000
FXUS61 KOKX 051749
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1249 PM EST Fri Jan 5 2024
.SYNOPSIS...
High pressure builds in from the southwest today, across the
area tonight, then offshore Saturday morning. Low pressure
passes to the south and east of the area Saturday night through
Sunday, bringing rain and snow to the region. High pressure
builds in on Monday and stays in control through early Tuesday.
A strong low pressure system will track to our west and impact
the area late Tuesday through Wednesday. High pressure then
slowly builds in from the south on Thursday.
&&
.NEAR TERM /THROUGH TONIGHT/...
A ridge of high pressure builds in through tonight, then
offshore by daybreak. This will maintain dry conditions and
mostly clear skies. NW winds will veer to the W around 10 mph.
While cold advection wanes, highs will only rise into the middle
to upper 30s.
Radiational cooling of interior locations tonight may allow
temperatures to drop into the teens with much of the rest of the
area having lows in the middle 20s.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
High pressure gives way to an approaching and strengthening low
pressure system late Saturday and into Saturday night.
The shield of precipitation begins to overspread the area Saturday
afternoon and into the evening from southwest to northeast. Marginal
temperatures over the southern tier of the area may allow for a mix
of rain and snow at the onset. As the low approaches and strengthens
to the south of the area, an increasing easterly flow will advect in
warmer air over the ocean to allow for a boundary layer to remain in
the middle 30s, likely transitioning any mix of rain and snow to
mostly rain for Long Island and the NYC metro.
Meanwhile, steady snow which may become heavy at times for portions
of the interior is expected through the evening and overnight. As
such, Winter Storm Watches remain in effect for interior portions of
the Lower Hudson Valley, NE NJ, and Southern Connecticut. There
remains a fair amount of uncertainty as to how far north the
rain/snow line moves. A stronger system may bring heavier mesoscale
banding and a more northerly component of the wind which may
allow for enhanced snow totals for the immediate CT coastline
and southern Westchester County, where a weaker system may allow
for warmer air to infiltrate further inland and provide for
more rain than snow. These details may not be known until the
storm is underway.
Models have recently hinted at a secondary piece of mid-level energy
phasing with the low and causing a further strengthening of the
system as it pushes to the east into Sunday morning which may result
in an expansion of the precipitation shield to the northwest of the
low into Sunday. This would both prolong the precipitation into
much of the day on Sunday and also provide for more opportunity
for cold air to infiltrate areas closer to the coast with a N to
NW wind. This may allow for a changeover back to a rain/snow
mix or all snow as the precipitation is coming to an end on
Sunday, but at which point is expected to be fairly light in
intensity. This may allow for some minor accumulations of an
inch of less for Long Island and the NYC metro.
Overall a widespread 1 - 1.25" of liquid equivalent is expected over
the area with coastal areas, such as Long Island and the NYC metro,
to be in the form of mostly rain. Total snowfall accumulations for
the watch areas are a widespread 6-10" of snow with some
localized elevated areas in the interior Lower Hudson Valley
possibly seeing 12-15", but this will depend highly on any heavy
mesoscale snow bands that develop. A sharp gradient of snowfall is
expected somewhere closer to the immediate coast with around an inch
forecast for the NYC metro.
Winds during the event will be initially easterly Saturday evening
and strengthening to be 15-25 mph with gusts upwards of 35-40 mph
along the coast as winds become more NE overnight. Highest wind
gusts will be for extreme eastern coastal locations, namely the east
end of Long Island.
Any precipitation comes to an end by Sunday evening with winds
diminishing and skies becoming gradually clearer through the
night.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
*Key Points*
* A strong low pressure system will impact the area late Tuesday
through Wednesday, with the potential for wind and flooding
impacts.
Quiet weather is expected Monday and Monday night as high pressure
shifts through the area.
Attention then turns to a strong low pressure system that will bring
the potential for strong winds and flooding impacts. Deterministic
and ensemble guidance continues to be in great agreement with
little change from run to run over the past several days. This
is leading to unusually higher than normal forecast confidence
this far out.
A shortwave trough will enter the northwest CONUS Saturday morning
and dig down to the Southern Plains before closing off and lifting
northeast. The associated surface low will track west of our area,
with all of the latest deterministic guidance showing a sub 980mb
low by the time it reaches the Great Lakes. The latest LREF run has
about a 60% chance of a 980mb low or lower over the Great Lakes.
