Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 191810
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
110 PM EST Sat Jan 19 2019

.SYNOPSIS...
A significant winter storm will impact the Tri-State beginning
this evening and continuing through Sunday. The storm will
deepen as it moves into the Canadian Maritimes Sunday night.
Arctic high pressure will then build in early next week. The
next frontal system will approach from the west on Wednesday,
and may stall nearby Thursday into Thursday night. The weather
pattern could remain unsettled into Friday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Minor updates, but tweaks made to precip timing (delay), and
sky. Will continue to monitor warming trend noted in available
guidance, but no changes at this time to winter headlines.

Developing storm system across the south central states will rapidly
approach this afternoon. High pressure builds across southeast
Canada. Much of the daylight hours will remain dry, but clouds
increase and thicken from west to east.

Light snow may begin to break out from NYC on west as warm advection
increases ahead of the low pressure/storm system later in the
day.

High temperatures will range from near 30 inland to the
middle/upper 30s at the coast.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
A significant winter storm will impact the Tri-State tonight
and continue through Sunday evening.

Changes to the winter weather headlines:

The winter storm watch is no longer in effect and has been
replaced with a winter weather advisory for NYC, northwest Long
Island, portions of NE NJ, and southern CT. The watch was
cancelled for southern Queens and southern Nassau with no
advisory in effect.

The Winter Storm Warning remains in effect for portions of
northeastern NJ, the lower Hudson Valley and for extreme western
CT.

There appears to be a growing consensus on the track of the
surface low associated with the winter storm system. The GFS and
its ensemble remains a northwest and warm outlier. However,
much of the rest of models are indicating the low will track
across the Middle Atlantic tonight and then along or just south
of the Long Island coast. What this ultimately means for
sensible weather is that there has been a trend towards slightly
warmer conditions and less snow/sleet accumulation close to the
coast and across southern Connecticut. With this track, the
potential exists for more freezing rain across the northwest
interior as surface temperatures should remain below freezing
for the entire event.

All locations will begin as snow this evening and the snow may
be moderate to locally heavy as an intense area of 850-700 mb
frontogenesis lifts across the region. As this occurs,
temperatures around this layer will begin warming above
freezing. The surface coastal front and its positioning are an
aspect of this event that still may change. As of this forecast
package, it appears to be close enough that surface
temperatures will begin warming above freezing from an
increasing easterly flow across Long Island around or just
after midnight. If the coastal front shift further north, then
temperatures may even be warmer than currently expected. On the
other hand, if the coastal front stays just south, winds may
stay NE longer and could hold temperatures down.

The precipitation transition zone lifts north through the rest
of the early morning hours. The precipitation may go from snow
to rain across southern and eastern Long Island. Temperatures
may take a bit longer to warm above freezing further north and
west, so some sleet or freezing rain is possible. All liquid is
expected across portions of NE NJ, NYC metro, Long Island, and
coastal Connecticut by day break Sunday morning. The rain may
also be heavy at times which create minor urban and small
drainage flooding.

The snow will likely hang on longest across the interior, but
the warm nose should lift north around or just after 06z early
transitioning the snow to a wintry mix of snow and sleet and
then sleet and/or freezing rain.

The intensity of the precipitation should begin to taper off
from west to east Sunday morning and come to end early Sunday
afternoon. There has been a trend in the models for less wrap
around precipitation as lift really shuts off Sunday morning.
Any wrap around may stay to the north of the region, but will
still mention a chance for mixed precip early Sunday afternoon.

Snow and sleet totals in the warning range from 4 inches across
NE NJ to around 8 inches across Orange and Putnam counties.
This will combine with around one tenth to around one quarter
inch of ice accretion. Snow and sleet totals in the advisory
area range from 1 to 3 with a trace of ice across NW Long
Island, NYC metro to 2 to 4 inches with trance to one tenth of
an inch of ice across coastal CT. 3 to 5 inches of snow/sleet
and one tenth to one quarter of an inch of ice forecast across
the interior of southern Connecticut.

Snowfall rates may reach an inch an hour at times tonight,
especially just before the transition zone and across the
interior. Rates could reach 2 inches an hour across the NW
interior.

If the storm track is further inland, snow and ice amounts will
be less. If the storm track is more south of Long Island, then
there could be more snow and ice even down to the coast.
However, this scenario appears to be a lower probability of
occurrence.

The next concern Sunday afternoon is the plummeting
temperatures. NW winds on the backside of the low will help
advect arctic air into the region. Any standing water on
untreated surfaces will freeze. This may be handled in another
winter weather advisory once the first portion of this event has
ended. The current forecast has temperatures falling into the
teens inland and 20s near the coast by early evening.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
An Arctic air mass will build Sunday night through Tuesday
behind the departing low which will be heading into the Canadian
Maritimes Sunday night. Cyclonic flow aloft with upper level
low moves in for Sunday night into Monday.

