discussion on 2023-09-16

000
FXUS61 KOKX 161446
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1046 AM EDT Sat Sep 16 2023

.SYNOPSIS...
-- Changed Discussion --High pressure centered to the north and west will begin to gradually
weaken today through Sunday. At the same time, Lee moves into
the Canadian Maritimes. A cold front approaches Sunday night and
moves through Monday as low pressure passes south and east of
the waters late Monday into Monday night. High pressure then
builds in through Friday.

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

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --Forecast is on track this morning with only minor changes made.

Lee will move into the Canadian Maritimes today as surface high
pressure to the northwest weakens. As the pressure gradient
weakens, winds will diminish, mainly from noon onward.
Therefore, expect northwest winds of 15 to around 20 mph
sustained, with gusts of 25 to around 30 mph, with the strongest
winds for eastern areas. Isolated gusts to 35 to 40 mph are
possible for these locations.

In the upper levels, ridging over the eastern Great Lakes region
slowly moves toward the area, allowing for dry conditions.
Clouds will diminish from mid morning onward.

Temperatures will be near normal for this time of year, in the
70s region-wide.-- End Changed Discussion --

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
Mainly clear skies expected overnight. Winds will continue to
diminish, but should be elevated enough to preclude optimal
radiational cooling conditions. However, if winds decouple
across these areas, temperatures will be lower than what is
currently forecast, which is anywhere in the upper 40s across
the interior, to the upper 50s in the metro area.

The upper level ridge axis moves offshore on Sunday as high
amplitude trough approaches the East Coast, with its surface
cold front just ahead of it. Precipitation looks to move in
mainly Sunday night, but there may be a few isolated showers
late in the day Sunday for western areas. As the upper trough
approaches the East Coast, a surface low will develop over the
Carolinas, head northeast Monday, and pass south and east of the
area Monday night, strengthening as it does so. Most deterministic
models have the low passing well south and east of the area,
however the ECMWF tracks the low well inside the 40/70
benchmark. This creates uncertainty in the overall rainfall
forecast. If the ECMWF solution is realized, more in the way of
rainfall will occur inland. However, right now this is an
outlier, and most models as well as NBM have the axis of heavy
rain more in line with the low passing east of the benchmark,
and thus eastern areas will see the heavier rain. 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 rise to 1.5 to 2 inches as
surface dew points rise into the lower to middle 60s.
Unidirectional flow through the column along with the deep
trough approaching will likely mean some training of showers.
There could be some minor flooding for areas that receive
multiple areas of heavy rainfall. Finally, some thunderstorms
are possible Sunday night into Monday with a few hundred J/kg of
CAPE noted in the models, so continue with slight chance of
thunder.

The cold front pushes offshore Monday night, allowing Canadian high
pressure to build in through Tuesday. Seasonable temperatures
are expected, with slightly warmer conditions on Sunday with a
southerly flow, clouds and rain cool temperatures slightly for
Monday. With more in the way of sun on Tuesday, temperatures
will be slightly warmer than Monday. Lower humidity levels are
also expected on Tuesday as dew points fall into the 50s and
possibly into the 40s in some areas.

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
Midlevel 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 in place and allow for dry & sunny
conditions.

Temperatures will not deviate much from normal values through the
long term period which are expected to be in the low/mid-70s.

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --High pressure centered to the west will gradually weaken and build
across today and tonight. At the same time, Post Tropical
Cyclone Lee is progged to move away to the northeast.

VFR. NW winds at 10-15 kts with gusts mainly 20 to 25 kts, highest
at the eastern most coastal terminals (mainly KGON) where a few
gusts through the early afternoon getting briefly 25 to 30 kt.

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

Timing of the wind gusts shutting off may occur 1-2 hr earlier than
currently reflected in TAFs.

OUTLOOK FOR 12Z SUNDAY THROUGH WEDNESDAY...

Sunday: VFR.

Sunday Night-Monday: MVFR possible. A chance of showers. VFR
conditions return late in the day Mon or Mon night.

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...
Non-ocean SCA remains in effect until 8PM Saturday and the
ocean SCA remains in effect until 6AM Sunday.

Cannot completely rule out a few gusts to around 35 kt today,
especially for the eastern ocean and easter sound zones. The
SCA on the ocean remains through tonight as seas will be slow
to subside below 5 ft. Winds will weaken below 25 kt late today
into tonight and should remain weak on Sunday with high
pressure over the waters.

Conditions are expected to remain below SCA criteria Tuesday night
through Thursday.

.HYDROLOGY...
-- Changed Discussion --No hydrologic impacts through this weekend. Total rainfall
forecast will range from around a third of an inch to around 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
this evening. There is a moderate risk of rip currents for
Sunday.

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 have been cancelled, and replaced with
coastal flood statements, and the coastal flood statement for
northeastern New Jersey and portions of New York City has been
discontinued. While anomalies are increasing slightly, water levels
during the next high tide cycle are expected to just reach minor
flooding thresholds in a few locations, with a worst case of up to 1
foot 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.

Residual surge could result in additional localized minor coastal
flooding in a few locations with tonight`s high tide, confidence is
low, however, additional coastal flood statements may be needed.-- End Changed Discussion --

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...None.
NY...High Risk for Rip Currents until 8 PM EDT this evening for NYZ075-
080-081-178-179.
High Surf Advisory until 8 PM EDT this evening for NYZ075-080-
081-178-179.
NJ...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ331-
332-335-338-340-345.
Small Craft Advisory until 6 AM EDT Sunday for ANZ350-353-355.-- End Changed Discussion --