000
FXUS61 KOKX 152335
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
635 PM EST Mon Jan 15 2024
.SYNOPSIS...
Low pressure approaches from the southwest tonight, and passes
nearby to the south and east on Tuesday. High pressure builds in
from the south and west midweek, sliding offshore Thursday. Low
pressure then develops off the Carolina coast Thursday night,
passing east of the region Friday. High pressure returns this
weekend.
&&
.NEAR TERM /THROUGH TUESDAY/...
-- Changed Discussion --
Minor changes were made to this forecast update. The timing of
likely snowfall for coastal areas was pushed back a few hours to
10pm. Other than a small adjustment to dewpoints, as well, the
forecast remains on track.
Snow breaks out this evening from SSW to NNE. It will be very light
at the start with the lower levels needing a few hours to get closer
to saturation. The winds will be light as high pressure in place
gets overrun by advancing moisture in the mid levels on a SW flow
aloft across the column. Expect snow to fall at the time ceilings
get to around 5 to 6 kft or so. With the first real sub freezing air
mass of the season preceding precipitation, at least for the coastal
sections, expect just about every flake to count as the ground, and
even the main and secondary roads to get snow covered.
As far as the intensity of the snow, expect it to be light and
powdery with higher snow ratios to start even at the coast. This
event will be driven mainly by lower to mid level warm advection.
Vertical motions, at least initially will not be impressive.
However, at 850 mb the winds start to increase to 20 to 30 kt based
on the guidance. The flow should get to at least 45 to 50 degrees
across isopleths, thus warm advection which is the driver for this
event should pick up towards 04-07z from south to north. At this
time snowfall rates could start getting close to a half inch per
hour. What is a bit different from some previous guidance runs is
that the column appears to be a bit more saturated in the snow
growth region. Thus did go higher than the traditional 10:1 snow to
liquid ratio.
Towards daybreak the snow / wintry mix / rain line will approach
quickly from the SE as the surface low reflection is closer to the
coast in the latest guidance. Not sure if some of the higher res
guidance is overdoing this since it is a progressive system with not
a lot of vorticity / energy bundled at 500 mb, but even with that
said if the system does not get the warmer air pushed further inland
then lighter precip could stay in the form of snow or mixed precip
and hour or two longer and you would get the same snow accumulations
regardless. This is not a big QPF event, but with the cold ground
and just about every flake counting at the onset thought it prudent
to go with a region wide Winter Wx. Advisory with this forecast
package. You will also have to brief mix to light freezing rain
towards daybreak at the coast and being around the time of the start
of the morning commute it prudent to have impact winter weather
advisories where snow totals fall below 3 inches. Overall this is a
2 to 4 in snow event, with locally higher amounts of around 5 inches
a possibility across interior NE NJ and the Lower Hudson Valley
having the highest chance of seeing 5 inch amounts locally.
Tuesday morning the warm air changes the precip to a light rain
along the coast and eventually in the city, but by this time much of
the precipitation from this event will have already fallen. Expect
mainly all snow well inland, with some mixing likely a touch further
SE which could result up to a tenth of an inch of ice in a few
spots. Again, the question remains is the thermal forcing / warming
a touch overdone as it certainly looks that way on the NAM guidance.
As far as upper jet dynamics implications, the overall feeling is
that with out noticeable cyclonic or anticyclonic curvature in the
upper jet structure not sure if the upper jet will enhance upper
level divergence
By the afternoon expect any precipitation to end, with the precip
tapering earlier across eastern and southeastern sections of the
area. Any precip should be light with the thermal forcing gone for
the afternoon. Not too concerned about impacts on the back side of
the low as it pulls away with any precip at that point being more
showery in nature and with temps overall warmer than they were
earlier in the morning.-- End Changed Discussion --
&&
.SHORT TERM /TUESDAY NIGHT/...
Clearing takes place toward mid evening from west to east. The
coldest air of the season then moves in. Towards late at night and
early Wednesday morning temperatures should get into teens inland,
and upper teens to around 20 for the city and the immediate coast.
Wind chills will get down to some of the coldest readings of the
season thus far with single digits wind chills widespread across the
area a few hours after midnight.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Anomalously low heights south of Hudson Bay and the Great Lakes
region into Wednesday will lead to some of the coldest air of the
season with highs in the 20s Wednesday afternoon and lows in the
teens Wednesday night (20s in the NYC metro). Some slight
temperature moderation then likely takes place Thursday and Thursday
night in advance of the next system as heights rise aloft with west
to east zonal flow.
A coastal low is expected to develop off of the Carolina coast
Thursday night with the southern branch of the jet stream. This will
then track north-northeast up the east coast in the Atlantic on
Friday then eastward out to sea on Saturday as it passes to our
southeast. With cold air in place, snow is likely Friday into
Saturday with this system. The general pattern remains the same with
most 12Z guidance, but solutions vary in terms of exact track and
magnitude to the coastal low. This will change the outcome of total
snowfall we see. For now, most solutions would give us is system.
For now, NBM probabilities hold a 50% chance of 1", 30-40% chance of
2" and a 20% chance for 3" or more. For now, expecting a prolonged
light snowfall event.
