000
FXUS61 KOKX 272110
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
410 PM EST Wed Dec 27 2023

.SYNOPSIS...
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Low pressure develops over the Mid Atlantic this evening, tracking
north along the Northeast coast Thursday. A series of weak lows
or surface troughs will linger over the region Thursday night
through Friday night. High pressure will then start to build this
weekend and into the first few days of the new year.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Surface low pressure develops over the Mid Atlantic late today and
this evening, tracking northward toward the region overnight into
Thursday. This will bring a period of steady moderate to locally
heavy rain.

     Key Messages...

*Rain will become widespread this evening and continue into early
Thursday morning. The bulk of the rain should be pushing east of the
NYC metro by day break Thursday with rain ongoing across Long Island
and southeast Connecticut. Coverage of rain diminishes further into
the afternoon.

*The rain will become moderate to locally heavy at times. Max
rainfall rates between 0.50 and 1 in/hr are possible. Highest
probabilities for heavier rain exist across NE NJ, NYC metro, and
Long Island.

*Total rainfall amounts through Thursday morning range between 1 and
2 inches, with isolated amounts up to 3 inches.

*Minor urban and poor drainage flooding is the primary threat.
Isolated areas of flash flooding can`t be ruled out. A few flashier
rivers and streams in NE NJ could approach minor flooding
benchmarks.

An axis of the enhanced lift thanks to a coupled jet structure and
mid level frontogenesis develops from NYC on west the first half of
the night, shifting to the east across Long Island and southern
Connecticut towards the early morning hours. There will also likely
be enhanced moisture convergence along and north of the track of the
low pressure. 12Z HREF continues to paint a widespread 1 to 2 inches
across the region, which seems reasonable and in line with WPC, with
the bulk of this falling in the late evening and overnight hours.
The steadiest should begin to enter the region from the west between
8 and 10 pm, pushing east of NYC by daybreak or so.

Recent heavy rainfall brings a concern for flooding along rivers and
streams. Based on the latest headwater guidance though, generally
more than 2 inches is needed in 6 hours for minor flood stages to be
reached on the main stem rivers. This appears to be a reasonable
worst case with this system. WPC has upgraded NE NJ, NYC, and
portions of western LI and the lower Hudson Valley to a slight risk
for excessive rainfall through 12Z Thu. While isolated flash
flooding is a possibility in areas that experience locally heavy
rainfall, this appears to be a limited threat given the duration and
rates. After collaboration with RFC, opted to hold off any any
Flood Watches for the CWA.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
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Conditions remain unsettled on Thursday as low pressure along the
Mid Atlantic coast tracks near Long Island in the morning, then
north toward Cape Cod by the evening. This will allow the axis of
moisture and lift to shift east. A sprawling parent upper low
remains well off to the west across the Ohio Valley.

The steadiest rain pushes east through the morning, though
the region doesn`t dry out entirely. Conditions remain gloomy,
with low stratus, mist, and occasional light rain with the
closed low off to west, and several spokes of energy rotating
around it. Maintained high end chance PoPs (50%) Thursday
afternoon and into the overnight. QPF will be light after the
morning hours, with minimal additional hydro concerns. Mostly
cloudy to overcast skies persist.

Temperatures will remain above normal Thursday with highs in the
low to mid 50s, or about 10 degrees above normal for late
December. Overnight lows only manage to fall into the 40s for
most.
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&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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No significant changes made to the long term and stuck close to the
NBM for this update.

*Key Points*

* Rain chances continue Friday and into early Saturday, before
  drying out on Sunday and into New Year`s Day.

* A cooldown to more seasonable temperatures Saturday through
  Wednesday.

Large-scale upper level troughing remains in places through much of
the end of the week and into the weekend. This is paired with
surface waves of low pressure and troughs that will likely make for
a continued unsettled end of the week and beginning of the weekend.

A mid-level vorticity max rounds the base of a trough over the Ohio
Valley into the Southeast US. This forces a more recognizable low
pressure south of the area off of the East Coast Friday night and
into Saturday. The surface low pressure likely quickly merges with
the departing low to the northeast resulting in mainly a chance for
showers through Saturday morning. As the low departs, slight
subsidence in its wake will dry out the mid-levels and likely shut
off precipitation into Sunday.

