769
FXUS61 KOKX 212224
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
624 PM EDT Tue May 21 2024

.SYNOPSIS...
High pressure off the coast will be in control through
Wednesday night. A cold front will approach on Thursday and
weaken as it moves into the area Thursday night into early
Friday. The front will eventually dissipate south of Long
Island on Friday as weak high pressure returns from the north.
Another low pressure system will approach from the west for
Saturday. Its associated cold front will move across Saturday
night. Weak high pressure will return for Sunday before more
frontal systems potentially impact the area early next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Just some minor adjustments made to hourly temperatures, dewpoints,
fog and cloud coverage for tonight. Forecast overall remains on
track.

Mostly clear skies over most of the area, with some sct Cu over
the higher elevations NW of NYC and along the sea breeze in NJ.
Skies should remain mostly clear through tonight except perhaps
over parts of coastal CT and the forks of Long Island which
could see some fog development late tonight. Confidence in this
not very high as winds veer SW tonight.

Low temps will range widely from east to west, from the lower
50s across the forks of Long Island and SE CT, to the mid/upper
50s most elsewhere, and lower/mid 60s for NYC and NE NJ.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
The high will remain in place daytime Wed, with more widespread
warmth as low level flow will be SW rather than S. Most areas
north/west of NYC should see high temps in the mid/upper 80s,
with 80-85 for most of NYC and interior CT, and 70s across Long
Island and coastal CT. Most of the south shore of Long Island
however may not make it any higher than the upper 60s.

A pre-frontal trough and associated mid level shortwave trough
approach late Wed night and may bring a few showers/tstms mainly
to areas from the NYC metro area north/west. Lows Wed night will
once again vary from east to west, with 55-60 for Long Island
and S CT, lower 60s most elsewhere, and mid 60s for NE NJ.

&&

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

* Very warm day Thursday upper 70s to near 90 for high
  temperatures. Lower 90s heat indices for parts of NYC, NE NJ,
  Lower Hudson Valley into SW CT.

* Marginal strong to severe thunderstorm threat for Thursday
  into Thursday night.

* Potential for some rounds of showers for the holiday weekend.

Upper levels feature a SW to NE jet streak of which its right
rear quad will be more in the central to northern New England
Thursday into Thursday night. Relatively weak jet level winds
are forecast over the area Friday into the weekend but another
jet streak moving north of the area Sunday night. Then SW flow
in jet levels early next week with a longer wavelength trough
approaching the Eastern Seaboard towards the middle of next
week.

At the surface, a parent low fills in while moving farther
northeast within Ontario Thursday. Its associated cold front
will weaken as it approaches the local region. Before the
arrival of the cold front, there will likely be a pre-frontal
trough making for early day showers and thunderstorms north and
west of NYC.

Regarding the thunderstorms, some of them have the possibility
of being strong to severe with hail and strong wind gusts for
the entire forecast area. However, higher severe chances near
NYC and locations to the north and west, including Western Long
Island, NE NJ, Lower Hudson Valley and SW CT. From NCAR Ensemble
Forecasts 00Z 5/20/24 initialization, highest CAPE Thursday
across most interior places, towards Passaic NJ, Orange NY,
Putnam NY, Rockland NY, Northern Westchester NY, Northern
Fairfield CT (around 1500 J/kg). Convective inhibition is shown
to the east. 0-6 km AGL bulk shear as shown by different
forecast models getting to range of 30-40 kt, allowing for some
organization of convection with strong downburst potential.

Farther west locations are forecast to have more CAPE, driving
the downburst potential with thunderstorms as well as greater
vertical development for hail growth.

Lots of uncertainty on timing and placement of showers and
thunderstorms. Not much rainfall total, approximately 0.25
inch or less. CAPE is highest in the 2 to 8PM timeframe so would
think this would be the window for much of the strong to severe
thunderstorm potential. General timeframe between 2PM and 8PM
from NW to SE for the thunderstorms to develop, grow and move
southeast. The convective mode will probably be a broken squall
line or a combination of convective clusters as well as a broken
squall line.

Parent low filling in Thursday within Ontario, decreasing
pressure over time, resulting weakening of cold front moving
through the area. Some models are indicating the front slows
down and stalls out as well as dissipate within the region. The
front is therefore becoming less well defined with time.

May very well be a situation where Eastern Long Island and
Southeast Connecticut do not receive any rainfall Thursday
into Thursday night as the more maritime environment stabilizes
the low levels enough for approaching showers and thunderstorms
to breakup and weaken as they approach.

Weak high pressure follows for Friday into Friday night. Some
shower chances remain early for coastal sections, especially
Long Island but drying conditions are expected going into the
afternoon. Dry conditions continue until late Friday night. This
is when another low pressure system will be approaching from
the west. More rain showers are in the forecast and these are
forecast as well for Saturday with possibly a few thunderstorms
with daytime heating. Chances for showers continue Saturday
night with an associated cold front moving across.

Weak high pressure returns for Sunday into Sunday night with
mainly dry conditions much of the time. Showers return to the
forecast late Sunday night into early next week with another
frontal system approaching.

Temperatures gradually on a cooling trend over the course of the
long term, staying above normal Thursday through Sunday but near
to below normal for early next week.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Weak surface high pressure remains in control through Wednesday.

VFR with S winds 10-12 kt with sea breeze enhancement into early
this evening.

S flow weakens and continues overnight, with a chance of MVFR
to IFR stratus developing late tonight at KISP, KBDR, and KGON.

VFR expected daytime Wednesday, with S-SW flow increasing to
10-12 kt again.

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

No unscheduled amendments expected.

OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY...

Wednesday afternoon: VFR.

Wednesday night: Chance of showers and possibly a tstm with MVFR
cond mainly from NYC metro north/west. IFR cond possible late
east of the NYC metro terminals.

Thursday: MVFR or lower cond, with showers and thunderstorms
likely mainly in the afternoon.

Friday: VFR.

Saturday and Sunday: Chance of showers with brief MVFR cond,
otherwise VFR.

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

&&

.MARINE...
Ocean seas may get close to 5 ft at times W of Fire Island
Inlet on increasing S flow 15-20 kt early this evening, and
again toward evening in S-SW flow at the same speeds in the late
day/early evening on Wed. Otherwise, sub SCA cond expected
through the weekend. Fog is possible tonight on the central/ern
Sound, Peconic/Gardiners Bays, and the ocean waters E of
Moriches Inlet.

&&

.HYDROLOGY...
No hydrologic impacts expected.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$

SYNOPSIS...BG/JM
NEAR TERM...BG/JM
SHORT TERM...BG
LONG TERM...JM
AVIATION...JT
MARINE...BG/JM
HYDROLOGY...BG/JM