672
FXUS61 KOKX 032336
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
736 PM EDT Sat Aug 3 2024

.SYNOPSIS...
Low pressure and a frontal boundary remain in the vicinity through
Sunday night. A cold front then approaches on Monday and passes
through late at night. The front then stalls nearby through
Tuesday night before pushing just south and east of the area
Wednesday into Wednesday night as a weak area of low pressure
passes south of the area. The frontal boundary and remnants from
a tropical system slowly approach from the south through the
end of the week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --
A flood watch and severe thunderstorm watch continue for this
evening for portions of the forecast area.

Shortwave lift and instability will continue to produce showers
and thunderstorms into this evening. Most of the forecast area
stands a good chance of seeing some rainfall by the end of
tonight, but parts of SE CT and eastern LI could end up dry for
the night as the shortwave exits NE and instability diminishes
as the night wears on. The late night hours should then be dry
for most areas.

Shear is just strong enough for severe wind gusts and large
hail in the strongest convection. Meanwhile, MLCAPEs range from
1500-2500 J/KG over approx the western half of the forecast
area. Isolated to scattered instances of severe thunderstorms
are possible from Nassau and Fairfield Counties to points west.
As such, a severe thunderstorm watch is in effect for these
areas through 9pm this evening.

Another concern is flash flooding. Flow through the mid levels
will be unidirectional and aligned with the orientation of the
stalled boundary in the vicinity of the northern/western zone.
So although the forward motion of the cells won`t be very slow,
training is a possibility. Combined with PWATs 1.75-2.00 inches,
hourly rainfall rates of 1-2 inches per hour and locally
briefly higher are possible. HREF probabilities show a 40-60%
chance of hourly rainfall rates of at least an inch per hour
this afternoon and evening in some areas. A flood watch for
flash flooding has therefore been issued for this afternoon
through midnight for NYC, Lower Hudson Valley, and NE NJ where
the combination of potential rainfall amount/rates and flash
flood guidance warrant a watch.

Otherwise, heat advisories remain unchanged into this evening
and muggy conditions continue overnight with lows mostly in the
70s.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/...
-- Changed Discussion --
A somewhat similar setup for Sunday as the frontal boundary
will still be over the area. A 500mb trough axis is progged to
pass through during the afternoon to evening hours, providing
some lift along with a 60-70kt jet streak region in the upper
levels. There will be a chance of showers and thunderstorms in
the morning, but they will become more likely starting in the
afternoon. Training is less of a concern this time, but the
steering flow will be a little weaker. PWATs still high enough
however for the threat of isolated flash flooding. The flooding
threat should become a little more clear after seeing how much
rain falls through tonight. The rain threat then diminishes
along with the instability and lift in the evening, with dry
conditions everywhere by midnight. With weaker shear and lower
instability, the severe weather threat will be very limited.

The frontal boundary dissipates just offshore and leaves us
with weak high pressure over the area during Monday. A cold
front will approach, bringing a chance of showers and
thunderstorms during the afternoon, mainly north of the city.
The flooding threat looks to be limited due to the relatively
quick forward motion of any cells that develop, and enough CAPE
and shear introduces a low chance of strong to severe wind
gusts.

850mb temps are progged at 18-19C. There should be enough
sunshine and SW flow for mid 90s in the normally warmest spots
with mostly upper 80s to lower 90s elsewhere. Wind direction and
low enough boundary layer RH should allow for surface dewpoints
to mix out a few degrees during peak heating, so max heat
indices will be generally in the lower and middle 90s. With
neither 100 degree heat indices on Monday, nor 2-day criteria of
95+ indices, no heat advisories are anticipated.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
A cold front will be draped across the area Monday night. A weak
area of low pressure along the frontal boundary over the Central
Plains states will move east along the boundary, passing south of
the Great Lakes during the day Tuesday, then just south of the
forecast area by Wednesday morning. As the low pushes east, it may
help to push the front just south of the area Wednesday afternoon
and night. Unsettled conditions are expected Monday night through
Wednesday with the front in the vicinity, then low pressure moving
nearby. However, the best chances for any showers and thunderstorms
will be with the low Tuesday night into Wednesday.

Chances for precipitation then drop off, and may drop off further
with more model runs if high pressure nudges more into the forecast
area than is currently forecast. However, given uncertainty in this
time frame onward, did not veer too far from NBM. Thereafter, even
more uncertainty in the forecast given the location of the remnants
of the potential tropical system and its interaction with the
frontal boundary leading to uncertainty in placement of any
potential for heavy rain during this time frame, so again stuck
close to the NBM. Therefore, unsettled weather is possible from the
middle of the week through the beginning of next weekend.

