoot.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Warning until 1 AM EDT Wednesday for NJZ012>014-
     020>027.
     High Surf Advisory until 6 AM EDT Wednesday for NJZ014-024>026.
     Coastal Flood Advisory until 1 AM EDT Wednesday for NJZ016.
DE...Coastal Flood Warning until 1 AM EDT Wednesday for DEZ002>004.
     High Surf Advisory until 6 AM EDT Wednesday for DEZ004.
     Coastal Flood Advisory until 1 AM EDT Wednesday for DEZ001.
MD...None.
MARINE...Tropical Storm Warning for ANZ450>455.
     Small Craft Advisory until 6 AM EDT Wednesday for ANZ430.
     Gale Warning until 6 AM EDT Wednesday for ANZ431.

&&

$$
Synopsis...Klein
Near Term...PO
Short Term...Gorse
Long Term...Klein
Aviation...Gorse/Klein/PO
Marine...Gorse/Klein/PO
Tides/Coastal Flooding...Kline/PO/MPS



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