000
FXUS61 KOKX 251737
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
137 PM EDT Tue Jul 25 2023

.SYNOPSIS...
High pressure will remain offshore this week. An upper level
disturbance will move across this afternoon and tonight, followed
by another disturbance on Thursday. A hot and humid air mass
will build in from Thursday through Saturday, with a cold
frontal passage expected on Saturday. Canadian high pressure
will build in on Sunday and remain to the west into the
beginning of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
A Severe Thunderstorm Watch is in effect for the entire area
through 8 PM. The primary threat is damaging wind gusts, with
the potential for large hail as well.

Daytime heating has lead to MLCAPE values between 1000-1500 J/kg
per SPC Mesoscale Analysis Page and further destabilization is
expected. A mid-level shortwave trough is approaching from our
west and can be seen on current satellite water vapor imagery.
Several discrete storms have popped up ahead of a preexisting
MCV over eastern PA. Showers and storms have also fired up along
the north shore of Long Island with the help of convergence from
a Sound breeze.

Successive CAM model cycles have been pinpointing areas from
central NJ up into the NYC metro area and Westchester/Putnam and
adjacent portions of SW CT. WPC includes NYC and NE NJ in a
slight risk of excessive rainfall. More robust cells have
potential to deliver a quick 1-2 inches of rain as well and
timing of this wx has potential to impact the late afternoon
rush hour. Scattered flash flooding is possible. This activity
should shift east mostly into Long Island and CT and weaken
after dark as the shortwave moves through.

High temps today should reach the lower and mid 80s which is
close seasonable.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
A weak shortwave ridge will slide across on Wed. Dry and warmer
conditions will prevail, with high temps 85-90 for most of the
interior, except lower 80s for the higher elevations and also
across a good portion of Long Island and SE CT.

On Thu, a strong upper ridge will build westward from the
Atlantic, while another shortwave trough aloft traverses the
Northeast. Temps will respond rapidly to the building ridge,
with highs in the mid/upper 90s in the NYC area and in most of
NE NJ, with 90-95 most elsewhere, and upper 80s along immediate
south facing shores especially out east. As is often the case,
dewpoints from NYC north/west should decrease in the afternoon
via mixing, with upper 60s expected, while dewpoints remain in
the lower 70s across Long Island and S CT. This combination will
yield widespread heat index values in the upper 90s and lower
100s, possibly approaching 105 in the urban corridor of NE NJ
near the NJ Turnpike.

The shortwave will also spark another round of showers/tstms.
SPC has the entire region in a slight risk for severe tstms, but
coverage should be more isolated in the NYC metro area and
across Long Island due to closer proximity of the ridge, and
attm think the greater svr threat will lie more to the north
across the lower Hudson Valley and S CT.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
H8 temps +20C over the forecast area will continue Fri into Sat. It
will therefore be hot across the region with highs generally in the
middle to upper 90s on Friday (slightly cooler on Saturday with
uncertainty in clouds and timing of cold frontal passage, especially
for northwest sections of the forecast area). Friday looks to be the
warmest of the week. It is not out of the question that portions of
northeast New Jersey reach the century mark. Combined with dew
points in the 70s heat indices will range from 100 to just over 105,
with the highest values across northeast New Jersey. Some portions
of northeast New Jersey could see heat index values close to 110.
The Weather Prediction Center is showing a 10-40% chance of heat
index values exceeding 110 on Friday. Lower temperatures and heat
index values can be expected as you head closer to the coast.

Low temperatures will be warm as well, in the 70s region-wide, but
in the upper 70s for the metro area. In fact, it would not be
surprising to see a low in the lower 80s, most likely Friday night
into Saturday.

A surface trough moves through Thursday evening, bringing a chance
for showers and thunderstorms into early Thursday night, but with
the loss of daytime heating and thus instability, precipitation
should end around or just after sunset.

A slight chance for showers Friday into Friday night mainly due to
model uncertainty and potential for another surface trough to move
through, but the best chances are with a cold frontal passage Sat.
Exact timing will determine coverage and intensity, so for now PoP
is capped at isolated to scattered coverage, with higher
chances across the interior.

