217
FXUS61 KOKX 202041
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
441 PM EDT Thu Aug 20 2026

.WHAT HAS CHANGED...
The Flood Watch has been expanded to include Rockland, N
Westchester, and Fairfield.

WPC upgraded portions of NE NJ and the NYC metro to a moderate
risk (Level 3/4) for excessive rainfall and expanded the slight
risk (Level 2/4) a bit further NE.

&&

.KEY MESSAGES...
1) Showers and a few thunderstorms will bring heavy rainfall and
increasing potential for flash flooding late this afternoon into
a portion of tonight.

2) Unsettled conditions may continue across eastern half of the
area on Friday.

3) Additional showers are expected Saturday into Sunday, but
impacts appear limited at this time.

4) Dry and seasonably warm early next week.

&&

.DISCUSSION...
.KEY MESSAGE 1...
Confidence is increasing that flash flooding will occur across
portions of the area late this afternoon into the evening.

Guidance has remained fairly steady in signaling a period of
heavy showers and embedded thunderstorms late this afternoon
into the evening.

A nearly stationary frontal boundary will be draped across the
area as an MCV currently across western PA approaches. The MCV
will interact with this boundary, afternoon sea breezes, and a
high PWAT airmass to develop heavy showers and embedded
thunderstorms from late this afternoon into the evening. There
will also be an amplifying upper jet streak across northern New
England. The upper jet quite strong for this time of year and
the region will lie in the favorable right entrance region,
which will supply large scale lift to the MCV. Despite
instability being maximized to our south and west, conditions
are favorable for convection and resulting flash flooding. These
ingredients will interact with PWATs of 2+ inches, and deep
warm cloud layer approaching 15kft supporting scattered to
numerous occurrences of flash flooding.

Peak hourly rainfall rates could reach 2-2.5 inches per hour in
the heaviest downpours. There is still a signal in the latest
HREF for potential of 3 inches in 3 hours, which has been
typically an indicator of flash flooding in the past. Average
QPF looks to have increased a bit further inland, but still
around 1.5 to 2.5 inches expected with locally higher amounts of
3 to 5 inches possible.

The most favorable region for numerous instances of flash
flooding appears to be the urban corridor of NE NJ and NYC
metro. This is where WPC has placed a moderate risk for
excessive rainfall (Level 3/4). A slight risk exists most
elsewhere (Level 2/4) However, flash flooding may occur into the
Lower Hudson Valley, especially in more prone areas of Rockland
and Westchester counties. There is also concern into southwest
CT this evening. For these reasons, have expanded the flood
watch to include Rockland, Westchester, and Fairfield.

The watch continues until 2am Friday morning. Some of the NE NJ
and NYC areas could be removed from the watch a bit sooner as
the axis of showers shifts to the east. There is some concern
for lingering showers through the night across Long Island and
southern CT as a surface wave may meander nearby. Heavy rainfall
should diminish in coverage, but some isolated downpours cannot
be ruled out on eastern Long Island and SE CT early Friday. Did
not expand the watch further east as rainfall rates should come
down from what is expected this evening.

The greatest severe thunderstorm threat remains to our south and
west. Still cannot completely rule out an isolated damaging wind
gust and isolated tornado across NE NJ and NYC metro area as
there is fairly strong low level shear. The location of the
surface boundary and sea breeze interactions will have to be
monitored.


.KEY MESSAGE 2...
Guidance is struggling with the handling of a weak surface low
on Friday. There are two solutions with one being
progressive/weaker, which would lead to mostly dry conditions on
Friday areawide. The other solution is for the wave to linger
near or just south of central/eastern Long Island. This solution
would support low clouds, patchy fog, and potential light
showers at times on Friday. Given the higher than normal
uncertainty in just a days time, have continued with the NBM
model consensus, which results in a chance of showers across the
eastern half of the area along with mostly cloudy conditions
through the day.


.KEY MESSAGE 3...
Guidance is coming into somewhat better agreement for the
upcoming weekend. Another amplifying mid-upper trough approaches
Saturday and will deepen through Sunday. The approaching trough
along with a warm front lifting towards the area supports
potential shower development on Saturday. Guidance has trended
slightly slower with the timing and the highest probabilities
may end up closer to the coast, which is near the potential
location of the surface boundary. The trailing cold front
follows at some point on Sunday with additional chances for
showers, possibly a thunderstorm. At this time, impacts appear
limited, but WPC has maintained a marginal risk (level 1/4) for
excessive rainfall on Saturday. CIPS and CSU MLP continue to
hint at a marginal risk for severe thunderstorms Sunday, but it
is still too far out for any specifics.


.KEY MESSAGE 4...
Upper troughing will linger over the northeast early next week,
but the trailing cold front from the weekend system should be
pushing offshore. The current expectation is for improving
conditions with dry weather and seasonably warm temperatures
early next week.

&&

.AVIATION /21Z THURSDAY THROUGH TUESDAY/...
A cold front approaches the terminals later today, with an
associated wave of low pressure forming along it. The front and
low pressure will move east of the region late tonight.

VFR conditions until mid to late this afternoon. Showers and
thunderstorms are moving in from the south and west and bring
periods of MVFR to IFR conditions along with the potential for
heavy rainfall. MVFR conditions are likely through tonight,
with an improvement back to VFR Friday morning.

Winds during the TAF period will be less than 10 kts but direction
will be quite variable. Low confidence with the wind direction
forecast. Towards end of TAF period, a general more northeast
to north flow is forecast.

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

Amendments possible to refine timing of showers/thunderstorms, which
could be 1-2 hours off from TAF.

Amendments possible for the timing of IFR and MVFR, which could be a
few hours off from TAF.

.OUTLOOK FOR 18Z FRIDAY THROUGH MONDAY...

Friday: Mainly VFR. A few showers and MVFR possible during the day.
Higher chances of showers and MVFR late at night.

Saturday: Showers likely. Possible thunderstorms. MVFR to IFR
at times.

Sunday: A chance of showers. Possible thunderstorms. Chance of MVFR
or lower at times.

Monday and Tuesday: VFR.

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

&&

.MARINE...
Conditions should largely remain below SCA levels through early next
week. There could be isolated gusts up to 25 kt this evening as a
wave of low pressure develops, mainly on the ocean. Otherwise,
gusts should remain 20 kt or less through the weekend. A weak
pressure gradient should prevail early next week.

Rip Currents: The rip current risk remains low through this evening.
The rip current risk increases to moderate on Friday and will remain
moderate on Saturday. While winds will be NE-E, a wave of low
pressure may bring a swell component with 3 ft seas.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch until 2 AM EDT Friday for CTZ005-009.
NY...Flood Watch until 2 AM EDT Friday for NYZ069>075-078-080-
     176>179.
NJ...Flood Watch until 2 AM EDT Friday for NJZ002-004-006-103>108.
MARINE...None.

&&

$$

DISCUSSION...DS
AVIATION...BC
MARINE...DS