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Forecast Discussion for New York City/Upton, NY

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021
FXUS61 KOKX 022330
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
730 PM EDT Sun Aug 2 2026

.WHAT HAS CHANGED...
Some changes with POPs tonight and enhanced forecast wording to
emphasize heavy rain. High surf and high rip current risk for
ocean beaches Monday.

&&

.KEY MESSAGES...
1) The potential remains for a period of heavy rainfall, and
thunderstorms, late tonight into Monday. A Flood Watch is in
effect for northern New Jersey through Monday evening.

2) Moderate rip current risk continues at the ocean beaches into
this evening. High surf and high rip current risk expected for the
ocean beaches Monday into Monday evening.

3) Unsettled weather at times once again Wednesday and Thursday
this week.

&&

.DISCUSSION...
.KEY MESSAGE 1...
Updated POPs for showers and made some minor adjustments to the
thunderstorm forecast. Basically, early this evening, isolated
to scattered showers mainly to areas north and west of NYC and
by Southeast CT and Eastern Long Island will occur. These
increase in coverage mid to late this evening and become more
widespread overnight. Chances for thunderstorms will gradually
increase also as elevated instability increases across the
region.

Ingredients are setting up for a period of heavy rainfall potential
across the area late tonight through Monday. General guidance has
been trending toward a faster cold frontal passage, but with such
high values of deep-layered moisture, any thunderstorms tonight and
into Monday will easily be able to produce >1" per hour rainfall
rates. The complicating factor is where these thunderstorms happen.
Even though coverage and locations of the heaviest rainfall is low
confidence, given the high rainfall rate potential, opted to issue a
Flood Watch for the most flash flood prone locations in the CWA,
primarily urban NE New Jersey, tonight through Monday evening. If
confidence in the heaviest rainfall axis increases for other areas,
the Flood Watch may need to be expanded in subsequent forecasts.

A positively tilted upper trough with attendant closed low over the
Central Plains ejects out into the OH Valley by this evening,
shearing out as it does so. In addition, a 300mb, 110kt jet streak
passes through New England on Monday, with the local area on the
favorable right rear quadrant. Surface low pressure with a slowly
moving frontal system accompany this feature, and approaches the
local area on Monday.

Brisk southerly flow continues into tonight with a tropical-like
airmass moving in place tonight through Monday. Deep-layer moisture
will continue to increase over the area with >2" PWAT expected to
overtake the area much of the next 24 hours. The potential for
shower and thunderstorm development increases into this evening
as a warm front moves in. Any convection has the potential to
train as well, increasing the heavy precipitation threat, with
low and upper level flow aligned.

Heaviest precipitation over the area looks to occur late tonight
into the day on Monday. In general, total rainfall amounts appear to
be 0.75 - 1.5" with localized amount of upward of 3-4" possible in
any training thunderstorms. CAMs have been hinting toward a general
eastward push of the heaviest rainfall with several models
indicating the potential of a training line of heavy showers and
thunderstorms over portions of Long Island in S CT.

Despite the trend, flash flood guidance remains low across NE
NJ (~1" in an hour and 1-3" in 3 hours) given the rain from last
week. 12Z HREF guidance has expanded the 10% chance of 3" in 3
hours over NE NJ into S CT. Though any flash flooding is
expected to be more isolated in coverage, the low threshold
needed for flash flooding in the most flood-prone areas of NE NJ
has resulted in a Flood Watch being issued. The WPC Urban
Rainfall Rate Dashboard is still advertising the possibility of
>1" per hour rainfall rates for NYC and surrounding areas on
Monday from this event. WPC expanded the slight risk of
excessive rainfall to include almost the entire area with the
exception of far eastern LI and SE CT where a marginal risk is
maintained for Monday.

A lesser threat would be an isolated thunderstorm tomorrow becoming
severe with around 1000 J/kg of CAPE and around 30kt of 0-6km shear.
Wind gusts would be the main hazard associated with the strongest
storms.

