discussion on 2023-11-20

000
FXUS61 KOKX 202059
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
359 PM EST Mon Nov 20 2023

.SYNOPSIS...
-- Changed Discussion --High pressure builds in from the northwest through tonight.
The high moves off the New England coast Tuesday as low
pressure approaches from the southwest. The low moves through
the region Tuesday night into early Wednesday. Low pressure slowly
departs to the east Wednesday night through Thanksgiving. High
pressure then builds in and likely remains in control through at
least the first half of the weekend. A low pressure system may
impact the area Sunday into Monday.-- End Changed Discussion --

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
-- Changed Discussion --Ridging aloft and surface high pressure stays in place early tonight
before beginning to move offshore early tomorrow. This allows for
mid/high level clouds to move in this evening and overnight from the
west. This is already beginning to occur with increasing clouds
to our west based on satellite imagery. Cloud cover will dampen
the effects of radiational cooling, but not totally negate its
effects since there are no low level clouds expected tonight
with light winds. Should still see lows in the low/mid-20s for
northern interior zones and the LI Pine Barrens. Lows in the
mid-30s for the NYC metro. A Freeze Warning is in effect for
overnight and early morning for the Bronx, Staten Island, Hudson
County, and Southern Nassau County with temperatures in those
locations to be around 32 degrees due to these areas` growing
seasons not officially ending until November 22.-- End Changed Discussion --

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
-- Changed Discussion --Low pressure tracks NE into the eastern Great Lakes Region on
Tuesday. Energy then gets transferred to a secondary low, with its
center passing through or very close to the forecast area early
Wednesday morning. The low will be east of us on Wednesday afternoon
with high pressure building in behind it.

Rain chances begin west to east late Tuesday afternoon to evening
before becoming likely mid/late evening into the night. There is a
chance for a brief mix of wet snow and rain at the onset across
northern Putnam and Orange counties with no snow accumulation. A low
level jet and strong isentropic lift right ahead of the approaching
secondary low will provide plenty of lift along with divergence in
the upper levels as the left exit region of a jet streak shifts
through during the overnight hours. These ingredients will combine
for periods of moderate to, at times, potentially heavy rainfall
after midnight. The stronger signal for this is generally over the
southern and eastern zones. The heaviest rainfall will probably be
over by sunrise Wednesday west of CT and LI, with the heavy rainfall
potential exiting east of eastern CT and eastern LI by mid-morning.
See the hydrology section below for additional information and
potential impacts. Another area of low pressure develops off of the
Carolina/Virginia coast, which keeps cyclonic flow over the ocean
through the period on Wednesday. It is possible some light isolated
showers or drizzle could be seen out of this Wednesday afternoon to
early evening only for far eastern Long Island and far eastern SE
Connecticut. Wednesday afternoon should be dry for everyone else.

One other aspect of this storm system will be winds, particularly
late Tuesday night/early Wednesday morning ahead of the secondary
low passage. 925mb winds for coastal areas during this time are
progged at 45-55kt. With a relatively weak low level inversion in
place, estimating 60-70% of this can mix down to the surface. Some
gusts in the 40-50mph range would therefore be possible. Not enough
confidence in a widespread enough event for a wind advisory in any
of the forecast zones, but do have far eastern areas in the Long
Island Forks reaching gusts of 45 mph. Peak wind gusts for coastal
sections are otherwise more likely to fall in the range of 30-40 mph.

Winds will quickly weaken as the center of low pressure moves
directly overhead Wednesday afternoon, reducing the pressure
gradient.

Highs Tuesday will be in the mid-40s for northern inland zones,
while southern coastal zones on Long Island, NYC, and NE NJ will be
in the low-50s. The warmer air here is thanks to increased southerly
flow.

Wednesday will be notably warmer with highs in the upper-50s to
lower-60s for southern zones and in the mid/low-50s for northern
zones. Strong warm air advection takes place from strong southerly
flow aloft with 850 mb temperatures around 6-8C (which is also
6-8C above average). Less cloud cover and rain will also help
things warm up some more.-- End Changed Discussion --

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
-- Changed Discussion --At the start of Wednesday night, low pressure will be exiting to the
east along with any associated rain. The forecast only includes a
slight chance of rain for New London County and far eastern Suffolk
County. The pressure gradient most of Wednesday night will actually
be relatively weak and expecting a lull period for winds. Aloft, a
mid-level shortwave trough will be passing to our south and an
associated surface low will be deepening as it passes to our south
and east early Thursday. This will strengthen the pressure gradient
over the area and lead to gusty conditions.

The low will gradually depart the area, with high pressure building
in thereafter. The high will likely remain in control through at
least the first half of the weekend with zonal flow aloft. The 12z
global guidance is in decent agreement with high pressure winning
out on Saturday. With previous wetter solutions likely impacting the
latest NBM PoP output, went lower with PoPs and expect this trend to
continue.

