710
FXUS61 KOKX 201819
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
119 PM EST Fri Dec 20 2024
.SYNOPSIS...
-- Changed Discussion --
A coastal low and a clipper system approach the area this
afternoon and moves by tonight. High pressure builds in from
the west late Saturday through early next week. A weak frontal
system then approaches move through the area Monday night into
Tuesday. High pressure builds back into the area for the middle
the week.-- End Changed Discussion --
&&
.NEAR TERM /THROUGH TONIGHT/...
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12z guidance has come in with the track of the offshore low a
bit closer to the coast and also some of the high res guidance
has been more expansive with the precipitation shield over the
area. No major changes to the forecast are needed at the moment,
but this trend will be monitored. It is also worth noting that high
res total snow depth products are still supporting the current
expected snowfall forecast, except in eastern New London
Counties where totals would be a bit higher.
The area remains in between a developing coastal low that is
poised to strengthen and move up the East Coast, but remain well
offshore this afternoon and into tonight and a clipper system
approaching from the west. The clipper system will be absorbed
into the strengthening coastal low and as the energy transfers
to the stronger low, the area may end up being a local minimum
of precipitation, but many complexities in the interaction
between these two lows make this forecast a particularly
uncertain one.
Widespread light precipitation is seen across the area currently
as the precip shield from the offshore low extends into our area
and lighter precip from the approaching upper level trough and
weakening clipper system approaches from the west. Much of the
area has been cold enough for at least a rain snow mix minus
locations right on the coast and in eastern Suffolk County. An
SPS is currently in effect for all of southern CT for bands of
moderate snow that could make for brief slick travel.
Overall, snow accumulations of an inch or less are expected with
the exception of portions of the Lower Hudson Valley and higher
elevations of NE NJ where 1-2.5 inches of snow are expected.-- End Changed Discussion --
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
By Saturday morning, any remaining snowfall over the coastal
areas should be largely coming to an end with high pressure
building in from the west. A tight pressure gradient will allow
gusty N/NW flow much of the day with strong CAA of a frigid
airmass expected. High temperatures on Saturday are expected to
be in the low to middle 30s. Gusts on Saturday of 20-25 mph are
possible.
Breezy conditions will continue into Saturday night and early
Sunday with continued advection of the arctic airmass. Lows on
Saturday will be in the teens along the coast with single
digits possible for interior portions of the area. Breezy
conditions may make the wind chill temperatures overnight
Saturday into Sunday morning feel like the low single digits or
near 0. Some interior locations may feel as cold as -5.
Clear skies but cold conditions continue Sunday with high
temperatures only in the 20s for the entire area. Interior
locations may not rise above the low 20s with coastal areas
topping out in the middle to possibly upper 20s. As the day
progresses and high pressure builds in, the pressure gradient
should relax and with it the winds. Sunday night will be colder
in terms of temperature, but a lighter wind should curb the
wind chill a bit more than Saturday night. Lows Sunday night
will be in the single digits for much of the interior areas with
the coastline dropping into the low to middle teens. Wind chill
temperatures should be closer to the actual temperature.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
Key Points:
* Unseasonably cold to start - then a gradual warmup to near normal
temperatures by the middle of next week.
* Potential for a light wintry precipitation event late Monday night
into Tuesday.
There is very good agreement in the global models this period. A
large dome of high pressure from eastern Canada south into the
southeast U.S. will work offshore late Monday as a fast moving area
of low pressure moves into the Great Lakes. The low takes a track to
the north of the area late Monday night into Tuesday, sending a weak
frontal system through the area. Light precipitation is expected at
this time with snow, possibly mixed with rain at the coast. Any
accumulation at this time looks to be minor. High pressure then
returns for the middle of the week. Due to the good agreement of the
00Z guidance and noted trends, stayed dry Wednesday and Thursday.
NBM has an endless period of chance low PoPs during this time.
As for temperatures, the NBM deterministic forecast for much of this
period resides near the 75th percentile. This may be more reflective
of the recent bias calculations. Decided to blend with a model
consensus (CONSALL) which nudges temperatures down slightly from the
NBM. Temperatures on Monday will be about 10 degrees below normal,
but will approach normal values by midweek as air mass having some
Pacific origin move into the area.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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High pressure to the north lifts further up into Eastern Canada this
afternoon, while a clipper low moves across the Ohio Valley and
another low deepens off the Mid Atlantic coast. The latter of which
will pass well east of the area tonight and up into the Canadian
maritimes on Saturday.
NE winds mainly 10-15kt, with some gusts at or just above 20 kt for
some of the city and coastal terminals, otherwise winds a bit
lighter for western / inland terminals. These wind speeds and gusts
should continue through the afternoon and into the beginning of the
evening push.
Primarily IFR and MVFR conditions through 0z with -SN. Afterwards
most terminals go back to MVFR as -SN ends. Another period of -SN is
likely towards 09-10Z for city terminals, give or take a couple of
hours west to east. Any -SN ends towards 13-16z with VFR conditions
returning for the remainder of Saturday.
An inch or two of snowfall at KSWF and out towards KGON remains
possible through Saturday morning, with less than 1 inch elsewhere
on runways. NYC terminals generally stay above freezing with runway
accumulation unlikely.
...NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
Amendments likely through late Saturday morning with changing flight
categories with difficult timing with regard to -SN. Precipitation
may be occasional at times tonight. Runway accumulation unlikely at
this time.
OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY...
Saturday afternoon: VFR, NW winds 12-17G25-30kt.
Sunday: VFR, NW winds 10G20kt.
Monday: VFR.
Monday night-Tuesday: Chance of MVFR in light snow or a light
rain/snow mix.
Wednesday: Mainly VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
SCA in effect for ocean waters this afternoon through at least
Saturday night. SCA in effect for Peconic and Gardiners Bay and
the Eastern LIS this afternoon through late tonight.
Weak pressure gradient will keep below SCA conditions across all
forecast waters through this morning. Then, winds and seas will
increase with the approach of coastal low pressure. SCA
conditions expected to develop on the ocean zones this
afternoon and maintain SCA conditions through Saturday. For non-
ocean zones, for Friday afternoon through Friday night, wind
gusts will be marginal for SCA, with more confidence in eastern
waters. Some occasional 25 kt gusts are forecast but most gusts
are expected to be near 20 kt. For Saturday, all waters are
likely to see 25 kt gusts and SCA conditions.
Winds will be slowly diminishing Saturday night through Sunday, but
gusts to 25kt will still be likely on all waters through Saturday
night, and probably continuing on the ocean all the way through
Sunday afternoon.
High pressure builds across the waters on Monday with a weak frontal
system passing through the area late Monday night into Tuesday.
Winds and seas during this time will remain below SCA criteria.
&&
.HYDROLOGY...
There are no hydrologic concerns through the middle of next
week.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 1 AM EST Saturday for ANZ331-332-
335-340-345.
Small Craft Advisory until 6 AM EST Sunday for ANZ350-353-355.
&&
$$
SYNOPSIS...DW/MW
NEAR TERM...JT/MW
SHORT TERM...MW
LONG TERM...DW
AVIATION...JE
MARINE...DW/MW
HYDROLOGY...DW/MW