Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 251426
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1026 AM EDT Thu May 25 2017

.SYNOPSIS...
Low pressure will deepen over the Mid-Atlantic today, track through
the Tri-State Region tonight and into the Maritimes on Friday. A
broad area of high pressures builds in for the first half of the
weekend, then a slow moving frontal system will bring the potential
for showers from Sunday into Tuesday.

&&

.NEAR TERM /THROUGH FRIDAY/...
Overall rainfall this morning not too impressive with the local
area split between two heavier batches of rain, one off to the
NW and one offshore. Rain intensity is expected to remain on the
light side for the remainder of the morning with just a few
pockets of moderate rain. Much of this rain is due to isentropic
lift/warm advection. No thunder is expected with this activity.

Middle level drying from the south will serve to cut off
widespread rain this afternoon. Have adjusted PoPs and Wx grids
to account for this trend, and included mention of a chance of
light rain or drizzle as the lowest 5,000 feet remain saturated.
Areas of fog are also possible this afternoon.

Easterly winds will be highest this morning with gusts as high
as 25-30 mph, strongest near the coast. Winds will gradually
weaken this afternoon as the pressure gradient slackens.

Attention then turns to the H5 low, which moves over tonight.
Initially middle levels look to dry to support anything more
than light rain or drizzle, but then significant dpva and lapse
rates from h85 to h4 range avg around 6.5C/km. The models all
produce convective pcpn. As a result, showers and embedded
thunderstorms are expected overnight.

The upper low reaches the Gulf of ME on Fri. This will allow
for decreasing coverage and intensity of showers through the
day. The downslope flow could allow for clearing, especially
along the coast, by the end of the day.

Temps will be below normal today, then will nudge closer on Fri
as the rain ends. A blend of the guidance and raw model data
was used.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
Weak ridging builds in Fri ngt and Sat which will attempt to
produce fair weather. There is a suggestion of shrtwv energy
swinging thru on Sat. If this materializes, isold-sct shwrs will
be possible. A rainy day however is not expected attm. A broad
upr lvl low then drops into the Midwest, producing sw flow aloft
across the fcst area Sun. This will produce an increasing
chance for shwrs, particularly Sun aftn thru Sun ngt.

Temps will remain close to or blw normal thru the period. The
Superblend was used.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
The upr low over the Midwest will drive a slow moving frontal
sys thru the region for the beginning of the week. There is
some uncertainty wrt the timing, with the ECMWF slightly faster
than the GFS. Chance POPs remain in the fcst.

Weak ridging builds in Tuesday, followed by more shortwaves
rotating around the S Canada closed low, which has slid a bit
farther E into Hudson bay/NW Ontario), Tuesday night and
Wednesday - with maybe some more isolated- scattered showers.

Temperatures should be within a few degrees of either side of
normal Sunday-Monday night, then run above normal Tuesday-
Wednesday.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
An area of low pressure will move across the region through the TAF
period.

IFR/LIFR conds developing this morning in band of light to
moderate rain...and expected to continue into this evening.
Steady rain moves north between 18-20z...with areas of
drizzle/light rain in its wake this afternoon. Potential for
LIFR visibilities this evening in fog.

Moderate potential for an area of showers and thunderstorms to
move through the region between 02z and 08z. Heavy downpours
are the main threat.

Easterly winds 10-20kt with gusts to 25kt this
morning...weakening late this afternoon into tonight. Northwest
flow develops Friday morning.


     NY Metro Enhanced Aviation Weather Support...

Detailed information, including hourly TAF wind component forecasts,
can be found at: http:/www.weather.gov/zny/n90

KJFK TAF Comments: Isolated gusts to 30 kt this morning.
IFR/LIFR Vsby this afternoon will be conditional on coverage of
drizzle.

KLGA TAF Comments: Isolated gusts to 30 kt this morning.
IFR/LIFR Vsby this afternoon will be conditional on coverage of
drizzle.

