000
FXUS61 KOKX 280846
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
446 AM EDT Thu Sep 28 2023
.SYNOPSIS...
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High pressure to the north today will give way to an inverted
surface trough and weak low moving northward along the coast tonight
into Friday. The low will move slowly strengthen and move east
Friday Night into Saturday, with high pressure building in its wake
and remaining dominant into next week.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Upper ridging over New England slowly slides east today as a
closed upper low over the Great Lakes slowly slides east towards
the area. At the surface, an inverted trough off the Mid
Atlantic coast gradually extends north this aft/eve as Canadian
high pressure slides off New England.
Increasingly moist onshore flow under an 850mb subsidence inversion
will have stratus working onshore this morning across southern
and western portions of the area, and gradually working N/NE
thru the aft/eve. Approaching closed low, strengthening llj and
theta-e advection will bring increasing chance for light
showers across NE NJ/NYC and LI this afternoon, gradually
working N through this evening. Timing and N/NE extent of
showers is a bit uncertain with subsidence and dry air to
contend with.
Onshore flow and cloud cover will keep temps several degrees below
seasonable today (mid 60s), warmest across SE CT with more in
the way of sunshine.-- End Changed Discussion --
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
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Models in good agreement with closed upper low continuing to
approach tonight into Friday, gradually sliding across the area
Friday Night into Saturday. At the surface, sprawling high
pressure remains over New England, although with its center
moving offshore. This will allow an inverted trough/surface low
sitting off the Mid Atlantic coast to slide towards the region
Friday and then gradually sliding southeast of the area Friday
Night/Saturday.
Good general agreement with increasing deep layered lift from
approaching upper low and right front quad of ULJ, combined
with a strengthening SE/E LLJ Tonight/Fri, transporting a sub-
tropical airmass (+1-1.5 STD PWATS) into the region, converging
in the vicinity of an inverted trough/coastal front (with
possible deformation zone and orographic enhancement) for a
6-12 hr period across portions of the area late tonight thru
Friday. Also can rule out a bit of elevated instability across
southern and western portions of the Tri-State with approach of
upper low on Friday, increasing deep convection. The signal for
an axis of heavy rain in the vicinity of the area is strong,
but model spread between ensemble, deterministic and high res
model solutions exists in the exact location and duration of
this mesoscale convergence zone where heaviest rain will fall.
As far as ensembles, prob of 2" rain in 24 hrs (mainly Friday)
ranges from High (60-70% GEPS prob for NYC and pts east), High
(70-80% ECE prob for eastern portions of the region), to Low
(10-20% GEFS prob for eastern portions of the region). NBM has
a 30-40% prob of 2"/24 hrs, 15% prob of 3"/24 hr for Friday across
NYC/NJ metro, Lower Hud, SW CT and LI. Note: This is a
considerable upward trend in 2" probs from single digit probs
over the last 24 hrs.
As far as high res solution guidance, 00z HREF, which is just now
covering the Friday day period has a broad 10% ensemble prob of
3"/3hr across NYC, NJ, and Lower Hud, with a bullseye of 30%
ensemble prob of 3"/3hr across NE NJ. This 30% 3"/3hr tends to
be an elevated signal for flash flooding potential (w/ typical
location uncertainty), if this heavy rain axis ends up over the
urban and flashy river basins in this area. Headwater guidance
for several of the flashy streams in NE NJ is around 2- 2 1/2"
in 6hr for minor, and 2 1/2 to 3 1/2 in 6 hr for moderate
flooding, which is a bit concerning if this all comes together
across this region (HREF 6 hr PMM is signaling potential for
3-5" in 6hr Fri morning in afternoon west of the Hudson R.).
So needless to say, a good signal for a heavy rain axis
presenting a urban and poor drainage and flashy river basin
flood threat, with a conditional localized to scattered flash
flood potential, but low confidence on location. With this
location/duration uncertainty, lack of model to model and run to
run consistency, and this being the first cycle of HREF
resolving this time period, will hold off on flood watch at this
time. But if the heavier QPF solutions remain consistent, a
Flood Watch will likely be needed for portions of the area,
particularly if the heavy rain axis is expected over NYC, NE NJ,
Lower Hud, and SW CT.
