770
FXUS61 KOKX 130910
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
410 AM EST Fri Dec 13 2019

.SYNOPSIS...
High pressure continues to move farther offshore today as
deepening low pressure approaches from the south. The low will
move through the region tonight and Saturday, moving to the
north Saturday night. The low lifts up into the Canadian
Maritimes Sunday as high pressure builds through Monday. Another
low pressure system impacts the area Monday night into Tuesday.
High pressure then builds for the end of the week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Weak upper ridging across the northeast moves offshore this
morning as a full amplitude tough slowly moves east. A
southerly stream shortwave will deepen the trough into tonight.
Meanwhile a surface low developing across the northern Gulf of
Mexico will move into the southeastern states. A developing
coastal front, and an extended trough along the coast, will
provide enough lift this morning for the development of light
precipitation. Temperatures have been slowly rising along the
coast and were nearing the freezing mark at 08Z. Timing of the
rising temperatures will affect precipitation types across the
interior. If the high holds longer, and keeps the cold air in
place, a longer period of light freezing rain, and maybe snow
will be possible inland. Currently have slight chance
probabilities with the wintry precipitation. Will hold off
likely probabilities until later when the high retreats and the
coastal front become more developed.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Both an upper level jet and low level jet move through the
region, mainly across the eastern forecast area late tonight.
The atmospheric column will be fully saturated tonight when the
beast lift and forcing occurs. Periods of moderate to heavy
rain will be possible, mainly 06z to 12Z Saturday, and across
eastern Long Island, and southeastern Connecticut. With the
forcing and  surface destabilization, a rumble of thunder is a
possibility, and this may be just offshore of eastern Long
Island. With the isolated nature, and brief timing, will not
include in the forecast at this time.

By Saturday morning the upper trough becomes negative and the
surface low lifts to the north of the region. This is a little
quicker than the previous, and precipitation will be winding
down during the day as a dry slot moves into the western and
southern areas.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Low pressure that impacts the region Friday night into Saturday
lifts north through New England Saturday night and then into
the Canadian Maritimes on Sunday. Large scale forcing for ascent
decreases significantly Saturday evening as the surface low
lifts north and the middle and upper trough axis swings across
the region. This will lead to mainly dry conditions returning
Saturday night. The pressure gradient steepens however as the
low lifts through New England. Westerly winds will increase
through the night with gusts 20-30 mph, highest near the coast.
The low will continue to deepen as it moves into the Canadian
Maritimes on Sunday with high pressure building to the west. The
gusty westerly winds will only increase further on Sunday with
the steepening pressure gradient. Gusts 25 to 35 mph are likely
with possibly a few peak gusts close to 40 mph near the coast.
Temperatures will only slowly fall Saturday night into the upper
30s and lower 40s and then slightly rise into the middle and
upper 40s during the day Sunday.

Upper low and trough lift away from New England Sunday night
with height rises and surface high pressure building across the
region. The coldest portion of the airmass resides across
southeast Canada and northern New England, so do not anticipate
any significant cold temperatures Sunday night. Lows should
range from the 20s inland to the lower 30s near the coast.

The next system will approach quickly on Monday as it gathers
moisture ahead of a digging upper trough across the Northern
Plains and Great Lakes. Warm advection and moisture being
transported north ahead of the system will increase clouds
through the day. The core of the surface high shifts south over
the Western Atlantic, but the models indicate a ridge axis
hanging on across New England. High temperatures on Monday will
be in the middle and upper 30s. The daytime hours should be
mostly dry, but light precipitation may be developing just to
our southwest as thermal forcing and a warm front approach.

