090
FXUS61 KOKX 060112
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
912 PM EDT Fri Jul 5 2024

.SYNOPSIS...
A trough of low pressure remains west of the area tonight. A cold
front then approaches on Saturday, slowly moving through the area
Saturday night. A cold front southeast of the region eventually
dissipates and allows for high pressure to briefly build in for
Sunday through Sunday night. Another frontal system approaches
early next week with its associated cold front moving in towards
midweek. This frontal boundary could very well linger nearby
from mid to late week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
The forecast is on track tonight. KOKX depicting a broken line
of showers and thunderstorms in western CT extending south into
NE NJ and just east of NYC. Storms continue to be sub-severe,
though frequent lighting and some gusts to near 35mph are noted
especially in the lower Hudson Valley/western CT. Precipitation rates
with these storms are in the 1-2" per hour range, and our coop-
observer from Harrison, NJ reported 0.7" in just 12 minutes.
The convection is moving east-northeast at 25-30mph limiting the
flash flooding threat thus far. As the activity continues to
push east over the next few hours, a more unfavorable
environment awaits with the influence of a more stable marine
layer, and am expecting activity to wane with time. Previous
discussion follows.

Cold front/trough appears to remain stalled across western portions
of the region tonight. here remains a potential for a few heavy
downpours and embedded tstms to develop and move northeast across
the area tonight with strengthening mid/upper support ahead of a
closed low to the west, and strengthening low-level jet ahead of pre-
frontal trough advecting in an increasingly sub-tropical (weak
elevated instability, deep moisture and warm cloud layer, and 2"+
PWATS) environment. One forecast concern is the NWP and CAMs
continue to remain mixed on location and how widespread any
shra/embedded tsra activity is, with the greater potential remaining
NW of NYC in vicinity of trough.

Otherwise, very warm and muggy conditions tonight, with stratus/fog
development likely across much of the area.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/...
The trough over the Great Lakes continues to lift northeast into
Ontario/Quebec Saturday into Saturday Night, with shortwave axis
pivoting across W PA/NY Saturday Night.

Heat advisory continues for NE NJ through Saturday for second day of
heat indices of 95 to 100 F. Have expanded the Heat Advisory to
include Western Passaic as well as Orange and Rockland in NY. There
is slightly greater coverage of 95 F heat indices likely across the
region on Saturday, but not enough confidence to expand heat
advisory into NYC and the remainder of the the Lower Hudson Valley.
Can not rule out parts of these areas reaching the criteria, however
one concern will be the potential for additional cloud cover/shower
activity which may limit temperatures a bit. Either way, expect
a rather muggy day with dew points in the lower to middle 70s.

The pre-frontal trough remains stalled over the area Saturday, with
the potential for a few rounds of heavy downpours and thunderstorms
ahead of and along it. Sat afternoon and evening appears to be the
best chance for a few strong to severe thunderstorms, once again,
mainly across NYC and points N&W.

The main threat with any storms on Saturday and saturday night will
be the potential for heavy rainfall. PWATS remain above 2"+ inches.

Again one of the forecast challenges remains the differences between
the NWP and CAMs which are varied in timing, location, intensity of
convection. So at this point an isolated severe/flash flood threat
exists on Saturday, mainly for NYC and points N&W.

Any thunderstorm activity should weaken in intensity as it slowly
moves eastward towards the coast Saturday evening and Saturday night
However, there is still the potential for locally heavy downpours
and embedded thunderstorms near the coast.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
After analysis of some large scale numerical weather prediction
models with their MSLP, surface winds, and precipitation forecasts
the following features are noted. The models analyzed were the NAM,
GFS, ECMWF, and the Canadian, although for forecasts of Monday night
onward, just the GFS, ECMWF and Canadian were compared.

The models exhibit better agreement with high pressure over the area
with mainly dry conditions Sunday through Sunday night. They have
agreement with southerly flow across the region for early next week
and more convective potential for Tuesday through Tuesday night. The
models show cold front lingering nearby for Wednesday but vary more
with rain from mid to late week. ECMWF particularly seems to be most
aggressive with convection showing a continual cycle of shower and
thunderstorm development along the front for mid to late week.

Some relatively drier dewpoints Sunday behind a cold front will have
some lower heat indices forecast within the region. Forecast highs
mostly in upper 80s to lower 90s with max heat indices in the lower
90s with some mid 90s for parts of the region, mostly in NE NJ. More
areas in mid 90s with max heat indices forecast for Monday with
relatively higher dewpoints compared to previous day. Forecast highs
are mostly in the 80s for Tuesday and the rest of the days of the
forecast.

