Area Forecast Discussion
Issued by NWS Upton, NY

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000
FXUS61 KOKX 241632
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1132 AM EST Tue Jan 24 2017

.SYNOPSIS...
Strong low pressure just south of Long Island this morning will
track slowly northeast through tonight and up into the Canadian
Maritimes on Wednesday. High pressure builds in briefly for
Wednesday. Low pressure moves across the Great Lakes Wednesday
night and deepens as it moves into southeast Canada, remaining
nearly stationary through the upcoming weekend. This low will send
a series of cold fronts through the area, one on Thursday and then
again over the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Will keep the Winter Weather Advisory up across the Lower Hudson
Valley and interior Southwest Connecticut for the duration of the
morning. Surface Temps have warmed slightly over the past couple
of hours and the biggest concern is that they still manage to cool
back to freezing in spots as the low level flow becomes more
northerly. Guidance suggest that this could happen roughly in the
vicinity of the Hudson River (north of the city) and points west.

Based on 12z soundings and latest ACARS soundings, it appears that
the 06/12z NAM is closest to reality regarding the strength of the
warm nose aloft and the cold air below it. Based on this, would
think that it`ll be mostly rain falling this afternoon with the
warm nose strengthening, with at least pockets of freezing rain
possible. Also, for the NW zones, perhaps some sleet mixing in as
well. Depending on the surface temp trends, might have to extend
the Advisory to cover the afternoon.

As a negatively tilted closed upper low lifts to northeast today,
models are keying in on a deformation zone on its west side with
the potential for banded moderate rain this afternoon, mainly
impacting NYC metro and points north and west. There is some
uncertainty as to where this will exactly set up. An additional
quarter to half inch of rainfall is possible with this band with
lesser amounts elsewhere.

Temperatures will be slow to rise to today, with many locations
holding nearly steady, ranging from the mid 30s inland to the
lower 40s at the coast. Gusty North winds up to 30 mph will be
possible into this afternoon.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
The vertically stacked low moves slowly along the New England
coast tonight with the chances of precipitation slowly lowering
from the southwest to the northeast. Heights begin to rise late
at night as weak ridging builds to the west.

Some of the rain on the backside of this system could transition
over to sleet or freezing rain briefly before coming an to end
tonight. Overnight lows will drop to around freezing inland, and
in the mid and upper 30s at the coast.

High pressure and sunny skies will be on tap for Wednesday.
Building heights aloft and winds backing to the west will result
in a much warmer day, with highs in the mid and upper 40s. This
is about 10 degrees above normal.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The next shortwave trough moves across the Great Lakes Wednesday
night and swings across the region on Thursday. The GFS and some
of its ensemble members indicate potential for showers as the cold
front associated with this shortwave moves through Thursday. Other
models and ensembles are drier. This appears to be due to the
amplitude of H5 energy and moisture return. Will cap pops off at
30 percent at this time.

Cold front moves offshore Thursday afternoon and evening. This front
signifies a return to more seasonable temperatures, potentially a
few degrees below normal. There is also good agreement among the
models and ensemble means with a hemispheric pattern change with
deep ridging across Western North America and mean troughing over
the east. Dry forecast into the weekend although there is enough
energy aloft within cyclonic flow that a few snow showers may reach
interior sections.

Late in the weekend into early next week, there are signals the mean
trough across the east may sharpen up, but it is a bit early to say
if there any impacts to sensible weather.

&&

.AVIATION /16Z TUESDAY THROUGH SATURDAY/...
Low pressure will stall south of Long Island today, then track
northeast into the Gulf of Maine tonight.

Ceilings will be right around 1000 ft/visibilities around 3 miles
into the afternoon, with conditions varying between IFR and MVFR
as a result. Conditions begin to improve this evening, eventually
becoming VFR by Wednesday morning. Most terminals will see rain,
however KSWF will see a mix of rain, sleet, and freezing rain this
morning and possibly into this afternoon. Sleet may also mix in
for a brief period this morning at KHPN. Steadier rain may return
in and around the city terminals this afternoon, although exactly
where any more persistent rain sets up remains in question.

Gusty northeast flow will gradually decrease and back to the
northwest this afternoon.

     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: Amendments likely into this afternoon for
varying conditions between IFR and MVFR.

KLGA TAF Comments: Amendments likely into this afternoon for
varying conditions between IFR and MVFR.

KEWR TAF Comments: Amendments likely into this afternoon for
varying conditions between IFR and MVFR.

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

KTEB TAF Comments: Amendments likely into this afternoon for
varying conditions between IFR and MVFR.

KHPN TAF Comments: Amendments likely into this afternoon for
varying conditions between IFR and MVFR.

KISP TAF Comments: Amendments likely into this afternoon for
varying conditions between IFR and MVFR.

.OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY...
.Wednesday and Thursday...VFR. NW winds become W-SW Wednesday near
10 kt. SW-W winds Thursday 10-15 kt gusts to near 20 kt.
.Friday...VFR. W winds 10-15 kt gusts to 20 kt.
.Saturday...VFR. W winds 10-15 kt.

&&

.MARINE...
Will continue the gale warning over the ocean waters into early
afternoon. Might need to extend it as the pressure gradient
remains pretty tight on the back side of the departing storm.

The low continues to pull away tonight with a tight enough
pressure gradient for SCA conditions to continue with NW gusts
25-30 kt.

Winds diminish on all waters Wednesday with a weakening pressure
gradient as high pressure settles over the waters. Ocean seas
should also subside below 5 ft by evening.

SCA conditions are likely on all waters on Thursday with a
steepening pressure gradient with a cold front passage. These
conditions may continue into Friday and possibly into Saturday,
especially on the ocean waters.

&&

.HYDROLOGY...
An additional quarter to half inch of rainfall is possible today
as a band of moderate rain develops on the backside of departing
low pressure. The exact placement is uncertain, but likely from
from around the NYC metro to points north and west. These amounts
should not pose any hydrologic issues.

&&

.TIDES/COASTAL FLOODING...
High tide has passed. However, there is some residual minor
coastal flooding for shorelines of Southwest Suffolk County on
Long Island, particularly at Lindenhurst. For Southern Nassau
County on Long Island, this is expected to be quite localized with
the residual minor coastal flooding. Expecting all gages to fall
below minor coastal flooding benchmarks by 1pm. Tidal departures
are approximately 2 to 2.5 ft above astronomical.

Tonight`s high tide levels will be the lower of the daily high
tidal cycles and along with increasing offshore flow, no other
coastal flooding is expected. However, Wednesday morning`s high
tides will be approximately 0.1 to 0.2ft higher than this
morning`s high tides. There will be increasing offshore flow as
winds become more westerly. There could be some isolated tidal
gages that touch or slightly exceed minor coastal flooding
thresholds across the South Shore Bays but this is a low
probability at this time.

The other continuing concern will be for widespread dune erosion
and localized washovers at Atlantic ocean beaches from elevated
waters levels and an east to west sweep of 9 to 13 ft surf.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory until noon EST today for CTZ005.
NY...Winter Weather Advisory until noon EST today for NYZ067>070.
     Coastal Flood Advisory until 1 PM EST this afternoon for
     NYZ080.
NJ...Winter Weather Advisory until noon EST today for NJZ002.
MARINE...Small Craft Advisory until 6 AM EST Wednesday for ANZ330-335-
     338-340-345.
     Gale Warning until 6 AM EST Wednesday for ANZ350-353-355.

&&

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


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