Easterly flow develops during this time frame, and in addition to
clouds and rain, this will lead to cooler conditions. Highs during
this time frame may will average below normal, and may not go above
80 for much of the region Wednesday, with slightly warmer, but still
below normal temperatures on Thursday. Conditions will still be
humid, but not like the extremely humid conditions we have been
experiencing as of late.

Low pressure over southeastern Canada, will slowly trek northeast
into the Canadian Maritimes by this evening. This will allow a cold
front to slowly approach today, moving through late in the
afternoon into the evening.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
Weak low pressure, along with a stationary front, remains in
the vicinity into Sunday evening, shifting east late Sunday
evening.

VFR with a chance of showers into late this evening at the NYC
terminals and west, and into the overnight east. Scattered
thunderstorms remain possible this evening with MVFR
conditions. MVFR to IFR stratus and fog is likely late overnight
into early Sunday morning outside of the NYC metro area. Another
round of showers and thunderstorms with MVFR is likely mid
afternoon into the early evening Sunday.

A light S to SW flow continues into Sunday, with winds at times
variable with showers and thunderstorms in the area of the
terminals. Winds Sunday are expected to be more SW to WSW, with
afternoon sea breezes.


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

Amendments possible with TSRA into early this evening.


OUTLOOK FOR 00Z MONDAY THROUGH THURSDAY...

Sunday night: Chance of MVFR or lower in evening SHRA/TSRA.

Monday: VFR.

Tuesday-Wednesday: MVFR or lower possible in SHRA/TSRA.

Thursday: Mainly VFR. Chance of MVFR or lower in SHRA/TSRA.

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

&&

.MARINE...
Sub-SCA conditions expected for non-ocean waters through Monday
night. For the ocean, southerly fetch and swell will maintain seas
of at least 5 ft through Sunday evening. Have extended the SCA west
of Fire Island Inlet to go through midnight Sunday night, and
extended the SCA through all of Sunday night farther east. Sub-SCA
conditions follow for Monday.

Waves build on the ocean waters Monday night into Tuesday as low
pressure approaches and moves over the waters. Waves diminish
Tuesday afternoon as the low pushes east of the region. Waves
increase again later in the week with building long period
southerly swells from a tropical cyclone. Refer to latest
forecast information from the NHC.

&&

.HYDROLOGY...
Rainfall rates of 1-2 inches per hour and locally higher will be
possible into this evening. Given 1 and 3-hour flash flood guidance,
isolated to scattered instances of flash flooding will be possible
during this time, then generally dry conditions overnight.

Another round of showers and thunderstorms is anticipated Sunday
afternoon, potentially lasting into the evening. The extent of
potential flash flooding will partly depend on what occurs
through this evening, but it appears at least isolated flash
flooding can occur. No hydrologic issues are expected after
early evening Sunday through Monday night.

There is the potential for heavy rainfall Tuesday into Wednesday as
a weak area of low pressure moves along a stalled frontal boundary
in the vicinity of the forecast area. However, there remains a good
deal of uncertainty in exactly where the axis of heavy rain will set
up.

Another round of heavy rainfall is possible for the end of the week
into the beginning of next weekend with the remnants of the
tropical system. There is even more uncertainty with this feature.

&&

.TIDES/COASTAL FLOODING...
A high risk of rip currents continues into this evening and is
expected to continue all the way through Monday evening. This is
due to southerly swells of around 5 feet.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...Air Quality Alert until 11 PM EDT this evening for CTZ005-006-
     009-010.
NY...Air Quality Alert until 11 PM EDT this evening for NYZ069>075-
     078>081-176>179.
     Flood Watch until midnight EDT tonight for NYZ067>075-176-178.
     High Risk for Rip Currents through Monday evening for NYZ075-080-
     081-178-179.
NJ...Flood Watch until midnight EDT tonight for NJZ002-004-006-
     103>108.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ350-353.
     Small Craft Advisory until midnight EDT Sunday night for
     ANZ355.
-- End Changed Discussion --

&&

$$

SYNOPSIS...JC/JP
NEAR TERM...JC
SHORT TERM...JC
LONG TERM...JP
AVIATION...MET
MARINE...JC/JP
HYDROLOGY...JC/JP
TIDES/COASTAL FLOODING...