This will place the area under a very tight pressure gradient as a
~1030mb high will be departing to our east. Confidence continues to
increase in strong winds, with the potential for damaging winds
(mainly across Long Island and the southeast CT coast). The heavy
rain is the other hazard as flooding impacts are expected (see
hydrology section below). This storm will bring mainly plain rain to
the area. However, with cold air in place across the interior, a
wintry mix is possible at the start of the event. This includes the
potential for a brief period of freezing rain as warm air moves
in aloft, but the surface remains cold, before warm air take
over the entire area. Confidence is low at this point and this
will also depend on timing of precip moving in. No mention in
forecast yet. By Tuesday night, heavy rain is expected and have
mentioned in the forecast in collaboration with neighboring
offices.
Rain chances end Wednesday night and although the guidance starts to
diverge a bit, it looks like high pressure will gradually start to
build in from the south and west on Thursday.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
VFR through the TAF period as high pressure over the region
slides off the Mid Atlantic coast tonight. Low pressure
approaches from the southwest Saturday morning. There is a low
chance of MVFR developing toward 18Z along the coast, depending
on the timing of the low.
NW flow backs toward the W this afternoon. Winds becoming light
and variable this evening and overnight. East to NE winds
develop Saturday morning.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
No unscheduled amendments expected.
OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY...
Saturday afternoon: MVFR, IFR possible especially late in the
afternoon. Rain/snow along the coast, becoming all rain. Snow
well inland.
Saturday Night: IFR or lower. Moderate to heavy snow inland and
moderate rain near the coast. E/NE winds 15-20kt gusting 25-35
kt.
Sunday: IFR or lower with snow inland and rain near the coast.
NYC metro and coast may end as snow during the afternoon.
Winds becoming N 10-15 kt gusting 20-30 kt, diminishing during
the afternoon.
Monday: VFR.
Tuesday: VFR early becoming MVFR or lower. Rain during the
afternoon. E winds 15-20 kt with gusts 25-30 kt in the
afternoon. SE winds increasing to 25-35kt, gusting 35-45kt,
highest winds along the coast. LLWS possible at night.
Wednesday: MVFR or lower with rain in the morning. Rain ending
late in the day with conditions improving. S SW wind 25-35kt
gusting 30-35kt.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
With high pressure building in from the SW through tonight,
winds will diminish tonight. Sub-SCA conditions persist through
Saturday afternoon with high pressure overhead.
An approaching low pressure will quickly allow widespread SCA
conditions for all waters by late Saturday afternoon. A Gale Watch
is now in effect for all waters except the NY Harbor from Saturday
night through Sunday afternoon for gusts of 35-45 kt as a
strengthening low pressure system moves by to the south and east.
Winds gradually subside Sunday night below SCA levels but elevated
waves on the ocean will allow for SCA to persist through at least
Sunday night.
Lingering 5 to 6 ft waves are expected on the ocean waters on
Monday. Otherwise, quiet conditions on the waters expected until
late Tuesday. Strong low pressure will then track to the west and
impact the area through Wednesday. Gale force wind gusts look likely
on all waters, as well as the potential for storm force gusts. Waves
on the ocean waters look to reach 15 to 20 ft. Continued mention of
gales and storm force gusts in the HWO.
&&
.HYDROLOGY...
Hydrologic impacts, including river flooding, are possible late
Tuesday into Wednesday as strong low pressure passes west of the
area. The NBM currently has a 70 to 80% chance across much of the
area for seeing 2 inches in 24 hours and a 50 to 60% chance of 3
inches. This would be on top of whatever snow pack there is from
this weekend`s storm. The Weather Prediction Center has placed the
entire area in a Day 5 "slight risk" for excessive rainfall.
&&
.TIDES/COASTAL FLOODING...
Widespread minor coastal flooding possible with the Sunday
morning high tide, especially along the southern and eastern
bays of LI and LI Sound.
Isolated dune erosion expected during the Sunday morning high tide,
overwashes not expected.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...Winter Storm Watch from Saturday evening through Sunday
afternoon for CTZ005>008.
Coastal Flood Advisory from 5 AM to 10 AM EST Sunday for
CTZ009>012.
NY...Winter Storm Watch from Saturday evening through Sunday
afternoon for NYZ067>070.
Coastal Flood Advisory from 5 AM to 10 AM EST Sunday for
NYZ071-078-177.
Coastal Flood Advisory from 2 AM to 10 AM EST Sunday for
NYZ079>081-179.
NJ...Winter Storm Watch from Saturday evening through Sunday
afternoon for NJZ002-004-103.
MARINE...Gale Watch from Saturday evening through Sunday morning for
ANZ331-335.
Gale Watch from Saturday evening through Sunday afternoon for
ANZ332-340-345-350-353-355.-- End Changed Discussion --
&&
$$
SYNOPSIS...JT/MW
NEAR TERM...DW/MW
SHORT TERM...MW
LONG TERM...JT
AVIATION...MET
MARINE...JT/MW
HYDROLOGY...JT/MW
TIDES/COASTAL FLOODING...