Though an upper level trough remains in place with mid-level energy
sheared throughout it, some surface ridging to the south may nose
into the area on Sunday and into Monday with mainly dry conditions.
Global models diverge on how they handle another round of mid-level
energy approaching from the west, embedded in the trough. It may
develop a quickly developing low pressure to the south of it but
with little blocking downstream, the low may quickly move offshore
with minimal if any impact to the area. As of now, kept it dry
through much of the beginning of next week, but subsequent updates
will need to be watched for any changes.
-- End Changed Discussion --


&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
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A steadier and more consistent rain moves in going into the evening push
as conditions fall mainly to IFR. Conditions then deteriorate further
into tonight to prevailing LIFR at most terminals. The rain will be heavy
at times towards and after 2-3z. There is uncertainty as to whether the
heavier rain can improve ceilings / cats slightly to IFR from LIFR, and
avoid VLIFR at some terminals overnight. The rain tapers Thursday
morning, but IFR or lower conditions will remain in place. Pockets of
VLIFR are possible as the rain tapers early Thu morning, before some
slight improvement back to IFR late Thu morning and closer to midday.

Winds will be ENE and light, under 10 kts through tonight. Winds
should be more northeast Thu morning, then more out of the north
around 10kt Thursday afternoon.

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

There remains uncertainty in the coverage and timing of LIFR and possible
VLIFR tonight into Thu AM.

OUTLOOK FOR 18Z THURSDAY THROUGH SUNDAY...

Thursday afternoon / night: MVFR possible with chance of showers.
N winds.

Friday: MVFR possible with chance of showers. Light winds.

Saturday: Mainly VFR. W winds 10-15kt G20kt.

Sunday: VFR. W winds.

Monday: Mainly VFR.  W / NW winds G20kt.

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

&&

.MARINE...
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Low pressure passes near the waters Thursday morning, then east
Thursday afternoon leaving behind a weak pressure gradient into
Friday night. Ocean seas will build tonight into Thursday with
potential to see 5 ft seas late Thursday into Friday, before
subsiding Friday afternoon into Friday night. Elsewhere, sub SCA
conditions are expected through Friday.

Marginal SCA conditions are expected on the ocean waters Saturday
morning. SCA conditions then become likely over the eastern ocean
zones with developing low pressure to the south late Saturday into
Sunday, with 5-7ft seas. Sub SCA conditions return by late
Sunday.
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&&

.HYDROLOGY...
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Storm total rainfall 1 to 2 inches is likely through Thursday
morning, with localized amounts up to 3 inches. Due to recent
heavy rainfall, minor flooding along a few quick responding
rivers in NE NJ is possible. Otherwise, minor urban and poor
drainage flooding should be the main hydrologic impact, though
isolated flash flooding cannot be ruled out.

There are no hydrologic impacts expected Thursday night through
early next week.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
Minor coastal flooding now looks more likely on Thursday
morning with possible impacts for vulnerable coastal
communities. This is associated with a passing low pressure
system with onshore flow and an astronomically high tide. A
coastal flood advisory is now in effect for the the south shore
of Nassau and Queens, with tidal departures of between 1.3 and
1.8ft. High tide peaks from about 7-10am Thursday morning.
Statements are in effect for parts of Queens and southwestern
Suffolk, where minor benchmarks are not expected to be reached,
but some inundation (less than 0.5ft) is possible during high
tide.

Elsewhere, coastal flood statements have been issued for
the SW CT coastline on the Western Sound. Tidal departures of
1.25-1.50 ft are needed for minor flooding, which are expected
to be reached during Thursday afternoon`s high tide between
about noon and 4pm. Localized minor flooding is possible in
these areas.

The threat for dune erosion appears to be low and isolated with
this event.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None.
NY...Coastal Flood Advisory from 6 AM to 11 AM EST Thursday for
     NYZ178-179.
NJ...None.
MARINE...None.
-- End Changed Discussion --

&&

$$

SYNOPSIS...DR
NEAR TERM...DR
SHORT TERM...DR
LONG TERM...MW
AVIATION...JE
MARINE...DR/MW
HYDROLOGY...DR/MW
TIDES/COASTAL FLOODING...