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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KOKX 280329
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1129 PM EDT Tue Oct 27 2020

.SYNOPSIS...
Weakening high pressure tonight gives way to an approaching
weak wave of low pressure for Wednesday. Frontal boundary
associated with weak low moves south of the region Wednesday
afternoon into Wednesday night. Remnants of Zeta enters the area
south of Long Island Thursday followed by an upper level trough
Friday. Strong high pressure then builds into the area over the
weekend followed by a second trough early next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Forecast is on track. The forecast temperatures and dewpoints
are within a few degrees of their respective observed values.
Temperatures generally in the upper 40s to mid 50s are only
expected to lower 3-5 degrees overnight. With initial
temperature and dewpoint differences near 10 degrees, enough
low level drier air will preclude any rain from making it to
the ground. Low levels will become more moist later overnight
with measurable rain forecast as it moves in from the west.

There will be an increasing chance of light rain tonight as high
pressure weakens and weak low pressure approaches from the
south and west. Models continue to show the trend of RH
increasing from approx 10kft and lower. An upper jet streak will
be nearby, but not in the best position for upper divergence
and enhanced synoptic lift for our area. Models however show
some disorganized mid- level shortwave lift with increasing
winds in the 850-700mb layer, and with models trending wetter in
the QPF fields over the past 24 hours, will increase PoPs from
the previous forecast. Greatest overall chances will be after
midnight and NW of the city. Low temperatures will be a few
degrees above normal.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
The best combination of moisture and lift for rain chances will
be in the morning on Wednesday with all locations likely seeing
some rain. Rainfall will be generally on the lighter side. Mid
levels begin to dry out thereafter, so PoPs lower in the
afternoon with partial clearing.

Any clearing in the afternoon and evening will be replaced by
increasing clouds Wednesday night in advance of tropical moisture
approaching from the Gulf states. There is a slight chance that some
areas see some rain before daybreak.

Daytime temperatures will be near normal with nighttime
temperatures above normal.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Thursday the remnants of Zeta enters the DelMarVa region promoting
initially warm frontal showers locally. As the day progresses an
area of precipitable water values around 1.2 to 1.6 inches soak the
forecast area with heavy rainfall throughout the evening. QPF totals
are around 1 to 1.5 inches with this initial round of rain could
induce localized street flooding. The good news is the rain is
progressive as a +160 kt jet streak over central New York quickly
moves the system out of the area.

A second round of moderate to heavy rain arrives Friday with the
main upper level trough. This second system is more complex as the
trough brings in 1000-500mb thickness less than 540dm meaning that
there is a potential for mixed precip within the rain. Model
soundings over the Lower Hudson Valley and northern Connecticut
Friday morning does show snow possible but the low levels below 1000
to 500 ft may remain above freezing. Nevertheless have opted to
include a rain snow mix in the grids for Friday morning.
Accumulations are unlikely but cannot be ruled out as surface
temperatures early Friday morning hover around 34-36 degrees. During
the day the region warms into the low 40s.

Over the weekend a strong high pressure system builds behind the
trough into the Northeast. Dew points drop dramatically into the 20s
and 30s particularly for our inland counties. This sets up the
possibility of widespread freezing temperatures Saturday morning.
The dry air zeros out the rain chances through most of the weekend.
The high slides off to the east Sunday afternoon as the next trough
enters the Northeast region. The trough and low pressure system
could initiate additional showers late Sunday into Monday.
Temperatures fall into the 50s to start the week following the cold
front.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Weakening high pressure tonight gives way to an approaching
weak wave of low pressure for Wednesday. Frontal boundary
associated with the low eventually pushes south of the region
Wednesday afternoon into Wednesday night.

VFR conditions expected through the evening but deteriorating
conditions expected overnight into Wednesday morning with
ceilings dropping to MVFR and eventually IFR. Visibilities are
expected to drop to MVFR. There will be some light rain moving
across during this time. Improvement to VFR is expected
Wednesday afternoon after the rain has ended.

Winds are less than 10 kts through the TAF period. Wind
direction is variable tonight into Wednesday morning before
becoming more west to northwest Wednesday afternoon into
Wednesday evening.

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

Amendments are expected to better refine timing of MVFR and IFR
which may vary a few hours from the TAF. Improvement timing from
IFR to MVFR and MVFR to VFR could also vary a few hours compared
to TAF.

.OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...
.Wed night...VFR with W to NW flow. MVFR possible late with a
slight chance of rain.
.Thu...Rain developing with increasing NE winds. IFR possible
by late in the day.
.Thu Night...Rain with NNE winds 20-30 kt. Higher gusts
possible near the coast. IFR.
.Fri...Rain ending, possible mixed with snow mainly N of NYC. N
winds gradually decreasing. NE-N winds near 20 kt with gusts
25-30 kt during the day along the coast.
.Sat...VFR with light SW flow.
.Sun...MVFR possible with SW winds near 15 kt with gusts near 20
kt.

Detailed information, including hourly TAF wind component forecasts,
can be found at: http:/www.weather.gov/zny/n90

&&

.MARINE...
Winds and seas forecast on track with similar forecast and
observed values.

Winds will be light and mainly offshore tonight before shifting SW
and increasing somewhat during Wednesday. The light winds and a lack
of significant swell will sustain sub-advisory conditions on all
waters through Wednesday night.

By Thursday night winds and seas increase to above SCA criteria.
Waves rise to 8-11 ft, with NE gales expected mainly on all but the
western Sound and NY Harbor by late Thu night, and continuing into
early Fri evening even as winds back N after the passage of low
pressure, the combination of the remnants of Zeta plus an
extratropical low developing to its west. Lingering hazardous ocean
seas will continue into late Fri night. By Saturday morning sub SCA
conditions return with south to southwest winds. The next system
passes late Sunday night into Monday. Winds increase to 20-25kts out
of the north with gusts possible up to 30kts with SCA conditions
lasting until Tuesday morning.

&&

.HYDROLOGY...
No hydrologic impacts through Wednesday night. Areal QPF for
Thursday into Friday averages around 2 to 2.5 inches. Most of
this should be of long duration, with only nuisance impacts, but
there could be a window for heavier rainfall and greater impact
from late day Thu into Thu night.

&&

.TIDES/COASTAL FLOODING...
The high tide cycle on Fri is of concern for widespread minor to
locally moderate coastal flooding as astronomical high tide
levels rise in association with the full moon on Halloween, and
as strong NE winds bring in surge. An early look per latest
guidance suggests total tide departures of at least 1-1/2 to 2
ft and locally 2-1/2 ft, with a worst case about 1/2 foot
higher than that.

&&

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

&&

$$
SYNOPSIS...JC/DJ
NEAR TERM...JC/JM
SHORT TERM...JC
LONG TERM...DJ
AVIATION...JM
MARINE...JC/DJ/JM
HYDROLOGY...JC/DJ
TIDES/COASTAL FLOODING...