208
FXUS61 KOKX 181926
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
226 PM EST Sat Jan 18 2025

.SYNOPSIS...
A frontal system passes by today with low pressure moving east
tonight. Another wave of low pressure develops the Mid Atlantic
coast on Sunday and pushes northeast into Sunday night. An
arctic airmass builds into the region for the rest of the week.
A weak low may pass offshore on Wednesday, with chances for
another low to impact the area during the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
No significant changes to the forecast today.

High pressure continues to push offshore with a cold front
approaching from the west through the day. Southerly flow will
warm temperatures and increase moisture ahead of the frontal
passage tonight. High temperatures today will be in the middle
to upper 40s for the coastal areas and low 40s for the interior.

Expect showers across the area this afternoon. Enhanced lift
and moisture over the eastern CWA will allow for more robust
development of showers as the front approaches this afternoon.
Generally less than a quarter of an inch of rain is expected.

The front passes by overnight which dries the area out and shifts
the wind back to the W and eventually NW into early Sunday morning.
Lows will be in the middle 20s to low 30s.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
Attention then turns to a developing low pressure system over the
Mid-Atlantic on Sunday being forced by a mid-level shortwave
rounding the base of a large trough. As the low pressure system
gradually strengthens into Sunday afternoon, moisture overruns the
northern side of the low and precipitation blossoms over the area.
This will be aided by large scale synoptic forcing as the area will
likely remain on the left-exit region of an upper-level jet streak.

It is worth mentioning that while confidence is high in the
development of a low pressure system, confidence in the strength and
track of the low remains more uncertain than typically expected
within a 48 hour timeframe. There are generally two solutions for
this system: A more amplified and stronger low that rides closer to
the coast with more synoptic lift and moisture; and a weaker, more
transient low that rides south of the CWA. These two solutions and
the possible variations between them make this forecast particularly
difficult for various reasons.

A more amplified, stronger low will result in more lift and the
realization of more precipitation on the northern periphery of the
low. This would make for a winter storm warning level snowfall for
the interior CWA with a widespread 4-8 inches of snow with
locally up to 10". Since this would likely result in a closer
pass of the low, coastal areas would see a combination of less
synoptic forcing with the center of the low passing nearby as
well as more moderate temperatures and a likelihood of a
primarily rain or mostly rain event, especially for Long Island.
The CMC has been consistent in this type of solution for the
last several days.

A weaker, more transient low that passes more to the south of the
CWA may result in generally lighter precipitation rates, but a
primarily snow event for much of the CWA, though some mixing for the
immediate south coast remains possible. This would result in a
snowier solution for the coast, but with lesser snowfall totals for
the entire CWA. A weaker and more transient low would result in a
widespread 2-5 inches for much of the CWA, or a winter weather
advisory-type event. The ECMWF and more recently the NAM have this
type of solution. The GFS has a type of hybrid solution with a
stronger low that passes more south of the areas resulting in a more
widespread warning level event for the interior and a high end
advisory level event for the coast.

Given the remaining large amount of uncertainty, haven`t changed the
forecast much from previous. The biggest change has been a slight
downward trend in the snowfall for Long Island and the SE CT
coastline due to the uncertainty of the p-type during the best
synoptic lift Sunday evening. A Winter Storm Watch remains in effect
for the interior portions of the CWA for the potential of 4-8 inches
of snow.

The low departs the area Sunday night with strong high pressure
building into the area from the est into Monday. A brisk NW
flow will allow for strong CAA. Highs on Monday will be in the
20s.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
It will be cold thru the extended, particularly thru Thu, as an
arctic airmass builds into the region. This has been a consistent
high confidence feature of the fcst. Min apparent temps Mon ngt and
Tue ngt around -10 per the latest data. If we develop a good
snowpack, some of the overnight temps may need to be adjusted down a
few degrees. Some modification in temps towards the end of the week,
with highs perhaps eclipsing freezing at the coasts on Fri.

Outside of the cold, there are two chances for pcpn. The first is
late Tue ngt and Wed with the area on the nrn edge of a moisture
shield as a shrtwv passes thru. The GFS and ECMWF are in pretty good
agreement with the overall idea of the sys. The sfc low is progged
to be well offshore, but it will not take much moisture with the
very cold airmass in place to produce some high ratio lgt snow. Srn
areas favored attm, with NBM blended pops coming in in the chc
category.

The next chc for pcpn is around Fri with a potentially stronger and
closer low. Right now, the GFS is would be a snow event for most of
the area, particularly ern areas. Strong waa on the ern side
however, so any wwd trend could bring rain or a mix to the coasts at
least. Of course, the ECMWF is too far out to sea to produce any
pcpn across the cwa, so confidence in the sys is low. The NBM pops
are actually dry, but based on the prev fcst and the GFS/pattern,
manually brought the entire cwa up to slight chc.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
A weak frontal wave and/or warm front approaches from the
southwest into early this evening. A cold front then passes
through later tonight (03Z-06Z). Low pressure develops along
the Mid Atlantic coast on Sunday, passing to the southeast of
the area Sunday night.

MVFR/IFR in mainly light rain through early this evening. VFR
returns from about 02Z to 04Z behind cold front with W/NW flow
less than 10 kt.

For Sunday, ceilings will lower to IFR/LIFR in snow during the
afternoon, persisting into Sunday evening. Winds will be N/NW
around 10kt with gusts developing in the afternoon at 15-20kt.

Expected Snowfall Accumulations:

NYC terminals and BDR: 4-6"
ISP: 3-5"
HPN/SWF: 5-7"

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

Timing of changing flight categories will likely vary +/- 1-2
hours.

.OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY...

Sunday Afternoon: IFR/LIFR developing in moderate to heavy snow,
ending overnight. NE-N wind gusts 15-20kt in the evening, becoming
NW 20-25kt overnight.

Monday: VFR. NW wind gusts 20-25 kt.

Tuesday: VFR. W wind gusts around 20 kt.

Wednesday: Chance of MVFR or lower in -SN, particularly coastal
terminals.

Thursday: VFR.

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

&&

.MARINE...
A SCA remains in effect for the ocean with increasing S wind gusts
and wave heights ahead of an approaching frontal system. More
marginal small craft conditions are expected along the south shore
bays of LI. The winds then switch to a more W direction with a cold
front swinging through tonight as sub-SCA conditions prevail through
the day Sunday, although visibilities will lower. Winds and seas
begin to increase late Sunday afternoon and evening with developing
low pressure moving closer. As the low pulls away Sunday night, SCA
conditions should prevail across all waters with a gusty WNW behind
another cold front. Gales force gusts will be possible on the ocean
zones Sunday night through early Monday morning. Freezing spray
will be likely on much of the ocean and LIS waters Monday.

Marginal SCA conditions on the ocean on Tuesday, then winds and
waves likely below SCA levels all waters Wednesday through
Thursday. Some freezing spray can be expected on Tuesday.

&&

.HYDROLOGY...
No hydrologic issues are anticipated through next Friday.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Storm Watch from Sunday afternoon through late Sunday
     night for CTZ005>007.
NY...Winter Storm Watch from Sunday afternoon through late Sunday
     night for NYZ067>070.
NJ...Winter Storm Watch from Sunday afternoon through late Sunday
     night for NJZ002-004-103>105-107.
MARINE...Small Craft Advisory until 9 PM EST this evening for ANZ350-
     353-355.

&&

$$

SYNOPSIS...JMC/MW
NEAR TERM...MW
SHORT TERM...MW
LONG TERM...JMC
AVIATION...DW
MARINE...JMC/MW
HYDROLOGY...JMC/MW