NYC Office Forecast Discussion

000
FXUS61 KOKX 222249
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
649 PM EDT Mon May 22 2017

.SYNOPSIS...
A weak frontal system passes through the region tonight, stalling
in the mid Atlantic region late tonight into Tuesday. Weak high
pressure builds in for Tuesday. Meanwhile, a wave of low
pressure will move along the frontal boundary, south of the
region, Tuesday and Tuesday night. Weak high pressure builds in
on Wednesday, followed by low pressure Thursday into Friday.
High pressure returns for the beginning half of the upcoming
holiday weekend, but low pressure may bring some unsettled
weather during the latter half.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Weak frontal system is located across east central PA and
upstate NY this evening. This boundary will continue moving east
and then through the region overnight.

Best lift, in the form of shortwave energy and 30-40 kt low
level jet, is shifting east, with steadiest rain across Long
Island and southern Connecticut. This activity is expected to
continue sliding east through the next few hours, with PoPs
decreasing as well. Attention then turns to a mesolow, currently
moving off the DelMarva coast. High resolution mesoscale
guidance takes the mesolow offshore, but then possibly link it
up with the approaching front to enhance showers along it across
eastern Long Island and southeast Connecticut. Will continue to
forecast highest PoPs here, with a gradual decreasing trend
into the early morning hours. Thunder not expected as little to
no CAPE and instability is present. Mainly dry conditions
expected from the city north and west after midnight.

Areas of fog are possible this evening as well. Visibilities
should not fall much below 2SM in any fog. Improving
visibilities are anticipated from west to east as the frontal
boundary moves across.

Gradual clearing expected behind the front. Temperatures remain
nearly steady for much of the night, but could fall into the
upper 40s/lower 50s NW of the city towards daybreak.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
The cold frontal boundary will remain stalled to the south,
through the mid Atlantic region and DELMARVA Tuesday, and weak
mid and low level ridging builds. Will keep the area dry through
most of the day and then bring in probabilities late in the day
to the south as a wave begins to move along the frontal
boundary.

The wave passes to the south with some differences in placement
Tuesday and Tuesday night with the NAM just about totally dry
while the GFS is a little farther north. At this time leaned a
little more closer to the GFS and brought chance across about
the south half of the area.

The wave does pass through quickly and precipitation may be
ended across the eastern zones by Wednesday morning.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Weak high pressure builds in behind a departing offshore low on
Wednesday. Only a slight chance of a shower in the morning mainly
over Long Island. Partly sunny otherwise, and a blend of MAV/NAM MOS
looked good for high temperatures.

The next system to bring rainfall to the area arrives late Wednesday
night, with rainfall being most likely Thursday into Thursday night.
Went a little cooler than most guidance, particularly over western
zones as a triple point low approaches, but the associated warm
front extending to its east might only push through some of the
eastern zones, if at all. Some elevated instability should be
present, so have included isolated TSTMs for Thurs and Thurs night.
Also included areas of fog for late Weds night into Thurs morning
with the warm front not too far off to the south.

For Friday, the storm exits to the NE, but is still close enough for
a chance of showers, especially over the NE zones. Some lower level
instability combined with a cold pool aloft may also result in a
TSTM over parts of CT as well.

Weak high pressure then returns for Saturday. Will go with a dry
forecast and slightly above normal temperatures for now. The timing
of the next low pressure system is still uncertain at this point.
Some overrunning rainfall could move in by daybreak Sunday. The
system would figure to move slowly enough for Monday to be affected
as well. Will go with CHC PoP for now for both days.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
A front will cross the area tonight, as weak low pressure tracks
slowly south of Long Island into Tuesday.

IFR/LIFR conditions should continue through at least 6z, and
probably last until after the front passes (4-9z from W to E).
There is quite a bit of uncertainty as to how quickly
improvement will occur behind the front. At this time, VFR is
expected everywhere by around midday Tuesday.

Light and variable winds (S-SE at around 10KT or less KLGA/KJFK
this evening), shift to the N-NE at 10KT behind the front.
After the wind shift, conditions should dry somewhat but there
is uncertainty with how quickly improvement will occur as some
the latest model guidance suggests a slower improvement in the
early morning. By midday...VFR is expected everywhere.

SE winds 5-10 kt gradually increase, generally 8 to 13 kt.
Occasional gusts up 15-18 kt possible. Winds shift north to
northeast 5-10 kt around 07-09z and continue into Tuesday
afternoon.

     NY Metro Enhanced Aviation Weather Support...

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

KJFK TAF Comments: Amendments possible due to changes in
ceilings and visibilities.

KLGA TAF Comments: Amendments possible due to changes in
ceilings and visibilities.

KEWR TAF Comments: Amendments possible due to changes in
ceilings and visibilities.

KTEB TAF Comments: Amendments possible due to changes in
ceilings and visibilities.

KHPN TAF Comments: Amendments possible due to changes in
ceilings and visibilities.

KISP TAF Comments: Amendments possible due to changes in
ceilings and visibilities.

.OUTLOOK FOR 18Z TUESDAY THROUGH SATURDAY...
.Tuesday afternoon-Wednesday evening...VFR.
.Wednesday night-Friday night...MVFR or lower possible. Slight
chance of thunderstorms Thursday evening.
.Saturday...VFR.

&&

.MARINE...
A southeast flow continues this evening and into tonight ahead
of an approaching cold front. Winds then shift to the northwest
to north with the frontal passage, and then shift to the
northeast to east Tuesday into Tuesday night as a wave of low
pressure passes to the south of the forecast waters. Winds and
seas are expected to remain below small craft levels tonight
through Tuesday night.

A weak pressure gradient will be over the waters on Wednesday with
weak high pressure ridging in behind a departing offshore low. NE
winds at 10 KT or less shift SE in the afternoon, and seas should
remain below 5 FT. The next storm system so far would not appear to
create a pressure gradient strong enough for advisory level winds
over the region. Relatively stronger winds associated with this
system would be on Friday when the center of this system is
northeast of the waters. Winds are therefore forecast to remain
below advisory levels through this period and should remain that way
on Saturday as winds diminish. However on the ocean, guidance
suggests a significant swell. Have gone with a forecast of wave
heights below guidance, but still at advisory criteria Wednesday
night through Saturday morning.

&&

.HYDROLOGY...
Hydrologic impacts are not expected with rainfall through
tonight. Additional amounts of one quarter to one half inch
possible across eastern Long Island and southern Connecticut.

Unsettled weather is expected mid to late week, but no
hydrologic impacts are anticipated at this time.

&&

.TIDES/COASTAL FLOODING...
Minor coastal flooding thresholds may be reached with Wednesday
night`s high tide cycle for southern sections of NY Harbor, the
south shore back bays of western LI/Queens/Brooklyn, and western
Long Island. A better chance of minor flooding arrives for Thursday
night, with northern NY Harbor and parts of central LI sound also
included. Chances then lower on Friday night as winds likely shift
offshore.

&&

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

&&

$$
SYNOPSIS...JC/MET
NEAR TERM...MET/DS
SHORT TERM...MET
LONG TERM...JC
AVIATION...IRD/Maloit
MARINE...JC/MET
HYDROLOGY...JC/MET/DS
TIDES/COASTAL FLOODING...

NWS OKX Office Area Forecast Discussion