340
FXUS61 KOKX 060736
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
336 AM EDT Sat Jul 6 2024

.SYNOPSIS...
A trough of low pressure lingers over the area through Saturday
afternoon as a cold front approaches. The front then stalls and
lingers into Sunday before dissipating as high pressure builds
from the west. 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 /THROUGH TONIGHT/...

***Key Points***

1.) Scattered showers/thunderstorms are likely this morning around
daybreak, particularly for areas north & west of NYC with isolated
instances of flashing flooding possible.

2.) Heat Advisories have been hoisted today across NE NJ, NYC, N
Nassau Co, Lower Hudson Valley and Fairfield Co. Heat index values
could reach up to 105F for southern portions of NE NJ. All other
areas under the Heat Advisory could see heat indices peak between 98-
100F.

3.) Showers and thunderstorms may re-develop this afternoon &
evening. Chances look better for interior locations, but confidence
is low in coverage and timing. For now, leaning toward isolated
thunderstorms.

A prefrontal surface trough is expected to linger over the area
through this morning and into the afternoon before a weak cold front
approaches from the west and slowly passes and stalls tonight. This
occurs in tandem with an upper-level trough to our north which
weakens through Saturday into Saturday night. The environment today
is weakly-forced, making the timing and location of showers and
thunderstorms hard to pinpoint. However, a few rounds of showers
and/or thunderstorms appear to occur based on the latest 00Z
guidance from CAMs and subsequent runs of the HRRR and RRFS.

This morning, scattered to numerous showers are possible for areas
north and west of NYC with all CAMs in agreement of occurrence,
likely stemming from a subtle shortwave modeled by some regional
and global guidance that brings pieces of mid-level energy into
the region. Location and coverage in areas east of NYC is
harder to determine, as not all CAMs agree, but coverage may be
more spotty, there. These showers and thunderstorms have already
initiated in eastern PA continue to expand in coverage as they
track eastward. The west- to- east window for showers and
thunderstorms this morning appears to be around 4am to 11am,
give or take an hour or so. SPC`s Mesoanalysis keeps an MLCAPE
environment of at least 500 J/kg across the CWA with a higher
concentration of 1000 J/kg west of NYC. MUCAPEs go even higher
around 1500-2000 across the area. Effective Bulk Shear appears
to to be strongest this morning in areas west and north of NYC,
so gusty to isolated instances of damaging wind can not be
completely ruled out. PWATs are currently between 2-2.2" inches
on SPC`s Mesoanalysis and remain elevated through the morning on
00Z and 03Z CAMs. 00Z HREF also brings a 20-30% chance of
>1"/hr in areas north and west of NYC. This increases to 30-50%
for the chances of >0.5"/hr. Moderate to heavy downpours may be
possible in these thunderstorms, but they should be moving quick
enough to limit any flash flood concern to isolated areas.
Currently they are moving at about 30-35kts. Primarily nuisance
urban and poor drainage flooding concerns with these morning
showers/thunderstorms.

Patchy fog is also being observed this morning and may continue
until mid-morning.

A break in the rain is expected mid/late morning into the afternoon.
There is some question to how much clearing occurs, but currently
keeping partly cloudy skies around for the afternoon. Despite the
cloud cover, dewpoints climb into the mid/low-70s with actual highs
in the upper-80s to low-90s in the NYC metro and areas N/W of NYC.
The rest of S CT and LI see highs in the mid/low-80s with far
eastern areas in the upper-70s for afternoon highs. Heat Advisories
have been hoisted today across NE NJ, NYC, N Nassau Co, Lower Hudson
Valley and Fairfield Co. Heat index values could reach up to 105F
for southern portions of NE NJ. All other areas under the Heat
Advisory could see heat indices peak between 98-100F. Some guidance
appears to veer winds from S to SW late in the day, advecting in
drier low-level air. Should this occur earlier than expected, heat
advisory criteria may be more on the marginal side, but for now,
expecting a later arrival of this drier air.

