discussion on 2023-09-15

000
FXUS61 KOKX 160045
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
845 PM EDT Fri Sep 15 2023

.SYNOPSIS...
-- Changed Discussion --High pressure centered to the north and west will begin to
gradually weaken Saturday into Sunday. At the same time,
Hurricane Lee passes well east. A wave of low pressure along a
cold front moves in Sunday night and slowly moves across on
Monday. The front and low depart east of the region Monday
night. High pressure will then build in and across the region
through Friday.

Monitor https:/www.weather.gov/okx/tropical or
https:/www.nhc.noaa.gov for the latest NHC forecasts on Hurricane
Lee.-- End Changed Discussion --

.NEAR TERM /THROUGH SATURDAY/...
-- Changed Discussion --Increased cloud coverage to account for the abundance of cirrus
moving across the entire region. Mostly cloudy sky conditions
expected through tonight. Otherwise, hourly temperatures and
dewpoints were slightly adjusted to better match with observed
trends. Min temperature forecast was not changed.

The official forecast from the National Hurricane Center
continues to take Lee about 275 miles east of Montauk, NY late
tonight into early Saturday morning. Lee will then track
northward towards northeastern New England and the Canadian
Maritimes into Saturday.

The main sensible weather as Lee passes well offshore will be
from expanding high level cloud cover tonight as the storm
interacts with a strong jet streak to our north. The cirrus will
likely be streaming across the sky through Saturday afternoon.
The clouds should begin to diminish from west to east late
Saturday afternoon.

Mainly dry conditions are expected as the atmosphere below 500
mb remains very dry. Gusty NW winds are expected, but the
strongest winds are expected to remain well to the east. Gusts
around 20-25 mph are possible across eastern Long Island tonight
and then will expand and incr ease to 25 to 30 mph on Saturday.
A few gusts to around 35 mph are possible across the forks of
Long Island and southeast Connecticut. Wind gusts from the NYC
metro on N and W will be weaker and generally around 20-25 mph
on Saturday. Winds diminish from west to east late Saturday
afternoon into the evening.

Lows tonight will fall into the 50s inland to around 60 degrees
near the coast. Highs on Saturday will be close to normal in the
lower to middle 70s.-- End Changed Discussion --

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/...
A weak upper level ridge will build over the northeast Saturday
night behind Lee. Surface high pressure will still be to our
north and west, but will gradually weaken. Any lingering high
clouds will clear leading to a cool night with lows in the upper
40s and low 50s inland and middle to upper 50s elsewhere.

The ridge shifts to the east ahead of the next shortwave trough that
approaches on Sunday. High pressure weakens further and shifts
offshore as a cold front associated with the trough begins to
approach from the west. Dry conditions will be maintained through
the day on Sunday, but should see increasing clouds from the west
late in the day. High temperatures trend slightly above normal in
the middle and upper 70s.

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Upper level trough and surface cold front will be the main
synoptic features Sunday night and Monday. This will bring rain
showers along with some possible thunderstorms especially along
the coast. Instability conveyed by numerical models is not very
high and only a few hundred J/kg of CAPE at most, so left as
slight chance for thunderstorm probabilities.

The rain showers could become heavy at times, especially late
Sunday night and Monday. The moisture transport from the
deepening SW flow including the jet will tap into moisture
sources from the Gulf of Mexico and Western Atlantic.
Precipitable waters are forecast to get to near 1.6 inches from
GFS and NAM models. Flow from low to upper levels is nearly
parallel with that deep trough approaching so there will likely
be training of showers. There could be some minor flooding for
areas that receive multiple areas of heavy rainfall.

Rain showers taper off from west to east Monday night. The mid
level trough axis moves across Monday night with highest
positive vorticity shifting east of the region by overnight. Mid
level heights will begin to rise overnight Monday night and
into early Tuesday.

Mid level heights rise Tuesday through Friday with ridging aloft.
At the surface, high pressure will build in from the north and
west. This will keep subsidence and allow for dry conditions.

Regarding temperatures, they will not deviate much from normal
values overall through the long term period.

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --High pressure centered to the north and west will begin to
gradually weaken on Saturday. At the same time, Hurricane Lee
is forecast to pass well to the east tonight into Saturday.

VFR. N winds at 10-15 kts with gusts up to 25 kts, highest at
the coastal terminals, will back to the NW overnight. Gusts may
be more occasional than frequent overnight. Gusts on Saturday
will ramp up a bit to 25 to 30 kt, highest at KGON.

