Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 260905

Area Forecast Discussion
National Weather Service New York NY
505 AM EDT Tue Sep 26 2017

High pressure slowly retreats to the east through Wednesday as
Hurricane Maria tracks northeast off the Mid Atlantic Coast.
Refer to statements form the National Hurricane Center for the
latest on Maria. A cold front moves through the region
Wednesday night, followed by brief high pressure building in
from the west through late week. Another cold front passes
through Friday night, followed by high pressure settling in
through the weekend. This high then slides offshore on Monday.


The main story today is that long period swells from Hurricane
Maria will produce high, dangerous surf and strong rip currents
at Atlantic Beaches. With swells at 44025 progged to 7-8 ft at
15 seconds at 44025 and 9-10 ft at 15 seconds at 44017, expect
to sea breaking waves up to 6 to 9 ft at western beaches and 7
to 10 ft at eastern beaches (and this might be a tad
conservative, depending on the exact angle of incidence with the
beach). As a result have extended the high surf advisory west to
encompass NYC and Nassau County Atlantic Beaches (was just for
Suffolk County Atlantic Beaches) and have continued with the
high risk of rip currents for all Atlantic Beaches.

Otherwise...the axis of a northern stream ridge builds over the
region today, as the northwest extension of the sub-tropical
ridge retreats to the east. The result should be sufficient
subsidence to keep the region dry.

This subsidence also will help keep moisture trapped beneath an
inversion with a base from 975-925 hPa over the area. As a
result expect low level stratus/fog to be slow to erode from W
to E with some possibility that the twin forks of Long Island
and maybe even coastal New London County never have the deck
fully erode.

The evolution of this stratus/fog deck will go a large way in
determining highs for today. For now leaned towards cooler MET
guidance over eastern areas and went more with a blend farther
W, and leaned towards warmer MAV/ECS guidance over W portions of
the lower Hudson Valley. Highs should range from 5-10 degrees
above normal, but could end up quite a bit cooler,e specially
over far E zones if the stratus deck does indeed maintain itself
all day.


Swells from Maria will continue to produce high, dangerous surf
through Wednesday and quite likely dangerous rip currents as
well, with swells progged to around 10 ft/14 seconds at 44025
and 10-11ft/14 seconds at 44017. As a result have extended the
high surf advisory for all Atlantic Beaches through 22z
Wednesday and have continued with the high rip current risk for

Otherwise, the northern stream ridge axis exits to the northeast
and WSW flow sets up aloft for Wednesday. There could be a weak
700 hPa shortwave passing Wednesday afternoon, so have a slight
chance of showers then, otherwise it should be dry.

The fog/stratus deck should return tonight, and likely will be
more extensive than it was last night/early this morning. The
main thing that is unknown is how dense the fog will be/will
the area be more mainly just stratus. So for now playing things
as patchy fog, but definitely cannot rule out areas of dense
fog, especially over eastern areas. Lows tonight should be
around 10-15 degrees above normal.

This deck should be slower to erode on Wednesday than today. As
a result, even with low level temperatures forecast to be a
degree or so warmer than today, did not change high temperatures
much from today. Once again, continue to have a bust potential
on the low side (by 5-10 degrees) if the stratus deck does not
erode at all.


A cold front moves through the region Wednesday night. Meanwhile,
moisture associated with Maria tries to sneak in mainly over the
eastern zones. Will go with low chances of showers for most areas,
but focused more to the east of the city.

Aside from a lingering shower possible early in the morning in the
vicinity of the twin forks, Thursday should be dry as high pressure
builds in. Leaned towards the warmer side of guidance for high
temperatures based on forecast 850-900mb temps during the afternoon.
It will begin to feel less muggy as well with dewpoints falling to
around 50 by the end of the day. A return to seasonable temperatures
then follows for Friday as high pressure remains over the region.

Global models differ in the timing of the next cold front, but best
guess right now is that it moves through at some point during Friday
night with a slight chance of showers. An upper trough/cold pool
aloft follows for Saturday so some instability showers are possible.
Kept PoPs at slight chance for this. Highs for Saturday mostly 65-70.

High pressure continues to build in for Sunday and Monday with dry
weather and high temperatures generally around 70.


Weakening high pressure remains across the region through the
TAF period.

Flight categories primarily in the IFR/LIFR range with
oscillating visibilities with KEWR, KTEB, AND KLGA right on the
edge of this sharp contrast in visibilities . The low
visibilities and ceilings will continue through 11-12z and then
start to mix out from W to E due to heating and daytime mixing.
KISP and KGON take a bit longer. The flow becomes onshore again
and then decreases again into the evening.

After light/vrb winds early this morning, NE/E winds 5-10 KT
develop this morning and shift to the SE again mainly during
the late morning/early afternoon.

...NY Metro Enhanced Aviation Weather Support...

Detailed information, including hourly TAF wind component forecasts,
can be found at:

KJFK TAF Comments: Timing of improving conditions may be off by
up to 2 hours.

The afternoon KJFK haze potential forecast is YELLOW...which
implies slant range visibility 4-6SM outside of cloud.

KLGA TAF Comments: Timing of improving conditions may be off by
up to 2 hours.

The afternoon KLGA haze potential forecast is YELLOW...which
implies slant range visibility 4-6SM outside of cloud.

KEWR TAF Comments: Timing of improving conditions may be off by
up to 2 hours.

The afternoon KEWR haze potential forecast is YELLOW...which
implies slant range visibility 4-6SM outside of cloud.

KTEB TAF Comments: Low confidence in how long visibilities
remain down early this morning. Amendments possible/likely.

KHPN TAF Comments: Low confidence in how long visibilities
remain down early this morning. Amendments possible/likely.

KISP TAF Comments: Timing of improving conditions may be off by
up to 2 hours.

.Tuesday night-Wednesday...MVFR to IFR possible with patchy
fog and/or stratus and a low chance of showers.
.Wednesday night-Thursday...MVFR or lower possible with isolated to
scattered shower activity.
.Thursday night-Friday...VFR.
.Friday night-Saturday...Mainly VFR, except MVFR possible in
any showers.


A marine dense fog advisory continues through 14z today. This
will be re-evaluated sing beach cams after the sunrises and
based on the rate of erosion as well. There is some chance this
may need to be extended, especially over E zones.

Swells from Hurricane Maria will keep seas on the coastal ocean
waters at well above Small Craft Advisory (SCA) levels through
at least Wednesday night, so have extended the SCA for Hazardous
seas through then.

As far as winds go through Wednesday night, a light pressure
gradient over the region will limit winds to around 10 kt or
less through then.

Lingering swell from Maria will likely allow seas to remain at SCA
levels through late week before gradually subsiding this weekend as
high pressure builds from the north. Gusts Thursday will be up to
around 25 kt behind a cold front, but mainly on the ocean waters.
Still a chance that a SCA could be needed on some of the other
waters. Winds otherwise subside back below advisory criteria from
Thursday night on.


No significant hydrologic impacts are expected over the next 7


NY...High Rip Current Risk through late tonight for NYZ075-080-081-
     High Surf Advisory until 6 PM EDT Wednesday for NYZ075-080-081-
MARINE...Dense Fog Advisory until 10 AM EDT this morning for ANZ330-335-
     Small Craft Advisory for hazardous seas until 6 AM EDT
     Thursday for ANZ350-353-355.


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