Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 241435
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1035 AM EDT Mon Apr 24 2017

.SYNOPSIS...
High pressure moves well east of the southern New England coast
today as a wave of low pressure moves off the southeastern
coast. The low then tracks up along the eastern seaboard
through Thursday. A weak front moves through Friday into Friday
night, lingering near the region next weekend as high pressure
tries to build along the eastern seaboard.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Updated forecast mainly for temps and dewpoints, but also
lowered high temp forecast by a little across the northernmost
zones with a broken to overcast mid or high deck of clouds
expected there for most of the rest of the day. Haven`t
completely removed the afternoon slight chc PoPs across the
southern fringe of the CWA, but might do so with the next
update. 12Z OKX sounding shows plenty of dry air below 600 mb,
with forecast models holding onto dry air below 850 mb through
the daytime.

Mixing will be limited with a low level inversion setting up.
Weak warm advection will occur under cloudy to mostly cloudy
conditions and temperatures should be able to rise to near
seasonal levels.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
The weak upper ridge remains into Tuesday then weakens while the
mid and lower level ridge weakens. The upper low will be slow to
track north, while a broad weak surface low track north.
Again precipitation will be slow to move north with
probabilities becoming likely by Tuesday morning, and
categorical by Tuesday afternoon. Precipitation will be light
through Tuesday and there may even be a few breaks at times.
Again a strong low level inversion will remain through Tuesday.
So despite an increasing pressure gradient force mixing of the
low level jet winds of 40 to 50 KTS will limited.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Upper closed low gradually weakens as it moves along the middle
Atlantic coast Tuesday night. Surface low and mid/upper level low
are stacked as well, so the overall trend for this system is to fill
as it approaches. The main mechanism for lift Tuesday night is from
isentropic lift as warm and moist air lifts over a warm front to the
south. This lift will be enhanced by a 40-55 kt low level jet. The
strongest portion of the jet is progged to be over Long Island and
southern Connecticut, and this is where highest rainfall totals are
expected. These winds will stay aloft with inverted low level
temperature profiles.

Deep moisture feed around the low off the Atlantic will likely lead
to precipitable water values around 200 percent of normal.
Moderate to locally heavy rain will be possible Tuesday night,
especially across Long Island and southern Connecticut. Totals range
from around a half inch west to around an inch east for the Tuesday
night period.

Low level jet and deepest moisture work east Wednesday morning.
Middle levels of the atmosphere dry out as the upper low continues
to track up the coast. The rain should transition to light rain or
possibly some drizzle with low levels remaining saturated through
the day. Saturated low levels look to remain in place Wednesday
night into Thursday as the stacked low slowly moves to the north and
east. Some question as to whether or not there will be any
precipitation. Light rain or possibly drizzle may linger across
portions of Long Island and southern CT through Wednesday night. A
larger upper trough developing over the CONUS should help to push
the low off to the north and east on Thursday, bringing an end to
any lingering precip. Low clouds may hang on through the day
however.

A weak front move through Friday into Friday night. Moisture and
lift with this front are not impressive, so not expecting anything
more than a few showers at this time. This boundary may linger near
the region into the weekend as upper level ridging builds along the
east coast. Stronger westerlies may remain over or just to our
north, so will need to watch any ripples in the flow as some energy
could ride along the periphery of the ridge from the trough out
west. Will show a dry forecast on Saturday and then slight chance
PoPs on Sunday.

A warming trend in temperatures is anticipated Wednesday into the
weekend. Highs will continue to increase each day, with temperatures
running 10 to 15 degrees above normal by the weekend. Coolest
locations will be near the coast as afternoon sea breeze
circulations develop.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
VFR through the first half of this evening as a low-level ridge
across the area gradually gives way to low pressure moving
slowly up the East Coast.

Mid and high level ceilings will gradually lower through the day
with the potential for MVFR/IFR conditions in light rain after
06Z.

Winds become E/SE at 10 kt or less late this morning into the
afternoon for most terminals. There will likely be some
variability of the flow by 20 to 30 degrees at times. Winds
begin to back around to the E/NE this evening.

     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: Winds may vary +/- 20 to 30 degrees.

KLGA TAF Comments: Winds may vary +/- 20 to 30 degrees.

KEWR TAF Comments: Winds may vary +/- 20 to 30 degrees.

The afternoon KEWR haze potential forecast is GREEN...which implies
slant range visibility 7SM or greater outside of cloud.

KTEB TAF Comments: Winds may vary +/- 20 to 30 degrees.

KHPN TAF Comments: Winds may vary +/- 20 to 30 degrees.

KISP TAF Comments: Winds may vary +/- 20 to 30 degrees.

.OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY...
.Tonight...MVFR/IFR in rain late.
.Tuesday...IFR/LIFR in rain. NE gusts 20-25 KT near coast
possible during the day.
.Wednesday...MVFR/IFR, possibly improving to VFR later in the
day.
.Thursday-Friday...VFR.

&&

.MARINE...
No changes to the forecast at this time as all appears to be on
track.

High pressure east of Long Island and extending west into the
forecast waters will move east through today as a low over the
southeastern states moves off the southeastern coast. The low
will slowly deepen and track north along the coast tonight into
Tuesday. A weak surface pressure gradient force will increase as
the low moves north. Sustained easterly winds will increase
tonight, reaching to near small craft advisory levels on the
ocean waters. Winds will also become gusty, however, with a
strong low level inversion developing mixing will be limited.
Gusts will be around small craft levels on the ocean late
tonight, and then on the remainder of the waters by Tuesday
morning, continuing into Tuesday evening. Seas build on the
ocean waters and will remain above small craft through at least
Tuesday.

SCA winds gradually weaken Tuesday night on LI Sound, LI Bays, and
the NY Harbor. However, SCA wind gusts are likely to continue on the
ocean and seas will continue to build. Winds will remain below gale
force as low level inversion prevents stronger winds from mixing
down. Winds diminish below SCA on Wednesday on the ocean, and will
remain under criteria on all waters until the end of the week. E-SE
swells will keep ocean seas elevated through Friday.

&&

.HYDROLOGY...
Total rainfall of 3/4 to 2 inches of rainfall is possible
tonight into Wednesday. The highest amounts are most likely to
occur across eastern Long Island and southeastern Connecticut,
where minor flooding of poor drainage and low lying areas is
possible.

&&

.TIDES/COASTAL FLOODING...
There is the potential for minor coastal flooding along the
southern bays of western Long Island and western Long Island
Sound with the Tuesday evening high tide cycle. This is in
response to a low pressure system moving northward along the
eastern seaboard. Only 1/2 to 1 foot of surge is needed to
reach minor flood thresholds Tuesday evening.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 6 AM to 8 PM EDT Tuesday for ANZ330-
     335-338-340-345.
     Small Craft Advisory from 2 AM Tuesday to 6 AM EDT Wednesday
     for ANZ350-353-355.

&&

$$
SYNOPSIS...DS/MET
NEAR TERM...JC/MET
SHORT TERM...MET
LONG TERM...DS
AVIATION...JM/DW
MARINE...DS/MET
HYDROLOGY...DS
TIDES/COASTAL FLOODING...


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