117
FXUS61 KOKX 080015
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
815 PM EDT Tue May 7 2024

.SYNOPSIS...
High pressure gives way to a low pressure system moving north of the
area Wednesday. Another low pressure approaches along a frontal
boundary south of the region Thursday into Thursday night. The
low pressure center moves across Friday and then east of the
region Friday night. Weak high pressure briefly builds in
Saturday before another low moves across Sunday. Weak offshore
high pressure establishes for early next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Slight adjustments were made to hourly temperatures, dewpoints,
cloud coverage as well as the patchy fog in the forecast. Patchy
fog expected for Eastern Long Island and SE Connecticut where
surface flow late tonight becomes more SE and these locations
will be the last within the local forecast region to receive
more steady rainfall showers. Forecast mainly on track.

High pressure over the area will weaken and shift east tonight
as a mid-level shortwave over the Great Lakes approaches from
the west. Initially much of the area is expected to have mostly
clear to partly cloudy sky conditions for early this evening
but cloud cover is expected to increase with mostly cloudy to
overcast sky conditions expected for the entire region
overnight. Light onshore flow will aid in the moistening of the
BL and prevent temperatures from dropping too low. Low
temperatures tonight will be in the 50s regionwide where lower
50s are more likely for areas east and upper 50s to near 60 will
be more likely for the NYC metro and surrounding areas.

A line of convection associated with the shortwave and developing
over the Midwest/Ohio Valley tonight will begin to make its way into
the area by late tonight and into the early morning on Wednesday.
This will result in the increasing chance for showers with
embedded thunderstorms overnight into early Wednesday morning,
with highest likelihood for this activity from SW CT, Western
Long Island and NYC west through NE NJ and the Lower Hudson
Valley.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
The batch of convective debris from the remnants of upstream storms
will continue to make its way through the area during the morning.
These showers and embedded storms will largely exit the area by mid
to late morning, allowing for clearing into the afternoon for areas
to the west. Clearing skies will allow for a rapid warming of
the surface as strong heating takes over behind the departing
showers. The timing and quickness of the clearing will depend on
how far east the warmth will get. As of now, highs for the
western areas like the Lower Hudson Valley, northeast NJ, and
the NYC metro will be in the middle 70s to middle 80s. A
relatively sharp gradient in high temperatures will occur where
eastern areas may only sees highs in the low to middle 60s.

As the shortwave approaches the area into the afternoon, heights
fall as a weak trough moves overhead. Steepening lapse rates
combined with the strong surface heating will allow for the
development of moderate instability, generally 500-1500 J/kg MUCAPE,
over much of the area by late afternoon. Despite the instability, a
mid-level cap is expected to prohibit widespread storm development.
Forcing for ascent appears to be limited to closer to the shortwave
up to the north. As such, kept coverage of showers and storms into
the afternoon at slight chance to chance, with a better chance of
seeing convection for areas further north and west.

If convection develops, storms may become strong to locally severe
with the primary threats being damaging wind gusts and hail. SPC has
the area in a marginal risk for severe storms but threat diminishes
in more stable and cooler air closer to the coast and further east
where less surface heating takes place during the day and
instability will be elevated as opposed to surface-based.

The chance for storms diminishes after sunset with the remainder of
the overnight period being fairly dry, though a moist BL may allow
for the development of low stratus and fog. Lows will once again be
in the low 50s east to upper 50s west.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Upper levels exhibit active jet stream pattern across the region
Thursday through Friday. Then the jet is positioned more to the
south of the region for the weekend and into early next week.

Mid levels convey a southward moving wide trough that gets closer
Thursday into Friday, bringing the area more positive vorticity
advection in the process. The same pattern generally remains going
through the weekend, with the trough moving farther east of the
region early next week.

At the surface, low pressure approaches the region Thursday into
Thursday night along a front south of the region. Model differences
still present with progression of the surface low, some more recent
model runs of NAM and GFS keeping low pressure west of the region by
early Friday whereas ECMWF and Canadian keep low pressure farther
east.