As the closed low moves overhead and low pressure becomes more
developed Fri Night into Saturday and gradually slides east,
the inverted trough/convergence axis should break down and slide
east with a more general deformation rain on the NW side of the
low continuing Friday Night into Saturday morning, gradually
tapering from w to e.
In addition to the rain, NE winds of 15-20g25-30mph likely along the
coast Fri AM through Sat AM. A few peak gusts to 35 mph possible.
Lighter winds for the interior.
High temps will run several degrees below seasonable in rain
and onshore flow, and near seasonable for overnight lows.-- End Changed Discussion --
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
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A high amplitude upper level ridge over the Mississippi Valley will
translate east during the period. This will result in a dry,
unseasonably warm period. A weakening backdoor cold front slips
through Sunday night into Monday morning with little if any change
in airmass. Surface high pressure builds in from the west through
Tuesday and then offshore by mid week.
High temperatures during the time will generally be in the 70s, even
approaching 80 across the NYC metro and inland areas. The warmest
days at this time look to be Tue and Wed with 85h temps around 15C,
possibly a bit higher. Lows will generally be 55 to 60. On average,
departures look to be about 5 degrees above normal.-- End Changed Discussion --
&&
.AVIATION /08Z THURSDAY THROUGH MONDAY/...
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High pressure remains across eastern Canada and the Northeast
through the end of the week. However, an offshore inverted trough
works toward the area today and across the area tonight into Friday.
MVFR ceilings will develop across the NYC terminals this morning,
possibly some of the outlying terminals as well. VFR conditions may
prevail through much of the day elsewhere. Even those locations that
go MVFR could see occasional VFR ceilings. Ceilings will then lower
tonight as showers move in off the Atlantic. The lowest conditions
will be across the NYC and Lower Hudson Valley terminals where IFR
ceilings are forecast to develop after 06Z with the likelihood of
heavy showers.
NE winds 10kt or less early this morning will veer a bit after 12Z,
increasing to 10-15 kt. The best chance for rain will be tonight,
but a few showers are possible in the afternoon, mainly at the
coastal terminals. Confidence is too low at this time to mention in
the TAFs.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of MVFR onset may be off by a couple of hours. A spotty
shower cannot be ruled out this afternoon.
OUTLOOK FOR 09Z FRIDAY THROUGH MONDAY...
Late Thursday night: MVFR or lower in rain showers. Best chance will
be across the NYC and Lower Hudson Valley terminals.
Friday: IFR and rain. ENE winds G15-25 kt, highest at the coastal
terminals.
Saturday: MVFR/IFR and rain in the morning, improving to VFR by
late. NE winds G15-20kt mainly at the coastal terminals.
Sunday and Monday: VFR.
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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An extended period of SCA conds is likely for the ocean into early
next week. SCA gusts are likely late tonight into Sat AM, with seas
elevating to 6 to 8 ft on E/SE wind swells, as well as background SE
swells from a developing offshore low and distant tropical systems
impact the coastal waters. Marginal SCA gusts possible on the
nearshore waters late tonight into Sat AM, but otherwise
expected to be below SCA.
Winds and seas will gradually subside Saturday aft through
Monday as high pressure builds in from the west with diminishing
winds and decreasing seas. SCA seas likely remain on the ocean
waters during this time, subsiding to around 5 ft by Monday.-- End Changed Discussion --
&&
.HYDROLOGY...
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Potential is increasing for a widespread 2-3" of rain across
the region Tonight into Saturday morning. High-res guidance
indicating potential for a localized swath of 3-5"+ in 6 hr Fri
AM/PM (10-30% prob of 3"/3hr, with spotty 10-20% prob of
1"/hr), but low confidence on development or location of this
type of rainfall axis at this time. Based on this conditional
threat, a slight risk of flash flooding has been coordinated
with WPC for the region.
