okx-afd on 2024-12-19

072
FXUS61 KOKX 192248
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
548 PM EST Thu Dec 19 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 FRIDAY MORNING/...
-- Changed Discussion --Main change to the near term forecast with this update was to
increase cloud cover over the next few hours. There`s enough
cirrus and/or stratocu for the appearance of mostly cloudy
conditions.

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.-- End Changed Discussion --

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 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 some eastern portions 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/...
-- Changed Discussion --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.-- End Changed Discussion --

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
High pressure will pass to the north through tonight.
Weakening low pressure will then approach from the west on
Friday, while another low passes to the southeast Friday
afternoon.

Winds NW either side of 10 kt this afternoon will then diminish
tonight while gradually veering N this evening and then NE after
midnight, and increasing to near 10 kt daytime Fri.

Flight cat VFR with lowering cigs late tonight, and MVFR cigs at
the NYC metros by 13Z-14Z, and spreading NE to the remaining
terminals by 15Z-17Z. Some light precip may be possible from the
NYC metros north/west toward the very end of the 24-hr TAF
period, with p-type most likely rain at the NYC metros, snow at
KSWF/KHPN.

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

No unscheduled AMD expected.

OUTLOOK FOR 18Z FRIDAY THROUGH MONDAY...

Friday afternoon: IFR in light snow possible at KSWF/KHPN. MVFR
expected elsewhere, with a rain/snow mix at the NYC
metros/KBDR/KGON, and rain at KISP.

Friday night: Chance of snow with MVFR/IFR cond. NE winds
G15-20kt, strongest 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

.MARINE...
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...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from noon Friday to 6 AM EST Sunday for
ANZ350-353-355.

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