The low pressure center moves across Friday and then shifts
farther east of the region for Friday night. High pressure then
briefly builds in Saturday but will be quite transient, quickly
giving way to another approaching low from the north and west
Saturday night. The low moves in Sunday and Sunday night but will be
of weak magnitude. Weak high pressure establishes offshore for early
next week.

Rain showers are in the forecast much of the time Thursday through
Friday night with the next main chance of rain showers Saturday
night through Sunday. Mainly dry conditions are forecast thereafter.

Some of the rain showers Thursday into Thursday evening could be
moderate to possibly heavy. Thunderstorms are possible Sunday into
Sunday night with cold pool aloft moving in with the upper level
trough.

Forecast high temperatures near normal Thursday, more below normal
Friday, and then near normal for the weekend. Potentially more above
normal temperatures could occur for early next week. However, there
is uncertainty.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
A warm front lifts through the region late tonight into
Wednesday morning. A cold front moves through the region late
Wednesday and Wednesday night.

VFR until late tonight, or toward Wednesday sunrise. However,
with timing uncertainties conditions may lower a couple of hours
earlier. Showers develop with the approach of a warm front
toward Wednesday morning with conditions lowering to IFR, and
possibly LIFR for a few hours as the warm front moves slowly
through the terminals. Isolated thunderstorms are possible
Wednesday morning, however, the chances are low and not
included in the forecast. Conditions improve back to VFR with
the warm front passage. Isolated showers and maybe a
thunderstorm will be possible Wednesday afternoon into the early
evening with the passage of the cold front. However, chances
and confidence too low to include at this time.

Winds remain light south to southeast tonight, and light and
variable in a few locations. Winds increase from the south to
southwest ahead of a cold front, and then become westerly and
gusty, up to 20kt, behind the front. Gusts may be briefly higher
with the initial cold frontal passage.


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

Timing uncertainties with the lowering conditions late tonight,
and may be a couple hours earlier than forecast. There is a low
chance of isolated thunderstorms early Wednesday morning.

Low chance of SHRA or TS Wed afternoon, too low to include in
TAF at this time.

OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...

Wednesday night: VFR, except MVFR in fog at KGON. A slight
chance of thunderstorms early in the evening east of the NYC
terminals.

Thursday: MVFR/IFR. Showers likely, especially in the afternoon
and at night.

Friday: MVFR/VFR with chance of showers.

Saturday: Chance of showers with MVFR cond at KSWF, otherwise
VFR. Chance of showers at night with MVFR.

Sunday: MVFR/IFR with a chance of showers and possibly a
thunderstorm.

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

&&

.MARINE...
Winds and seas are expected to remain below SCA conditions
through Wednesday night as seas will essentially average close
to 3 ft.

Long term from Thursday through the weekend, sub-SCA conditions
forecast for non-ocean marine zones but on the ocean, potential
for SCA conditions due to seas. SCA seas forecast on the ocean
at times mainly between Thursday night through the weekend.

&&

.HYDROLOGY...
Minor nuisance flooding possible with rain showers Thursday
into Thursday evening. WPC contains much of the region in a
marginal risk for excessive rainfall for Thursday into Thursday
evening.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides run high the next several days with a new moon
tonight.

Minor flood benchmarks are likely to be exceeded during the
evening high tide cycles tonight through Thursday across
coastal southern Nassau, Queens, and Fairfield counties with
inundation up to a foot. Localized moderate flooding is possible
during Wed and Thu evening`s high tides, particularly in the
most vulnerable spots of southern Nassau and Queens.

Elsewhere, localized minor flooding for this evening`s high tide in
coastal Westchester, Brookyln, and northern Nassau/Queens.
Inundation up to a half foot is possible. Additional minor
flooding is possible thru Thursday evening.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Coastal Flood Advisory until 2 AM EDT Wednesday for CTZ009.
NY...Coastal Flood Advisory until 10 PM EDT this evening for NYZ178-
     179.
NJ...None.
MARINE...None.

&&

$$

SYNOPSIS...JM/MW
NEAR TERM...JM/MW
SHORT TERM...MW
LONG TERM...JM
AVIATION...MET
MARINE...JM/MW
HYDROLOGY...JM/MW
TIDES/COASTAL FLOODING...