Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 240747

Area Forecast Discussion
National Weather Service New York NY
347 AM EDT Mon Jul 24 2017

A frontal boundary will remain south of the area through Tuesday.
High pressure builds over the northeast late Tuesday through
Wednesday, then drifts off the coast Wednesday night. Another
wave of low pressure follows for Thursday into Saturday. High
pressure returns Sunday.


Showers and thunderstorms will spread across the region this
morning as a weak area of low pressure moves northeast across
the area. The steadier rain should taper off to showers this afternoon
and into tonight. High temperatures today will be in the mid to
upper 70s.

There is a high risk for the development of rip currents at
ocean beaches today.


Showers continue through late tonight as an upper level trough
remains over the area. Low temperatures tonight will be in the
low to mid 60s along the coast and in the upper 50s inland. Dry
conditions return on Tuesday as high pressure builds over the
area. High temperatures will be in the low to mid 70s.


The extended forecast mainly remains consistent with the
previous forecast with the exception that precipitation is
expected remain into Saturday as was hinted at by the ECMWF late
Saturday, as an upper trough is slower to move east.

The northern stream flow along the US/Canadian border remains
nearly zonal and progressive with embedded shortwaves moving
through the flow.

One shortwave will be exiting the northeastern coast, along
with the accompanying surface low, Tuesday. CAPE and instability
remain limited so will continue with showers.

A weak ridge axis builds into southern Canada from the southern
ridge over the southwest and moving into the plain states mid

Another shortwave was coming onshore of the Canadian Pacific
coast as seem on the upper level water vapor loop. And these
system has been picked up by the models. This shortwave open and
tracks quickly across southern Canada then digs and large trough
along the eastern United States late in the week into the weekend
as a western north Atlantic ridge builds and blocks the eastern
trough. This will keep waves of low pressure tracking along a
frontal boundary Thursday into Saturday before the last one exits
later Saturday. So now have chances of precipitation through
Friday into Saturday.

The upper trough weakens Sunday as surface high pressure builds
to the north resulting in a dry Sunday.

Temperatures through the extended period will be near seasonal
normals, except for being below normal Tuesday.


Low pressure will move along a front to the south overnight, then
pass over or just south of NYC metro and Long Island today.

Widespread MVFR cigs are already in place NW of NYC metro, with
some patches of lower clouds farther east. Moderate to locally
heavy showers and a few tstms extending from SE PA into nearby
NJ/DE will weaken and move NE toward the NYC metro terminals,
arriving 08Z-09Z and bringing widespread MVFR/local IFR
conditions there until about 11Z. Additional activity over
NE/Central PA should then move E and impact mainly the Lower
Hudson Valley and CT terminals from about 12Z-16Z, with IFR
conditions expected at KBDR/KGON.

After these showers exit east, MVFR cigs should linger at the NYC
metro terminals until about 19Z, and at KISP until about 22Z. MVFR
conditions should linger north of there through the rest of the 06Z
TAF period.

E flow should gradually increase this morning, with gusts around
20 kt at the NYC metros, and higher out east especially at KBDR/KGON
where gusts over 25 kt likely. Winds should back N and then NW after
this low passes, then become NE again tonight.

.Late tonight...MVFR conds likely, IFR possible, with chance of
showers. Diminishing NE winds.
.Tuesday...Becoming VFR. NE winds 10-15 kt.
.Tuesday night...Patchy fog with MVFR vsby possible late at KSWF,
otherwise VFR.
.Wednesday and Wednesday night...VFR.
.Thursday...Chance of showers and possibly a tstm with MVFR or
lower conds NW of the NYC metros in the afternoon, otherwise
.Thursday night and Friday...MVFR or lower conditions possible, with
chance of showers/tstms.


Gusty winds ahead of a wave of low pressure riding along a front can
be expected this morning. By afternoon, the low and front track
across the ocean waters, just south of Long Island. This wave of low
pressure moves east tonight, with another low along the front
passing to the south. High pressure then builds to the north of the
waters Tuesday and Wednesday.

SCA has been posted for most waters this morning, except NY Harbor
and south shore bays of LI. Winds diminish this afternoon. Across
the eastern waters, a few gusts in excess of 30 kt are possible

Ocean seas remain rather rough today, and tonight. Will extend the
SCA for the ocean waters through tonight for now, but it likely
will need to extend into Tuesday as well.

The easterly flow continues into Wednesday and then gradually
diminishes and becomes southeasterly as high pressure moves well
east of the forecast waters. Ocean seas are expected to subside
below 5 feet by mid week. Then winds and seas remain below small
craft levels Wednesday night into Friday.


Heavy rainfall possible this morning for the entire area.
Generally, 1 to 1.5 inches is forecast, with locally higher
amounts possible in any thunderstorms. Ponding of water on
roadways would occur with the heavier rainfall along with some
minor flooding of poor drainage and low lying areas possible.

A Flash Flood Watch has been issued for portions of the area.

Additional rainfall is possible Thursday through Friday night.
Hydrologic impacts are not expected at this time.


With the new moon that occurred early yesterday morning, tides are
running astronomically high. Tidal departures of 1 1/2 to 2 ft are
needed for minor flooding during daytime high tide. Only 1/2 to 1 ft
departures are needed at night.

With easterly winds, will issue a coastal flood statement for the
south shore back bays of Nassau, Queens and Kings, and across the
western LI Sound as tides approach minor benchmarks. Elsewhere, feel
tides remain below minor benchmarks.

For tonight, coastal flood advisories may ne needed, but will wait
on another run of guidance to determine potential headlines for
this subsequent high tide cycle.


NY...Flash Flood Watch until 11 AM EDT this morning for NYZ067-069-
     High Rip Current Risk through this evening for NYZ075-080-081-
NJ...Flash Flood Watch until 11 AM EDT this morning for NJZ002-004-
MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ330-
     Small Craft Advisory until 2 PM EDT this afternoon for ANZ335.
     Small Craft Advisory until 6 AM EDT Tuesday for ANZ350-353-355.


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