okx-afd on 2025-05-20

757
FXUS61 KOKX 201454
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1054 AM EDT Tue May 20 2025

.SYNOPSIS...
-- Changed Discussion --High pressure will nose down from the northwest today, with a
back door cold front moving through from east to west tonight.
An expansive low pressure system will then approach from the
west on Wednesday, with a secondary low developing off the Mid
Atlantic coast on Thursday. This second low will then move
northeast into the Canadian Maritimes from Thursday night
through Saturday, and become nearly stationary through Sunday.
Weak high pressure will build in from Sunday night into Monday.-- End Changed Discussion --

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --It will be the last nice weather day for a while as a high
pressure noses down into the eastern Great Lakes and Northeast
into this afternoon. The pressure gradient finally relaxes as a
result as the gusty breezes from the previous couple of days
come to an end. More in the way of sunshine is anticipated
during this morning in comparison to later in the day. Scattered
to broken cloud cover should prevail going through the day.
Temperatures overall should average a few degrees below normal,
but all in all a fairly good spring day.

Clouds gradually increase through tonight. A back door cool
front entering the area could generate a few showers as it
pushes east across Long Island and S CT initially, then into the
NYC metro and the lower Hudson Valley later tonight.

Temperatures should fall close to the seasonal averages with
night time lows mainly in the lower/mid 50s.-- End Changed Discussion --

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
A difficult forecast for Wednesday with respect to how far east any
organized rain gets. The NWP guidance has timing differences with
regard to the progression of the arrival of the leading edge of
organized stratiform rain in advance of an old warm / occluded
frontal boundary. The timing differences stem mainly from varying
amounts of dry air in the mid levels that needs to be overcome.
Forecast soundings indicate a good deal of mid level dry air and the
questions is how long will it take for the column to moisten
sufficiently to develop the steadier rainfall. For now have taken
more of a consensus / middle of the road approach and steadily raise
PoPs through the day from SW to NE. With an onshore flow steadily
increasing into the afternoon look for winds closer to the coast to
gust during the afternoon and evening. With the onshore winds and
clouds temperatures should average at least 10, maybe as much as 15
degrees below average with mainly upper 50s for daytime max
temperatures.

For Wednesday night carry likely to categorical PoPs. A coastal low
begins to develop into early Thursday morning. This should focus a
surge of mid level warm advection into the region with a LLJ out of
the east at around 30 kt. This will be the main forcing function of
the steadier rainfall that arrives late Wed night / early Thu
morning. This steadier rain will fall through at least the first
half of the day, and perhaps carry into a portion of the afternoon.
With the clouds, rain, and wind temperatures will remain well below
normal into Thursday. Max temperatures will in all likelihood not
get out of the 50s region wide. Minimum temperatures Wed night will
average close to the seasonal averages with a cool onshore wind. For
rainfall totals and more detailed hydrology information see the
Hydrology section.

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
The forecast guidance remains rather consistent from previous
forecasts as a developing coastal low Wednesday night tracks
northeast of the region Thursday night through Friday night and
remains over the Canadian Maritimes Saturday into Sunday. Shower
chances taper off Thursday night as the low departs. However,
chances of showers remain through Saturday as a closed upper low and
trough remain over the northeast. The upper trough weakening
Saturday night into Sunday as heights slowly rise. As a result the
area will likely be dry. Additional energy tracks through the near
zonal flow and into the region Monday into Monday night, and may
brings a few showers to the area for Memorial Day. The NBM guidance
was used through the extended period. And blended in the 90th
percentile for winds and gusts Thursday night into Friday as the low
departs to the northeast. Temperatures will be near or just below
normal Thursday night through Sunday, and return to near normal
levels for Memorial Day.

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --Weakening low pressure over the Canadian Maritimes tracks slowly
southeast out into the western Atlantic, while weak high
pressure builds in from the west through today. The high moves
east while a frontal system approaches to the southwest tonight.

VFR until late tonight, with MVFR cigs developing east of the NYC
terminals 04Z to 06Z, and in the NYC metro area 07Z to 09Z.

N wind 10-14kt through most of today, weakening late day and
becoming NE. The flow could weaken enough for seabreeze
development, mainly at KJFK, and possibly KISP and KLGA.
Therefore, lower confidence in wind direction at the coastal
terminals this afternoon. Winds become easterly during the
evening and increase late tonight into Wednesday morning.

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

Occasional gusts to around 20kt possible til 18Z.

Chance of a late afternoon seabreeze, mainly at KJFK, but low
confidence at this time. Low confidence wind direction as winds
become light mid to late afternoon at KJFK and KLGA.

.OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY...

Wednesday: MVFR or lower with rain developing from west to east
through the day. E wind gusts up to 20kt, increasing to 20-25kt
at night.

Thursday: MVFR or lower with rain. E winds backing to the NE late in
the day with gusts up to 30kt. Wind diminishing at night and
becoming N.

Friday: MVFR or lower with a chance of showers.

Saturday: Chance of MVFR in showers.

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

.MARINE...
-- Changed Discussion --Sub advisory conditions on all waters through tonight with
diminishing winds with a weak pressure gradient getting
briefly established through the first half of Tuesday night.
Towards Wednesday morning an easterly flow quickly ramps up,
especially into the late day and evening as SCA conditions
develop. SCA conditions prevail Wednesday night across all
waters as a coastal low begins to develop, with a period of gale
force winds a possibility into the day Thursday out on the
ocean on a stronger east to northeasterly fetch.

SCA conditions will likely be ongoing across the forecast
waters Thursday evening, with gusts falling below 25 kt by late
Thursday night. However, ocean seas will remain elevated at
SCA levels through most of Friday. Thereafter, winds and seas
will remain below advisory levels Friday night through Sunday
night.-- End Changed Discussion --

.HYDROLOGY...
-- Changed Discussion --Average rainfall amounts of 1 to 1.5 inches expected for mid
week (mainly Wednesday through Thursday), with additional 0.25
inch amounts across SE CT and lighter amounts elsewhere into
Thursday night. Rainfall will be light to moderate, with rates
not expected to exceed 1/2 inch per hour. At worst nuisance
urban poor drainage type flooding could occur late Wed night
into Thu. Some streams and rivers mainly across S CT basins may
rise some, but should not result in flooding as the rain
should fall over a long enough duration.-- End Changed Discussion --

.TIDES/COASTAL FLOODING...
-- Changed Discussion --A strengthening/persistent E-NE flow Wednesday through Thursday
may result in minor coastal flooding mid to late week. The
latest information indicates that water levels should remain
below minor coastal flood benchmarks during time of high tide
late Wednesday and early Thursday. Based on the latest data the
two high tides of most concern are the Thursday afternoon /
evening and the late Friday afternoon / evening cycles. The
second of these may result in only localized minor flooding in
and around the tidal waterways of NE NJ and Staten Island, and
along the south shore bays of Nassau County despite being higher
astronomically. The first round should result in more
widespread minor flooding due to a stronger and more onshore
wind component, with departures 2.0 to 2.5 ft, as winds appear
more likely to remain mainly NE through most of the day Thursday
before backing to the N into Thursday night.-- End Changed Discussion --

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

SYNOPSIS...JE/BG/MET
NEAR TERM...BG
SHORT TERM...JE
LONG TERM...MET
AVIATION...MET/JMC
MARINE...JE/BG/MET
HYDROLOGY...JE/MET
TIDES/COASTAL FLOODING...