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Forecast Discussion for New York City/Upton, NY

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542
FXUS61 KOKX 131959
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
259 PM EST Sat Dec 13 2025

.SYNOPSIS...
Weak high pressure slides offshore with a weak cold front
passing through this evening. Low pressure develops along the
front, tracking well to the south and east of the area through
Sunday morning. High pressure builds southwest of the region
Monday into Monday night as a weak low pressure system
approaches and eventually moves across from the Great Lakes.
High pressure returns for Tuesday building in briefly, before
moving offshore by Tuesday night. A cold front moves across
Wednesday night. High pressure follows for Thursday. A strong
cold front approaches from the west Thursday night and moves
across Friday. High pressure returns thereafter into the start
of next weekend.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Key Points:

* Winter Weather Advisories have been expanded across most of the
  local Tri-State region from 10pm tonight through 1pm Sunday.

* 2 to 3" of snow expected across much of the interior, 3 to 5"
  for NYC/NJ metro and coast, and 4 to 6" for E LI, tonight into
  Sunday morning. Locally higher amounts possible.

A strong polar low (-2 std 500mb height) digs southeast from
Ontario into the Great Lakes into tonight. Trend over the last
24-48 hours has been for this feature to take on a slightly
more neutral tilt (from positive) as it pivots towards the area
tonight into Sunday morning. This will provide a bit more
theta-e advection into the area, and also shift the the ULJ
slightly farther NW of the region. At the surface, a weak cold
front moves through the region this evening, with combination
of approaching shortwave PVA and RRQ of 150kt ULJ inducing weak
low pressure development along the front across Mid Atlantic
this evening, tracking southeast of the 40/70 lat/lon tonight
into Sunday AM.

Although surface features are weak, the deep layered lift overnight
into Sunday AM (including RRQ of ULJ, and modest mid-level
frontogenesis/lift in the snow growth region along the coast), and
slightly more depth of moisture for low pressure to work with has
resulted in a gradual increase in QPF and snowfall totals over
the last 48 hrs.

Good agreement in liquid equivalent of .3 to .5 for coast and .1 to
.2 for interior. Main snowfall amount forecast challenge is from
northward extent and duration of moderate snow banding, and snow
ratios during peak dendritic snow growth late tonight. SLRs
should exceed typical 10:1 late tonight into Sunday morning
during best snow growth period and dropping 850 hpa temps, with
12-14:1 seeming reasonable late tonight into Sun AM. This has
resulted in a general 1" increase in snow amounts across the
area. 3-5" likely across much of the coast including NYC/NJ
metro, with locally 6" possible. 4-6" across E LI, with locally
7" possible. 2 to 4" across interior. WPC Superensemble and
experimental NBM 5.0 have pretty good clustering in these
ranges, with reasonable worst case (10% prob of exceeding) a
couple of inches higher.

In terms of timing, snow could develop as early as 6-7pm this
evening, perhaps mixing with rain for city/coast at onset with
air temps in the upper 30s/lower 40s. Steadier snow likely
develops after 9pm from w to e, with a steady light to moderate
snow from midnight through Sunday morning. Snowfall rates of up
to 1/2"/hr likely develop after midnight through mid to late
morning for much of the area, with potential for brief 1"/hr
rates along the coast from 4am to 11am during best snow growth.
This signal is evident in the high-res CAMs, with highest prob
across southern and E LI. This will be time period of greatest
travel impacts in terms of reduced vsby and snow covered roads
with freezing/sub freezing air temps, higher snow rates, and
reduced vsby. Initially above freezing air/surface temps for
city/coast this evening, dropping below freezing late tonight
into Sunday AM, may resulted in icy spots on untreated surfaces.

Steady snow exits from w to e mid to late morning, except early
afternoon for far SE areas.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Key Points:

* Steady snow ending mid to late Sunday morning. A few afternoon
  snow showers possible. Unseasonably cold with temps remaining
  below freezing, and high temps nearly 15 degrees below
  seasonable.

