000
FXUS61 KOKX 241945
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
345 PM EDT Thu Aug 24 2023

.SYNOPSIS...
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Low pressure and its associated warm front approach tonight.
The warm front slowly moves over the area on Friday and will be
followed by a cold front passage Friday night. A couple of cold
fronts will affect the area Saturday into Saturday night. High
pressure builds in for Sunday through Monday. A slow moving
frontal system will approach for Tuesday and late Tuesday night
into Wednesday.
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&&

.NEAR TERM /THROUGH FRIDAY/...
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A warm front currently draped over far western PA will slowly
approach tonight. Weak middle level energy will also continue
passing through this evening along with increasing warm advection.
Scattered showers are possible early this evening in this
regime, but coverage should not be widespread. There is also
little to no instability, so have left mention of thunder out
the first half of the night.

Another shortwave traversing within the NW flow aloft between
the heat ridge across the central states and troughing over the
North Atlantic will approach. An MCS will likely develop with
this shortwave as it moves out of the Great Lakes region
tonight. There is still fairly high confidence that the majority
of this complex will pass well to our west across PA following
the greater instability and along and west of the warm front.
However, there will also be a 30-40 kt LLJ over the northeast
and New England overnight into Friday morning. Showers will
increase in coverage during this time associated with the LLJ
and warm advection. While the majority of the convective complex
moves to the west, a weaker, more stratified eastern edge may
push through NE NJ, Lower Hudson Valley and portions of the NYC
metro. The combination of these features support widespread
showers late tonight into Friday morning. PWATs should reach
1.75-2 inches and there will be a deep warm cloud layer of
around 13 kft, supporting locally heavy rainfall potential. Low
level lapse rates may be fairly steep, but surface instability
will be limited by a cap/inversion around 6-8 kft. There is
enough elevated instability to support some embedded thunder.

Uncertainty remains on whether or not the warm front will
remain just to our west Friday morning and afternoon. Some
guidance hints that the boundary may linger over the area or
remain just off to our west. There also remains some question on
how quickly the more organized lift will pass east. The recent
model trends signal potential for showers to continue on and off
Friday afternoon out east. However, if the warm front remains
just to our west, showers could linger just about anywhere
across the region into the afternoon. This will also play a role
in any improvement with clouds, if the warm front does shift
through or further east, then some improved sky conditions could
occur in the afternoon. Otherwise, it could remain cloudy
through the day. Will continue show chances for showers,
possibly a thunderstorm in the afternoon with greatest potential
out east. Locally heavy downpours remain possible in the
afternoon, especially across eastern Long Island and southeast
Connecticut closer to the departing low level jet.

Average QPF amounts around 1 inch are forecast with locally
higher amounts possible. Minor urban and poor drainage flooding
is the main threat, but an isolated flash flood occurrence
cannot be ruled out. Shear and helicity does bear watching with
a warm front nearby, but limited surface instability and the
aforementioned cap/inversion should preclude a severe threat.
Will have to watch trends with surface instability Friday
morning and whether or not the warm front lingers over portions
of the area.
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&&

.SHORT TERM /FRIDAY NIGHT/...
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The wave of low pressure and its associated cold front will move
through Friday night. Showers and a few thunderstorms remain
possible especially Long Island and southeastern CT. Some guidance
continues to show the front lingering out east for much of the
night, but overall probabilities for showers decrease from west to
east through the night. Otherwise, mostly cloudy conditions will
continue across the area. It will remain muggy with lows in the
upper 60s to lower 70s.
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&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
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Upper level trough expected to be over the area Saturday. At the
surface, one cold front will be moving through eastern areas and
pushes offshore early in the morning as another one approaches from
the west. There is a fair amount of uncertainty with these features
among the deterministic models, so stuck fairly close to the NBM
POPs. Some lingering chance POPs for eastern areas as the first cold
front continues to push through these locations and then offshore.
Then, slight chance, mainly for southern Connecticut and eastern
Long Island as the second front approaches, weakening as it does so.
With the upper trough still in the area, it is not out of the
question for more places may see a passing shower or thunderstorm.
The second cold front may dissipate before making it through the
area.

High pressure builds in for Sunday through Monday. However, the
trough remains over the Northeast US Sunday with a weak shortwave
moving through, then begins to deamplify Sunday night. The ECMWF and
GFS produce some showers. Going with a dry forecast for, but will
have to watch this feature with further runs.

The surface high retreats into the Canadian Maritimes on Tuesday.
Meanwhile, Tropical Cyclone Franklin will move northward over the
western Atlantic (staying well offshore). In terms of indirect
impacts, swells from tropical cyclone Franklin will likely build
late Monday into Tuesday and continue into mid week, bringing
increasing potential for dangerous rip currents and high surf.
Models seem to be hinting at a potential predecessor rain event
(PRE) with the cyclone, as the area comes under the right entrance
region of a 200 hPa jet Tuesday night into Wednesday morning, along
with a 925 hPa equivalent potential temperature ridge east of a 700
hPa trough as per the GFS. Additionally, tropical moisture will be
on the increase with PWATs around 2 inches and we are in a
climatologically favorable time of year for PRE. However, the jet
may be a bit too far west and will have to see how strong Franklin
becomes. A weaker system will mean less chance for PRE development.
Will obviously have to continue to monitor this feature as it is
climatologically favorable and associated with heavy rain.