The coldest and most frigid air of the season this far will take
hold Sunday night through Monday night. Dangerous wind chills
are also expected. The air mass should moderate thereafter
with more ridging aloft. Tuesday`s forecast highs are in the mid
and upper 20s, with Tuesday night`s lows from the upper teens
to upper 20s.

A low pressure system moves in for Wednesday into Thursday
timeframe with perhaps a stalled front nearby. Aloft, a large
longwave trough develops west of the region. Unsettled weather
then remains with low pressure not that far away and high
pressure well to the north of the region for the end of next
week with a deep trough still remaining aloft in the Northeast.
The pattern results in a more mild temperature trend for the
region. Highs will be more in the lower and mid 40s for
Wednesday and upper 30s and lower 40s for Thursday. Temperatures
should return closer to avg values for the end of next week.

Sunday evening starts well below freezing for the entire region
(temperatures range from interior in mid to upper teens to mid
to upper 20s for coast including NYC). Temperatures will
continue to plummet during Sunday night with lows by early
Monday expected to be the coldest thus far experienced this
season with most locations having forecast min temperatures from
0 to 10. Gusty NW winds will help advect in a significantly
colder airmass with subzero wind chills starting Sunday night
and continuing into early Tuesday. Gusts are forecast to reach
up to 35 to 40 mph. These gusts reach 40 to 45 mph at times on
Monday. There is a chance for gusts to peak out slightly higher
across parts of the region (close to 50 mph) on Monday which is
indicated within particularly the GFS Bufkit profiles.

Potential for wind chill advisory criteria to be met mainly for
locations north and west of NYC (wind chills of -15 to -20) for
Sunday night into early Monday and for a small part of the interior
(parts of Western Passaic NJ, Orange NY, Putnam NY, Northern
Fairfield CT) for wind chills near -15 for late Monday night into
early Tuesday.

Then, another system approaching from the south and west could give
the next wintry precipitation to the region but for now, the
models have the center of the low either near or west of the
region. A lot of uncertainty exists with this system and model
depictions of its evolution and track. There is the possibility
of snow changing to a wintry mix for mainly interior and western
parts of the region Tuesday night into early Wednesday as well
as Wednesday night into early Thursday for far interior
locations. Otherwise, for Wednesday through Thursday, mostly
rain is in the forecast. Another chance of snow is forecast for
Thursday night into Friday of next week behind the system. This
will all be tied to the evolution and progress of a low
pressure system and associated front. Timing of the
precipitation and amounts of precipitation will be affected by
changes in the magnitude and track of the low and associated
system.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
***HIGH IMPACT WEATHER TONIGHT INTO SUNDAY***

High pressure passes to the north as a significant winter storm
approaches from the southwest. The storm will impact the region
this evening into the day on Sunday.

VFR conditions this afternoon will quickly lower after 21Z as
precipitation begins overspreads the area from west to east.
Expect precipitation to begin as snow at all terminals, but
duration may be very brief at KJFK/KISP. Precipitation then
transitions to rain between 03-06Z at KLGA/KEWR/KTEB, with a
period of mixed snow, sleet, and freezing rain possible at KEWR
and KTEB. Transition zone then continues to move north, with
mixed precipitation at KHPN/KBDR/KGON between 03-06Z becoming
all rain by 08Z. KSWF will likely maintain some form of frozen
or freezing precipitation throughout the event.

Snowfall accumulations will generally remain one inch or less at
KJFK and KISP, and between 1-2 inches at KGON. At KLGA and KEWR,
accumulations will range from 1-2 inches with a light glaze of
freezing rain possible. For KTEB, KBDR, and KHPN, snowfall
totals will range from 2-3 inches with less than a tenth of an
inch of ice. At KSWF 6-8 inches of snow and sleet are possible
along with a tenth to a quarter inch of freezing rain.

Easterly winds will increase to 10-15 kt this evening, with a
few gusts possible into tonight. Winds then turn out of the
south Sunday morning before shifting to the northwest and
becoming gusty Sunday afternoon.


.OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY...
.Sunday Afternoon...Becoming MVFR and eventually VFR as
precipitation ends from west to east. Precipitation may end as a
brief period of snow or wintry mix, even at the coast.
Northwest winds G25-35kt with falling temperatures and a flash
freeze likely in the afternoon.
.Sunday Night-Monday night...VFR. NW winds G25-35KT,
diminishing to G20-25KT Monday evening.
.Tuesday...VFR.
.Wednesday-Thursday...MVFR or lower developing in wintry mix
changing to rain. Rain may then change back to a wintry mix
before ending on Thursday.

&&

.MARINE...
Sub advisory conditions will continue on the waters through the
afternoon as high pressure passes to the north a a deepening,
and significant storm approaches from the southwest.

