128
FXUS61 KOKX 061823
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
223 PM 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 /UNTIL 6 AM SUNDAY MORNING/...
Forecast remains on track with minor changes needed. Very humid
conditions across the area with dew points in the lower to
middle 70s. Highs should top out in the upper 80s to lower 90s
for across the NYC metro area and points north and west. Lower
to middle 80s are expected for Long island and southeastern
Connecticut, with even cooler conditions expected at the
immediate shore. Widespread heat index values over 95 expected
where Heat Advisories are currently in effect: NE NJ, NYC,
northern Nassau, the Lower Hudson Valley, and Fairfield county
in CT. Heat index values of 100-104 are expected across NE NJ,
and much of NYC. An isolated heat index reading 105 or slightly
higher is not out of the question. This would of course be
dependent on high much more humid it becomes and how much
warmer it gets (or doesn`t get), especially given convection
that is starting to develop across the interior and the
development of clouds in association with the convection. Parts
of NJ earlier today saw dew points in the upper 70s and even
some lower 80s, but they have now come down to the lower to
middle 70s.

***Key Points***

1.) Heat Advisories remains in effect 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.

2.) Isolated to scattered showers and thunderstorms re-develop
this afternoon & evening. Chances look better for western
locations.

A prefrontal surface trough is expected to linger just west of
the Hudson River this 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 tonight.

First round of showers and thunderstorms are moving out east
late this morning. CAPEs recuperate this afternoon, especially
INVOF NYC metro and areas north and west with partly sunny
conditions and a moist boundary layer. SBCAPES of 1500-2500
J/kg anticipated for these areas. With the trough in place and
subtle shortwave energy providing some mechanical lift, iso-sct
showers and thunderstorms anticipated for approx the western
half of the forecast area mid afternoon into early evening. Bulk
shear in combination with CAPE is enough for at least some
consideration of severe wind gust potential in thunderstorms,
mainly NW of NYC where conditions will be slightly more
favorable. Freezing/wet-bulb zero heights are rather high, so
while hail will be possible given CAPE and shear aloft, chances
are it won`t reach severe thresholds. 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.

Flash flooding threat remains lows this afternoon into evening.
PWATs have lowered to around 1.75" in the area where showers and
storms are more likely to occur, and the flow aloft is strong
enough to prevent very slow-moving cells. Should training occur,
there could be a low threat of flash flooding, but looking at
mainly minor urban/poor drainage flooding potential.

Dewpoints generally in the mid 70s this afternoon 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 remain posted across NE NJ, NYC, N Nassau Co,
Lower Hudson Valley and Fairfield Co. Heat index values could
reach up to 105F in spots for the urban corridor of NE NJ. All
other areas under the Heat Advisory could see heat indices peak
between 95-100F. 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 for some areas outside of NE NJ, but
for now, expecting a later arrival of this drier air.

&&

.SHORT TERM /6 AM SUNDAY MORNING 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 SATURDAY/...
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 /18Z SATURDAY THROUGH THURSDAY/...
A slow moving frontal system impacts the terminals through
tonight.

VFR outside of any shra/tstms. Exceptions are KISP/KGON which
should remain sub-vfr through the afternoon, although KISP could
be VFR for a few hours.

MVFR/IFR conditions probably work back as far west as KBDR
tonight due to weak flow and residual moisture and could get
close to KJFK as well overnight.

Winds S-SW 10-15 kt this afternoon. SW to light and variable
winds tonight.

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

TEMPO tsra this afternoon might not occur and might be just
shra. Threat of shra/tsra might end an hour earlier than
indicated in TAFs.

OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY...

Sunday PM: VFR

Monday: VFR.

Tuesday PM through Thursday : Periods of sub-VFR with
shra/tstms.

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 through
tonight 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...
Isolated to scattered convection this afternoon into early
evening brings a localized flash flood from any training
convection, with the threat maximized across NYC/NJ metro and
points N&W.

Enhanced moisture with a slow-moving cold front will bring a
chance of widespread minor/poor drainage flooding as well as
potential localized flash flooding Tuesday afternoon through
Wednesday morning.

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 until 8 PM EDT this evening for CTZ005-009.
NY...Heat Advisory until 8 PM EDT this evening for NYZ067>075-
     176>178.
     High Risk for Rip Currents until 9 PM EDT this evening for NYZ075-
     080-081-178-179.
NJ...Heat Advisory until 8 PM EDT this evening for NJZ002-004-006-
     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...JP/BR
SHORT TERM...BR
LONG TERM...JM
AVIATION...JC
MARINE...JM/BR
HYDROLOGY...JM/BR
TIDES/COASTAL FLOODING...