000
FXUS61 KOKX 280342
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1042 PM EST Wed Dec 27 2023
.SYNOPSIS...
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.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
-- Changed Discussion --
Slight adjustments to POPs for rain and made lows temperatures
less of a range, mainly between 43 and 48 degrees.
Moderate rain starting to make its way into interior parts of
the region mid to late this evening, so far within Orange
County NY and Western Passaic NJ. KOKX Doppler radar showing
bright banding across Orange County with the higher
reflectivities where the radar beam is intersecting the freezing
layer. MRMS rain accumulations are verifying better than dual-
pol radar estimates compared to surface rainfall observations.
A developing surface low will moves northward tonight, tracking
toward the region into Thursday. This will allow for a period
of steady moderate to locally heavy rain late tonight into
early Thu AM.
Key Messages...
*Rain will become widespread overnight and continue into early
Thursday morning. The bulk of the rain should be pushing east
of the NYC metro near daybreak 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.
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/...
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 chance PoPs (35%) 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 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.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
Low pressure approaches tonight and eventually moves east of
Long Island Thursday.
Still have a vast range of conditions within the forecast
region this evening, ranging from LIFR to VFR. Expecting mainly
LIFR tonight with steadier rainfall moving in from the west and
becoming more widespread going into overnight. Occasionally
locally heavy rainfall can be expected for most terminals.
Low level moisture after main steady rainfall ends will keep IFR
to LIFR conditions in place. Also, more rain showers are
forecast to develop during the day, especially in the afternoon.
Winds generally ENE 5-10 kt during the TAF period, becoming more
northerly late in the TAF period.
Occasional gusts to near 15 kt will be possible Thursday
afternoon.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Fluctuation between categories possible. Timing of LIFR and IFR
could vary a few hours from TAF.
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 WSW to W winds.
Saturday: Mainly VFR. W winds 10-15kt G20kt. Gusts subside at
night.
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...
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 conds 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.
&&
.HYDROLOGY...
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.
&&
.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...
CT...None.
NY...Coastal Flood Advisory from 6 AM to 11 AM EST Thursday for
NYZ178-179.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...DR
NEAR TERM...JM/DR
SHORT TERM...DR
LONG TERM...MW
AVIATION...JM
MARINE...DR/MW
HYDROLOGY...DR/MW
TIDES/COASTAL FLOODING...