.KEY MESSAGE 2...
Wavewatch has trended higher compared to the previous day run
regarding wave heights at the offshore buoys for Monday.

44017 has potential with this forecast from Wavewatch to get to 11
ft waves. 44025 has potential with this forecast from Wavewatch to
get to 9 ft waves.

NWPS guidance also increased slightly as well compared to previous
forecast regarding wave heights.

The increasing southerly flow will become more gusty and increase
the fetch, building the waves and swell tonight into Monday. S-SW
winds increase to near 15-20 kt along the coast Monday.

Forecast wave heights reach up to 8 ft. The main swell will be
around 8 ft from the south with period of 8 to 9 seconds.

For ocean beaches, the moderate risk of rip currents will transition
to a high risk of rip currents for Monday and high surf can be
expected for Monday as well.

There could be another high risk of rip currents for Suffolk ocean
beaches Tuesday with otherwise a moderate risk of rip currents for
the ocean beaches. For Tuesday, the winds will be decreasing to near
5-10 kt from northerly in the morning to more southerly in the
afternoon. Ocean southerly swells decrease Tuesday to near 4 ft with
near 7 second period.


.KEY MESSAGE 3...
Rain tapers by Monday night and Tuesday looks mostly dry. The
frontal system that stalled to the south on Monday returns by
Wednesday AM as a warm front. Thus, additional showers and
thunderstorms are possible with the front in the area, at least
into Thursday.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
A slow moving frontal system will impact the terminals through
Monday. A weak warm front moves through this evening, followed
by a cold frontal passage Monday evening.

MVFR and IFR become increasingly likely into this evening.
Widespread MVFR and IFR conditions late tonight into Monday
morning. Thunderstorm chances increase after 06Z. LIFR
conditions are likely for KGON and possible for KISP late at
night and into early Monday morning.

S/SSE gusts diminish this evening as winds back more to the SE ahead
of the warm front. Winds will then veer back to the south late tonight
into Monday morning. Low chance of LLWS for KISP and KGON early Monday
morning into the afternoon. Winds lower to 10 kt or below Monday
evening behind the cold frontal passage.

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

AMD likely with changing flight cats through the TAF period.

Most likely TSRA timing is included in TEMPO groups. An isolated
thunderstorm outside of those times can not be completely ruled
out, mainly after 06z Monday through Monday evening.

.OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY...

Monday night: Becoming VFR. Winds shifting to the NW-N at 5-10
kt.

Tuesday: VFR.

Wednesday-Friday: Sub-VFR at times in showers and thunderstorms.

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

&&

.MARINE...
Sub advisory conditions prevail on the waters through the first half
of tonight. Small craft conditions become increasingly likely
for the ocean and some eastern non-ocean zones late tonight into
Monday as a south wind picks up and seas build. Small craft
conditions will likely continue for the ocean through Monday night
as the winds veer more to the SW and seas remaining elevated around
5 to 7 ft. Sub advisory conditions should develop thereafter.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Risk for Rip Currents from 6 AM EDT Monday through Monday
     evening for NYZ075-080-081-178-179.
     High Surf Advisory from 6 AM to 9 PM EDT Monday for NYZ075-080-
     081-178-179.
NJ...Flood Watch through Monday evening for NJZ002-004-006-103>108.
MARINE...Small Craft Advisory from 4 AM to 8 PM EDT Monday for ANZ331-
     332-340-345.
     Small Craft Advisory from midnight tonight to 6 AM EDT Tuesday
     for ANZ350-353.
     Small Craft Advisory from midnight tonight to midnight EDT
     Monday night for ANZ355.

&&

$$

DISCUSSION...JM/MW
AVIATION...JT
MARINE...MW

Previous Forecast Discussions may be found at
NWS New York City/Upton, NY (OKX) Office Forecast Discussions.
(Click 'Previous Version' there to view past versions successively.
Some may differ only in time posted.)

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