000
FXUS61 KOKX 261518
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1018 AM EST Tue Dec 26 2023
.SYNOPSIS...
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High pressure over the region will slowly weaken through
tonight. Low pressure and its associated frontal system
will approach on Wednesday and pass nearby Wednesday night into
Thursday. Another low will develop to the north and offshore
Friday into Friday night, then head northeast on Saturday.-- End Changed Discussion --
&&
.NEAR TERM /THROUGH TONIGHT/...
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Continued dense fog advy til 11 AM in areas where nearby ASOS
obs still showed 1/4SM vsby, across Long Island, interior SE CT,
and areas well NW of NYC. Otherwise, visibilities have been
improving, but there will likely be plenty of low clouds for
the remainder of the morning, potentially into the afternoon.
There are conflicting signals with the degree of clouds this
afternoon. The fog this morning is shallow and should improve,
but there are hints at a low level inversion around 2 kft. This
may help keep low clouds in place. If the inversion is weaker
and moisture can mix out, some places could see sunny conditions
for a time this afternoon. Broken cirrus should begin to move
overhead ahead of approaching low pressure. Another day of above
normal temperatures are forecast with highs in the upper 40s to
lower 50s.
The surface high weakens tonight as it begins to move offshore.
A large closed low over the central states will send low pressure
and its associated frontal system towards the region. A general
model consensus keeps the region dry tonight with just a chance
at some light rain late across the western half of the area.
Latest guidance indicates a deep low level inversion tonight,
with winds atop it increasing to only around or just over 10 kt
overnight, so areas of fog should redevelop tonight. Raw
guidance argues for a return of dense fog throughout tonight,
but increasing mid level clouds may limit the radiation fog
potential, so the fog may not be as dense.
Low temps will be mild and generally in the 40s.-- End Changed Discussion --
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
The frontal system slowly moves into the area on Wednesday.
The system will initially struggle as it moves closer to the area
as it encounters lingering ridging aloft just offshore.
However, guidance has started to come into more agreement on a
wave of low pressure developing along the front over the Middle
Atlantic on Wednesday. This should help reinvigorate rainfall as
the system moves over the area Wednesday night. The new low
does not look particularly strong, but will have some enhanced
lift from the left exit region of a subtropical jet over the
southeast. Rain will start to enter the area during the late
morning and afternoon, but become widespread Wednesday night.
The majority of the rain with this system will fall in about
a 12 hour period late Wednesday into early Thursday morning.
The latest NBM probabilities for greater than 1 inch in 12 hours
late Wednesday during this time period are generally 20 to 30
percent. NBM probabilities for seeing greater than 2 inches in
12 hours during the same time period are generally less than 5
percent. These probabilities continue to signal limited rainfall
impacts.
The rain could become moderate to locally heavy, especially
where any enhanced moisture convergence occurs with the low
pressure. Ensemble means and global deterministic models signal
this potential exists north and west of the NYC metro across NE
NJ and the Lower Hudson Valley. Wednesday night falls beyond the
timeframe of most of the HREF members, so there is limited
higher resolution model data available at this time. Where this
axis of briefly heavier rain occurs should begin to come into
focus in the next 24 hours.
Forecast rain totals from late Wednesday through Wednesday
night range from 3/4" to 1 1/4". Due to recent heavy rain and
high streamflows, some of the flashier rivers and streams in NE
NJ could come close to minor flooding benchmarks if reasonable
worst case scenario solutions verify with rainfall 1.5" to 2"
Otherwise, just minor urban and poor drainage flooding is
possible.
The rain will taper off from west to east early Thursday morning.
A consensus of the modeling puts the steadiest rain offshore by
12z Thursday. The main closed low will still be well to our
west on Thursday. Low pressure will likely linger near or just
south and east of the area. The pattern does not change too much
Thursday night with low pressure nearby. Not expecting a
washout Thursday into Thursday night, but a few showers cannot
be ruled out with any organized areas of lift from weak energy
rotating around the upper low.
Temperatures continue above normal Wednesday and Thursday with highs
in the upper 40s to lower 50s.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
No significant changes made to the long term and stuck close to
the NBM for this update.
*Key Points*
* Rain chances continue Friday with a dry period to follow into New
Year`s Day.
* A slight cooldown to more seasonable temperatures Friday into
Saturday, and to begin 2024.
A closed upper low over the Central Plains slowly works to the
east to begin the period, as a weak surface low develops and
heads northeast of the are during the day on Friday. Have
maintained the chance PoPs for much of the day on Friday, and
given the Pacific origin of the air mass associated with this
system, expect ptype to be all rain. The low and attendant
moisture head northeast by Friday evening. Some weak CAA behind
the system results in lower thicknesses across the interior, so
cannot rule out a few snowflakes mixing in late Friday or early
on Saturday as the system pulls away. Highs on Saturday will be
in the low 40s; more seasonable than the days prior.