With recent rains, headwater guidance for several of the flashy
streams in NE NJ is around 2-2 1/2" in 6hr for minor flooding,
and 2 1/2 to 3 1/2" in 6 hr for moderate flooding, which is a
bit concerning if this all comes together across this region.
Another consideration is that the period of heaviest rain Fri AM
into PM will coincide with two high tidal cycles where minor
flood thresholds are expected to be reached. This will limit
storm drainage capacity for coastal locations during these
times.
So, a good signal for a heavy rain axis presenting a urban and
poor drainage and flashy river basin flood threat, with a
conditional localized to scattered flash flood potential, but
low confidence on location. With this location/duration
uncertainty, lack of model to model and run to run consistency,
and this being the first cycle of HREF resolving this time
period, will hold off on flood watch at this time. But if the
heavier QPF solutions remain consistent, a Flood Watch will
likely be needed for portions of the area, particularly if the
heavy rain axis is expected over NYC, NE NJ, Lower Hud, and SW
CT.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
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An approaching full moon will have rising astronomical tides
(as low as 1/4-1/2 ft needed to reach minor thresholds),
combined with a persistent and slightly strengthening E-NE flow
and E wind wave/swell today into Sat Am will have water levels
solidly at minor flood levels (up to 1 1/2 ft inundation) for
vulnerable NY/NJ harbor, Jamaica Bay, western Great South Bay,
and coastal Westchester/Fairfield communities, with localized
minor elsewhere across LI and NYC for tonight, Fri AM, Fri PM
and likely the Sat AM high tidal cycles.
A bit more uncertainty on how widepsread the minor coastal
flooding will be with the Sat PM into Sun high tidal cycles as
astronomical tides will peak, but winds will turn more to the
N/NE and gradually susbide. Highest confidnce in additional
cycles of widepsread minor flooding are for the southern bays of
Nassau and Queens due to restricted tidal drainage, with
perhpas more localized minro floding elsehwere.
In addition, continued beach erosion/escarpment will continue
through at least Saturday due to elevated water levels, 4 to 7
ft breaking surf, and a strong E to W long shore current. Dune
erosion potential looks to be localized, with overwashes not
expected.
Although our surf zone forecast season in over, the risk for
dangerous rip current will continue into at least early next
week based on the wave conditions.
NOTE: The Peconic River at Riverhead tidal gauge is out of
service (had been reading too high). The gauge is being looked
into by our partners at the USGS.
NOTE: The Peconic River at Riverhead tidal gauge is out of
service (had been reading too high). The gauge is being looked
into by our partners at the USGS.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT
Friday for CTZ009.
Coastal Flood Advisory from 10 AM to 1 PM EDT Friday for
CTZ009.
Coastal Flood Advisory from 10 PM Friday to 2 AM EDT Saturday
for CTZ009.
NY...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT
Friday for NYZ071.
Coastal Flood Advisory from 10 AM to 1 PM EDT Friday for
NYZ071.
Coastal Flood Advisory from 10 PM Friday to 2 AM EDT Saturday
for NYZ071.
Coastal Flood Advisory from 6 PM this evening to midnight EDT
tonight for NYZ178-179.
Coastal Flood Advisory from 7 AM to 1 PM EDT Friday for NYZ178-
179.
Coastal Flood Advisory from 7 PM Friday to 2 AM EDT Saturday
for NYZ178-179.
NJ...Coastal Flood Advisory from 6 PM to 10 PM EDT this evening for
NJZ006-106-108.
Coastal Flood Advisory from 7 AM to 11 AM EDT Friday for
NJZ006-106-108.
Coastal Flood Advisory from 7 PM Friday to midnight EDT Friday
night for NJZ006-106-108.
MARINE...Small Craft Advisory until 8 PM EDT Saturday for ANZ350-353-
355.-- End Changed Discussion --
&&
$$
SYNOPSIS...NV/DW
NEAR TERM...NV
SHORT TERM...NV
LONG TERM...DW
AVIATION...DW
MARINE...NV/DW
HYDROLOGY...NV/DW
TIDES/COASTAL FLOODING...NV