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Forecast Discussion for New York City/Upton, NY
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657
FXUS61 KOKX 131209
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
709 AM EST Sat Dec 13 2025
.SYNOPSIS...
Weak high pressure today gives way to a cold front passing through
tonight. As it does, low pressure strengthens along the front to our
south and east. High pressure then builds back Sunday afternoon
and remains in control through Wednesday, when a warm front
lifts to the north. A frontal system approaches into Thursday
with a cold front pushing through Thursday night. High pressure
then builds into Friday.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
High pressure weakens over the region today as its center shifts
farther offshore. Clouds lower and thicken and cannot rule out a
late day rain shower for southern portions of the forecast area,
which could be mixed with snow north and west of the city. High
temperatures closer to normal, but still only in the upper 30s to
lower 40s for most areas.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
Key Points:
* 1 to 4 inches of snow are expected across the area tonight into
Sunday morning, with up to 5 inches in eastern Long Island.
* Winter Weather Advisories have been expanded slightly west and
north to include all coastal zones from 10pm tonight through 1pm
Sunday.
* Windy and cold Sunday night into Monday morning with wind chills
below zero in some areas.
A strong closed h5 low dives SE through the Great lakes tonight.
Associated positively tilted trough helps send a cold front through
the area tonight. An area of low pressure forms along the front to
our south in response. Because of the positive tilt, the low will be
progressive and not really strengthen more rapidly until it is well
off to our east. The precip shield with this system is however still
expected well north of the weak low center and into our area thanks
to synoptic lift courtesy of the right-entrance region of a strong
upper jet streak adding to shortwave lift and the cold front itself.
NBM and WPC liquid equivalent precip are in line with consensus of
deterministic and ensemble model output. While there appears to be
only modest omega in the dendritic snow growth zone, the zone is
large due the magnitude of the cold aloft and is saturated. Upward
motion is still there with the upper divergence and PVA. This, along
with much of snowfall occurring at night and cold/low wet-bulb
zeroes, should help offset the more typical lower liquid to snow
ratios one would expect with surface temperatures close to freezing,
which will be the case for the coastal areas for much of the event.
Generally speaking, precip type starts as rain or a rain/snow mix at
the coast with mainly snow inland this evening before a changeover
to snow everywhere by midnight. Greatest impacts will be from late
evening through at least mid-morning Sunday when the snow will have
an easier time sticking to untreated surfaces. Snow should be
exiting east out of area by around noontime Sunday.
Snow amounts have not changed much from the previous forecasts, but
with more confidence in the totals, Winter Weather Advisories for
tonight into Sunday have expanded to include coastal CT, Southern
Westchester County, and additional parts of NE NJ.
Winds then pick up Sunday night into Monday and will be gusty with
strong cold advection and a tightening pressure gradient. Wind
chills late at night into Monday morning dip to -5 to 10 above, but
are short of Cold Weather Advisory criteria. Highs on Monday will be
averaging only around 30 - well below normal. Winds then diminish
Monday night with wind chills not as cold this time, but still in
the single digits to teens.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
Key Points:
* Temperature moderation begins Tuesday night with a warm up
Wednesday through Thursday night.
* Chance of rain Thursday into Thursday night with no hydrologic
impacts anticipated.
A quasi zonal flow across the Lower 48 takes shape during the
period. There are some differences in the operational models with
the potential for amplification of an upper trough over the Upper
Midwest and Great Lakes region during the second half of the week.
The latter seems to hinge on the interaction of multiple streams of
energy moving in from the North Pacific along with energy rounding
the polar vortex, which will be bottled up well to the north. Thus,
looking at a warmup during the mid week after temperatures start off
well below normal, but end up climbing a touch above normal with
highs forecast to top out in the upper 40s to lower 50s by Thursday.
Some cooler air arrives on Friday, but due to the aforementioned
complexities, the magnitude of colder air remains somewhat uncertain
and would likely have some pacific air involved. Thus at this time
the colder air late in the week should not be as cold as previous
colder air masses. The NBM (which was followed) returns the region
back to normal on Friday following the passage of a frontal system
with a consensus approach being most prudent.
The next realistic chance of precipitation will be Thursday into
Thursday night in the form of rain due to warm advection ahead of
the system. Behind the cold front drier air moves in during Friday.
&&
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Weak high pressure remains in place this morning before pushing
offshore later today. A cold front approaches this evening and
pushes through later tonight. Low pressure develops along the
front to the south and pushes well offshore Sunday morning.
VFR conditions through the afternoon. Lowering cigs begin this
afternoon and eventually result in MVFR conditions around or shortly
after 03Z Sunday. -SN is expected to develop over the terminals 3-6Z
with MVFR at first, with IFR conditions expected at most terminals
shortly thereafter. Snow prevails with MVFR to IFR, and possibly
LIFR at times which will be more likely for eastern most terminals,
mainly after 06z.
SW/WSW winds will slowly increase this morning and get around 10-13
kt. Some occasional gusts up to 20kt are possible, but confidence
was too low to include in TAFs.
Expected Runway accumulations:
ISP 3-5, KGON 2-4, JFK 2-4, LGA 2-3, EWR 2-4, TEB 2-3, HPN 2-3, BDR
2-3, SWF 1-2
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
A few gusts to around 20 kt are possible towards late morning and
afternoon. Amendments become more likely late Saturday evening with
the arrival of snow and lowering flight categories.
.OUTLOOK FOR 12Z SUNDAY THROUGH WEDNESDAY...
Sunday: MVFR to IFR, possibly LIFR at times to the east, in snow,
mainly in the morning. Snow tapers off from west to east during the
morning, and possibly as late as the early afternoon for far eastern
terminals as conditions improve to VFR. NW winds gust around 25kt in
the afternoon and night with peak gusts around 30kt.
Monday: Mainly VFR. NW winds G20-25kt. Gusts lower at night.
Tuesday-Wednesday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
After collaboration with the surrounding offices, have issued a Gale
Watch for the ocean waters for Sunday night into a portion of Monday
morning. Before this, SCA conds expected today, followed by sub-
advisory conds tonight before rising back to advisory thresholds
Sunday morning. Decided to simply headlines and stretch the SCA
leading up to the Gale Watch to from today through Sunday afternoon.
As for the non-ocean waters, SCA in effect from late Sunday morning
through Monday afternoon. Can`t rule out occasional gale force gusts
during Sunday night, but not enough coverage and confidence to go
with a watch for these zones. Sub-SCA conditions are then forecast
for all waters Tuesday as high pressure builds in from the west.
&&
.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 CTZ009>012.
NY...Winter Weather Advisory from 10 PM this evening to 1 PM EST
Sunday for NYZ071>075-078>081-176>179.
NJ...Winter Weather Advisory from 10 PM this evening to 1 PM EST
Sunday for NJZ004-006-104>108.
MARINE...Small Craft Advisory from 10 AM Sunday to 6 PM EST Monday for
ANZ331-332-335-338-340-345.
Small Craft Advisory from 10 AM this morning to 6 PM EST
Sunday for ANZ350-353-355.
Gale Watch from Sunday evening through Monday morning for
ANZ350-353-355.
&&
$$
SYNOPSIS...JC/JE
NEAR TERM...JC
SHORT TERM...JC
LONG TERM...JE
AVIATION...JE/MW
MARINE...JC/JE
HYDROLOGY...JC/JE
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