-- Discussion containing changed information from previous version are highlighted. --
499
FXUS61 KOKX 051835
AFDOKX

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

.SYNOPSIS...
A trough of low pressure stalls west of the area today with a warm
front lifting through the region late today into tonight. A cold
front then approaches on Saturday, slowly moving through the area
Saturday night. The front stalls just southeast of the area Sunday
into Monday. Weak high pressure across the area on Monday gives way
to a frontal system tracking east across the Great Lakes and Ohio
Valley states Monday night into Tuesday. The associated cold front
moves through the area on Wednesday, followed by weak high
pressure.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Forecast remains on track with no significant changes. Just a
few minor adjustments to reflect current observations.

Otherwise...An upper level low moves into the Great Lakes
region today into tonight. A convectively enhanced weak
shortwave approaches late this evening.

At the surface, a weak front remains nearly stationary over
western portions of the region. This front then develops a
warm frontal feature and lifts back north as a warm front late
this afternoon into this evening, aided by afternoon seabreeze
development.

Subsidence and mid-level drying this afternoon has allowed for
some good heating across for NYC, NE NJ and portions of Lower
Hud. Expect very warm temps (upper 80s to around 90 for NE NJ
and LoHud) and increasingly humid conditions. Heat advisory
continues for NE NJ for heat indices of 95 to 100 F. Lower 90 to
locally 95 F heat indices across NYC, LoHuD, and surroundings
today. Stratus may be stubborn across E LI and S CT into the
afternoon with moist onshore flow and warm front in vicinity,
holding temps in the lower 80s.

Scattered aft/eve convection likely, mainly for areas N&W of
NYC with approach of next shortwave, and in vicinity of weak
trough and seabreeze boundary, in a marginally unstable and
modestly sheared environment. An isolated strong to severe
tstorm is possible. Lack of focus and stabilizing marine layer
to the east across the coast should limit shra/tsra activity
thru this eve.

Cold front/trough appears to remain stalled across western
portions of the region tonight, with its warm frontal feature
dissipating or moving north. Potential for a few heavy downpours
and embedded tstms to develop and move ne across the area
tonight with strengthening mid/upper support ahead of shearing
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. NWP and CAMs are mixed on location
and how widespread this shra/embedded tsra activity is, with
greater potential 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 NIGHT/...
Great Lakes trough continues to shear northeast into
Ontario/Quebec Saturday into Saturday Night, with shortwave axis
pivoting across W PA/NY Saturday Night. Heights gradually rise
on Sunday in its wake with western Atlantic ridging building a
bit towards the area.

Heat advisory continues for NE NJ through Saturday for second
day of heat indices of 95 to 100 F. Slightly greater coverage
of 95 F heat indices likely across NYC, LoHuD, and surroundings
on Saturday, but not enough confidence to expand heat advisory
into this area with only small areal coverage of 2 day mid 90 HI
expected.

Pre-frontal trough remains stalled over the area Sat, with potential
for a few rounds of heavy downpours and tstms ahead/along it. Sat
aft/eve appears to be the best conditional chance of a few strong to
severe tstms, particularly NYC and points N&W, based on mid- upper
level support ahead of shearing shortwave trough axis, moderate deep
layer shear, approaching cold front and marginal instability
environment. This relatively better environment is supported by
greater coverage of 15% svr wind threat in CSU MLP on Sat vs
today.

Conditional ingredients for torrential downpours in vicinity of
pre- frontal trough in place for Sat aft/eve as well with
approaching synoptic forcing, sub-tropical environment (2 1/4"+
PWATS, 13-14 kft warm cloud layer), marginal instability,
moderate deep layer shear, and steering flow/llj paralleling the
slow moving trough. The forecast challenge in determining flash
flood threat is the location of the trough, potential
morning/early afternoon convection, prominent 800-900mb capping,
and late timing of shortwave energy. NWP and CAMs are varied in
these factors and resultant 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, with
potential for this threat to trend upwards if things come
together for more widespread convective threat and resultant
increased training potential in the aft/eve. More clarity on
this part of the forecast in the next 24 hrs.

Any tstm activity should weaken in intensity as it slowly translates
east over the coast Sat eve/night with waning instability and
deepening coastal stable layer, but still potential for locally
heavy downpours and embedded thunderstorms.

Shortwave trough axis shears northeast of the area Sunday AM,
with cold front continuing to slowly slide just south and east.
Morning stratus/fog likely for coastal plain and lingering
morning shower activity possible for eastern areas, with gradual
drying from w to e expected as moist conveyor belt slides east
of the region. Afternoon sunshine on Sunday should lead to
another very warm day (lower to mid 80s coast, upper 80s to 90
NYC/NJ metro and interior), but significantly less humid,
keeping heat indices in lower 90s to 95 F.