Generally fair and slightly cooler than seasonable on Sunday with a
drier air mass building in. Some afternoon 20% PoP with a NW flow
regime. Cooler and less humid conditions continue into the new work
week.

Dry and cooler on Mon with highs fcst blw avg attm with H8 temps in
the 10-11C range, about 10 degrees cooler than what is expected
during the end of this week.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
Offshore high pressure remains during the TAF period.

An upper level disturbance will move through the area this aftn
and produce showers and thunderstorms into this evening. Timing
is for an area of storms to move through after 18Z (getting
into the metro terminals by 19-20Z). There may be strong gusts
associated with these storms of up to 50 kt. Some weakening of
the tstms is possible as they track east of the NYC arpts.

VFR conditions are expected to prevail for much of the TAF
period. MVFR or lower is expected in any thunderstorms. MVFR to
IFR fog/stratus is possible overnight, but mainly for outlying
terminals.

Outside of thunderstorms, winds will be mainly S to SW around
10 kt for the city terminals today. There may be an occasional
gust to 15 to 20 kt into this eve. Speeds of 5 to 10 kt
expected outside the city terminals. Winds diminish overnight,
becoming light and variable for most terminals, including the
city, then become SSW to around 10 kt aft 16Z Wed.

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

Timing of TSRA may be off +/- 1-2 hours. In general, gusts in
the 30-40kt range are most likely in tstms. However, the
strongest tstms will be capable of producing winds aoa 50kt.
Some hail will also be possible.

OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY...

Wednesday: VFR.

Thursday: Possible showers and thunderstorms at times afternoon
into evening with brief MVFR to IFR possible. Higher chances
of showers and thunderstorms near KSWF. If tstms develop, they
could become severe. Otherwise, VFR. SW wind gusts along coast
15-20 kt.

Friday: Possible showers and thunderstorms at times afternoon
into evening with brief MVFR to IFR possible. Otherwise, VFR.
SW wind gusts along coast 15-20 kt.

Saturday: Chance of showers and thunderstorms afternoon into
evening with brief MVFR to IFR possible. Otherwise, VFR.

Sunday: VFR.

Detailed information. including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
A Severe Thunderstorm Watch is in effect for all waters through
8PM.

A Marine Weather Statement continues for Long Island Sound. The
US Coast Guard still indicates a large debris field caused by
recent flooding across New England.

SW flow should increase to SCA criteria on Thu, sustained at
25-30 kt toward evening on the ocean waters, and with gusts in
the afternoon/evening about that high on the bays of Long
Island and also E of Orient Point. Ocean seas should increase to
6-9 ft during this time as well.

Longer term, although seas on the ocean waters diminish
Thursday night, and could even fall below 5 ft for a time W of
Moriches Inlet, 5+ ft seas should return across all ocean waters
Friday night and continue through Sat as S flow increases ahead
of an approaching cold front. Sea then subside by late Saturday
night. Elsewhere, winds and seas should remain below SCA
levels, although tstms may pose a potential hazard at times.
-- End Changed Discussion --

&&

.HYDROLOGY...
-- Changed Discussion --
Locally heavy rain in thunderstorms late today may lead to
scattered flash flooding, mainly for NYC north and west.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
Have increased the rip current risk to moderate for the Nassau
and Suffolk ocean beaches for today due to incoming easterly
2-ft swell with 9-11 second period (apparently from former
Hurricane Don), which should run up to 2-3 ft in the surf zone.
The moderate risk should continue for the Suffolk beaches on
Wednesday.

There may be a high risk for rip currents from Thu into Sat,
especially for the ocean beaches of eastern Long Island.

&&

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

&&

$$
SYNOPSIS...BG/JP
NEAR TERM...BG/JT
SHORT TERM...BG
LONG TERM...JP
AVIATION...JMC/JP
MARINE...BG/JP
HYDROLOGY...BG/JP
TIDES/COASTAL FLOODING...