Precipitation should overspread the region from south to north
Monday night. The precipitation will continue early Tuesday
morning before ending in the afternoon. The main question will
be determining PTYPE, especially away from the coast. There is
still a good deal of spread with the model solutions on the
timing of the retreating cold air ahead of the low as well as
the exact track of the low. The lingering colder air ahead of
the low should be enough to create a wintry mix at the onset
Monday night for much of the region. The middle levels are
likely to warm significantly as the low and warm front approach
through the night. This should change precip to mostly liquid
form by early Tuesday morning. Further inland, the depth of the
boundary layer cold air and warm advection aloft will determine
how much snow/sleet and/or freezing rain occurs. The GFS and
ECMWF as well as many of their ensemble members depict the low
tracking over the region early Tuesday morning. This solution is
favored given the synoptic pattern. However, if the low does
track further south, then the wintry mix could last a bit longer
closer to the coast. Plain rain is expected for much of the
region by middle morning Tuesday. The low slides east of the
area by Tuesday afternoon bringing an end to the precipitation.
Temperatures warm into the lower and middle 40s in the
afternoon.

A deep upper trough swings across the eastern states Tuesday night
into Wednesday and then offshore on Thursday. This will bring in a
much colder airmass with temperatures in the 30s during the day and
teens and 20s at night. Despite the trough passage, dry conditions
are forecast on Wednesday.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
High pressure will continue to retreat offshore this morning,
while an area of low pressure works up the eastern seaboard
today into tonight.

MVFR ceilings have yet to develop early this morning, with
indications that development may hold off until the tail end of
the morning push or slightly after. To the east, VFR conditions
may hold on through early afternoon.

High confidence in conditions gradually deteriorate to MVFR and
then IFR with increasing chances of rain from late this
afternoon into this evening. IFR/LIFR likely tonight in moderate
to heavy rain and stratus/fog.

Note if light precip starts this morning, there could be a
light wintry mix for KHPN and KSWF but probabilities for this
are too low so this is not in TAFs.

Light NE winds this morning, should gradually veer to E/SE for
coastal terminals this morning, before backing to E/NE late this
afternoon and increasing to 10 to 15 kt with gusts to 20 kt at
the coastal terminals in the afternoon/evening. Winds should
veer back to SE/S for most terminals late tonight into Saturday,
before a windshift to SW late Saturday. LLWS possible tonight
for eastern terminals with SE winds around 50kt at 2kft.

 ...NY Metro Enhanced Aviation Weather Support...

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

KJFK TAF Comments:

Increasing potential for MVFR conds after morning push.
Likelihood for IFR conds developing in RA during evening push.
E/SE gusts to 20 kt possible this afternoon into evening.

The afternoon KJFK haze potential forecast is GREEN...which
implies slant range visibility 7SM or greater outside of cloud.


KLGA TAF Comments:

Increasing potential for MVFR conds after morning push.
Likelihood for IFR conds developing in RA during evening push.
E/NE gusts to 20 kt possible this afternoon into evening.

The afternoon KLGA haze potential forecast is GREEN...which
implies slant range visibility 7SM or greater outside of cloud.


KEWR TAF Comments:

Increasing potential for MVFR conds after morning push.
Likelihood for IFR conds developing in RA during evening push.
Winds may remain NE through the morning and evening push,
generally 10 kt or less.

The afternoon KEWR haze potential forecast is YELLOW...which
implies slant range visibility 4-6SM outside of cloud.


KTEB TAF Comments:

Increasing potential for MVFR conds after morning push.
Likelihood for IFR conds developing in RA during evening push.
Winds may remain NE through the morning and evening push,
generally 10 kt or less.

KHPN TAF Comments:

Increasing potential for MVFR conds after morning push.
Likelihood for IFR conds developing in RA during evening push.
E/NE gusts to 20 kt possible this afternoon into evening.

KISP TAF Comments:

Increasing potential for MVFR conds after morning push.
Likelihood for IFR conds developing in RA during evening push.
E/SE gusts to 20 kt possible this afternoon into evening.

.OUTLOOK FOR 06Z SATURDAY THROUGH TUESDAY...
.Late Tonight...Mainly IFR in rain. SE/S winds. LLWS possible late
for eastern terminals.
.Saturday...IFR in rain. SE/S winds, shifting SW late. LLWS possible
early.
.Saturday Night...Scattered showers, mainly early. Improving to
VFR with W winds increasing to 15-20ktG25-30kt.
.Sunday...VFR. West winds 15-20ktG25-35kt.
.Sunday night-Monday...VFR. Some West wind gusts to 20 kt Sunday
night.
.Monday night-Tuesday...MVFR to IFR possible. Chance of snow
for inland terminals changing to a wintry mix and then to rain.
Chance of mainly rain for coastal terminals, with a period of
snow or a wintry mix at the start early Monday night.


