274
FXUS61 KOKX 182018
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
418 PM EDT Fri Sep 18 2026

.WHAT HAS CHANGED...
Potential for localized flash flooding Sunday afternoon and
evening. Potential for coastal flood and shoreline impacts mid
to late next week.

&&

.KEY MESSAGES...

1) Increasing likelihood for showers Sunday morning into
afternoon, with a period of heavy downpours and embedded
thunderstorms possible Sunday afternoon into Sunday Night.
Widespread minor urban and poor drainage flooding likely Sunday
afternoon into night, with a localized flash flood threat.

2) Breezy and cool conditions likely mid to late next week,
with periods of unsettled weather possible. Potential for minor
to moderate coastal flood and shoreline impacts mid to late
next week.

&&

.DISCUSSION...
.KEY MESSAGE 1...
Models in good agreement with region lying under a confluent
westerly flow aloft later this weekend, in between broad
southern US ridging and a northern stream shortwave digging
through central Quebec. A couple of weak mid-level disturbances
shearing and rotating around the upper ridge will approach the
region on Sunday, with associated low pressure system.

At the surface, Canadian high pressure will slide offshore on
Sunday, lifting a stationary front to the south back north as a
warm front, while the weak area of low pressure approaches from
the west. Still quite a bit of spread in terms of low pressure
track and warm front placement with this system (from the local
area to central New England), which will be predicated by
shortwave track/timing details and associated jet streak
placement.

Increasingly moist conditions are expected through the day Sunday as
gulf moisture pooled over the Mid-Upper Mississippi River
valley advects west towards the region around the upper ridge
and ahead of approaching shortwaves. Expect an increasing
likelihood for rain Sunday morning, particularly for NYC and pts
N&W ahead of approaching synoptic features and a strengthening
S/SE llj providing orographic enhancement. General indication
are for a broad area of overrunning moderate to locally heavy
rain developing along ahead of low pressure and warm front from
broad ascent of an increasingly tropical airmass (1 3/4-2"
PWATs, tall skinny CAPE/weak instability, 13 kft warm cloud
layer) under RRQ of ULJ and nose of developing LLJ.

Current medium range AI and NWP ensembles are expressing a low
probs (less than 30%) for greater than 1" of rain in 24 hrs
from the last several runs, as well as NWS National Blend of
Models. Individual medium range models are a bit more bullish
with a general 1 to 2" across the region. Note: 12z REFS does
have a high prob of 1" in 24 hr thru 8pm into NYC and points
N&W, but low prob of greater than 2". 84hr RRFS indicated
potential for localized rates up to 2"/hr, and averaging 1 to 1
1/2" in 24 hrs.

This type of setup with tropical airmass and frontal wave is
certainly one to watch for a narrow swath of heavy downpours and
embedded convection in vicinity of low pressure track and warm front
from enhanced moisture convergence and lift (up to 2 1/2" PWATs).
In addition, W-E aligned MBE vectors less than 10 kt in
vicinity of the frontal wave/warm front are indicating potential
for some slow moving/training, or even briefly back building
convection, within an overall fast moving flow. This would at
least point to an isolated flash flood threat. Inhibiting
factors for a high end/more widespread flash flood event are the
progressive nature of this system (40kt steering flow), depth
of saturation limited to mid- levels, and weak instability
feed.

Overall the setup and model guidance indicate a widespread 1-2"
rainfall, with much of it falling over a 6 hr period. This would
point to a widespread minor urban and poor drainage threat,
with localized instances of flash flooding. General rainfall
rates at this point are looking like 1/4 to 1/2"/hr, but cant
rule out localized rates of 1-2"/hr with any training
convection.

Will also have to watch for a conditional isolated strong to
severe threat (particularly across souther tier), with high
moisture (low- LCL), high shear, weak CAPE environment Sun
aft/eve if warm front lifts into the area and especially with
surface wave tracking through.

More clarity on low pressure track, peak rainfall rates and
location/coverage, and tstm threat, over the next 36 hrs as the
synoptic features are further resolved by model and CAMs
resolve mesoscale details.

General agreement of surface low moving east after midnight
Sunday Night with brief drying conditions.

.KEY MESSAGE 3...
Continued potential for a period of unsettled weather Tuesday thru
Friday between strong Canadian high pressure anchoring across
SE Canada and northern New England, while a broad southern and
mid Atlantic low pressure develops, followed by late week
coastal/offshore low development. The lows in response to
closed upper low currently over the PAC NW slowly drifting
across the US to the Great Lakes and then east coast during the
mid to late week.

Good NWP and AI model agreement pushing the front south of the
area on Monday. This will get the region on the drier and cooler side
of the frontal boundary, with only a low chance of showers as
high pressure builds from the north.

Confidence in sensible weather forecast details from day to day
thereafter remains below average for much of next week as there
is quite a bit of spread on how far north and how quickly the
front works back towards the area, which would determine how
much rainfall the area sees.

Regardless of rainfall, a persistent cool and breezy east to
northeast flow regime (gusts 30-40 mph) looks possible for the
mid to late week period. Canadian maritime flow along with
potential for increased cloud cover and showers this should keep
daytime temperatures below seasonal norms thru the week.

One additional note, if persistent and long fetch E/NE gales
materialize during the mid to late week period, ahead of the
approaching full moon next weekend, this will bring potential
for minor to moderate coastal flood and shoreline impacts during
time of high tide.

Low pressure likely develops offshore by mid to late week as the
closed upper lows drifts to the coast, which could increase the
potential for rainfall, particularly for eastern area.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
High pressure centered well north and west of the area will
build south and east through Saturday, building across eastern
Canada and the Northeast.

VFR.

Northerly winds around 10 kt will become NE tonight, strengthening
a bit overnight. Occasional gust 15-20kt are possible, especially
at the coastal terminals. Winds will then gradually veer toward
the E/SE late Saturday morning into the afternoon.

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

Gust 15-20kt could be more frequent overnight.

.OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY...

Saturday Afternoon: VFR.

Saturday Night: Showers move in late Saturday night with MVFR
possible, north and west of NYC terminals. Otherwise, mainly VFR.

Sunday: Showers expected, potentially heavy at times. A slight
chance of a thunderstorm. MVFR or lower at times. Southeasterly wind
gusts near 15-20 kt Sunday afternoon into Sunday evening,
especially at the coastal terminals.

Monday: MVFR or lower possible with chances of showers. N-NE
wind gusts near 20 kt.

Tuesday and Wednesday: MVFR or lower possible at times. A
chance of showers. NE wind gusts 20-25 kt Tuesday and to 20 to
30 kt Wednesday, highest at the coastal terminals.

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

&&

.MARINE...
A brief period of small craft wind gusts are expected on the
ocean waters late this evening into early Saturday morning. This
should subside towards towards Saturday afternoon as the
pressure gradient weakens.

Potential for another round of marginal SCA southerly wind gusts,
mainly on the ocean, Sunday afternoon into evening ahead of a
frontal system.

A better chance at prevailing and more widespread small craft
conditions for all water develops by early Monday morning for all
waters Tuesday thru late week. This could build wave heights on the
ocean 12-15ft+ and 4-7ft+ on LI sound.

Rip Currents:
The rip current risk for Saturday will be low  with a wind more out
of the ENE and parallel to the ocean beaches. Strengthening onshore
flow on Sunday with a building surf will result in a moderate risk
of rip currents initially, possibly increasing to a high risk later
Sunday afternoon.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from midnight tonight to noon EDT
     Saturday for ANZ350-353-355.

&&

$$

DISCUSSION...NV
AVIATION...DW
MARINE...NV