533
FXUS61 KOKX 181053
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
653 AM EDT Sun Aug 18 2024

.SYNOPSIS...
Low pressure tracks slowly eastward through the Great Lakes
today as a secondary low develops over the Mid Atlantic. This low
moves north and east into the local area tonight, sending a cold
front through the area Monday. A secondary frontal passage moves
through Tuesday. High pressure then builds in for the middle and
end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Slow moving frontal system tracks into the region today, bringing
a couple rounds of heavy rainfall with it.

Ribbons of showers, some moderate to heavy, have moved into the
region overnight and early this morning. This activity could
produce locally heavy downpours that result in flooding. In
addition, with recent thunderstorms over SE PA and NJ, have
included the mention of possible thunder in a corridor extending
northward thru NJ into NYC and the Lower Hudson Valley. A quick
inch of rainfall is possible with this activity, and could lead
to urban and poor drainage flooding depending on placement and
duration.

This entire system will be slow moving eastward as downstream ridging
remains across the western North Atlantic. A frontal wave
develops along the Mid Atlantic coast into this evening, before
pushing north into the local area. This low provides lift for
additional heavy rainfall later today and tonight. Limited
shear and instability should keep activity mainly sub-severe and
disorganized, but can`t rule out thunderstorms. Of greater
concern is the potential for training convection and heavy
downpours that lead to flooding. PWATs already over 1.5 inches
in the OKX 00Z sounding increases toward 2 inches today, and
efficient warm cloud processes could allow for elevated rainfall
rates with this activity. 00Z HREF signals the potential for
rainfall rates perhaps as high as 2 inches in an hour, especially
over New Jersey and Lower Hudson Valley zones. While total QPF
looks to average a general 1 to 2 inches for locations along and
west of the Hudson River, including the NYC metro, localized
amount could approach 3 or 4 inches depending on placement and
training of cells.

All this said, the Flood Watch remains in effect through late
tonight for zones west of the Hudson River for the potential of
scattered flash flooding, urban and poor drainage flooding, and
possibly flooding of faster responding streams in NE NJ. Areas to
the east look to miss out on the axis of heaviest rainfall based on
latest hi-res guidance, so opted not to expand the watch any further
east with this update. Certainly, if the axis shifts a bit east,
or if training convection develops, flooding could be an issue
here as well, including in NYC and urban centers. WPC has kept
the slight risk for excessive rainfall in place for similar
areas, expanding just a bit to the east to include the entire
NYC metro and SE CT.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
An unsettled start to the work week as the upper trough and
frontal system continue to impact the region.

Cold front and weak coastal wave of low pressure approach on
Monday as the trough axis begins to shift into the Northeast.
Another round of showers and possible thunderstorms likely
Monday into Monday night. This will mainly be associated with
the cold front, but the nearby low could enhanced rainfall.
Still some uncertainty on severity and placement, but there will
remain a threat for locally heavy rainfall, nuisance flooding,
and an isolated flash flooding occurrence.

The area remains under a broad trough with vorticity maxima
moving through Monday night and into Tuesday. As the trough
tries to lift during the day on Tuesday, additional energy
descends from the north to allow for another round of forcing.
At the surface, this should translate into the form of a
secondary frontal passage that brings another round of showers
with possible embedded thunderstorms, especially Monday night
into Tuesday morning. Any residual showers should diminish into
the afternoon on Tuesday with the passage of the surface cold
front. This will set the stage for drier and cooler conditions
to take hold into midweek. Behind the fropa, highs on Tuesday
could be the coolest since late May for some, generally in the
upper 60s and lower 70s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
No significant changes in the long term. A drier, cooler pattern
develops midweek behind the frontal system as dry air advects
south with surface high pressure building in. Lingering trough
over the Northeast may persist into late week, reinforced by a
closed upper low dropping south out of Canada.

This high pressure will be accompanied with primarily N/NW winds
and a much cooler regime, perhaps the coolest since late spring.
High temperatures Wednesday may not rise out of the low 70s for
much of the area. Lows Wednesday night and Thursday night will
likely be fairly chilly, with some locations for the interior
and outlying areas possibly dropping into the low 50s or upper
40s, depending on the strength of any radiational cooling.
Temperatures will gradually moderate into late week and the
weekend with highs by Friday and Saturday rising back into the
upper 70s to low 80s.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
A frontal system slowly approaches the terminals through the TAF
period.

Becoming mostly MVFR with some local IFR farther east. Showers
possible at any time, and for the city terminals as points west,
brief heavy downpours through 11-12z, and possibly again in the 12z
to 15z time frame.