Confidence in the details of afternoon and evening
thunderstorms is lower, but currently expecting isolated
showers and thunderstorms across the area. Its possible they
may be scattered in interior areas. The latest CAMS show MLCAPE
and MUCAPE values around 2000+ J/kg for Nassau Co, Fairfield Co,
and all points west. This area will be the main focus for any
stronger thunderstorms that occur with overlapping values of
30-45 kts of 0-6km Bulk Shear. PWATs will be dropping below 2
inches around this time frame, so heavier downpours, while still
possible, are less likely to occur compared to this morning`s
round.

After about 9 or 10pm, most of the shower and thunderstorm
activity should be cleared out of the area with a front stalling
across the area. Patchy fog may occur with persistent cloud
cover across eastern areas, but will mainly depend on where the
weak front stalls. Overnight lows will drop into the
low/mid-70s.

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
The stalled cold front will dissipate on Sunday as surface high
pressure builds in from the west under upper-level ridging.
Southerly flow will continue with another warm day expected as
highs reach the mid-80s to low-90s again. Heat index values are
expected to be right around 95 for much of the area on Sunday
which may or may not require another Heat Advisory, depending on
location. These heat indices are much lower for areas of the
NYC metro and areas N & W of NYC compared to Saturday`s because
of somewhat drier air behind the front. We`ll have a break from
rain chances starting on Sunday.

&&

.LONG TERM /MONDAY 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. 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.

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 /07Z SATURDAY THROUGH WEDNESDAY/...
A slow moving frontal system impacts the terminals through
Saturday night.

Another round of showers and thunderstorms developing across
eastern PA looks to impact the NYC and Lower Hudson Valley
terminals from 09Z to 13Z. The eastern terminals right now look
to be on the eastern edge and coverage looks more spotty at
this time. Otherwise, expect widespread IFR/LIFR conditions
overnight. KSWF and the NYC terminals will be on the western
edge of the low clouds and ceilings. These areas may see more
variability in flight categories .

VFR conditions are forecast to return to all terminals by
early this afternoon with the exception of KGON where low
clouds/fog are likely to persist into Saturday night. It is
possible that the eastern terminals, KISP and KBDR hold on to
ceilings longer than currently forecast and could also see a
brief return during the evening hours Saturday.

S-SE winds under 10 kt this morning, become S-SW and increase
to 10-15 kt by afternoon. A few gusts up to 20 kt possible in
the afternoon west of the Hudson River.

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

Amendments are likely for changing flight categories as well as
timing of showers and thunderstorms through the day.

The best chance at this time for showers and thunderstorms looks
to be this morning between 09Z-13Z. Another round is possible
late this afternoon/early this evening, but confidence is lower
and activity should be more scattered in nature.

OUTLOOK FOR 06Z SATURDAY THROUGH WEDNESDAY...

Late Saturday Night: MVFR or lower possible, especially Long
Island and Southern CT.

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.

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...
Approaching shortwave and slow moving frontal boundary crossing
this morning into Saturday night will bring potential for
localized 1- 2"/hr rainfall rates with isolated to scattered
thunderstorms. The better chance will be SAturday morning, with
more isolated convection expected in the afternoon. 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.

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...Heat Advisory from noon today to 8 PM EDT this evening for
     CTZ005-009.
NY...Heat Advisory from noon today to 8 PM EDT this evening for
     NYZ067>075-176>178.
     High Risk for Rip Currents through this evening for NYZ075-080-081-
     178-179.
NJ...Heat Advisory from noon today to 8 PM EDT this evening for
     NJZ002.
     Heat Advisory until 8 PM EDT this evening for NJZ004-006-
     103>108.
MARINE...Small Craft Advisory until 8 AM EDT Sunday for ANZ350-353.
     Small Craft Advisory until 5 AM EDT Sunday for ANZ355.

&&

$$

SYNOPSIS...JM/BR
NEAR TERM...BR
SHORT TERM...BR
LONG TERM...JM
AVIATION...DW
MARINE...JM/BR
HYDROLOGY...JM/BR
TIDES/COASTAL FLOODING...