Area Forecast Discussion
Issued by NWS Upton, NY

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956
FXUS61 KOKX 222311
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
711 PM EDT Tue Aug 22 2017

.SYNOPSIS...
A cold front approaches tonight and passes through Wednesday
morning. High pressure then dominates the weather pattern from
Wednesday afternoon into early next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Forecast is on track with some minor changes made to reflect
current conditions. Earlier this afternoon, 2 lines of
convection were moving toward the area, with some of the
thunderstorms becoming severe. A fair amount of weakening has
occurred with these lines over the last couple of hours and
much of the dynamics to support severe thunderstorms have pushed
well north of the tri- state. Also, the 2 lines have become one
larger area of showers and thunderstorms, with a more
stratiform look to it over central Pennsylvania. Cloud top
warming is also noted in the IR. With that said, there still is
a chance for some of the storms that form ahead of this main
area to become strong to severe, with the main threat being
damaging winds in the strongest storms.


A Severe Thunderstorm Watch has been issued for Passaic, Orange,
and Putnam counties until midnight tonight.


A pre-frontal trough and cold front move in from the west. Showers
and thunderstorms are expected with both boundaries. CAPE and shear
values are sufficient for strong storms with gusty winds. Some
of these storms may become severe, with damaging winds being the
main threat across Passaic, Orange, and Putnam counties and a
Severe Thunderstorm Watch has been issued until midnight tonight
for these areas. Better chances for the stronger gusts would be
along the pre- frontal trough as CAPE will be greater during
the evening hours. The trailing cold front will have less CAPE
to work with during the overnight hours, but winds aloft may
still allow for strong gusts.

The steering flow should be quick enough to mitigate chances of
flash flooding and training of cells is not expected to be a factor,
but with high moisture content around, minor nuisance/urbanized
flooding is possible.

A high rip current risk remains in effect into tonight.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
The cold front will be right over the tri state area at the start of
Wednesday morning and should be east of Montauk by late morning.
Still cannot rule out a lingering shower or thunderstorm mainly east
of the city in the morning. Much drier air then filters in behind
the cold front for the afternoon with mostly sunny conditions. It
will start to feel less muggy as well, and highs will be in the
lower and mid 80s. Mainly clear for Wednesday night. Low
temperatures across the northernmost suburbs and the Pine Barrens
Region are expected to drop into the mid 50s.

There is a moderate rip current risk for Wednesday.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
A mainly quiet weather pattern takes shape in the long term as
canadian high pressure will dominate with below normal temperatures
and mainly dry conditions.

Anomalous longwave trough will be swinging across the eastern states
on Thursday, with a vigorous piece of energy trailing behind the
main trough axis. This energy is progged to dive towards the region
Thursday night into early Friday morning at the same time of some
upper jet support. While ensemble members and deterministic runs are
dry with this feature, there is enough lift and brief moisture
return to warrant a low chance pop for showers. The shortwave energy
shifts offshore Friday morning, with the main upper trough lingering
just to the east through the weekend with tranquil conditions. The
surface high settles over the northeast for the weekend, then
centers itself off the New England coast early next week as ridging
builds aloft.

850 temperature anomalies will run 3-6C below normal into the
weekend. This will result in surface temperatures running several
degrees below normal. Forecast highs may be warmest on Thursday, in
the upper 70s and low 80s, and then run in the middle and upper 70s
through Sunday. A more easterly flow sets up early next week which
should help keep highs below normal. Nighttime temperatures will
range from the lower 50s inland to the lower 60s near the coast.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
A cold front approaches the region late today and crosses tonight.

South/Southwest winds will remain gusty into the evening push. Gusts
of 20 to 25 knots expected, with occasional higher gusts possible
along the coastal terminals.

A line of showers/thunderstorms will track across Central NY/PA
this evening. Majority of hi-res guidance, including last
several runs of HRRR, is indicating weakening, with stronger
looking storms passing to the N, as they approach NYC/NJ
terminals between 04z and 07z. Due to this, have not included a
tempo in the 21z TAF amendments as confidence is not high enough
for it or a prevailing VCTS and prob30 can no longer be used.
Not completely ruled out, still a 20-30% chance at the metro
terminals. Confidence slightly higher to the N, thus have
maintained mention at KSWF/KHPN. Gusty winds and MVFR possible
in any stronger thunderstorm. This activity slowly moves through
the area overnight. MVFR to IFR conds may redevelop/persist
especially at KBDR/KISP/KGON until cold fropa passes.

Northwest flow may be just strong enough to preclude seabreeze
development Wed aftn. Otherwise...VFR.

 ...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: 20-30% chc tstms 04z-07z. Seabreeze possible,
but more unlikely to occur Wed aftn.

KLGA TAF Comments: 20-30% chc tstms 04z-07z.

KEWR TAF Comments: 20-30% chc tstms 04z-07z.

KTEB TAF Comments: 20-30% chc tstms 04z-07z.

KHPN TAF Comments: 30-40% chc tstms 04z-07z.

KISP TAF Comments: MVFR to IFR possibly redeveloping this eve
and persisting until late tonight.

.OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY...
.Wednesday...Low prob of -shra/MVFR AM...mainly eastern
terminals. Becoming VFR in AM. W-NW G15KT possible.
.Wednesday night-Sunday...VFR.

&&

.MARINE...
SCA remains on all waters for tonight. Extended the SCA on the ocean
waters until late morning/early afternoon Wednesday as seas at 5 ft
probably linger at least into Wednesday morning. Sub-SCA conditions
then for all waters by late Wednesday afternoon, lasting into the
night.

Tranquil conditions and sub-SCA winds and seas are forecast on the
waters Thursday through the weekend as high pressure will be in
control.

&&

.HYDROLOGY...
Showers and thunderstorms through tonight may cause minor
nuisance/urbanized flooding. No widespread hydrologic impacts are
forecast through the rest of the week.

&&

.TIDES/COASTAL FLOODING...
Tides are running high astronomically. Water levels will
approach minor flood levels across mainly the south shore bays
areas with tonight`s high tide, but are likely to remain just
below.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Rip Current Risk until 9 PM EDT this evening for NYZ075-
     080-081-178-179.
NJ...None.
MARINE...Small Craft Advisory until 6 AM EDT Wednesday for ANZ330-335-
     338-340-345.
     Small Craft Advisory until 11 AM EDT Wednesday for ANZ353-355.
     Small Craft Advisory until 2 PM EDT Wednesday for ANZ350.

&&

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



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