MVFR conditions are likely to continue through this evening
although there could be some brief improvement to VFR at times
in the afternoon. Showers remain possible into this evening,
especially along and west of the Hudson River corridor. Farther
east, a brief shower is possible, but the most widespread
shower activity likely holds off until after 00z Monday.

There could be an isolated thunderstorm this morning, mainly NYC
metro terminals on north and west. After a potential relatively lull
late morning to early afternoon, chances of thunderstorms and heavy
downpours increase a bit late this afternoon/evening for the same
terminals. Have therefore included a PROB30 for this time period.

Winds will mainly be SE around 10 kt or less through the TAF period.
Coastal terminals could see winds a few kt higher at times,
especially this afternoon. There is also a chance for a few gusts 15-
20 kt this afternoon.

 ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of return to MVFR may be off by 1-3 hours. Amendments
for changing flight categories and shower timing likely through
the TAF period.

Isolated thunderstorms possible 10-16z Sunday.

Timing of PROB30 TSRA this afternoon and evening may be off by
several hours with adjustments likely.

OUTLOOK FOR 06Z MONDAY THROUGH THURSDAY...

Late Tonight: Showers with MVFR, except IFR north and east of
the city terminals.

Monday: Showers with possible thunderstorms, especially
afternoon and evening. MVFR or lower at times.

Tuesday: Mainly VFR. A chance of showers with MVFR possible. NW
wind gusts 15-20 kt.

Wednesday-Thursday: VFR.

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

&&

.MARINE...
Rough ocean seas and long period swells, 12 to 15 second, will
persist through Monday as distant TC Ernesto passes well
offshore in the open Atlantic. This is also leading to rough
conditions around inlets. Please refer to the National Hurricane
Center for official forecasts regarding Ernesto. A Small Craft
Advisory remains in effect for the ocean zones thru Monday
night. Seas on the eastern LI Sound could also approach 5 ft at
times today, though thinking this may be more occasional.

Thereafter, elevated wave heights on the ocean zones will allow
for SCA conditions to continue Monday night and possibly into
the day on Tuesday. By Late Tuesday, wind diminish and wave
heights should fall below 5 feet. Sub-SCA conditions are then
expected with high pressure moving into the area by midweek.

&&

.HYDROLOGY...
A Flood Watch remains in effect thru late tonight for NE New
Jersey and into the Lower Hudson Valley west of the Hudson
River. Isolated to scattered instances of flash flooding are
possible across the more flood prone areas of NE NJ and adjacent
areas of the Lower Hudson Valley, and perhaps as far east as
NYC. Locally heavy rainfall is possible, mainly this morning,
and again this late today into tonight, with rainfall rates up
to an inch or two per hour. Farther east, the risk for flash
flooding is lower, but cannot be entirely ruled out. Ponding and
poor drainage flooding is the most likely solution here with
any heavier activity.

Additional rainfall expected on Monday and Monday night will
lead to a more widespread threat for localized flash flooding,
along with nuisance flooding of urban and poor drainage areas.

Total rainfall through Monday night ranges from around a half
inch east to between 1 and 2 inches from NYC metro on north and
west. Locally higher amounts, possibly up to 3 or 4 inches, are
possible across northeastern New Jersey into the Lower Hudson
Valley.

No hydrologic concerns Tuesday through next weekend.

&&

.TIDES/COASTAL FLOODING...
A high rip current risk is in place through Monday due to elevated,
long period swells from passing TC Ernesto.

Ocean seas are forecast to be highest today and Monday, and
with surf heights up to 6 ft, local beach erosion is possible.

A full moon on Monday as well as swell from distant TC Ernesto
will elevated tide levels today into early this week. Minor
coastal flooding is expected with high tide this evening across
the back bays of Nassau and Western Sound along the southwest CT
and S Westchester coast. Have issued a Coastal Flood Advisory
for these locations. Localized minor coastal flooding is
possible across southern Queens, Southern Brooklyn and lower NY
Harbor. Locations may just touch minor benchmarks and a
statement has been issued. Additional minor flooding is possible
for high tide Monday evening and statements/Advisories will
likely be needed for similar locations as with high tide this
evening.

Please refer to NHC for official forecasts regarding Hurricane
Ernesto.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT
     Monday for CTZ009.
NY...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT
     Monday for NYZ071.
     Flood Watch through late tonight for NYZ067-069.
     High Risk for Rip Currents through Monday evening for NYZ075-080-
     081-178-179.
     Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for
     NYZ179.
NJ...Flood Watch through late tonight for NJZ002-004-006-103>108.
MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ350-353-355.

&&

$$

SYNOPSIS...DR
NEAR TERM...DR
SHORT TERM...DR
LONG TERM...MW
AVIATION...JC
MARINE...DR
HYDROLOGY...DR
TIDES/COASTAL FLOODING...