942
FXUS61 KOKX 172217
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
617 PM EDT Tue Jun 17 2025

.SYNOPSIS...
A warm front approaches tonight and moves across by early
Wednesday. Low pressure develops along a cold front to the west
on Wednesday into Wednesday night with the local area in the
warm sector. The area remains in the warm sector of a low
pressure system Thursday before a cold frontal passage Thursday
evening/night. High pressure then builds in for the weekend and
dominates through the middle of next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A warm front approaches tonight and eventually moves into the
region. As it gets closer, low level winds become more
southerly. The winds will be light and from the southeast. This
will help draw in more moisture into the low levels. With some
slight cooling tonight, fog is expected to advect into the area.
Areas of fog are expected which could very well be dense at
times.

Associated with the approach of the warm front, models indicate
an increase in vertical lift with isentropic lift indicated.
There are chances of showers tonight into early Wednesday, with
highest likelihood north and west of NYC. With models also
indicating some elevated instability towards early Wednesday as
diagnosed from near zero to slightly negative Showalter Indices,
isolated thunderstorms are also part of the forecast.

For the low temperatures, used a blend of MAV and MET MOS,
ranging from the low to upper 60s.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
The warm front is expected to traverse the region early
Wednesday and move northeast of the entire region by late
Wednesday morning into Wednesday afternoon.

This will leave the region in the warm sector. Models indicate
multiple areas of low pressure developing along a cold front
well west of the region. This front stays west of the region
through Wednesday night.

However, there is forecast to be an upper level disturbance with
an associated trough at the surface moving into the region late
Wednesday into Wednesday evening. Models exhibit in the mid
levels a slight undulation of the 500mb height and associated
positive vorticity advection moving in towards Wednesday
evening.

At the surface, winds are expected to become more southerly and
even SW in some interior locations. More warm air advection is
expected just above the surface, allowing for a little more
vertical mixing. Fog is expected to burn off in the morning but
clouds are going to remain abundant in coverage. Warmer
temperatures are forecast, taking a MAV and MET MOS blend, with
values ranging from lower 70s to lower 80s for highs. There is
some extra uncertainty on the highs and convective forecast as low
clouds and fog lingering longer than forecast would result in
lower temperatures than forecast and less instability.

Western parts of the region will be on the higher end of the
temperature range. Surfaced based instability will be greater
for those locations as well. Enough instability and forcing
aloft is expected to result in the development of showers and
thunderstorms late morning north and west of NYC. This
convection then spreads farther east into the rest of the region
for the afternoon into evening hours.

Layer precipitable waters reach near 2 to 2.2 inches. Heavy
downpours will be possible with thunderstorms. Also put in gusty
winds with the potential for some strong thunderstorms Wednesday
into Wednesday night. Mid to upper level winds getting near 25
to 30 kt.

Rain tapers off late Wednesday evening into overnight. Warm and
continued humid at night. Lows only in the mid 60s to near 70 for
Wednesday night. Some fog will be possible especially in areas
that received rainfall.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Key Points:

* Strong to Severe Thunderstorms possible Thursday afternoon/evening

* The potential for an extended period of high heat and humidity is
  increasing for next week.

The area will be positioned in the warm sector of a low pressure
system over the Great Lakes and moving northeast into Southeastern
Canada on Thursday. Thursday should be mostly clear much of the day
under a SW wind. Given the ample sunshine and warm air aloft, the
mixing of the boundary layer into the afternoon will promote high
temperatures into the upper 80s and lower 90s. A SW flow will
continue to advect moisture into the area so that dew points are in
the upper 60s to low 70s.

In addition to the heat and humidity resulting in heat index values
in the 90s to possibly 100 for the warmest spots away from the
coast, this will also result in a fairly unstable environment that
will be favorable for the development of showers and thunderstorms
as the cold front approaches from the west into the afternoon and
evening. Given the lowering heights and subtle cooling in the mid-
levels as the trough associated with the low pressure moves
overhead, the warm lower levels should allow for the development of
instability on the order of 1500-2500 J/kg. There may be a subtle
cap for coastal areas that may prevent the development of convection
in those areas much of the day. In addition to the instability,
shear will increase through the day as the cold front approaches
from the west. 0-6km shear values will be on the order of 25-40 kt
which is enough to support organized convection.

Given the combination of CAPE and shear and with the approaching
cold front in the evening, there is the potential for strong to
severe thunderstorms with damaging wind gusts. SPC has placed the
western half of the CWA in a slight risk for severe thunderstorms.
While damaging winds will be the primary threat, heavy rain,
frequent lightning, and hail will be possible as well. The lower
atmosphere should become stable very shortly after sunset with the
dissipating surface heating. This should limit the severe threat to
being in the afternoon to very early evening hours. Any remaining
thunderstorms that are able to sustain themselves and make it to
eastern areas should be elevated and thus much less likely to be
severe, though it can`t be ruled out.