Thereafter, weak ridging and mainly dry conditions look to prevail
through New Year`s Day. The aforementioned closed upper low finally
shears out to our south and heads east on Saturday. A weak surface
low associated with this upper feature then develops offshore and to
our south on Sunday. At this time, the area remains on the north
side of its precip shield as it heads to the northeast on
Monday.
&&
.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
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Visibilities and cigs are slow to improve today. Mainly IFR, with a
few remnant pockets of LIFR through 17z. Overall, slow improvement
is forecasted into this afternoon. KISP and KJFK may experience the
slowest and least improvement among the terminals. By 18z current
thinking has most terminals going to VFR visibilities, and a fight
between MVFR and VFR with respect to ceilings. Conditions will then
lower again tonight. The timing of the lowering is very low
confidence, with perhaps the timing of the lowering moved up in
future updates / amendments. Essentially looking at MVFR and IFR
overnight. The greatest chance for LIFR would be for the coastal
terminals. Confidence in precise visibility forecast is low through
tonight with fog possibly coming back.
Winds will be light and variable through today and tonight, with
some terminals going light out of the east late tonight.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments highly likely for changing flight categories. Lowering
flight cats and fog development for early tonight to be updated in
subsequent TAF updates.
OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY...
Wednesday: Rain with MVFR conditions, mainly in the afternoon and
evening.
Wednesday night: Rain with IFR cond. SE winds G20-25kt and marginal
LLWS possible at terminals closer to the coast
(KGON/KBDR/KISP/KLGA/KJFK).
Thursday: MVFR possible with chance of showers.
Friday: MVFR possible with chance of showers. N winds 10-15G20kt.
Saturday: Mainly VFR. NW winds 10-15G20kt.
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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Marine Dense Fog Advisory cancelled on the wrn Sound and NY
Harbor, and extended elsewhere til 12 PM, for vsby less than 1
nm. The fog is likely to return tonight, if not sooner on the
ocean waters and bays of Long Island.
Conditions are forecast to remain below SCA thresholds through
Wednesday with a relatively weak pressure gradient in place, but
with a persistent 2-3 ft SE swell. A frontal system and low
pressure system pass over the waters Wednesday night into
Thursday night. Winds will increase a bit, but should remain
below 25 kt. Ocean seas will likely build close to 5 ft
Wednesday night through Thursday night.
Sub SCA conditions are expected on all waters on Friday. By late
Friday and into Saturday, SCA conditions are possible over the
eastern ocean zones with developing low pressure to the south.-- End Changed Discussion --
&&
.HYDROLOGY...
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Storm total rainfall 0.75 to 1.25 inches is likely late
Wednesday through Wednesday night, with the higher amounts more
likely to occur W-NW of NYC. Due to recent heavy rainfall and
continued high streamflows, there is a concern for minor
flooding along a few quick responding rivers in NE NJ and
potentially the Lower Hudson Valley. Per collab with MARFC, we
think rainfall of this magnitude would not even bring rivers in
NE NJ and the lower Hudson Valley to action stage. However, the
reasonable worst case scenario of 1.5-2.0 inches as depicted
by the 00Z ECMWF (and supported by the 12Z HRRR forecast of
2.0-2.5 inches across NE NJ and NYC metro) would bring the
Saddle River at Lodi and the Ramapo River at Mahwah above minor
flood stage. Otherwise, minor urban and poor drainage flooding
should be the main hydrologic impact.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
The potential remains for minor coastal flood impacts for
vulnerable coastal communities Thu with a passing low pressure
system. The threat exists for mainly the morning high tide,
particularly along the south shore of Nassau and Queens, and
possibly along the SW CT coastline on the Western Sound. Tidal
departures of 1.25-1.50 ft are needed for minor flooding, and
2.25-2.50 for moderate flooding during the morning high tides.
About 1 ft additional surge is needed for the evening high
tides.
The threat for dune erosion appears to be low and isolated with
this event.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Dense Fog Advisory until 11 AM EST this morning for CTZ007-008.
NY...Dense Fog Advisory until 11 AM EST this morning for NYZ067-068-
078>081-177-179.
NJ...Dense Fog Advisory until 11 AM EST this morning for NJZ002.
MARINE...Dense Fog Advisory until noon EST today for ANZ331-332-340-345-
350-353-355.-- End Changed Discussion --
&&
$$
SYNOPSIS...BG/DBR/DS
NEAR TERM...BG/DS
SHORT TERM...DS
LONG TERM...DBR
AVIATION...DBR
MARINE...BG/DBR/DS
HYDROLOGY...DBR/DS
TIDES/COASTAL FLOODING...