discussion on 2024-01-16

000
FXUS61 KOKX 170039
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
739 PM EST Tue Jan 16 2024

.SYNOPSIS...
-- Changed Discussion --High pressure builds in from the south and west tonight through
Wednesday night before sliding offshore Thursday. Low pressure
then strengthens off the Carolina coast Thursday night, passing
south and east of the area Friday. High pressure slowly builds
in this weekend and remains in control through early next week.-- End Changed Discussion --

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
-- Changed Discussion --The pressure gradient steepens over the region as high pressure
builds in behind deepening low pressure shifting away to the
NE. Strong cold air advection with gusty NW winds will therefore
continue for a good portion of tonight.

Forecast lows are going to be in the lower teens to near 20.
Wind chills will be dropping into the single digits to near 10
late tonight for much of the region. With temperatures falling well
below freezing, any leftover moisture/snowmelt will freeze and
untreated icy surfaces will make for slippery conditions.
Thinking is that there will be many locations like this, so an
SPS has been issued for the entire area for tonight.-- End Changed Discussion --

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Dry conditions prevail but temperatures will be very cold and
well below normal.

Mid level flow transitions to more zonal. Surface high pressure
builds in from the south and west. Very cold 850mb temperatures
decrease to near -14 to -15 degrees C.

Mid level negative vorticity advection should allow for more sun
Wednesday but despite this, temperatures will remain very cold.
The gusty westerly flow will continue. With the aforementioned
very cold 850mb temperatures, daytime highs with daytime mixing
only are expected to reach the mid 20s to lower 30s.

High pressure still builds in Wednesday night but its center
remains far removed from the local area. The pressure gradient
still remains tight enough to allow for gusty winds along the
coast with winds decreasing more away from the coast. Similar low
temperatures to those of the previous night are forecast, ranging
once again from the lower teens to near 20.

.LONG TERM /THURSDAY THROUGH TUESDAY/...
* KEY POINTS *

* Potential for a light snowfall Friday into Friday night

* Coldest airmass of the season builds in for the weekend

High pressure slides offshore early on Thursday and heights briefly
rise aloft. Thursday will feature decreasing winds with temperatures
about 5 to 10 degrees below normal.

Attention then turns to a coastal low that has potential to bring a
light snowfall to the area Friday into Friday night. Low pressure
will strengthen off the Carolina coast and track north, passing our
area to the south and east. There remains uncertainty with the exact
track in the latest guidance. However, with enough cold air in
place, most of the current track solutions would bring a widespread
light accumulating snowfall to the area. The 50th percentile storm
total QPF from the 12z LREF members was about 0.15 inches across the
area, with any of the higher outliers coming from some GEPS members.
The current forecast has about 2 inches of snow across the southern
half of the area and an inch for the northern half taking the QPF
forecast and using a snow ration of 14+:1. A closer solution doesn`t
necessarily bring the concern for rain at the coast, like with other
systems this year, it would likely instead bring higher snowfall
totals. Right now the NBM only has a 20% for an advisory level
snowfall (3 inches) across the southern half of the area.

Behind this system high pressure slowly builds in through the
weekend, bringing in the coldest airmass of the year. The pressure
gradient will be tight over the area leading to windy conditions. 30
mph gusts are expected Saturday through Sunday. The winds combined
with the cold temperatures will bring low wind chill values. Minimum
wind chill values Friday night and Saturday night will be below 0
for most, with the low single digits for NYC. Maximum wind chill
values during the day on Saturday will be in the mid single digits
to the low teens for most. A slow warming trend starts after
Saturday and by Tuesday highs will be back in the low 40s. High
pressure remains in control through Tuesday.

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --High pressure builds in through the TAF period.

VFR. NW gusts should gradually weaken starting around midnight
as winds back more westerly, with an extended period of no or
very few gusts likely during the upcoming morning push. West
gusts around 25kt starting late in the morning and continuing
through the day.

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

Sustained winds and gusts may average around 5kt stronger than
the current forecast until around 02z.

Winds likely prevail north of 310 magnetic until around 09z,
then prevail south of it thereafter.

OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...

Wednesday night: VFR. W wind gusts 20-25 kt.

Thursday: Mainly VFR. W wind gusts 15-20 kt during the day.

Friday...IFR with snow likely, mainly during the day. Chances for
snow lower at night. NE-N wind gusts 20 kt in the afternoon and at
night.

Saturday...Mainly VFR. N-NW wind gusts 25-30 kt.

Sunday...Mainly VFR. N-NW gusts 20-25kt.

Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --

.MARINE...
With colder air advecting in on the relatively warmer waters,
gusty winds to SCA levels should easily materialize across all
waters tonight. SCA is in effect for all waters tonight.

For Wednesday, with high pressure building in, some decrease in
winds is forecast for the early part of the day. Gusts to SCA
levels remain for the ocean while the non-ocean waters are only
expected to gust to near 20 kt. Forecast for wind gusts for
non-ocean zones increases back to 25 kt but not until mid to
late afternoon Wednesday. So SCA only remains for the ocean
Wednesday.

For Wednesday night, gusts increase all waters, with likely SCA
wind gusts. The ocean already has SCA going through Wednesday
night but non-ocean waters may very well need another SCA for
this time period.

In addition, with the very cold air and gusty winds, there will
be a chance for light freezing spray for the ocean waters and
Eastern Long Island Sound late tonight and on Wednesday.

Winds lower Thursday with sub SCA conditions returning to non
ocean waters early in the day, and on the ocean by Thursday
night due to lingering 5 ft seas.

SCA conditions redevelop late Friday or Friday night, and may
persist on all waters through the weekend under NW flow. Sub SCA
conditions then expected through much of early next week.

.HYDROLOGY...
No hydrologic impacts are expected through the forecast period.

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 6 AM EST Wednesday for ANZ331-332-
335-338-340-345.
Small Craft Advisory until 6 AM EST Thursday for ANZ350-353-
355.-- End Changed Discussion --

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