000
FXUS61 KOKX 181807
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
107 PM EST Tue Jan 18 2022

.SYNOPSIS...
Intense low pressure will move north through eastern Canada today,
while high pressure builds from the west. The high will slide to the
south tonight. A frontal system will approach on Wednesday, with
polar front move across Wednesday night into Thursday morning. A
polar large high pressure system builds in from the west
through the end of the week and east of the area Friday night
into Sunday. High pressure builds in for Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Have added iso/sct flurries for portions of the forecast area
for this afternoon based on obs and radar. ACARS soundings and
LAPS date show the freezing height about 500-750 ft, so precip
should remain frozen.

Deep polar trough slides east through the region today with
briefly zonal flow tonight. At the surface, a reinforcing cold
front continues caa on breezy NW flow (NW 15-25G30-40mph).
Highs generally in the mid 30s for the coast and lower 30s
interior.

High pressure noses in overnight with a small window of good
radiational cooling conditions likely overnight, before S/SW
flow increase along the coast ahead of approaching frontal
system. Lows tonight well down into the teens for Interior and
far outlying areas, with 20s elsewhere for the city/coast.
Temps likely rise along the coast late tonight,

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Polar front digs from the northern plains into the Great lakes
Wednesday into Thursday, while California closed low shears
northeast in southern stream towards the region/Mid Atlantic
Wed night into Thursday. At the surface, a clipper system tracks
through southern Ontario into northern New England Wed into Wed
Night, with trailing cold front approaching the region Wed
Night and crossing Thursday morning.

Models in fairly good agreement with southern stream short wave
energy helping induce weak low pressure wave development along
the front across Lower Mississippi and Tennessee River Valleys
Wed, tracking northeast towards the region Wed Night into Thu
morning. Broad lift of Baja and Gulf moisture streaming ahead
of the polar trough, in vicinity of the right rear quad of
northern stream jet and left front quad of southern stream jet
and thermal gradient aloft, will help support prefrontal and
post frontal precipitation across the region Wed Night into
Thursday morning. Overall this looks to be a light precip event,
but QPF has trended higher over the last 24 hrs.

Temps expected to rise into the 40s on Wednesday in gusty S/SW
flow (25-35mph) ahead of the cold front. Light precip potential
increases Wednesday evening. Thermal profiles ahead of cold
frontal passage Wed Night indicate a start as snow for NW hills
and rain for the city/coast with temps still well above
freezing. A change to snow from NW to SE all the way to the
coast likely late Wed night into early Thursday morning in wake
of cold front with polar airmass gradually advecting. This
scenario could result in hazardous travel conditions for Thu
morning commute with potential for untreated roads become snow
covered or even icy NW of NYC as temps drop below freeing.
Timing of changeover and intensity of snowfall will determine
the road conditions for the city/coast as surface temps may
still be warm from the 40 degree temps on Wednesday and cold
advection looks to be gradual (dropping to around freezing for
Thu morning). Will have to monitor these factors in high res
models over the next 36 hrs.

As mentioned, deterministic/ensemble models have trended
progressively wetter with this system. In terms of snowfall, WPC
superensemble spread of T to 2" for much of the region late Wed
Night into Thu morning. NBM potential for a light snow accum has
trended higher as well over the last 24 hrs, now around 20-30
percent for >1", and moderate probs for > .1". So potential is
increasing for a light snowfall for Thu morning commute. Will
have to assess these trends over the next 36 hrs, and examine high
res models to get a sense of an moderate snow banding potential
under thermal gradient.

