508
FXUS61 KOKX 211143
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
643 AM EST Sat Dec 21 2024
.SYNOPSIS...
Deepening low pressure to the northeast tracks into the Canadian
Maritimes today. Meanwhile high pressure builds into the region
through Sunday, and then remains in control into Monday. A weak
frontal system approaches and moves through the area Monday
night into Tuesday. High pressure builds back into the area
Wednesday and remains in control through Friday.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Light to briefly moderate snow continues to fall across much of
the region early this morning in response to an upper shortwave
tracking into western New York state and into central
Pennsylvania as seen on water vapor satellite loops, and a weak
surface trough across Long Island and into northeastern New
Jersey. The shortwave and upper trough move east of the area,
and offshore late morning into this afternoon, as the surface
trough moves southeast as offshore low pressure tracks into the
Canadian Maritimes. The HRRR continues to handle the area and
timing of the light snow, and updated probabilities leaning
toward the HRRR. Generally 1" to 2" of snow are likely with
isolated up to 3" to 4", mainly across higher terrain, and with
temperatures below freezing.
A Special Weather Statement remains for much of the area for the
possibility of snow covered untreated surfaces and slick travel
this morning.
High pressure building into the region behind departing low
pressure will bring the coldest airmass of the season so far,
and temperatures will be near steady through the day.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
Surface high pressure builds in tonight through Sunday and
remains over the region into Monday. The NBM and MAV guidance
handle temperatures well tonight into Monday. With gusty
northwest winds continuing tonight wind chill values will be as
low as 3 below zero to around 5 above zero, and is above the
thresholds for cold weather advisories. Temperatures begin to
moderate a little Monday.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Two upper level shortwaves approach the Northeast US by Monday
night, one moving in from the west over the Great lakes and one
diving down from Hudson Bay region of Canada. These two shortwaves
phase together over upstate NY and interior New England Monday night
into Tuesday. At the surface, a weak low passes by dragging a
cold front through the area. Most of the forcing should be north of
the area and without much moisture, only a chance of precipitation
will be possible, which depending on the timing of the passage may
be in the form of snow or rain, especially closer to the coast.
Either way, not much in the way of accumulating precipitation is
expected with perhaps a few tenths of snow for northern interior
portions of the CWA.
Beyond then, upper level ridging moves in for Christmas Day and into
the end of the week as the area will remain generally under high
pressure with two areas of low pressure to the east over the Western
Atlantic and to the west over the Central US by the end of the week.
A few weak upper level shortwaves may try to move overhead, but
given large scale subsidence, chance of any precipitation is low at
this time. The low over the Central US may approach the area by
Friday or Saturday, but guidance disagrees on strength and timing.
Temperatures should be fairly seasonable through the long term with
highs generally in the upper 30s for the interior and low to middle
40s along the coast through much of the week. A slight warm up may
occur as the frontal system approaches by the end of the week.
&&
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Strengthening low pressure exits towards the Canadian Maritimes
early this morning. A polar front moves through this morning,
then high pressure begins to build in late today into tonight.
NNW winds 5-10 kt for the morning push become more NW and
increase in speed mid to late morning in wake of frontal
passage to 15-20ktG25-30kt for the afternoon and into the
evening. Gusts continue into the overnight, but weakened to
20-25kt. Gusts become more occasional Sunday morning before
ending after 18Z Sunday.
MVFR/IFR conditions in -SN this morning. -SN ends from W to E
between 13-16z with VFR conditions returning for the remainder
of today.
1-2" of snowfall expected at KSWF. 1" for EWR/TEB, and 1/2" to
1" for remainder of terminals, except little accum at KGON.
These accumulations will be maximized on elevated and grassy
surfaces.
...NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
Amendments possible for timing of end of -SN and improvement of
categories to VFR. NW gusts to 30 kt likely for this
afternoon/evening push.
OUTLOOK FOR 12Z SUNDAY THROUGH WEDNESDAY...
Sunday: VFR. NW winds 10-15G20-25kt early.
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
&&
.MARINE...
Deepening low pressure south of Nova Scotia tracks into the
Canadian Maritimes today as high pressure builds in from the
west. Ocean seas remain elevated at 5 to 7 feet, and gusty
northwest winds will develop this morning as cold air moves into
the region. Small Craft Advisories remain in effect for all the
forecast waters today into this evening. As the high builds
toward the waters tonight, winds and gusts will fall below
advisory levels on the non ocean waters, and on the ocean waters
early Sunday morning, with seas remaining elevated into early
Sunday afternoon. Once the advisories end, conditions remain
below advisory levels into Monday.
Freezing spray is not expected to meet advisory levels as ocean
water temperatures remain around 50 and into the lower 50s,
despite marginal gusts and air temperatures.
High pressure builds across the waters on Monday with a weak
frontal system passing through the area late Monday night into
Tuesday. High pressure builds back in for Wednesday with a weak
pressure gradient. Winds and seas during this time will
therefore remain below SCA criteria.
&&
.HYDROLOGY...
There are no hydrologic concerns through next weekend.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until midnight EST tonight for ANZ331-332-
335-340-345.
Small Craft Advisory until midnight EST tonight for ANZ338.
Small Craft Advisory until 1 PM EST Sunday for ANZ350-353-355.
&&
$$
SYNOPSIS...MET/MW
NEAR TERM...MET
SHORT TERM...MET
LONG TERM...MW
AVIATION...MW
MARINE...MET/MW
HYDROLOGY...MET/MW
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