&&

.MARINE...
Southeasterly winds will be increasing later this morning into
this afternoon. Wind gusts will be minimal, however, by mid to
late afternoon gusts on the ocean waters may be near 25 kt, as
low pressure to the south of the waters begins to deepen and
high pressure remains to the east. The strong and gusty winds
will remain on the ocean waters through tonight. As the low
moves across the waters during Saturday winds will likely
diminish below SCA levels, however, ocean seas will remain
elevated. So, the small craft advisory remains beginning this
afternoon, however, the advisory was extended through Saturday.
For the non ocean waters conditions are expected to remain below
SCA levels. However, for a few hours tonight gusts on the
eastern Long Island bays may be near 25 kt.

A steepening pressure gradient behind departing low pressure
and building high pressure Saturday night into Sunday should
bring SCA conditions on the non-ocean waters and gales to the
ocean. There is enough confidence in the gale force winds during
this time for the issuance of a gale watch. Ocean seas will
remain elevated during this time as well. SCA winds are likely
to continue on all waters Sunday night, with seas gradually
subsiding. Winds diminish on Monday with high pressure settling
over the waters. Seas will also fall below 5 ft. These
conditions will be short-lived as the next low pressure
approaches Monday night and moves across the waters Tuesday. SCA
conditions are likely on the ocean waters on Tuesday. At this
time, it looks like winds will stay below 25 kt on the non-ocean
waters.

&&

.HYDROLOGY...
One to two inches of rainfall, with locally higher amounts,
are likely today through Saturday. The highest amounts are
expected across eastern Long Island and portions of southeastern
Connecticut. Minor nuisance flooding will be possible,
especially tonight when the bulk of the rain falls.

Another low pressure moves across the region Monday night into
Tuesday. No hydrologic impacts are anticipated at this time.

&&

.TIDES/COASTAL FLOODING...
There is increasing potential for minor coastal flooding with
the high tide cycle during Saturday morning (departures of 1 to
2 ft are needed to reach minor benchmarks). This will be due to
onshore winds with an approaching storm combined with relatively
high astronomical tides due to a nearly full moon.

There is a bit of uncertainty on timing of windshift from SE to
SW Saturday morning, which is reflected in a sizable spread of
Stevens ensemble. Forecast below is based on a blend of ETSS,
ESTOFS and approximately a 75th percentile Stevens forecast.

Minor coastal flooding is expected along the south shore bays
of Nassau and Queens counties, as well as along the coast of SW
CT and S Westchester due to a combo of water levels around minor
flood levels and some wave actions. Localized minor flooding is
likely along the most vulnerable locales of lower NY Harbor,
eastern bays and north shore of LI, and along SE CT.

Along the Atlantic Ocean beach front breaking surf of 8 to 13
ft (highest eastern LI) will cause significant beach flooding
and erosion during the times of high tide Saturday into Saturday
Night. Scattered areas of dune erosion and localized washovers
are possible during the times of high tide Saturday morning into
afternoon.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO35 (162.55 MHz) is still
operating at reduced power.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Coastal Flood Advisory from noon to 3 PM EST Saturday for
     CTZ009-010.
NY...Coastal Flood Advisory from noon to 3 PM EST Saturday for
     NYZ071.
     Coastal Flood Advisory from 7 AM to noon EST Saturday for
     NYZ178-179.
NJ...None.
MARINE...Gale Watch from Saturday evening through Sunday afternoon for
     ANZ350-353-355.
     Small Craft Advisory from 4 PM this afternoon to 6 PM EST
     Saturday for ANZ350-353-355.

&&

$$
SYNOPSIS...DS/19
NEAR TERM...19
SHORT TERM...19
LONG TERM...DS
AVIATION...NV
MARINE...DS/19
HYDROLOGY...19
TIDES/COASTAL FLOODING...NV
EQUIPMENT...

NWS OKX Office Area Forecast Discussion