Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 240617
AFDOKX

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

.SYNOPSIS...
Strong low pressure moving up the east coast passes southeast of
Long Island Tuesday afternoon into Tuesday night. High pressure
then builds in on Wednesday. Low pressure moves across the Great
Lakes Wednesday night and deepens as it moves into SE 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 /THROUGH TUESDAY/...
Flood watch was cancelled as rainfall amounts were generally
around an inch or less with an additional half inch by daybreak.
These amounts should not pose any hydrologic issues.

Additionally, winds were gradually coming down and the wind
advisory has expired for NYC metro, southern Westchester in NY,
and Fairfield County in CT. It remains up for LI and the remainder
of southern CT through 6 AM.

Reports of 1-2 inches of sleet have been received across Orange
County with even some icing in northern Westchester. Winter
Weather Advisories remain up for Orange and Putnam Counties in
the Lower Hudson Valley and Passaic County in NE NJ. Most reports
indicate sleet or pockets of freezing rain. No snowfall reports as
of yet. Thus, still looking for 1-2 inches of mainly sleet and a
light coating of ice across the advisory area. An SPS was also
issued for areas outside the advisory across the Lower Hudson
Valley and interior SW CT where there could be pockets of freezing
rain. Some warming aloft will likely allow for a transition to
rain toward daybreak.

Winds and heavy precip should fall off after 06Z, but rain still
remains likely by daybreak.

The center of the storm slowly shifts east through the day south of
Long Island as the surface low becomes stacked with the 500mb low.
Rain remains likely through at least early afternoon with chances
dropping off by the evening. It could be cold enough across mainly
the higher elevations of Orange County for sleet to be mixed in.
It`ll be breezy to start, but winds will diminish through the day
as they shift more northerly behind the departing storm.

&&

.SHORT TERM /TUESDAY NIGHT/...
The vertically stacked low moves slowly along the New England
coast during the night with the chances of precipitation slowly
lowering from the southwest to the northeast. Height begin to rise
late at night as weak ridging builds to the west.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Global models and ensembles are in general agreement through the
long term period. The main story will be a return to more
seasonable temperatures late in the week into the weekend with
drier than normal conditions favored.

For Tuesday night...Strong low pressure affecting the area early
this week will gradually depart to the east as negatively tilted
trough axis swings across. Energetic flow and moisture wrapping
around the low could still bring some precipitation Tuesday evening,
tapering off from west to east after midnight. Will need to watch
thermal profiles mainly across Orange county as warm nose aloft may
still support a rain/sleet mix. Precipitation ends after midnight as
lift departs to the east. Lows range from the lower 30s inland to
the middle and upper 30s near the coast.

High pressure ridge briefly returns on Wednesday. Temperatures will
still be on average ten degrees above normal with forecast highs in
the upper 40s to near 50 degrees. 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 /06Z TUESDAY THROUGH SATURDAY/...
Low pressure off the Mid-Atlantic coast will stall south of Long
Island today, then track into the Gulf of Maine tonight.

Northeasterly flow will continue this morning before backing to
the north today. Winds will lessen and back to the northwest
tonight.

Rain will continue into this morning, with a mix of rain and sleet
at KSWF. The heavy rain will end by 10Z, with light rain and
drizzle lingering thereafter. The light rain and drizzle is
expected to end after 00-06Z Wednesday, with winds backing to the
northwest and weakening significantly.

.OUTLOOK FOR 06Z WEDNESDAY THROUGH SATURDAY...
.Tuesday night...MVFR improving to VFR. Decreasing winds.
.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...
Deep low pressure remains off the southern NJ coast and will
track northward along the coast overnight and through Tuesday. Low
level winds to around 65 KT were not fully mixing to the water
surface, however near storm force gusts are possible on the ocean
waters with gale force gusts across the remainder of the waters.

As heavier precipitation occurs into the overnight, and the low
tracks into the eastern ocean waters an occasional gust may still
approach or reach hurricane force.

Max seas could peak at around 20 ft on the ocean, 9-12 ft from
Orient Point east in the sound, and 8-9 ft on central Long Island
Sound, per combo of WaveWatch/NWPS guidance and wind/wave
climatology.

Winds and seas then diminish throughout the day Tuesday, but with
Gales still likely early on.

The low pressure system departs Tuesday night with a steep enough
pressure gradient to bring potential for SCA winds on all waters.
Ocean seas will also range from 6 to 9 ft. 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.

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...
QPF through tonight will likely be in the 1-2 inch range, with
locally higher amounts possible with the heaviest rainfall. These
amounts should not pose any hydrologic issues.

&&

.TIDES/COASTAL FLOODING...
One more round of minor to moderate coastal flooding in the
southern and eastern bays of Long Island Tuesday morning.
Elsewhere mainly localized minor coastal flooding.

An ensemble of guidances is showing surge falling to 2 1/2 to 3
ft for Tuesday morning but with a higher astro tide. Based on a
weaker storm evolution and winds backing to n/ne for Tue morning
high tide...could see water levels fall on the lower end of
guidance.

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 8 to 14 ft surf today
into Tue.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory until 6 AM EST early this morning for CTZ006>008-
     010>012.
     Wind Advisory until 1 AM EST early this morning for CTZ005-009.
NY...Coastal Flood Warning from 4 AM to 11 AM EST this morning for
     NYZ079>081-179.
     Wind Advisory until 6 AM EST early this morning for NYZ078>081-
     177-179.
     Winter Weather Advisory until 7 AM EST this morning for NYZ067-
     068.
     Coastal Flood Advisory from 4 AM to 8 AM EST this morning for
     NYZ074-075-178.
     Wind Advisory until 1 AM EST early this morning for NYZ071>075-
     176-178.
NJ...Winter Weather Advisory until 7 AM EST this morning for NJZ002.
     Coastal Flood Advisory from 4 AM to 8 AM EST this morning for
     NJZ006-106-108.
MARINE...Gale Warning until 6 AM EST early this morning for ANZ330-335-
     338-340-345.
     Storm Warning until 6 AM EST early this morning for ANZ350-353-
     355.

&&

$$

UPDATE...DW
AVIATION...FEB/JMC



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