Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 181244
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
744 AM EST Wed Jan 18 2017

.SYNOPSIS...
Weak low pressure passing south of Long Island early this morning
will move out to sea and gradually strengthen through tonight.
Meanwhile weak high pressure will build from the west tonight into
Thursday, and settle overhead Thursday night into early Friday. A
weakening frontal system will approach Friday night into Saturday,
and then dissipate. Strengthening low pressure will approach from
the southwest from Sunday into Monday while a gradually
strengthening high builds into the Canadian Maritimes. The low
will continue to approach Monday night into Tuesday while slowly
weakening.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Sfc obs indicate a 1010 mb low still south of eastern Long Island
as of 11Z. Most of the associated steady light rain has moved to
the east, with leftover patchy fog and drizzle remaining. Spotty
light freezing rain/freezing drizzle is likely still occurring
early this AM in the highest elevations of Orange/Western
Passaic/Rockland/Putnam, primarily above 750 ft, where air and
ground temps remain at or just below freezing.

After the surface low passes, and as a mid level low moves into
the Mid Atlantic region, weak sfc troughing and cyclonic flow
should linger, maintaining overcast skies and lingering light
rain/drizzle, especially across central/eastern Long Island where
orographic lift of the nearly saturated air mass will also come
into play as sfc flow backs northerly.

Highs today should be from the upper 30s well inland, to the
lower/mid 40s elsewhere, per MAV/MET blend which was on the mark
yesterday.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Low level moisture will remain trapped beneath an inversion, but
as shortwave mid level ridging passes across this evening behind
the mid level low moving out over the Atlantic, there could be a
break in any light rain/drizzle before another mid level
shortwave trough approaches and moves across NY and New England
after midnight. Still the possibility for some spotty light
freezing rain/freezing drizzle well inland as temps drop to the
upper 20s well inland, to the mid 30s across NYC metro and Long
Island.

Deep layer high pressure should return on Thu as this next
shortwave trough passes east. After any early to mid morning
clouds and patchy fog, afternoon sunshine and a drying downslope
NW flow should send temps into the lower 50s across NYC metro and
Long Island on Thu, with mid/upper 40s inland.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
In the mid to upper levels, a more amplified pattern is shaping
up starting Thursday night and going into early next week. There
will be intermittent influences from the upper level subtropical
jet, the most prominent being Sunday night through Monday night.
This is when jet stream speeds will be the highest on average.

At the surface, two frontal systems will be featured in the long
term making for the next chances of precipitation. The first being
Friday night into Saturday associated with a weakening frontal
system. These features essentially dissipate Saturday leaving the
region on the western side of a broad weak area of high pressure.
A stronger frontal system approaches late Sunday into early next
week with some more baroclinicity as evidenced from the sharpening
wavelengths.

The winds pick up and set up an easterly fetch in response to an
increasing pressure gradient as a strengthening high pressure builds
southward from Southeast Canada and this strong frontal system
approaches from the Southeast U.S. The persistent fetch may lead to
some possible coastal flooding as we approach a new moon which will
be a few days later. Too soon to tell how much surge there will be
though. The high eventually traverses Nova Scotia and settles
southeast of there in the Northern Atlantic, keeping the region in
an easterly flow.

With a cool maritime airmass in place, there will be a low chance
of rain mainly on Friday night associated with the approach of the
first week frontal system. Amounts of rain forecast from this
look to remain under a quarter of an inch. The second stronger
frontal system will have both higher chances of rain plus larger
rainfall amounts due to the longer period of time of rain
forecast. Chances of rain begin mainly Sunday afternoon and will
be highest (mainly between 50-60 percent) on Monday and Monday
night. See hydro section for further details on this event.

Both of the aforementioned systems look to be mainly rainfall with
the setup and positioning of the forecast high and low pressure
areas. Across the interior areas, some mixing with sleet will be
possible late Sunday night into early Monday.

Temperatures during the long term look to remain above normal. Highs
mainly in the 40s except for Saturday and Tuesday when highs are
forecast more into the low 50s on average. Relatively coldest night
forecast is Thursday night when lows are forecast to range from the
mid 20s to mid 30s. Otherwise other nights in the long term are
forecast to have lows mainly in the 30s with NYC not deviating too
much from the 40 degree mark.

&&

.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
Low pressure moves south and east of Long Island today followed by
high pressure building in from the west tonight.

Mainly IFR this morning with pockets of LIFR. IFR is expected to
continue through the morning with gradual improvements to MVFR
this afternoon. There is some potential for IFR conditions to
linger through the afternoon and possibly into the evening.
Improvements in flight categories should occur tonight with VFR
likely by daybreak Thursday morning.

NE winds this morning will back to the N and then NW this
afternoon and evening. Speeds around 10 kt or less expected,
highest at city terminals.

     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 for flight categories as
IFR may last longer than indicated. Winds back to the NW this
afternoon staying to the right of 310 magnetic.

KLGA TAF Comments: Amendments likely for flight categories as
IFR may last longer than indicated. Winds back to the NW this
afternoon staying to the right of 310 magnetic.

KEWR TAF Comments: Amendments likely for flight categories as
IFR may last longer than indicated. Winds back to the NW this
afternoon staying to the right of 310 magnetic.

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

KTEB TAF Comments: Amendments likely for flight categories as
IFR may last longer than indicated.

KHPN TAF Comments: Improvement in flight category from LIFR to
IFR this morning could be off by a few hours. IFR may linger
longer this afternoon than indicated.

KISP TAF Comments: Amendments likely for flight categories as
IFR may last longer than indicated.

.OUTLOOK FOR 12Z THURSDAY THROUGH SUNDAY...
.Thursday-Friday...VFR.
.Friday night...Chance of MVFR or lower in -RA.
.Saturday-Saturday night...VFR.
.Sunday...Chance of MVFR of lower in -RA, with best chance at
CT/Long Island Terminals.

&&

.MARINE...
Easterly flow ahead of the low south of Long Island is producing
SCA conditions on the ocean E of Fire Island Inlet, and wind gusts
on the eastern Sound/Bays have briefly peaked at 25 kt per Central
Sound buoy ob. As the surface low just south of Long Island
passes, winds should back northerly and increase once again, with
gusts up to 25 kt, and 5+ ft seas spreading westward to all ocean
waters late today. These SCA conds should continue into Thu
afternoon, with some residual 5-ft seas still possible
Thu evening.

SCA conditions are possible on the ocean on Sunday, and for all
waters on Monday, with the approach of the next storm. Gales may
be possible on the ocean Monday afternoon/evening, and ocean seas
could reach 6-11 ft Sunday night into early next week as an
easterly fetch sets up.

&&

.HYDROLOGY...
For Sunday night into early next week, low pressure could bring a
significant rainfall of 1-2 inches. Some minor flooding may be
possible.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 4 PM this afternoon to 6 PM EST
     Thursday for ANZ355.
     Small Craft Advisory until 6 PM EST Thursday for ANZ350-353.

&&

$$
SYNOPSIS...Goodman/JM
NEAR TERM...Goodman
SHORT TERM...Goodman
LONG TERM...JM
AVIATION...DS
MARINE...Goodman/JM
HYDROLOGY...Goodman/JM


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