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

Gusts may be more occasional than frequent overnight.

OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY...

Saturday Night: VFR. Diminishing NW flow.

Sunday: VFR.

Sunday Night-Monday: MVFR possible. A chance of showers.

Tuesday-Wednesday: 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 --Some gusts to around 25 kt were observed across different parts
of the waters as well as near the shoreline of Western Long
Island and Central Long Island Sound as well as the Bays of
Long Island and NY Harbor.

Added in the rest of LI Sound as well as NY Harbor and the Long
Island Bays into the SCA that is already in effect. End times
of SCAs were not changed. Non-ocean SCA remains in effect until
8PM Saturday and the ocean SCA remains in effect until 6AM
Sunday.

Confidence continues to increase for solid gales to occur
further east of our ocean zones. Cannot completely rule out a
few gusts to around 35 kt late tonight into Saturday and that is
covered in the SCA. The SCA on the ocean remains through
Saturday night as seas will be slow to subside below 5 ft. This
may occur Sunday morning. Winds will weaken below 25 kt late
Saturday into Saturday night and should remain weak on Sunday
with high pressure over the waters.

Conditions on the waters are forecast to remain below SCA criteria
Sunday night through Wednesday night with a relatively weak
pressure gradient in place.-- End Changed Discussion --

.HYDROLOGY...
-- Changed Discussion --Total rainfall forecast will range from around a half to 1 inch
Sunday night through Monday evening. There could be locally
higher amounts and the range could change with subsequent
forecasts. Heavy rain will be possible at times, with possible
minor flooding in low lying and poor drainage areas.

Otherwise, no hydrologic problems expected through next week.-- End Changed Discussion --

.TIDES/COASTAL FLOODING...
-- Changed Discussion --High surf advisory and high rip current risk continue through
Saturday evening.

For Suffolk and Nassau ocean beaches, large breaking waves will
peak at 10 to 16 ft in the surf zone tonight into Saturday
morning, and for Brooklyn and Queens ocean beaches, peaking at 6
to 10 ft. This will cause widespread dune erosion and scattered
overwashes, causing some minor to moderate flooding to roads
and properties on the landward side of the dune. Areas along
Dune Rd in the Hamptons have experienced overwashes with the
last couple of high tides, with an increase expected.

Coastal flood advisories continue for most of the shoreline,
with potential for reasonable worst case water levels bringing
minor coastal flooding of 1 to 2 ft of inundation for vulnerable
shoreline/coastal locations along LI Sound, the eastern bays of
LI and southern bays of LI/NYC. The most vulnerable locations
will be for north facing areas of the twin forks, Jamaica Bay
and Great South Bay exposed to open waters from a northerly wind
fetch.

Due to uncertainty of timing of surge with respect to high
tides Tonight or Sat late morning/early afternoon or in between,
the contribution of wave setup from tidal piling over several
tidal cycles, and the hybrid extra- tropical/tropical nature of
this storm, the forecast has been geared to a reasonable worst
case P-Surge/P-ETSS blended forecast.

Residual surge could result in localized minor coastal flooding
in bay areas with the Sat Night high tide, but low confidence on
this.

Waves lower on Sunday with surf height of 3 to 4 ft with still
some long period swell. There is a moderate risk of rip
currents at ocean beaches Sunday.-- End Changed Discussion --

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...Coastal Flood Advisory until 5 AM EDT Sunday for CTZ009>012.
NY...Coastal Flood Advisory until 5 AM EDT Sunday for NYZ071-078-
079-177.
High Risk for Rip Currents through Saturday evening for NYZ075-080-
081-178-179.
High Surf Advisory until 8 PM EDT Saturday for NYZ075-080-081-
178-179.
Coastal Flood Advisory until 3 AM EDT Sunday for NYZ080-081-
178-179.
NJ...None.
MARINE...Small Craft Advisory until 8 PM EDT Saturday for ANZ331-332-
335-338-340-345.
Small Craft Advisory until 6 AM EDT Sunday for ANZ350-353-355.-- End Changed Discussion --

SYNOPSIS...JM/DS
NEAR TERM...JM/DS
SHORT TERM...DS
LONG TERM...JM
AVIATION...DW
MARINE...JM/DS
HYDROLOGY...JM/DS
TIDES/COASTAL FLOODING...NV