Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 072049
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
449 PM EDT Tue Apr 7 2020

.SYNOPSIS...
A warm front approaches tonight along with an area of low pressure.
The low passes through late tonight and exits east Wednesday. A cold
front then passes through on Thursday. An associated low will
pull away into the Canadian Maritimes on Friday, followed by
high pressure building from the west on Saturday. Low pressure
will then approach from the west on Sunday and impact the area
Sunday night into Monday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A warm front will approach from the SW tonight. At the same time,
low pressure across the Great Lakes will track along the approaching
warm front. Models remain in fairly good agreement with timing of
the arrival of rain ahead of the front. Chances of rain begin west
of the Hudson this evening, then rain eventually becomes likely west
to east overnight. Will leave in a low chance of thunder for parts
of the forecast area as models show some elevated instability and
enough low-mid level lift.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
A weak north to northeast flow occurs behind the departure of low
pressure Wednesday morning. Plenty of moisture remains beneath
800mb, so clouds won`t have much of any chance to scour out. Even
after rain chances drop off early in the morning, cannot rule out a
chance of an afternoon. This chance will be focused more towards the
western zones during the afternoon where models depict convergence
along a surface trough just off to our west. Prefer the cooler
guidance for high temperatures given the anticipated cloud cover and
NE low level flow in the afternoon. Dry weather should then follow
for Wednesday night.

A cold front approaches on Thursday and passes through late in the
morning/earlier portion of the afternoon. Models in good agreement
with rain/showers with this cold front. Shear will be strong and
synoptic lift will be deep with the core of a jet streak eventually
passing not too far to our south. How much CAPE we actually get
ahead of the cold front is questionable as an onshore flow and low
level moisture probably starts us off with mostly cloudy conditions.
Even with low CAPE, strong lift and shear probably results in a line
of showers with embedded thunderstorms moving through. Biggest
threat with these showers would be strong wind gusts. Breezy and dry
behind the front late in the day into Thursday night. Just a slight
chance of mixed rain/snow showers well NW of the city late at
night.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Reasoning from previous forecasts remains relatively similar, with
some changes based on latest guidance that were hinted at yesterday.
To start, expect brisk conds on Fri, with isold-sct showers as low
pressure pulls away. Inland sections especially the higher
elevations could see some snow mixed in during the morning.
W-NW winds will be on the brisk side due to the departing low`s
tight pres gradient, so expect winds at or near advy criteria in
the greater NYC metro area and across Long Island, and possibly
elsewhere.

High pressure then builds across Sat into Sat night. Guidance shows
more nrn stream interaction with a srn stream low pressure system
approaching for Sunday into Mon, and so have gone with its slower
trend. That guidance is also decidedly wetter and windier, which
makes sense given the strengthening offshore high and long S fetch,
at least per ECMWF. GFS fcsts a secondary low to develop along
the coast which, if it develops, would probably result in a
stout E-SE rather than S flow. Given the very good
warmth/moisture transport via either a S fetch or enhanced
convergence/lift via a secondary low, heavy rain also looks
like a good bet, with axis of heaviest rain a little to early to
know for certain.

Temps about 5-8 deg below normal on Fri, with highs in the lower/mid
50s, will moderate somewhat on Sat to mid/upper 50s, still slightly
below avg. Temps on Sunday/Mon ahead of the approaching low should
warm up, with upper 50s to mid 60s on Sunday, and 60s to lower 70s
on Mon, highest away from the coast.

&&

.AVIATION /21Z TUESDAY THROUGH SUNDAY/...
A frontal sys passes late tngt into Wed mrng.

VFR thru at least 3Z, then -ra develops with MVFR likely. There is a
low chc of IFR cigs 6-12Z. Mainly MVFR is expected to linger on Wed.
The best chc for breaks to VFR will be aft 16Z.

Sea breeze flow will continue to develop this aftn. Amendments can
be expected for timing. Winds decrease tngt, then aft the fropa, NW
flow veers gradually to the E on Wed. Speeds generally aob 10 kt.

.OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY...
.Rest of Wed...Mainly MVFR.
.Thu...MVFR in the mrng, becoming VFR. LLWS possible in the mrng.
.Fri...VFR with W winds 25-35kt.
.Sat-Sun...VFR.

&&

.MARINE...
Sub-SCA conditions are expected to remain on all waters through
Wednesday night.

A cold front will approach the waters on Thursday increasing wind
gusts to SCA levels on all waters. Ocean seas will also build,
reaching 6-7 feet Thursday night and up to 10 feet on Friday.

W-NW gales may be possible on Friday, especially near shore and also
on the outer ocean waters. SCA conds in all waters Fri evening
should take some time to diminish, with quiet conds not returning
til late day Sat or Sat night.

Increasing S flow between a strengthening offshore high and
approaching low pressure may bring SCA conds to all waters Sunday
night. Some gale force wind gusts may be possible on the ocean
waters late.

&&

.FIRE WEATHER...
Wetting rains on Thu should help limit fire growth potential on Fri
despite string winds and low afternoon RH. With some drying out Sat
could be a day of concern, with W winds still gusting to 30 mph and
min RH 20-30%.

&&

.HYDROLOGY...
Just a quarter to half inch of rainfall expected late tonight
through Wednesday morning. Same amounts for Thursday`s system, but
locally higher amounts could be realized. Low chance of minor
nuisance flooding on Thursday.

QPF for the low pressure system Sunday night into Mon has
trended wetter, with amts of 1-2 inches fcst. This may be
capable of causing some minor areal and small stream issues.

&&

.TIDES/COASTAL FLOODING...
High astronomical tides due to the supermoon and a positive
tidal anomaly will be factors for the total water level forecast
through Wednesday. Winds will not be strong, about a 10 kt
onshore flow or less so tidal piling and wind forcing will not
be too much, limiting the coastal flood potential.

Hazards are as follows:

Tonight through Wednesday: Coastal flood statements across much
of the shorelines of NY Harbor, Western Long Island Sound, and
South Shore Bays. The total water level will around 1/2 to 1
foot above astronomical tides, so about 1/2 to 1 foot of surge
during times of high tide. Isolated minor coastal flooding will
be the result.

Wednesday Night: Coastal flood advisories for the more
vulnerable coastal locations across NY Harbor, Western Long
Island Sound, South Shore Bays and SW Suffolk NY. The total
water level will be 1 to 2 feet above astronomical tides, so
about 1 to 2 feet of surge during times of high tide. Widespread
minor coastal flooding will be the result. Other nearby
locations such as Eastern Union NJ, Eastern Essex NJ, Manhattan,
Bronx, Northern Queens will get close to touching minor coastal
flood benchmarks. These less exposed coastal locations have a
coastal flood statement for Wednesday night, more of an isolated
minor coastal flood situation.

Minor coastal flooding is also possible on Thursday as
astronomical tides remain high. There will also be a strong cold
front passage that may bring a bit stronger onshore wind
forcing.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO35 (162.55 MHz) is undergoing
its final stages of testing, and is operating at full power.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Coastal Flood Advisory from 11 PM Wednesday to 2 AM EDT
     Thursday for CTZ009-010.
NY...Coastal Flood Advisory from 11 PM Wednesday to 2 AM EDT
     Thursday for NYZ071-078-177.
     Coastal Flood Advisory from 8 PM to 11 PM EDT Wednesday for
     NYZ074-075-178-179.
     Coastal Flood Advisory from 10 PM Wednesday to 1 AM EDT
     Thursday for NYZ080.
NJ...Coastal Flood Advisory from 8 PM to 11 PM EDT Wednesday for
     NJZ006.
MARINE...None.

&&

$$
SYNOPSIS...JC/Goodman
NEAR TERM...JC
SHORT TERM...JC
LONG TERM...Goodman
AVIATION...
MARINE...JC/Goodman
FIRE WEATHER...
HYDROLOGY...JC/Goodman
TIDES/COASTAL FLOODING...
EQUIPMENT...



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