KEWR TAF Comments: Amendments may be needed for changing flight
categories. IFR/LIFR Vsby this afternoon will be conditional on
coverage of drizzle.

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

KTEB TAF Comments: Amendments may be needed for changing flight
categories. IFR/LIFR Vsby this afternoon will be conditional on
coverage of drizzle.

KHPN TAF Comments: Amendments may be needed for changing flight
categories. IFR/LIFR Vsby this afternoon will be conditional on
coverage of drizzle.

KISP TAF Comments: Isolated gusts to 30 kt this morning.
IFR/LIFR Vsby this afternoon will be conditional on coverage of
drizzle.

.OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...
.Friday...MVFR/IFR possible. Chance of showers.
.Saturday...VFR.
.Sunday-Monday...MVFR/IFR possible in showers.

&&

.MARINE...
E winds will increase today with SCA criteria across all the
waters. Low pressure will track over the area tonight, so winds
will lighten below SCA levels. Seas on the ocean however will
remain in the 5-10 ft range thru Fri. The SCA has therefore been
extended for these areas. Winds and seas currently look to
remain below SCA levels for entire Memorial Day Weekend.

&&

.HYDROLOGY...
0.75-1.5 inches of rain is forecast through Fri. Locally higher
amounts possible where thunderstorms occur tonight. Minor urban
and poor drainage flooding is possible. Hydrologic impacts are
otherwise not expected Sat-Tue.

&&

.TIDES/COASTAL FLOODING...
A Coastal Flood Warning has been issued for south shore back
bay locations of Nassau County for tonight, otherwise advisories
are in place for areas adjacent to western Long Island Sound,
NY Harbor, and the south shore back bays of the western Long
Island.

While astronomical tides are lower this morning, a strengthening
easterly flow will bring the potential for localized brief minor
flooding for those areas under either a warning or advisory
later tonight. A statement is in effect for this morning.

The primary threat for minor to moderate coastal flooding will
be during the high tide cycle tonight. How quickly easterly
winds begin to weaken this afternoon/evening will be key to the
potential for seeing widespread versus localized moderate
coastal flooding along the southern bays of NYC and Western LI.
The best chance for widespread moderate coastal flooding at this
time appears to be across the south shore back bays of Nassau
County, where a warning is in effect.

Along Western LI Sound, NY/NJ Harbor including Manhattan, and
the southern bays of Suffolk County, widespread minor coastal
flooding is likely with less than 1/2 ft of surge needed in many
places to reach minor flood thresholds. Minor flood thresholds
could briefly be touched along the eastern bays of LI and SE CT.

The potential for dune erosion looks to be low and localized.

Minor coastal flooding is likely during the nighttime high tides
for the southern bays of Western LI through the memorial day
weekend. While along western Long Island Sound, lower NY
Harbor, and the southern bays of NYC minor coastal flooding it is
a possible at those times.


&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT
     Friday for CTZ009-010.
NY...Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for
     NYZ074-075-178.
     Coastal Flood Advisory from 10 PM this evening to 1 AM EDT
     Friday for NYZ071-073-078-176-177.
     Coastal Flood Advisory from 8 PM this evening to midnight EDT
     tonight for NYZ080.
     Coastal Flood Advisory from 7 PM this evening to 1 AM EDT
     Friday for NYZ072.
     Coastal Flood Warning from 7 PM to 11 PM EDT this evening for
     NYZ179.
NJ...Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for
     NJZ006-106-108.
MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ330-
     335-338-340-345.
     Small Craft Advisory until 6 PM EDT Friday for ANZ350-353-355.

&&

$$
SYNOPSIS...JMC
NEAR TERM...JMC/DS/DW
SHORT TERM...JMC
LONG TERM...JMC/Maloit
AVIATION...BC/NV
MARINE...JMC
HYDROLOGY...JMC
TIDES/COASTAL FLOODING...


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