Sunday through Monday the guidance spread really increases. Stuck
close to NBM during this period because of low confidence. There is
potential for a low pressure system to impact the area, but
strength, timing and location are all in question.-- End Changed Discussion --

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
-- Changed Discussion --High pressure builds to the north of the area tonight and then
off the New England coast Tuesday. Low pressure will approach
from the southwest Tuesday, moving across the area Tuesday night
into Wednesday morning.

VFR conditions are forecast through Tuesday morning with MVFR
conditions developing for the 30h TAF sites Tuesday afternoon
(around 21Z).

With high pressure passing to the north tonight and then offshore
on Tuesday, NNE winds of 5-10kt will gradually veer around to
the E by morning, becoming ESE by afternoon and strengthening to
10-15 G15-20kt. For the 30h TAf sites, gusts of 20-25kt are
forecast by early evening.

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

Amendments are unlikely through tonight.

OUTLOOK FOR 18Z TUESDAY THROUGH SATURDAY...

Tuesday Afternoon: Becoming MVFR. SE winds 10-15 kt G20-25kt by
early evening.

Tue night: IFR with rain. SE winds near 15 to 20 kt. Gusts near
25 to 35 kt. A few higher gusts possible at the coastal terminals,
especially at KGON. Potential for LLWS with forecast 2 kft
winds around 40-50 kt late at night.

Wed: MVFR to IFR early with lingering rain. Rain tapers off late
morning into afternoon with eventual improvement to VFR late.
SW-W winds 10-15 kt with gusts near 20 to 25 kt AM. NW winds
10-15 kt with gusts 15-20 kt PM. Potential for LLWS with
forecast 2k ft winds around 45-50 kt in the morning near KGON.

Thu: VFR with NW to W winds 10-15 kt with gusts 20-25kt. Winds
gradually diminish late day into night.

Fri-Sat: VFR.

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

.MARINE...
-- Changed Discussion --Sub-advisory conditions then prevail tonight through a good portion
of Tuesday. Low pressure will then bring increasing winds and seas
late in the day into Tuesday night. A Gale Watch is in effect for
all waters Tuesday night. With only a short period of advisory
conditions preceding the gales, have decided to not issue an
advisory stepping up to the warning. A gusty NW flow follows in the
storm`s wake on Wednesday with advisory level conditions possible on
most waters.

There will be a lull period for winds Wednesday night as the
pressure gradient briefly decreases with low pressure passing to the
east. However, waves will remain elevated. by Thursday morning the
pressure gradient increases again and SCA wind gusts return likely
to all waters. Thereafter, winds and waves remain below SCA
criteria. There is potential for elevated winds and waves Sunday
into early next with with a potential low pressure system.-- End Changed Discussion --

.HYDROLOGY...
-- Changed Discussion --No hydrologic impacts are expected through Tuesday afternoon.

Total rainfall from late Tuesday afternoon through Wednesday morning
is expected to range from 1 to 2 inches. The highest amounts are
more likely to occur over NE NJ, NYC, and LI. Given these rain
amounts with antecedent dry conditions and flash flood guidance,
only minor/nuisance flooding is anticipated. The heaviest rainfall
is anticipated after midnight Tuesday night with the threat of heavy
downpours over for most spots by the start of the Wednesday morning
commute.

There are no hydrologic concerns Wednesday night through early next
week.-- End Changed Discussion --

.TIDES/COASTAL FLOODING...
-- Changed Discussion --An approaching storm system Tuesday into Tuesday night will
produce SE gale force gusts along the coastline, which will
produce a storm surge that could potentially raise waters levels
2 to 3 ft. There is some uncertainty with the timing of the max
winds/surge and how closely it will coincide with the time of
high tide. At this time, this looks to be a widespread minor
coastal flood event for the Wednesday morning high tide cycle,
with the most vulnerable areas being the south shore back bays
of western LI and the coastline of SW Connecticut. In addition,
heavy rainfall and wave action along the Connecticut coast could
enhance the flood threat. Localized moderate coastal flooding
is a possibility, especially across southern Nassau.

This is likely to be a one-high tide cycle event, but a lingering
SE swell could pose a localized minor coastal flood threat across
the south shore back bays of LI Wednesday afternoon/evening.
This is only being shown in the PETSS guidance (GEFS)at this
time. Westerly winds behind the system will aid in lowering
water levels.

Along the oceanfront, surf could build as high as 10 ft, resulting
in beach flooding and localized dune erosion.-- End Changed Discussion --

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Freeze Warning from midnight tonight to 8 AM EST Tuesday for
NYZ073-074-179.
NJ...Freeze Warning from midnight tonight to 8 AM EST Tuesday for
NJZ006.
MARINE...Gale Watch from Tuesday evening through late Tuesday night for
ANZ331-332-335-338-340-345-350-353-355.

SYNOPSIS...BR/JT
NEAR TERM...BR
SHORT TERM...BR
LONG TERM...JT
AVIATION...DW
MARINE...BR/JT
HYDROLOGY...BR/JT
TIDES/COASTAL FLOODING...DW