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000
FXUS61 KOKX 181424
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
924 AM EST Fri Jan 18 2019

.SYNOPSIS...
A weak area of low pressure passes to the south, followed by
another to the north later today. A cold front will cross the
area tonight. A significant winter storm impacts the region late
Saturday into Sunday and will be followed by arctic high
pressure Monday into Tuesday. The next frontal system approaches
Wednesday and moves across the region on Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Any lingering light snow has tapered off. Temps warm through the
day as pesky clouds hang on through much of the day. Highs will
approach or reach 40.

A weak area of low pres will pass to the N resulting in the
passage of a weak warm front into early this afternoon. A cold
front then passes this evening. Lows tonight drop into the 20s
area wide with partially clearing skies.

&&

.SHORT TERM /SATURDAY/...
High pressure nosing in from the north will shift east on Sat
with an easterly wind flow developing and low pres moving from
the mid Mississippi Valley into the Ohio Valley. Overrunning
pcpn well out ahead of the center of the storm could begin to
move into western portions of the forecast area as early as mid
to late aftn, but more likely during the late aftn/early eve
hours. Thermal profiles support snow across the entire Tri State
Area into the evening.

High on Sat will generally range in the lower to mid 30s,
although the normally colder spots across the interior could
struggle to get out of the 20s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
A significant winter storm will impact the Tri-State area Saturday
night into Sunday with the coldest air of the season Sunday night
into Monday.

A winter storm watch remains in effect for much of the region late
Saturday into Sunday.

Models have slowly come into better agreement over the last 24
hours, but there still remains a good deal of uncertainty regarding
the exact track, thermal profiles, and precipitation types and
amounts for the winter storm. The southern stream energy with this
system is now over the western US, so continued RAOB sampling should
help establish better agreement today. However, changes in track
forecast are still possible. High confidence remains on this storm
being a high liquid equivalent event.

Strong warm advection will be underway Saturday night with snow
increasing in intensity across the entire region. A corridor of
intense 850-700 mb frontogenesis will move across from 00z Sunday
through 12z Sunday ahead of a broad middle level low. Strong
southerly low level winds will likely bring a tight thermal gradient
and warm nose from south to north through the night. Snow will
change to a wintry mix at the coast around midnight and then across
much of the interior by Sunday morning. Much of Long Island, NYC,
and southeast Connecticut should change to plain rain early Sunday
morning, but the interior may see a mix of sleet and freezing rain.
The depth of the low level cold on the NAM and NAM 3-km is quite
impressive, which may cut down on the freezing rain somewhat and
bring more sleet once the changeover occurs. This may also mean a
greater chance for freezing rain closer to the coast. Confidence in
this scenario is still low, so will continue to show a general sleet
and freezing rain mix across the interior once the warm nose moves
in aloft.

Surface temperatures are also uncertain and dependent on how much
cold air damming occurs. There is a high amount of spread from
temperatures barely rising above freezing even at the coast to
warming well into the 40s. All of this will ultimately depend on the
track of the low. If the low tracks just south of the region, then a
colder profile with potential for more ice at the coast would be
realized. If the low track is further north and over portions of the
region, then warmer air would likely occur with less ice.

The low shifts east of the region on Sunday morning into Sunday
afternoon. Once the low passes east, winds will shift to the north
and north west with a rapid cooling occurring both at the surface
and aloft. There has been a trend in the models for less precip on
the back side of the low, so there may be limited amount of frozen
precipitation as the storm pulls away Sunday afternoon.

As temperatures fall below freezing late Sunday morning into Sunday
afternoon, any standing water on untreated surfaces could quickly
freeze, creating hazardous travel conditions even where little
wintry precipitation occurs.

Highest snow/sleet accumulations are expected mainly NW of NYC where
mostly 4 to 8 inches is currently forecast, and possibly even higher
towards Putnam and Orange Counties. Most other areas are expected to
see less than 6 inches of snow/sleet, however with the potential of
at up to around a tenth or two of ice accretion in addition to
snow/sleet, hazardous conditions are possible for these locations as
well. The only areas not under a watch are parts of Long Island
where 1-3 inches of snow/sleet is expected and maybe at least a
trace of ice could occur. Some of the watch across coastal locations
and possibly NYC may eventually be converted to an advisory
depending on the forecast trends.

Temperatures continue to plummet as arctic air advects into the
region behind the storm. Lows Monday morning will generally be in
the single digits. There is a possibility of a few locations in
interior falling to near 0, especially with a new snow/sleet pack.
Gusty northwest winds will result in wind chills around 10 to around
15 degrees below zero. The lowest wind chills are most likely to
occur across the interior.

