NYC Office Forecast Discussion

FXUS61 KOKX 170953

Area Forecast Discussion
National Weather Service New York NY
453 AM EST Sun Nov 17 2019

High pressure centered across northern New England will drift
east today as low pressure off the southeastern coast moves to
the northeast. The low passes well to the south and east of Long
Island tonight into Monday, and to the northeast through
Tuesday. A second weaker system is expected to develop well
offshore Tuesday night and move away during Wednesday. High
pressure will build by Wednesday night and settle nearby on
Thursday. A cold front will move through on Friday followed by
high pressure to begin next weekend.


High pressure centered across northern New England at 08Z was
gradually weakening across the region as low pressure off the
South Carolina coast was slowly deepening. A strong pressure
gradient remains between the two systems. Meanwhile an
amplifying long wave trough was moving into the upper midwest
to the southern plains. This trough will begin to interact with
the coastal low later this morning and into tonight. The upper
trough has been a little slower to track to the east. With the
slower interaction between the approaching trough and the upper
low, the coastal low will be tracking a little farther
offshore. Low level lift and convergence under the subsidence
inversion, along with a moistening under the inversion has
allowed for light rain to develop along the southern New Jersey
coast. This precipitation may move to the southern coast of Long
Island early this morning. Have brought probabilities to near
the coast at 11Z, and these these may need to be brought
farther to the north as some of the rapid update and hi res
models have been indicating light precipitation near the coast.
Otherwise, much of the area remains dry through the day as the
high will be slower to retreat to the east.


The subsidence really weakens across the region after 00Z Monday
as heights begin to fall with the upper long wave trough
approaching. Will still be slow to increase the chances of
precipitation across the region. Low level warm advection and
dry upper levels will keep the precipitation light. Surface cold
air will be in place tonight as temperatures fall to near or
just below freezing. There is some uncertainty as to how low
temperatures will be dropping as clouds will be lowering and
thickening, and as warm advection continues. Some of the
interior valleys of the lower Hudson Valley into northeastern
New Jersey may be at or below freezing as the precipitation
begins later tonight. With the low level warm layer and no snow
crystals in the snow growth region precipitation will be light
freezing rain and or sleet. Have only chance probabilities for
precipitation inland late tonight, however, with the possibility
of a light glaze tonight into early Monday morning, have issued
a winter weather advisory for western Passaic and Orange
counties. The remainder of the area will see light rain.

During Monday precipitation will be light rain across the
forecast area as lower levels continue to warm and the surface
cold air is scoured out across the interior.


It will be a progressive long wave pattern during the period.
The eastern US trough will sort of redevelop Monday night, with
the upper coastal low interacting with the trough, and as
various areas of energy rotate into the long wave trough, with
mean upper level troughing through Tuesday night. In the wake of
low pressure in the short term period, moisture will be lacking
in the mid levels. Therefore precipitation chances will
generally lower Monday night into Tuesday. The only fly in the
ointment is with a vort max rounding the trough which will have
some good PVA with it towards and after midnight late Monday
night and into early Tuesday morning. Guidance continues to hint
at the potential for measurable precip for northwestern zones
during this time frame as temperatures begin to cool. The rain
will likely mix with or change over to light snow inland as the
low moves northeast and cold air returns. For the time being
straying away any measurable frozen precip for far northwestern
zones, but it will be close. Precip amounts would be very light
if it does in fact take place. This will have to be monitored
with subsequent forecast cycles as surface temperatures in these
areas get close to freezing early Tuesday morning. With mean
upper level troughing in place and a surface trough nearby think
it is prudent to maintain at least low end chance and slight
chance POPs into early Tuesday morning for the remainder of the
area. Despite a good deal of clouds during much of Tuesday,
much of the day should go by generally dry with cool advection
aloft beginning to take hold. This along with a lack of mid
level moisture should limit precipitation despite the clouds
Tuesday and Tuesday night. Overall there will be a lack of
meaningful synoptic scale lift despite the upper level trough
being in place. A storm system will develop well offshore for
Tuesday night into Wednesday morning in response to the actual
upper level low, but will develop too late and too far to the
east and northeast to impact the region.

The 500 mb trough axis then pivots through by 12z Wednesday
morning, followed by transient height rises and ridging late
Wednesday into Thursday. This will lead to high pressure
building in at the surface from the southwest on Wednesday, with
dry conditions expected during the day Wednesday through the
day on Thursday. The baroclinicity and colder air will be
lacking with this high pressure system, therefore temperatures
are expected to average near normal for the mid week.

By Thursday night a northern branch shortwave will dive into
the Upper Midwest and Great Lakes. This will translate east and
drag a cold front through the region during Friday. The timing
of the front is difficult, but appears to be more likely during
the first half of Friday. Chance POPs for late Thursday night
into much of the first half of Friday seems prudent at this
time. A broad west coast ridge and broad eastern US trough then
is forecast to follow into next weekend. The source region will
not be nearly as cold as previous high pressure systems,
therefore temperatures should be somewhat seasonable into next
weekend despite the mean upper level trough into the northeast.