Regardless of the outcome of this system, in its wake the coldest
air mass of the season since last February is expected. In fact,
much of the region away from the coast may have to wait until early
next week to see the temperatures climb above freezing. The coldest
day appears to be Saturday, when 12Z global ensemble means
(including GEFS, EPS, CMCE) prog 500 mb heights 25-30 dam below
normal as the trough axis swings through. At this time, highs on
Saturday top out in the 20s, and perhaps the teens across the
interior if colder guidance is realized. With a blustery NW wind,
wind chill values could fall into the single digits or below zero at
points Friday and Saturday night.
A strong ridge nudges in from the west on Sunday as the trough exits
farther to our east with surface high pressure building in from the
southwest. It effects likely won`t be fully realized until Monday,
since Sunday still has highs in the low-30s to upper-20s.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
Developing low pressure along the southeast coast tonight will track
towards the region Tuesday morning and then south and east of the
area Tuesday afternoon.
VFR to start will lower to MVFR and then IFR tonight as snow
begins to develop from south to north. IFR and snow will
continue through day break and there is a chance at some period
of moderate snow with LIFR conditions.
The snow will likely change to a wintry mix across central/eastern
Long Island during the morning by 13-15z and could work its way
north and west into the afternoon. There is a chance at some
freezing rain within this wintry mix. Lower Hudson Valley terminals
should remain predominately snow for the duration of the event.
Southern CT terminals could see a wintry mix late morning and early
afternoon. The precip may end as a brief period of snow before
ending 20-22z.
Total snow accumulations: KJFK/KISP/KGON: 2-3"
KLGA/KEWR/KTEB/KHPN/KSWF: 3-4"
Winds will become light and variable briefly this evening before
shifting to the NE under 10 kt through early Tuesday morning.
Winds will gradually shift towards the N and then NE by Tuesday
afternoon and evening. Wind speeds increase to around 10 kt late
morning into the afternoon.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Onset of snow could be off by 1-2 hours.
Sleet and freezing rain are possible 14-18z.
OUTLOOK FOR 00Z WEDNESDAY THROUGH SATURDAY...
Tuesday Night: Becoming VFR. NW wind gusts 15-20 kt.
Wednesday: VFR. W wind gusts near 15-20 kt.
Thursday: Mainly VFR. W wind gusts near 15-20 kt during the day.
Friday...IFR with snow likely, mainly during the day. Chances for
snow lower at night. NE-N wind gusts near 20 kt in the afternoon and
at night.
Saturday...Mainly VFR. NW wind gusts near 25-30 kt.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Winds and seas across the forecast waters will remain below advisory
levels through tonight and into the first half of Tuesday. Then as
low pressure shifts away to the east and eventually northeast later
on Tuesday small craft conditions develop, first across the ocean
and western waters, then during the evening for the near shore
eastern most waters. Ocean seas should get up to around 5 ft Tuesday
night.
Departing low pressure and a building high to the west on Wednesday
allows small craft advisory conditions to develop once again on all
waters by the evening under increasing westerly flow. Gales possible
on the ocean and eastern nearshore waters Wed night into Thu. Winds
lower Thursday with sub SCA conditions returning to non ocean waters
early in the day, and on the ocean by Thu night.
SCA conditions redevelop late Friday or Friday night, and may
persist on all waters through the weekend under NW flow. Gales on
the ocean will be possible once again Sat night into Sunday.
&&
.HYDROLOGY...
No hydrologic impacts are expected through the forecast period.
&&
.TIDES/COASTAL FLOODING...
Localized minor coastal flood impacts likely for the Tue
afternoon high tide along NJ harbor and tidally affected rivers,
southern bays of Nassau and Queens, and along Western LI Sound
with onshore flow around an area of low pressure tracking SE of
the area and only 1 1/2 ft of surge needed for minor flooding.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory from 10 PM this evening to 7 PM EST
Tuesday for CTZ005>009.
Winter Weather Advisory until 10 AM EST Tuesday for CTZ010>012.
NY...Winter Weather Advisory from 10 PM this evening to 7 PM EST
Tuesday for NYZ067>071.
Winter Weather Advisory until 10 AM EST Tuesday for NYZ078>081.
Winter Weather Advisory until 1 PM EST Tuesday for NYZ072>075-
176>179.
NJ...Winter Weather Advisory from 10 PM this evening to 7 PM EST
Tuesday for NJZ002-004-103-104.
Winter Weather Advisory until 1 PM EST Tuesday for NJZ006-
105>108.
MARINE...Small Craft Advisory from 6 PM Tuesday to 6 AM EST Wednesday
for ANZ331-332-335-338-340-345.
Small Craft Advisory from 3 PM Tuesday to 6 AM EST Wednesday
for ANZ350-353-355.
&&
$$
SYNOPSIS...JE/BR
NEAR TERM...JE
SHORT TERM...JE
LONG TERM...BR
AVIATION...DS
MARINE...JE/BR
HYDROLOGY...JE/BR
TIDES/COASTAL FLOODING...