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Forecast Discussion for New York City/Upton, NY
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201
FXUS61 KOKX 271441
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1041 AM EDT Mon Jul 27 2026
.WHAT HAS CHANGED...
No significant changes made with the latest forecast.
&&
.KEY MESSAGES...
1) Showers and thunderstorms today for NYC and north and west. An
isolated severe thunderstorm is possible.
2) Unsettled weather expected Tuesday through Thursday due to a slow
moving low pressure system. Heavy showers and thunderstorms will
bring the potential for flash flooding, mainly Tuesday afternoon
through Wednesday.
3) Potential for minor coastal flooding mid to late week with
a coastal low.
&&
.DISCUSSION...
.KEY MESSAGE 1...
The stretch of dry, pleasant weather looks to end for some
today. Several weak shortwaves will move through the mean upper
level trough over the area. There is decent agreement that the
western half of the area is able to destabilize to about
1000-2000 J/kg of MLCAPE. This could lead to isolated to
scattered showers and thunderstorms for NYC and north and west.
Shear looks to be weak, so this will be more of a pulse storm
environment. DCAPE is progged to peak around 500-600 J/kg, so
an isolated damaging wind gust can not be ruled out. The SPC
continues the marginal risk of severe weather for NYC and north
and west. While pwats are expected to only be around 1.5 inches,
a long skinny CAPE profile and slow moving storms will likely
result in isolated heavy downpours. A quick inch in an hour can
not be ruled out. This will likely result in more of a nuisance
flooding than a flash flood threat.
.KEY MESSAGE 2...
The threat for a more substantial rainfall/flood event will come
Tuesday into Wednesday. Within the mean upper level troughing, a
strong shortwave is progged to dive down towards the area on Tuesday
and become closed off Tuesday night. There is great agreement with
the 00z global guidance that this closed upper low is centered over
or near the area Wednesday through at least Thursday, before
gradually shifting northeast Thursday night. There are still
difference with how the global guidance is handling the surface
low/potential secondary low. The NAM continues to be the outlier
showing a stronger low centered to our south. Regardless, heavy rain
can be expected, but exact location is still uncertain.
Now while embedded convection is likely with a moderate to heavy
rainfall at the onset, a low track to the south of the area will
keep the airmass more stable, with a better chance of a stratiform
rain as we get into Wednesday. Even so, deep moisture and an
anomalously deep low, will make for very efficient rain processes.
The flood threat could transition to more of a long duration versus
flash flood threat. WPC has the area in a slight risk of excessive
rainfall during this time.
The rainfall forecast generally remains unchanged at this time and
ranges from 1.50 inches across eastern LI/SE CT, to 2 to 3 inches
across the rest of the area. Hourly rainfall rates are more of
question based on the low track and how unstable the airmass gets.
The heavy rainfall axis will likely fluctuate the next couple of
days and it is too early to be specific with rainfall amounts.
However, know the ingredients are there for a significant
rainfall.
.KEY MESSAGE 3...
With the approach of a full moon midweek and an onshore E/SE
flow with low pressure passing close by, minor coastal flooding
is a possibility. There is still a fair amount of uncertainty
at this time. Latest forecast brings some of the south shore
back bay locations of LI and western LI Sound to just below
minor coastal flood benchmarks during the evening/nighttime
high tide cycles.
&&
.AVIATION /15Z MONDAY THROUGH FRIDAY/...
Mostly VFR, however MVFR in PROB30 for TSRA possible this
afternoon into early evening for all but KISP/KBDR/KGON.
MVFR cigs possibly return late tonight into the Tuesday morning
push, primarily N and W of NYC.
S/SE winds around 10kt.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
PROB30 timing this aft/eve could be adjusted an hour or two.
Also a chance that PROB30 gets removed with amendments.
.OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY...
Tuesday: MVFR or lower conditions possible in chance showers
and chance thunderstorms, especially in the afternoon and
evening. S winds G15- 20kt.
Wednesday: MVFR or lower conditions likely with showers, possibly a
thunderstorm. E winds G15-20kt.
Thursday: MVFR or lower possible. Showers possible and a slight
chance of a thunderstorm. N-NW wind G15-20kt.
Friday: Mainly VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
A slow moving low pressure system will bring Small Craft Advisory
conditions to the waters starting Tuesday afternoon. As of right
now, conditions look marginal, with gusts peaking around 25 to 30 kt
Tuesday evening through Wednesday morning and ocean seas peaking at
5 to 6 ft Tuesday night through Wednesday. There is still some
uncertainty with exact low track and strength of winds.
Thereafter, the pressure gradient looks to decrease and sub SCA
conditions are then expected through the weekend.
Rip Currents...
There is a moderate risk of rip currents today with a S flow peaking
around 10 kt and a weak E swell at 2 ft 7s.
The moderate risk continues on Tuesday, but there is potential for a
high risk late in the day. For now stuck with a moderate, but
continue to monitor the forecast as a Rip Current Statement might be
needed. A S/SE flow increases to 15-20 kt with a 4ft 5s S/SE swell.
Both RCMOS and local guidance show borderline moderate/high risk by
the afternoon.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 6 PM Tuesday to 6 AM EDT Wednesday
for ANZ331-332-340-350.
Small Craft Advisory from noon Tuesday to 6 AM EDT Wednesday
for ANZ335-338-345-353-355.
&&
$$
AVIATION...JC
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