High pressure over New England will move east into the Canadian
Maritimes on Sunday as low pressure off the Southeast coast
gradually drifts northward.

VFR with only a few high clouds overnight. Cigs in the 035-040
range encroach from the south Sunday morning, lowering to MVFR
at the NYC metro and coastal terminals between 13Z-16Z. Rain
will also begin to overspread the coastal terminals toward
daybreak Monday, with continued MVFR conditions.

Winds remain N/NE through the period. G20-25kt should return
after 14Z and continue through the rest of the TAF period.

.Late Sunday night and Monday...IFR conditions are possible
late Sunday night/Monday morning as rain develops, otherwise
MVFR. A brief period of FZRA is possible at KSWF if
precipitation develops early enough. NE winds G20-25kt.
.Monday night and Tuesday...Mainly VFR.
.Wednesday...VFR. NW winds G15-20kt.


Gale warning continues on the ocean E of Fire Island Inlet, but
has been dropped west of there. While winds should still
expected to increase through tonight in response to a re-
tightening pressure gradient ahead of an ocean storm that should
pass SE of Long Island on Monday, model guidance has overdone
winds slightly, and thus do not think the ocean waters W of Fire
Island Inlet will see gales. Gales E of there should begin by
afternoon, mainly on the outer waters at first, then spread
farther north tonight, with seas peaking at 10-15 kt on Mon.
Meanwhile SCA conds still expected elsewhere, with some 5+ ft
seas sneaking into the NY Harbor entrance waters and also into
far ern Long Island Sound past Orient.

SCA conds on the ocean in the form of hazardous seas will take
until Tue evening to subside.

Marginal SCA conditions could return to the ocean water late
Wednesday due to a tightening pressure gradient due as high
pressure builds.


No hydrologic impacts are anticipated through the forecast


Update was to convert the Coastal Flood Watch to a Coastal Flood
Warning for the Sunday high tide cycle for those south shore back
bay locations of Nassau and southwest Suffolk.

However, expected tide levels were lowered slightly across the board
for the Sunday and Monday high tide cycles per latest guidance and
overall synoptic evaluation of storm, wind, etc. Fairly large spread
in ensemble guidance is noted, which leads to lower confidence in
exact tide level forecasts.

This timeframe is between full and new moons, which has helped as
large tidal departures are needed for coastal flooding due to
relatively low astronomical tides.

1-2 ft foot departures are needed for minor thresholds, and 2 to 3
ft is needed for moderate during the day. At night, astronomical
tides are about a foot lower, so only localized moderate coastal
flooding would be possible, with areas of minor and some locations
likely falling short of minor coastal flood benchmarks at night.

All of this is due to prolonged E-NE ocean gales through
Monday, accompanied by long period easterly swells of 9-13 ft by
Sunday, and 10-15 ft on Monday. Winds do back to the north
Sunday night and Monday which may help keep departures down
somewhat in spots (areas where northerly winds push water away
from the shoreline).

Elevated water levels with 8-12 ft breakers along the ocean
beachfront will result in beach erosion and flooding, with areas
of dune erosion and localized washovers likely during the times
of high tide Sunday into Monday. The north shore of Long Island
and the north facing shoreline of the south fork will also
likely have beach erosion and localized wave splashover issues
due to rough waves as well.

Perhaps some south shore back bay locations may still hover at
or just below minor coastal flood benchmarks for the Monday
night high tide cycle. Otherwise the threat for coastal flooding
will generally subside Monday night into Tuesday.


NYC NOAA Weather Radio Station KWO35 (162.55 MHz) is operating
at reduced power until further notice.


CT...Coastal Flood Advisory from noon today to 4 PM EST this
     afternoon for CTZ009-010.
NY...Winter Weather Advisory from midnight tonight to 10 AM EST
     Monday for NYZ067.
     Coastal Flood Advisory from 9 AM this morning to 1 PM EST this
     afternoon for NYZ072-074-075-178.
     Coastal Flood Advisory from noon today to 4 PM EST this
     afternoon for NYZ071-073-078-176-177.
     Coastal Flood Warning from 9 AM this morning to 3 PM EST this
     afternoon for NYZ080-179.
     Coastal Flood Watch from 3 PM EST this afternoon through
     Monday afternoon for NYZ080-179.
     Coastal Flood Advisory from 11 AM this morning to 5 PM EST
     this afternoon for NYZ079-081.
NJ...Winter Weather Advisory from midnight tonight to 10 AM EST
     Monday for NJZ002.
     Coastal Flood Advisory from 9 AM this morning to 1 PM EST this
     afternoon for NJZ006-106-108.
MARINE...Small Craft Advisory until 6 PM EST Monday for ANZ330-335-338-
     Gale Warning until 6 PM EST Monday for ANZ350.
     Gale Warning until 1 PM EST Monday for ANZ353.



NWS OKX Office Area Forecast Discussion