As the storm approaches this evening, easterly winds and gusts will
quickly increase with gales on the eastern ocean waters, eastern
Long Island Sound and eastern bays, with SCA winds and gusts on the
western Long Island Sound, the south shore bays, New York Harbor,
and the ocean waters west of Fire Island Inlet.
The gales will be marginal as a low level inversion quickly sets up
and limits the mixing of higher winds to the water surface.

Late tonight and into Sunday morning winds and gusts may briefly
fall below advisory levels as the low moves into the northern mid
Atlantic region, and a warm front reaches the coastal plain.
Ocean seas will remain elevated as an easterly flow shifts to the
southeast.

Then as the low tracks through the region and to the east, much
colder air moves in on a strong and gusty northwest flow.
Gale conditions will be across all the forecast waters, mainly from
midday through the afternoon. Gale conditions possibly continue into
Sunday evening across all the waters, then diminish to small craft
advisory levels as the low begins to pull away to the northeast.
However, gales may continue on the ocean waters Sunday night into
Monday.

There will be a chance of freezing spray, mainly on the ocean
waters, from late Sunday into Monday.

Winds and seas trend down Tuesday through Tuesday evening. Late
Tuesday night through Wednesday night, wind gusts return to SCA
range for ocean and eastern waters around Long Island and ocean seas
return to at least 5 ft as well.

&&

.HYDROLOGY...
Liquid equivalent amounts for the winter storm range from around
1.50 inches to around 2 inches. Locally higher amounts are
possible, especially across Long Island and southeast
Connecticut. Frozen precipitation may be predominate across the
interior. Liquid rain is likely closer to the coast late
tonight into Sunday morning where minor urban and poor drainage
flooding is possible.

There is too much uncertainty to determine exact liquid amounts
and resulting impacts with mid to late week system.

&&

.TIDES/COASTAL FLOODING...
Model guidance is in close enough agreement to issue warnings and
advsys along coastal locations during the Sunday morning high tide
cycle, with tidal departures expected to range between 1 and 2 ft,
locally 2 to 3 ft. Minor tweaks may be made in subsequent
forecast packages, but feel confident enough water levels in the
south shore bays of Queens and Nassau county will exceed
moderate benchmarks, with Freeport even coming close to major
flooding levels. Thus a coastal flood warning has been issued
here. Widespread minor to locally moderate coastal flooding is
expected at the remainder of coastal locations.

Heavy rain during the time of high tide will exacerbate street
flooding across coastal areas.

&&

.EQUIPMENT...
NYC Central Park winds are out of service until further notice.
Loss of data is due to a severed cable. Parts are on order.

NYC NOAA Weather Radio Station KWO35 (162.55 MHz) will remain off
the air for an extended period of time.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Coastal Flood Advisory from 6 AM to 1 PM EST Sunday for
     CTZ009>012.
     Winter Storm Warning until 6 PM EST Sunday for CTZ005.
     Winter Weather Advisory from 4 PM this afternoon to 10 AM EST
     Sunday for CTZ009>012.
     Winter Weather Advisory from 4 PM this afternoon to 6 PM EST
     Sunday for CTZ006>008.
NY...Coastal Flood Advisory from 6 AM to 1 PM EST Sunday for NYZ071-
     073-078>081-176-177.
     Winter Storm Warning until 6 PM EST Sunday for NYZ067>070.
     Winter Weather Advisory from 4 PM this afternoon to 10 AM EST
     Sunday for NYZ071.
     Coastal Flood Advisory from 5 AM to 9 AM EST Sunday for NYZ072-
     074-075.
     Coastal Flood Warning from 4 AM to 11 AM EST Sunday for NYZ178-
     179.
     Winter Weather Advisory from 4 PM this afternoon to 4 AM EST
     Sunday for NYZ072>075-078-176-177.
NJ...Winter Storm Warning until 6 PM EST Sunday for NJZ002-004-103-
     105.
     Winter Weather Advisory from 4 PM this afternoon to 10 AM EST
     Sunday for NJZ006-104-106>108.
     Coastal Flood Advisory from 5 AM to 9 AM EST Sunday for NJZ006-
     106-108.
MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EST Sunday
     for ANZ335-338-345-355.
     Gale Warning from 6 AM to 6 PM EST Sunday for ANZ335-338-345-
     355.
     Gale Warning from 6 PM this evening to 6 PM EST Sunday for
     ANZ330-340-350-353.

&&

$$
SYNOPSIS...JM/DS
NEAR TERM...DS/PW
SHORT TERM...DS
LONG TERM...JM/DS
AVIATION...FEB
MARINE...JM/MET
HYDROLOGY...JM/DS
TIDES/COASTAL FLOODING...
EQUIPMENT...



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