Rain begins to move in from the west late Monday night into Tuesday
morning as a cold front approaches from the west and continues
through Wednesday night. Canadian high pressure builds in behind it
and bring a drier, cooler, less humid air mass for Thursday.

Monitor https:/www.weather.gov/okx/tropical for the latest NHC
forecasts on this tropical system and others.
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&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
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A warm front approaches from the west into tonight. An associated
low pressure system gradually crosses the region Friday into Friday
Night.

Mainly MVFR/VFR but variable flight categories including pockets of
IFR possible across the region this evening. Stratiform showers are
expected across the area making any one condition temporary.

Widespread shower activity and MVFR conditions develop from W to E
tonight, after 04-06z and continue thru Fri AM push. Isolated tsra
threat, mainly across western terminals, late tonight into Fri AM
(between 08z and 15z) as warm front nears.

By midday Friday, limited improvement in flight categories are
expected with guidance suggesting MVFR ceilings with a chance of
showers continuing throughout much of the day.

S/SE winds 10-15g20kt this evening for coastal terminals, and
continuing into tonight and Friday morning. Peak gusts to 25 kt for
NYC and eastern terminals especially into Friday.

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

Amendments for changing flight categories likely this evening,
tonight and Friday.

OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY...

Friday: MVFR/IFR conds in showers and embedded TSRA. S gusts
20-25 kt afternoon.

Friday Night: Isolated Shra/Tsra threat, mainly east late.

Saturday: VFR, early AM isolated shower/tstm threat across
eastern terminals. Isolated shower threat across northern
terminals in PM.

Sunday and Monday: VFR.

Tuesday: MVFR or lower in SHRA/TSRA especially in the afternoon
and evening.

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

.MARINE...
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SE winds will continue to increase tonight, approaching SCA levels
west of Moriches inlet around midnight and then further east into
early Friday morning. SCA gusts are then likely on the ocean, LI
Bays, and central and eastern LI Sound during the day on Friday.
Winds will diminish below SCA levels Friday evening. Ocean seas
should begin to build to around 4 ft Friday morning and then around
5-6 ft Friday afternoon and evening. These elevated seas will
continue on Friday night. Have extended the SCA into Friday night to
account for the elevated seas.

Residual SCA southerly wind swell on the ocean should gradually
subside below SCA on Saturday, although brief marginal SCA conds may
be extended into Sat Night with gusty NW flow in wake of cold
frontal passage. Thereafter, sub SCA conditions favored for Sun into
Mon on all waters (although ocean seas may run 3-4 ft in long period
SE swell), with high pressure building in. Waves build to 5 ft on
the ocean Tuesday due to SE flow and swells from Franklin moving in.
Waves continue to build to 5 to 7 ft by Tuesday night. The eastern
sound may also build to around 5 ft by Tuesday night.

Energetic SE swells likely build in from tropical cyclone Franklin
late Monday into Tuesday, likely bringing a return of SCA conditions
on the ocean.
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&&

.HYDROLOGY...
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Showers will become more widespread tonight into Friday morning with
some embedded thunderstorms possible. Moderate to heavy downpours
may also linger across eastern Long Island and southeastern
Connecticut into Friday afternoon. Locally heavy rainfall is
possible with the main concern from minor urban and poor drainage
flooding. An isolated flash flood occurrence or two cannot be ruled
out.

No hydrological concerns at this time from Saturday through the
Thursday. Large uncertainty exists with any heavy rain associated
with a potential PRE Tuesday night into Wednesday of next week,
including strength and track of Franklin and where the right
entrance region of the upper trough actually sets up.
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&&

.TIDES/COASTAL FLOODING...
The risk of rip current development increases from low to moderate
for all beaches this afternoon, with strengthening SE/S winds and
building southerly wind waves this afternoon and this evening.

A high rip current risk is likely Friday into Saturday with 5 ft+
southerly wind waves.

Swells from tropical cyclone Franklin will likely build late Monday
into Tuesday, continuing into midweek, increasing likelihood for
high surf and dangerous rip currents.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 6 AM to 6 PM EDT Friday for ANZ331-
     332-340-345.
     Small Craft Advisory from 3 AM Friday to 6 AM EDT Saturday for
     ANZ350.
     Small Craft Advisory from midnight tonight to 6 AM EDT
     Saturday for ANZ353.
     Small Craft Advisory from midnight tonight to 2 AM EDT
     Saturday for ANZ355.
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&&

$$

SYNOPSIS...JP/DS
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...JP
AVIATION...IRD
MARINE...JP/DS
HYDROLOGY...JP/DS
TIDES/COASTAL FLOODING...