Still warm, but less humid conditions Sunday Night. Patchy
radiation fog possible across outlying areas.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
The upper air pattern continues to feature a longwave trough over
central Canada into the midsection of the country with a ridge over
the western Atlantic. The pattern will gradually translate east.
Shortwave energy embedded within the longwave trough to the west
will then send a frontal system east across the Great Lakes and Ohio
Valley states Monday night into Tuesday. This will bring increasing
chances of convection Tuesday into Wednesday. While the forecast
follows closely the National Blend of Models, the 00Z operational
globals do point to drying the second half of Wednesday into
Thursday behind the cold front. This looks to hinge on the magnitude
of the shortwave trough lifting across the Northeast on Wednesday
and how quickly heights rise ahead of a pending frontal wave. Thus,
low chances of convection will continue during the midweek period.

The pattern also supports warm heights aloft and a deep-layered SW
flow over the area that will maintain above normal temperatures and
high humidity. There could be a slight cool down Thursday but this
will depend on how far east the aforementioned cold front is able to
progress. Daytime highs during this time will generally be in the
mid and upper 80s away from the immediate coast, along with some
lower 90s across metro NJ. Lows will mainly be in the upper 60s to
lower 70s, warmest across the NYC metro. Max heat indices have crept
up to around 95 for NE NJ into the Lower Hudson Valley for Monday
and Tuesday. Largely stayed close to national blended guidance for
this update.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
A trough of low pressure slowly shifts in from the west today
and remains in the vicinity through Saturday before a cold
front passes through Saturday night.

Mainly VFR with the exception of KGON today, and in any
shra/tstms this aftn/early eve. Lowering flight categories
otherwise tonight, with just about all terminals eventually
IFR/LIFR.

S to SE winds around 10kt this afternoon, then S 5-10kt tonight.


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

Occasional S wind G20kt possible at KJFK after 20Z.

Amendments will be likely for the timing of showers and
thunderstorms late this afternoon into this evening. There is
low confidence of seeing convection at any one terminal, but it
is likely to be in close proximity.

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

OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY...

Saturday: MVFR or lower conditions possible at times with
continued chance of showers/tstms.

Sunday and Monday: VFR.

Tuesday: Chance of sub-VFR in showers and thunderstorms in the
afternoon, mainly west of NYC.

Wednesday: Chance of sub-VFR in showers and thunderstorms.

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

&&

.MARINE...
Sub-advisory conditions this morning, giving way to gusts up to
25kt this aft/eve near the entrance to NY Harbor eastward to
western Great South Bay.

SCA cond likely tonight into Sat Night on the ocean as
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.

High pressure building across the waters Sunday into Tuesday will
result in a weak flow and sub-SCA conditions.

&&

.HYDROLOGY...
Isolated to scattered slow moving thunderstorms producing 1-2"/hr
rainfall rates are likely this aft/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. More clarity on this flash flood threat in the
next 24 hrs.

At this time, no widespread hydrologic concerns expected for Monday
through Thursday. However, there is the threat for localized heavy
rain with any thunderstorms that may develop Tuesday into
Wednesday.

&&

.TIDES/COASTAL FLOODING...
There is a moderate to high risk for rip current development along
NYC/LI ocean beaches today with a combo of 3-4ft S wind wave and 2
ft E/SE swell. The high risk is for W LI and NYC beaches this
aft/eve due to enhanced seabreeze formation and large tidal range.

There is a high risk of rip currents for all NYC and LI ocean
beaches on Saturday as S wind waves continues to build to 5 ft, with
continued 2 ft E/SE swell.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Risk for Rip Currents through Saturday evening for NYZ075-178-
     179.
     High Risk for Rip Currents from Saturday morning through Saturday
     evening for NYZ080-081.
NJ...Heat Advisory until 8 PM EDT Saturday for NJZ004-006-103>108.
MARINE...Small Craft Advisory from 8 PM this evening to 2 PM EDT Sunday
     for ANZ350-353.
     Small Craft Advisory until 2 PM EDT Sunday for ANZ355.

&&

$$

SYNOPSIS...NV/DW
NEAR TERM...BC/NV
SHORT TERM...NV
LONG TERM...DW
AVIATION...JC
MARINE...NV/DW
HYDROLOGY...NV/DW
TIDES/COASTAL FLOODING...