The front passes by Thursday night and the trough moves overhead
into Friday. The main focus for the extended timeframe then shifts
to a large strong ridge of high pressure poised to develop south of
the area. This is likely to result in an extended period of hot and
humid conditions late weekend into at least the middle of next week.

Temperatures Friday and Saturday will be around average or slightly
above for this time of year, generally in the 80s to possible near
90 for the warmest areas. As the ridge of high pressure establishes
itself to the south, a W/SW flow develops advecting both warm air
and moisture into the area. By Sunday, highs will begin to increase
across the entire area into the middle 80s to low 90s. The heat and
humidity continues to increase Monday and Tuesday. Highs for both
days will be in the 90s for much of the area, perhaps with the
exception of the coast where middle to upper 80s are still expected.
For portions of NE NJ and the NYC Metro, the Lower Hudson Valley,
and interior southern Connecticut, widespread 90s are expected, with
upper 90s possible. Dew points during this time are expected to be
in the upper 60s to low 70s which may result in heat index values in
excess of 95-100 degrees in spots. Lows each night will also not
offer much relief from the heat as low temperatures Sunday night
through at least Tuesday night will likely not drop below the 70s
for much of the area. The NYC metro may not drop below the middle to
upper 70s.

Confidence in the occurrence of this extended heat and humidity is
increasing, though exact high temperatures and heat index values are
likely to change as the event nears. Regardless, prepare for an
extended period of high heat and humidity from Sunday through at
least Tuesday, but possibly through Wednesday of next week.

&&

.AVIATION /22Z TUESDAY THROUGH SUNDAY/...
High pressure east of New England will retreat eastward farther
out into the Atlantic as a warm front approaches from the south.
The front will slowly lift through Wednesday morning.

Widespread LIFR conditions, with low stratus, drizzle and fog,
should persist into early Wed morning. There could still be a
window for brief improvement to IFR at KLGA/KTEB late this
afternoon. Showers and possibly a tstm move across ahead of warm
fropa between 08Z-09Z to 12Z-13Z at most terminals, later at
KGON. Have not yet mentioned thunder in TAF due to very sparse
coverage and uncertainty on exact timing/placement.

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

AMD possible for flight categories deviating from forecast.

.OUTLOOK FOR 18Z WEDNESDAY THROUGH SATURDAY...

Wednesday afternoon: Showers likely with chance of tstms.
MVFR cond expected, brief IFR cond possible.

Wednesday night: Low stratus and fog mainly at the Long
Island/CT terminals with IFR/LIFR cond. MVFR cond possible at
the NYC metros north/west. Showers also likely in the evening,
with chance of tstms mainly E of the NYC metros.

Thursday: Any early morning low cloud/fog improve to VFR by 15Z.
Showers/tstms with IFR then possible in the afternoon/early
evening, some with locally strong winds from the NYC metros
north/west.

Friday through Sunday: Mainly VFR.

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

&&

.MARINE...
Below SCA conditions forecast through Wednesday night. Dense fog
expected into early Wednesday on the ocean and South Shore Bays.
Dense fog possible on other waters as well but did not put up
advisory yet for those other waters due to uncertainty.

A developing SW flow on Thursday will allow for gusts of 25kt on the
ocean zones by the afternoon along with wave heights of 5 feet,
resulting in SCA conditions through at least Friday morning. High
pressure then builds into the area through the weekend resulting in
sub-SCA conditions.

&&

.HYDROLOGY...
Around a quarter to half inch rain forecast tonight through
Wednesday night with locally higher amounts possible.

Locally heavy downpours are possible with any showers/thunderstorms
Wednesday morning, Wednesday afternoon and again Thursday
afternoon into the evening. However, the risk of flooding will
be mitigated by the speed of any cells and lack of overall cell
training.

No hydrologic impacts expected thereafter through the beginning
of next week.

&&

.TIDES/COASTAL FLOODING...
Rip current risk remains moderate Wednesday and Thursday with a
continued E/SE 3ft 7s wave component and parallel/onshore flow.
Increasing SW flow late Thursday afternoon may result in an
elevated risk for rip currents later in the day.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Dense Fog Advisory until 7 AM EDT Wednesday for ANZ345.
     Dense Fog Advisory until 7 AM EDT Wednesday for ANZ350-353-355.

&&

$$

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