The arctic air remains in place on Monday as high pressure builds
into the region. Highs will only be in the teens with wind chills
staying 0 to 10 below. Temperatures should warm into to the 20s and
low 30s on Tuesday and then potentially above normal on Wednesday
ahead of the next system approaching the area.

Timing and thermal profiles with this next system are uncertain due
to model disagreement. Precip chances are in the forecast late
Wednesday into Wednesday night. The primary low tracks up into
southeast Canada, so the majority of the precip should be liquid
with warmer air ahead of the system. Precip may also occur on
Thursday depending on if low pressure develops along the front.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
One weak low pressure system passes to the south and east of
Long Island while another low passes well to the north through
early this afternoon. High pressure briefly builds in this
afternoon into tonight. A deeper low approaches from the
southwest toward 12Z Saturday.

Any lingering light snow ends with conditions continuing to
vary, mainly IFR, and at times MVFR. Ceilings will take some
time to lift, remaining IFR to low MVFR into the early
afternoon. MVFR ceilings likely linger until early this
evening, when conditions improve to VFR.

Winds light NE, become light southerly around midday, then
W-NW this evening and tonight.

   ...NY Metro Enhanced Aviation Weather Support...

Detailed information, including hourly TAF wind component fcsts,
can be found at: http:/www.weather.gov/zny/n90

KJFK TAF Comments: Amendments likely with timing and durations
of IFR uncertain.

The afternoon KJFK haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KLGA TAF Comments: Amendments likely with timing and durations
of IFR uncertain.

The afternoon KLGA haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KEWR TAF Comments: Amendments likely with timing and durations
of IFR uncertain.

The afternoon KEWR haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KTEB TAF Comments: Amendments likely with timing and durations
of IFR uncertain.

KHPN TAF Comments: Amendments likely with timing and durations
of IFR uncertain.

KISP TAF Comments: Amendments likely with timing and durations
of IFR uncertain.


.OUTLOOK FOR 12Z SATURDAY THROUGH MONDAY...

***HIGH IMPACT WEATHER SATURDAY NIGHT INTO SUNDAY NIGHT***

.Saturday...VFR AM, then snow with IFR vsby developing in the
afternoon, especially from the NYC metros north/west.

.Saturday night...IFR or lower conds throughout. Snow changing
to rain after midnight at NYC/Long Island terminals, and to a
wintry mix at northern terminals. LLWS likely NYC metro/coastal
terminals.

.Sunday and Sunday night...IFR or lower likely. Rain from metro
New Jersey, into NYC, and Long Island, and along the
Connecticut coast, with a wintry mix continuing inland, in the
morning. The precipitation transitions back to snow and a wintry
mix, before ending early Sunday evening, then becoming VFR.
LLWS possible in the morning. N-NW winds G25-35kt and flash
freeze likely in the afternoon.

.Monday-Monday night...VFR. NW winds G25-35KT, G25kt in the
evening.

.Tuesday...VFR.

&&

.MARINE...
Sub-advsy conds are expected through Sat although an increasing
easterly flow will be developing Sat aftn.

SCA conditions are expected to develop beginning Saturday
night. Gale force gusts on the waters east of Fire Island inlet,
eastern LI Bays, and eastern LI sound Saturday night. A gale
watch is now in effect for this time period. Gusty winds will
continue into Sunday into Monday with the possibility of gales
on the ocean waters and potentially the near shore waters Sunday
afternoon into Monday. Winds should begin to subside below SCA
levels Monday night, but ocean seas may remain elevated. Sub-SCA
conditions return on Tuesday.

&&

.HYDROLOGY...
One and a half to around two inches of liquid equivalent
precipitation is likely Saturday night through the day on
Sunday. Frozen precipitation may be predominate across the
interior. Liquid rain is probable closer to the coast late
Saturday night into Sunday morning into early Sunday afternoon
where minor urban and poor drainage flooding is possible in any
periods of heavier rain.

&&

.TIDES/COASTAL FLOODING...
Minor to locally moderate coastal flood impacts are possible during
the Sunday morning high tide cycle. Departures of one to one and a
half feet, locally two feet, are needed for minor benchmarks to be
reached and two and a half to three feet are needed for moderate
benchmarks to be reached.

&&

.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...Winter Storm Watch from Saturday afternoon through Sunday
     afternoon for CTZ005>012.
NY...Winter Storm Watch from Saturday afternoon through Sunday
     afternoon for NYZ067>075-078-176>179.
NJ...Winter Storm Watch from Saturday afternoon through Sunday
     afternoon for NJZ002-004-006-103>108.
MARINE...Gale Watch from Saturday evening through late Saturday night
     for ANZ330-340-350-353.

&&

$$
Update...PW