Showers with mostly chance POPs return to the forecast Tuesday
afternoon through the rest of the forecast. Forecast has chances of
thunderstorms Tuesday afternoon through Wednesday night. Otherwise,
thunderstorms have slight chance. Highest coverage and thunderstorm
potential appear to be Tuesday afternoon into early Wednesday
surrounding the cold front moving and how fast it makes its way
through.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
A slow moving frontal system impacts the terminals through Saturday
night.

Showers and thunderstorms are expected at the start of the TAF
period for NYC terminals, KSWF, and KHPN. This activity should
weaken as it moves across southern CT and Long Island.
Confidence is not high enough to include thunder east of NYC
terminals, but a shower is possible at least until around 04z.

Another round of showers is possible early Saturday morning, with
potential of thunder. Have gone with VCSH for now due to lower
confidence in timing and coverage. Showers/storms are also
possible Saturday afternoon and evening.

Otherwise, VFR to start at most terminals but MVFR-IFR is likely to
develop through the evening and eventually become IFR to LIFR,
lowest across Long Island and southeast CT. Some improvement is
expected after 12z with VFR likely NYC terminals on NW, but
conditions may remain IFR into early afternoon across Long Island
and southeast CT.

S-SE winds generally below 10 kt tonight and then 10-15 kt Saturday.
Winds begin to shift to the SW Saturday evening.

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

Showers/thunderstorms through 01z. Additional showers possible late
tonight into Saturday morning and a thunderstorms cannot be ruled
out.

Timing for flight category changes tonight through Saturday morning
may be off by 1-2 hours.

Timing of TSRA Saturday afternoon will likely be refined in
subsequent forecasts.

OUTLOOK FOR 00Z SATURDAY THROUGH WEDNESDAY...

Saturday Night: MVFR or lower possible, especially Long Island and
Southern CT. Continued chance of showers/tstms east of NYC metro.

Sunday and Monday: VFR.

Tuesday: Chance of MVFR in showers and thunderstorms in the
afternoon, mainly west of NYC.

Wednesday: Chance of MVFR in showers and thunderstorms.

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

&&

.MARINE...
Small craft advisories remain in effect for the ocean tonight
through Saturday night as a strengthening S flow increases to
15-20kt and seas build to 4 to 6 ft. Potential for occasional
Great South Bay gusts to 25 kt as well.

With a relatively weak pressure gradient in place, conditions on the
waters are expected to remain below small craft advisory thresholds
Sunday through the middle of next week.

&&

.HYDROLOGY...
Isolated to scattered thunderstorms producing 1-2"/hr rainfall
rates are likely this eve, primarily W&NW of NYC. Primary threat
is for minor/poor drainage flooding, with an isolated flash
flood threat.

Approaching shortwave and slow moving frontal boundary crossing
tonight into Saturday night will bring potential for localized 1-
2"/hr rainfall rates with isolated to scattered thunderstorms.
Localized flash flood threat exists for the area from any
training convection during this timeframe, with the threat
maximized across NYC/NJ metro and points N&W during peak heating
Sat aft/eve.

Model precipitable waters show an increase up to near 2.2 to 2.4
inches Tuesday into Tuesday night. With cold front moving in, there
will be a marginal risk for excessive rainfall. There will be a
chance for flooding with widespread minor flooding potential as
well as a low percentage probability for localized flash flooding.

Otherwise, no other widespread hydrologic issues are expected.

&&

.TIDES/COASTAL FLOODING...
High risk of rip currents until 9pm Saturday evening for all
ocean beaches.

Building onshore swell observed at ocean buoys around 4 ft with
wave period of 6 to 10 seconds going into this evening.

Ocean seas are expected to continue to build Saturday to near 5
ft and then slightly subside Sunday to near 4 ft. Onshore winds
will be relatively higher Saturday along the ocean beaches with
wind speeds of around 10 to 15 mph. The winds become more
variable in direction and decrease in speed for Sunday.

These factors will result in the high risk of rip currents
remaining at all ocean beaches of NYC and Long Island through
Saturday and into the first half of Saturday evening. There is
a moderate risk of rip currents forecast for the ocean beaches
on Sunday.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Heat Advisory from noon to 8 PM EDT Saturday for NYZ067-069.
     High Risk for Rip Currents through Saturday evening for NYZ075-080-
     081-178-179.
NJ...Heat Advisory from noon to 8 PM EDT Saturday for NJZ002.
     Heat Advisory until 8 PM EDT Saturday for NJZ004-006-103>108.
MARINE...Small Craft Advisory until 2 PM EDT Sunday for ANZ350-353-355.

&&

$$

SYNOPSIS...BC/JM
NEAR TERM...BC/DBR
SHORT TERM...BC
LONG TERM...JM
AVIATION...DS
MARINE...BC/JM
HYDROLOGY...BC/JM
TIDES/COASTAL FLOODING...JM