* Windy with NW winds gusts 30 to 40 mph and unseasonably cold
  Sunday night into Monday morning with wind chills near zero
  city/coast and below zero across interior.

Strong polar low (-2 std 500mb heights) pivots into northern
New England Sunday into Sunday Night, with trough axis
approaching Sunday and then across Sunday NIght.

Steady snow exits from w to e mid to late Sun morning, except early
afternoon for far SE areas. Although with approaching shortwave
and polar front in the afternoon, could have some scattered
snow showers lingering or crossing the region in the afternoon
(particularly NW hill terrain and across central and E LI.

Otherwise, unseasonably cold conditions on Sunday with gusty NW
flow continuing to advecting in a polar airmass into Sun eve
(850mb temps down to -18 to -20 C). This will have temps holding
in the mid to upper 20s interior, to upper 20s/lower 30s along
the coast. Windchills in the teens.

Coldest airmass of the season ushered in Sunday Night into Mon
AM on brisk NW winds of 15-25G30-40mph, with temps falling into
the lower teens interior and mid teens coast (upper teens NYC/NJ
metro). Windchills of 0 to 5 F for coast, and 0 to -5 F for
interior.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Key Points

* Arctic airmass Monday through Tuesday. Airmass moderates towards
  midweek. Forecast high temperatures only in the 30s. Monday night
  lows forecast from teens to lower 20s for most of the area.

* Winds will be NW and gusty Monday with decreasing and more
  westerly winds Monday night, making for temperatures to feel about
  10 degrees colder than the actual temperature.

* Temperatures moderate Wednesday and Thursday, getting back into
  the 40s with even some 50s for Thursday, before trending colder
  Friday and Saturday.

* Next main precipitation event Thursday night into early Friday,
  primarily in the form of rain.

Active forecast period with upper level jet remaining near or within
the Northeast for next week. This will provide more steering flow
for a more rapid progressive pattern with quick passage of high and
low pressure areas. Aloft, there will be a series of troughs that
move across the area next week.

An airmass of arctic origin will be moving in from the west Monday
into Monday night. The center of high pressure will stay well south
and west of the local region. A weak low pressure system from the
Great Lakes will approach Monday and eventually move across the
region Monday night. A few possible snow showers could result but
probabilities are low due to lack of moisture and strength of the
aforementioned low pressure system.

High pressure then briefly builds in Tuesday before moving offshore
Tuesday night. Airmass will begin to moderate during this time
period. A strengthening low pressure area moving eastward within
Southeast Canada for midweek will bring an associated cold front
towards the local area. This front will move through Wednesday into
Wednesday night but its main forcing remains well north of the area.
Therefore, no precipitation is forecast with dry conditions
prevailing through midweek. Another quick residing high pressure
area traverses the region Thursday before another cold front moves
across early Friday. The increase in southerly flow ahead of each
cold front will advect in warmer air, with Wednesday high
temperatures forecast to reach well above freezing for the first
time since Saturday, December 13th. Temperatures continue to trend
warmer for high temperatures forecast Thursday, getting in the upper
40s to lower 50s for much of the region. These ambient forecast
temperatures will make the next main precipitation event mainly rain
from Thursday night through early Friday.

Another high pressure area builds in later Friday into the start of
next weekend before another cold front approaches for late next
Saturday with more chances for rain and snow. Temperatures trend
cooler but much of the period will keep mainly dry conditions.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
Weak high pressure will slide east this afternoon and evening. A
cold front will move through tonight, with weak low pressure
developing along it off the Mid Atlantic coast late tonight and
passing well south Sunday morning.

VFR into most of this evening, with snow developing late this
evening and continuing into Sunday morning. Greatest uncertainty
centers around timing of LIFR vsby, and between that and slightly
higher snowfall fcst for this time frame have adjusted/expanded the
window when these conditions should occur, roughly from 08Z-13Z for
the NYC metros/KHPN, 08Z-15Z KISP/KGON, and 10Z-12Z KBDR. Snow
tapers off late Sunday morning with cond improving to MVFR/VFR.

