978
FXUS61 KOKX 200549
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1249 AM EST Fri Dec 20 2024
.SYNOPSIS...
High pressure to the north of the region will gradually weaken
tonight and give way to approaching areas of low pressure for Friday
into Friday night. High pressure builds in from the west late
Saturday through early next week. A weak frontal system then
approaches Tuesday into Wednesday.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Updated for current conditions, and with calm winds across the
Pine Barrens of Long Island have lowered overnight temperatures
a couple of degrees. However, high and mid clouds may hinder
radiational cooling enough to keep temperatures a little higher
than forecast.
For tonight, dry and very cold. 850mb temperatures lower to
near -6 to -7 degrees C.
Temperatures at the surface will be decreasing into the lower 20s to
lower 30s.
High pressure center slowly weakens moves farther east within Quebec
tonight. The pressure gradient will keep winds near a 5-10 kt range.
Winds chills as a result are in the upper teens to upper 20s.
The wind direction trends from northerly to more northeasterly
tonight into early Friday.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/...
Taking a model consensus, the local forecast region is not
forecast to be in the most favorable synoptic lift region. The
region will have some light precipitation Friday into Saturday
with low pressure passing by offshore.
For Friday, temperatures, winds become more easterly and increase
during the day in advance of approaching and developing low pressure
from the south. With clouds increasing and eventual commencement of
precipitation, high temperatures will be limited to lower 30s across
parts of the interior to near 40 for parts of the coast and within
NYC. For Friday night, temperatures will lower as winds become more
northerly allowing for cold air advection. With precipitation
becoming more probable, temperatures more likely to be close to the
dewpoint. Temperatures lowering for the evening and then lowering
more after precipitation trends down late.
For Friday, clouds become overcast and precipitation chances
increase as low pressure develops and approaches from the south.
Precipitation chances increase Friday afternoon into Friday night,
becoming likely for much of the region. This is when the low
offshore intensifies with its center passing to the south and
east of Long Island. Precipitation type transitions from
rain/snow mix inland and rain along the coast to all snow going
into Friday night.
The precipitation could have some banding to the north and west of
the low center. This would be heavier precipitation for Friday
afternoon into Friday night. Most models have this precipitation
offshore but a few models have low pressure overall closer to Long
Island, bringing this heavier band of precipitation across eastern
portions of the region. If trend closer to coast occurs, snow
amounts of a few inches could be seen for most of the region,
locally higher possible.
When precipitation trends down late Friday night, another surge of
cold air advection moves in. This will make colder highs
Saturday, mostly in the 30s for highs. Some leftover snow is
possible with vort max moving across in the mid levels and upper
level jet streak moving southeast of the region. Any snow amounts
look to be quite light with lowering dewpoints moving in.
When looking aloft, the forecast models convey phasing of upper
level jet southeast of the region. There is one jet streak
moving across and just east of the local area early Friday and
then another jet streak from NW to SE moving towards the
Carolinas. This NW to SE jet streak then eventually moves over
the Carolinas and into the Western Atlantic and this part is a
key part to this and subsequent forecasts as this begins the
phasing process and this when there begins more negative tilt in
the mid to upper level trough. The phasing causes more of a
coupling of this upper level jet, with strengthening of surface
low pressure.
With the strengthening of low pressure comes an increase in
synoptic lift especially to the north and west of the low.
However, across the local area, the area is in between higher
PVA area, closer to some NVA late Friday night. The coupled jet
pattern is far offshore where the highest lift will be.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Deep layered ridging occurs over the region through Monday
morning with a surface ridge axis shifting through later in the
day. The pressure gradient will be tight with gusty conditions
Saturday night through Sunday. This will enhance the cold air in
place with wind chills near zero inland and in the single
digits for coastal areas late at night into Sunday morning. High
temperatures for Sunday remain below freezing with wind chills
rising only into the teens. The airmass moderates a little on
Monday with high temperatures from the mid 20s to the low 30s,
but at least winds will be much lighter this time around and not
make it feel much colder.
The flow aloft becomes more cyclonic Monday night through
Tuesday night with two separate shortwaves attempting to phase
to our north. This introduces some uncertainty regarding the
consequential surface features that would impact the local area.
A weak low center may pass nearby or to our north Tuesday into
Tuesday night, but at the least, a surface trough passes through
the area. Will go with slight chance/chance PoPs with
simplified precip types for the time being, starting from late
Monday night through Christmas Day night. Overall best chances
of precip at this point appear to be Tuesday and Tuesday night.
High pressure with dry weather follows for Thursday.
Temperatures will be near normal Tuesday through Thursday.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
High pressure to the north moves into the Canadian Maritimes Friday
morning. Weakening low pressure will then approach from the west on
Friday, while another, deeper, low moves northward along the coast,
and then passes to the southeast late Friday into Friday night.
North/northeast winds become more NE through the overnight,
remaining under 10 kt. Northeast winds then increase during the day
Friday to around 10 kt. Winds back to N/NW Friday night.
VFR, possibly lowering to MVFR toward morning. MVFR overspreading
the terminals by late morning. Light precipitation develops from the
NYC metros north/west during the afternoon with mainly rain at the
NYC metros, snow may be mixed in at times especially late in the
day. All snow, with MVFR lowering to IFR at KSWF/KHPN. Precipitation
likely become lighter or briefly ends. There is a chance of snow
Friday evening into the overnight with MVFR to IFR.
...NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
No unscheduled AMD expected through the overnight.
Amendments likely for Friday for timing of onset of precipitation,
with the possibility of more of a rain/snow mix during the
afternoon, and for lowering flight categories.
Changeover to all snow Friday evening may be earlier.
OUTLOOK FOR 06Z SATURDAY THROUGH TUESDAY...
Late Friday night: Chance of snow with MVFR/IFR. N winds G15-20kt at
the coastal terminals.
Saturday: Chance of MVFR or IFR in light snow into early afternoon.
NW winds G25kt.
Sunday: VFR. NW winds G20kt.
Monday: VFR.
Tuesday: Mainly VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
No changes with this update.
SCA in effect for ocean waters Friday afternoon through
Saturday night.
Weak pressure gradient will keep below SCA conditions across all
forecast waters through Friday morning. Then, winds and seas will
increase with the approach of low pressure. SCA conditions expected
to develop on the ocean zones Friday afternoon and maintain SCA
conditions through Saturday. For non-ocean zones, for Friday
afternoon through Friday night, wind gusts will be marginal for SCA.
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 SCA
level 25 kt gusts.
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. A high pressure ridge then shifts in early next
week with lighter winds and sub-advisory conditions for Monday and
Tuesday.
&&
.HYDROLOGY...
There are no hydrologic concerns through the middle of next
week.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from noon today to 6 AM EST Sunday for
ANZ350-353-355.-- End Changed Discussion --
&&
$$
SYNOPSIS...JC/JM
NEAR TERM...JM/MET
SHORT TERM...JM
LONG TERM...JC
AVIATION...MET/DW
MARINE...JC/JM
HYDROLOGY...JC/JM