Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 231645

Area Forecast Discussion
National Weather Service New York NY
1245 PM EDT Sun Jul 23 2017

A frontal boundary remains to our south today. Low then moves
along the front, tracking off the mid-Atlantic coast Monday.
High pressure builds over the northeast late Tuesday through
Wednesday, then drifts off the coast Wednesday night. Another
wave of low pressure follows for Wednesday night into Friday,
with a cold front moving through Friday. High pressure returns


As of 1240 pm, showers were developing over the New York City
metro area, generally along the sea breeze. Convergence along
this boundary has provided enough lift for these showers to
develop. Additionally, light showers from the northwest have
made their way into portions of the Lower Hudson Valley and are
headed for portions of southwest Connecticut. Therefore, have
added a slight chance for showers for New York City, northeast
New Jersey, the Lower Hudson Valley, Nassau County, and
southwest Connecticut. The threat for these showers should
continue for the afternoon.

Initial shortwave passes to the east early this morning, with a
wave of low pressure doing the same. High pressure, with weak
ridging aloft, builds across New England.

Other than an isolated shower, subsidence behind shortwave will
likely keep the area dry today. Some sunshine will appear,
particularly in southern CT.

Temperatures today will be cooler, closer to seasonal norms of
the lower to mid 80s.

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


Weak ridge yields to approaching trough through this time

At the sfc, two areas of low pressure approach and pass. the
area looks to remain on the north side of the frontal boundary
as the coastal low passes juts south Monday.

Ample forcing ahead of this system will result in increasing
coverage for showers and possible thunderstorms tonight, from
west to east. Best chance occurs from late evening and through
the overnight hours. At this time, instability appears to be
weak, so widespread thunder is not anticipated.

On Monday, showers are possible, but the main area in the
morning departs in the afternoon.

For tonight, the rain and clouds will result in normal overnight
low temps. However, cool temperatures are anticipated during the
day Monday. With easterly flow, and plenty of clouds, leaned
toward the lower end of the guidance, with a 2/3 and 1/2 blend


An upper level shortwave and accompanying wave of surface low
pressure will be exiting to the east Monday night into early
Tuesday. A few showers will be on-going at the beginning of the
extended forecast period. CAPE values look meager.

A weak ridge builds Tuesday and Wednesday. Then another
shortwave amplifies into a significant trough into the eastern
states Wednesday night into Thursday with a high amplitude
trough, of 1 to 2 standard deviations above normal, digging all
the way to northern Florida by Friday. The flow looked to be
still progressive with a surface low moving through Thursday and
Friday. However, there are hints that the upper low will close
off again Friday into Saturday and remain along the northern
coast into next weekend. At this time will keep with persistence
and the more progressive flow and keep Friday night into
Saturday dry as upper ridging builds to the north.

Temperatures through the extended period will be near to slightly
below seasonal normals.


A stationary front will remain to our south into Monday morning,
with a wave of low pressure moving along it towards the region

Conditions vary from MVFR to VFR over NYC Metro terminals, with
mainly VFR conditions elsewhere. Conditions become MVFR
throughout by mid evening, with showers overspreading the area
after midnight. An isolated rumble of thunder cannot be ruled
out during the overnight hours as well, with the best chance
from the city terminals on N/W.

Light and variable winds (NE at around 10 kt CT terminals and
KHPN) becoming E-SE at around 10kt or less throughout this
afternoon. Isolated gusts to around 15kt are possible this
afternoon. Winds become E throughout overnight at around
10-15kt. Gusts to around 20kt are possible overnight at
KLGA/KBDR, with isolated gusts possible at other coastal

.Monday-Tuesday night...MVFR likely, IFR possible.
.Wednesday-Wednesday night...VFR.
.Thursday...Mainly VFR. There is a chance of showers and
possibly a thunderstorm mainly to the N/W of city terminals in
the afternoon/evening.


Increasing E-SE flow tonight and then E-NE flow on Monday ahead of
an approaching low, with a warm front remaining to the south or only
briefly entering the ocean waters, should eventually build ocean
seas to minimal SCA criteria of 5 ft. This could happen in the NY
Bight area as early as late tonight, but certainty in this is higher
for daytime Monday. Wind gusts up to 25-30 kt are also possible on
the eastern ocean/sound/bay waters daytime Monday.

Ocean seas may also approach 5 ft Wed night-Thu as increasing S flow
develops ahead of a cold front. Waves of low pressure passing
through could also bring a chance of tstms on Thu.


An additional 1/2 to 1 inch of rainfall is likely from late tonight
through Monday, with locally higher amounts possible. There is
a small chance for minor flooding or urban and poor drainage
areas, if any experience locally heavy rainfall.

More rain is possible Thursday through Friday. Significant
hydrologic impacts are not expected at this time.


With the new moon phase today, tides are running high.
Positive tidal departures of 1/2 to 1 ft are needed for minor
flooding during the night time high tide. With east flow
expected, and looking at what occurred earlier tonight, will
issue a coastal flood advisory for western LI sound, the south
shore bays of LI, and lower NY Harbor for the evening and
night time high tides. A few locations could reach or slightly
exceed moderate benchmarks across the south shore bays of
Nassau and Queens.

The threat for minor flooding could continue into Monday, with
E/NE flow progged to continue.


CT...Coastal Flood Advisory from 11 PM this evening to 2 AM EDT
     Monday for CTZ009.
NY...Coastal Flood Advisory from 11 PM this evening to 2 AM EDT
     Monday for NYZ071-073-176-177.
     Coastal Flood Advisory from 8 PM to 11 PM EDT this evening for


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