SW winds 8-12 kt will become will veer WSW and diminish to under 10
kt throughout this evening, then become NW overnight before
increasing to 10-15G20kt around midday Sunday.

Expected total accumulations have increased about an inch from the
previous forecast:

ISP 4-6, KGON 3-4, JFK 3-5, LGA 3-5, EWR 3-5, TEB 2-4, HPN 2-4, BDR
2-4, SWF 2-3 inches.

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

AMD likely to adjust timing of snow onset and time frame of LIFR
cond.

.OUTLOOK FOR 18Z SUNDAY THROUGH WEDNESDAY...

Sunday afternoon and night: VFR. NW winds 15-20 kt with G25-30kt.
Peak gusts up to 35 kt possible NYC metros.

Monday: VFR. NW winds 10-15 kt with G20-25kt, becoming W
late afternoon.

Monday night: Mainly VFR with maybe a passing snow shower north/east
of the NYC metros.

Tuesday: VFR.

Wednesday: VFR. SW winds G15-20kt in the afternoon.

Thursday: VFR. S winds G15-20kt in the afternoon.

Thursday night: MVFR or lower cond with rain likely, especially
after midnight. S winds 15G20-25kt.

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


&&

.MARINE...
SW SCA gusts into this evening for ocean and souther/eastern
nearshore waters. Winds diminish below SCA for a period for all
water tonight into Sunday morning as weak low pressure tracks SE of
the region.

Winds gradually ramp up in wake of low pressure to SCA for all
water Sun AM into early Sun aft, and then marginal gales Sun
Night into Monday AM. Gale Watch continues for ocean waters
where confidence is highest in frequent gusts, otherwise
occasional gusts possible. Seas building to 4 to 7 ft on the
ocean waters.

For Monday regarding wind gusts, gales are forecast on the ocean
waters with SCA level wind gusts for non-ocean waters. The non-ocean
waters have wind gusts dropping below SCA thresholds Monday night
while the ocean will have mainly SCA level wind gusts Monday night
into early Tuesday. After a brief period of sub-SCA wind gusts for
rest of Tuesday into Tuesday night, SCA level wind gusts develop
again for the ocean late Tuesday night into Wednesday. Sub-SCA wind
gusts forecast for later Wednesday through early Thursday with SCA
level wind gusts redeveloping on the waters later Thursday through
Thursday night. Some waters, especially the ocean, could have gales
Thursday night.

SCA levels seas remain on the ocean Monday through early Tuesday.
Brief period of sub-SCA seas then forecast for rest of Tuesday
through much of Tuesday night. SCA level seas are also forecast
towards mid to late week on the ocean. By Thursday night, parts of
LI Sound are also forecast to reach SCA levels.

&&

.HYDROLOGY...
There are no hydrologic impacts expected through the entire
forecast period.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory from 10 PM this evening to 1 PM EST
     Sunday for CTZ005>012.
NY...Winter Weather Advisory from 10 PM this evening to 1 PM EST
     Sunday for NYZ068>075-078>081-176>179.
NJ...Winter Weather Advisory from 10 PM this evening to 1 PM EST
     Sunday for NJZ002-004-006-103>108.
MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ331-
     332-340-345.
     Small Craft Advisory from 10 AM Sunday to 6 PM EST Monday for
     ANZ331-332-335-338-340-345.
     Small Craft Advisory until 6 PM EST Sunday for ANZ350-353-355.
     Gale Watch from Sunday evening through Monday morning for
     ANZ350-353-355.

&&

$$

SYNOPSIS...JM/NV
NEAR TERM...NV
SHORT TERM...NV
LONG TERM...JM
AVIATION...BG
MARINE...JM/NV
HYDROLOGY...JM/NV

Previous Forecast Discussions may be found at
NWS New York City/Upton, NY (OKX) Office Forecast Discussions.
(Click 'Previous Version' there to view past versions successively.
Some may differ only in time posted.)

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