General agreement that polar front moves far enough southeast
Thursday afternoon for any snow to taper off, with continued
caa Thu aft into Thu Night on gusty N winds. Temps on Thursday
likely don`t move much from the morning, generally lower to mid
30s coast, upper 20s interior. Polar airmass works in Thursday
Night, with lows in the single digits and lower teens, and
windchills by Friday morning 0 to -10 F.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
There is uncertainty with the track of low pressure that is
forecast to track south of of the area Friday night into Saturday
and then pass to the east Saturday night into Sunday.
The track will be determined by two scenarios, one being how quickly
the polar high across northern New England weakens and moves east,
and how amplified and progressive the upper trough is. The GFS is a
little stronger with the high and keeps it over New England longer.
And the upper trough is much more amplified with the trough well into
Mexico Friday and the surface low tracking farther south of the area
Friday night. Also there is some upper energy lagging in the upper
trough and the GFS develops another wave Saturday night into Sunday
that also passes to the south. Meanwhile the ECMWF is a little
weaker with the polar high and weakens and moves the high off the
coast more quickly than the GFS. And the ECMWF has the shortwave in
the upper trough farther to the north, rather than south into Mexico
like the GFS. The surface low develops farther north and brings
precipitation into the region Friday night into Saturday. The ECMWF
also becomes more negative with shortwave with the surface low
passing closer to the New England coast Saturday night into Sunday,
and does not develop a second wave. This keeps some precipitation
along the coast into Sunday. Mainly followed the NBM for
probabilities as a compromise, with some minor adjusts south and
east. With cold air in place precipitation across the entire forecast
area will be snow. And at this time there is a chance of a light
accumulating snow.

High pressure returns for later Sunday into Monday. Once again there
is a lot of uncertainty with the timing of a clipper system for
Monday into Tuesday with the GFS quicker then the ECMWF. Used the
NBM probabilities for this system.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
High pressure will quickly build in this evening and then
offshore by morning. Low pressure near the Great Lakes will
track into eastern Canada on Wednesday, sending a cold front
toward the region.

VFR through the TAF period.

WNW winds 15-20kt, gusting 25-30kt will begin to diminish late
this afternoon and through the evening. Winds become SW late
tonight along the coast, and light and variable inland. SW winds
quickly ramp up Wednesday morning to around 15kt G20-25kt.

 ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

Timing of diminishing winds and gusts may be off by +/- 1 to 2
hours. Winds will be primarily left of 310 magnetic.

.OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY...
.Wednesday...VFR. SW winds G20-30kt.
.Wednesday night-Thursday...Chance of rain becoming snow at the
coastal terminals Thursday morning, and rain and snow inland,
becoming snow late Wednesday night. Precipitation ends from west
to east in the afternoon. MVFR or lower conditions expected,
with conditions improving to VFR late Thursday and into the
evening.
.Friday...VFR.
.Friday night and Saturday...Chance of snow with MVFR or lower
conditions.
.Sunday...Chance of snow with MVFR or lower conditions.

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

&&

.MARINE...
Based on recent observations and trends, have decided to extend
the gale warning through this afternoon for the western ocean
waters and central/eastern LI Sound. Elsewhere, there could
event be a gust or two to gale force, but not enough to upgrade
to a warning in these areas. Sub SCa winds return by around
midnight for all waters as high pressure noses in.

High seas on the ocean will be slow to subside today with slowly
subsiding S/SE swells. sub SCA conds return to ocean water from w to
e tonight as high pressure builds in.

A return flow gets established quickly on Wednesday with any brief
sub SCA conditions tonight short lived. SW SCA winds likely to re-
develop Wed morning, with moderate potential for a period of gales
on the ocean. Ocean seas will quickly climb during the day on
Wednesday.

Winds weaken below SCA Wednesday night from NW to SE as llj slides
east, with marginal sca gusts likely (particularly ocean waters)
Thursday into Thursday Night in wake of cold frontal passage Thu
morning. Ocean seas will slowly subside Wed Night, but may remain
marginal SCA on outer and eastern ocean waters through Thu
Night.

On-going SCA conditions continue into Friday morning on the ocean
waters as high pressure builds to the north. Sub SCA conditions will
be short-lived as low pressure will approach the waters from the
south Friday night and Saturday. SCA conditions return to the ocean
waters Friday night and remain into Saturday night. The non ocean
forecast waters are expected to remain below SCA levels Friday
through Saturday night.

&&

.HYDROLOGY...
No hydrologic impacts expected through early next week.

The river gauge at the Wallkill River at Gardiner may be
impacted by ice.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ335-
     338-340-345.
     Gale Warning until 6 PM EST this evening for ANZ331-332-350-
     353-355.

&&

$$

SYNOPSIS...MET/NV
NEAR TERM...JC/NV
SHORT TERM...NV
LONG TERM...MET
AVIATION...DW
MARINE...JC/MET/NV
HYDROLOGY...MET/NV

NWS OKX Office Area Forecast Discussion