discussion on 2023-07-20

000
FXUS61 KOKX 201135
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
735 AM EDT Thu Jul 20 2023

.SYNOPSIS...
A frontal boundary sags south of the area today as high pressure
passes to the north. A frontal system will then impact the
region Friday through Friday night. Weak Canadian high pressure
gradually pushes into the region for the weekend and settles
nearby through mid week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --Any bit of radiative fog and mist that developed with the low
dew pt depressions clears as we move past further past sunrise
and later into the morning, leaving behind a mix of sun and
clouds for the remainder of the day. Forecast remains on track.

As a weak frontal boundary drifts south of the region, surface high
pressure tracks east through northern New England, helping to keep
conditions predominantly dry through the day. Still can`t rule out a
few stray pop-up showers, especially along the sea breeze as we go
through the afternoon, though coverage and duration should remain
limited.

With less cloud cover and precipitation, temperatures will be
several degrees warmer than Wednesday, and track close to normals
for the time of year. Afternoon highs top out toward the mid 80s for
most as a light NE flow veers SE as the high shifts east of the
region. A shortwave approaches late in the day with a frontal system
pushing east from the Ohio Valley.-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
A shortwave embedded in a broad upper trough over the eastern U.S.
swings east late this week. As it does so, the associated
surface low tracks through the Great Lakes and across Upstate NY
Friday, sending attendant fronts through the region.

The boundary that drifted south of the region returns north early
Friday as a warm front, with a weak wave of low pressure likely
developing along it as well. This will increase rain chances as we
go into early Friday morning. The moist air mass in place (PWATs
progged around 1.75 inches) with limited instability in the
morning leads me to think the initial primary hazard from this
activity is the locally heavy rainfall threat that could lead to
isolated to scattered areas of flash flooding, particularly if
training were to occur. In agreement, WPC has a slight risk of
excessive rainfall running south through the lower Hudson
Valley, NE NJ and NYC, mainly due to the antecedent conditions
producing low FFG, with a marginal risk for much of Long Island
and southern Connecticut. After the initial slug associated in
the morning hours, there may be redevelopment of convection
ahead of the trailing cold front. Increasing instability and
deep-layered wind shear (25-35 kt) could allow for a few strong
or severe thunderstorms to develop during this time, but will
depend on timing and placement of these surface features, and
how much the air mass can recover in the following the morning
convection and cloud cover. SPC has maintained a marginal risk
of severe weather mostly to the southwest of our area. Overall
QPF through this period has increased, and looks to be highest
across the lower Hudson Valley and NE NJ, where 0.5 to 1.5
inches is forecast (locally higher amounts expected here),
falling to under a quarter of an inch as you go east into SE CT
and eastern Long Island.

What redevelops in the daytime gradually tracks from west to east
through the afternoon and into the evening hours as the cold front
pushes through the region. A drier air mass looks to begin to advect
into the area overnight as the flow turns WNW behind the fropa. With
only subtle adjustment, followed a consensus of short-term guidance
for this update.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Aloft the broad trough across the Northeast and Great Lakes will
continue. The trough however gradually lifts north as heights rise a
bit into Monday and Tuesday. At the sfc weak Canadian high pressure
will gradually work in from the west and southwest for the weekend
and into the first half of the week.

A dry weekend shapes up with a subtle drop in dew points. Dew point
readings should get into the lower and middle 60s for the most part
for both Saturday and Sunday, so it will feel slightly more
comfortable than it has been. Temperatures will average right around
normal through the weekend.

Into next week temperatures will climb slightly, along with a climb
in the humidity. Much of the time it will be dry for Monday and
Tuesday, with just some diurnally driven slight chance to chance
PoPs. Towards late Tue night and Wed continued with 20 percent
chance PoPs with a potential cold front and weak upper level
disturbance approaching. The chances for a few urban locations to
reach 90 increases towards Wed, with night time minimums in the
lower half of the 70s for the metro and the coast.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --Weak high pressure will be in control today. A slow moving warm
front approaches tonight, with the entire frontal system pivoting
through on Friday.

VFR conditions for today and through this evening. MVFR to possibly
IFR conditions develop late tonight mainly after 6-9z. SHRA arrives
towards the morning push Fri, with PROB30 TSRA Fri AM beginning
around 11-12z for city and western terminals.

The winds will be light out of the NE and E this morning, before
becoming SE by this afternoon, with more of a southerly component
towards evening at a few terminals. The winds should remain under
10kt. The winds remain light through tonight.

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

Amendments may be needed towards and after 6z Fri for lowering
flight categories.


OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...

Friday: Showers likely with a chance of thunderstorms along with
pockets of MVFR/IFR with SE winds.

Saturday-Sunday: VFR.

Monday: Slight chance of showers/thunderstorms in the afternoon with
brief MVFR possible.

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

&&

.MARINE...
A Marine Weather Statement is in effect for the Long Island Sound.
The National Weather Service in coordination with the United States
Coast Guard have received reports of a large debris field across
Long Island Sound, caused by recent flooding across New England.
This will create some hazards for boaters, swimmers, and watercraft
in the affected area. The debris vary from trees, logs, coolers, and
docks and may not be easily visible.

Sub small craft conditions should prevail through the weekend
and into next week with a relatively weak pressure gradient in
place. Ocean seas will be at 2 to 3 ft throughout.

&&

.HYDROLOGY...
No hydrologic impacts expected through tonight.

While widespread hydrologic impacts appear unlikely Friday,
localized nuisance flooding and isolated to scattered areas of
flash flooding will be possible, especially in urban centers of
NYC and NE NJ, as well as the lower Hudson Valley due to the wet
antecedent conditions and high soil moisture content. WPC
currently has a slight risk for excessive rainfall outlined in
the areas mentioned above, with a marginal risk for eastern Long
Island and southern Connecticut. Total basin rainfall through
Friday night averages between 1 to 2 inches west of the Hudson
River, with lesser as you go east. Locally higher amounts can be
expected should convection train over one area.

No hydrologic impacts are expected for the weekend and through the
middle of next week.

&&

.TIDES/COASTAL FLOODING...
For today and Friday, NYC and Nassau Co beaches have a low risk
for rip current development, with Suffolk Co beaches in a
moderate risk.

&&

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

&&

$$
SYNOPSIS...JE/DR
NEAR TERM...DR
SHORT TERM...DR
LONG TERM...JE
AVIATION...JE
MARINE...JE/DR
HYDROLOGY...JE/DR
TIDES/COASTAL FLOODING...