467
FXUS61 KOKX 121436
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1036 AM EDT Fri Jul 12 2024

.SYNOPSIS...
A stationary front along the east coast, from Maine into the
southeastern states, remains into Saturday as a wave of low
pressure tracks slowly northward from the Carolina coast.
The front washes out just south of the area on Sunday, otherwise,
a thermal trough sets up over the region Monday and Tuesday. A
cold front then approaches from the west on Wednesday, moving
through mid to late next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Only minor changes to the forecast with this update, mainly to
hourly temperatures, and lowered the highs a degree or two with
the extensive cloud cover, and scattered to numerous showers
expected.

Rain eventually becomes likely across the entire area today
into tonight. A stationary front will remain in close proximity
to the area during this period. A band of high moisture with
PWATS of 2-2.25 inches along the western periphery of a western
Atlantic ridge shifts NW into the vicinity of our western zones
today. The band then stalls/pivots late day into this evening
before beginning to shift back east late tonight. Showers will
be focused along this shifting band as shortwaves aloft provide
some lift, and moisture convergence will be enhanced along the
stalled front with further enhancement inland on a southerly
flow. With the front progged to remain somewhere within the
western half of the forecast area and coincide with enhanced
PWATs, flooding concerns have increased. Thunderstorms will be
possible starting late this morning, and while they are not
expected to be severe, they would still serve to help realize
potential rainfall amounts in this moist airmass.

With the threat of flash flooding remaining, a flood watch
remains in effect from this afternoon through Saturday
afternoon for NE NJ, NYC the Lower Hudson Valley, as well as
Nassau and Fairfield Counties. Given flash flood guidance and
where rainfall is currently forecast to be the greatest, did not
have confidence to include any areas east of Fairfield and
Nassau Counties. This is in line with WPC`s ERO slight risk for
day 1. Will however buffer the timing to include all of Saturday
afternoon after collaboration with all of the surrounding
offices. See the hydrology section below for more details.

High temperatures today will be mostly the the middle and upper 80s,
with lows 70-75.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
PWAT axis and heavy rainfall potential shift back east through the
forecast area during the day on Saturday. PoPs lower in the
afternoon, but rain still appears to be likely east of the city by
early to mid afternoon. The frontal boundary doesn`t make much
progress, and may even begin to dissipate. Will need to monitor
trends to see if other areas of southern CT need to be added to the
Flood Watch. The steering flow will strengthen as Saturday wears on,
so this along with current FFG will be mitigating factors for the
flash flooding potential farther east from where the watch currently
exists.

Conditions then dry out Saturday night with dewpoints slowly
lowering. Highs on Saturday in the 80s with mostly 70s for overnight
lows.

Weak high pressure will be in control for Sunday with dry
weather anticipated. 850mb temps increase 17-19C, highest over
western sections. NBM looked reasonable for ambient
temperatures, but probably too high for areas outside of an
onshore flow. W to SW winds will probably help mix out the
surface dewpoints a little during peak heating as the boundary
layer is progged to be dry enough to support. Took a blend of
NBM, CONSALL and superblend for dewpoints. This results in heat
indices reaching at least 95 for portions of the forecast area.
A heat advisory may be needed for these areas as it would be the
start of potentially 4 consecutive days of heat advisory
criteria for parts of the forecast area.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Key points:

* Increasing confidence in an early to mid week heat wave. Afternoon
  heat indices may approach or exceed 100F at times. Highest across
  urban and interior locations.

* Chance for PM showers and thunderstorms, mainly north and west of
  NYC Monday and Tuesday. More widespread chances Wednesday into
  Wednesday night ahead of a frontal passage.

No significant changes with this update in the long term. The period
starts hot and humid, and while heights will not be remarkably high,
the forecast area will reside at the southern edge of the westerlies
and result in a deep-layered westerly flow, transporting anomalously
warm air into the region. Ensemble means prog H85 temps around 20C
by Monday, and into the low 20s Tuesday into Wednesday. In addition,
the low-level flow will be more from the SW, which will lessen the
marine influence, especially just inland from the coast. High temps
for much of the area early to mid week will be in the low to mid 90s
with the exception of immediate coastal locations. Upper 90s are
possible in the urban NE NJ corridor, and not out of the question a
few locales touch triple digits. Forecast stayed very close to the
NBM. For dew points however, continued to blend CONSALL in with the
NBM to bring values down a few degrees. With more of westerly flow
than the past heat event, expecting a bit drier air to mix down each
afternoon. This still results in widespread heat indices of 95 to
100 Monday through Wednesday. Heat headlines appear likely, and some
of the interior and urban locations could approach warning criteria
(heat indices of 105F+).

In addition, being at the southern edge of the westerlies will
result in less capping with the potential for diurnally driven
convection Monday and Tuesday afternoon, mainly north and west of
the NYC metro. A more widespread convective event is possible
Wednesday into Wednesday night as a cold front approaches from the
west and PWAT values increase to around 2 inches. Still some spread
in global ensembles, but it appears the fropa should help usher in a
drier and bit cooler regime behind it by late next week.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
A stationary front remains nearby into Saturday.

Varying categories with SHRA/TSRA at times thru the TAF period.
Showers pushing inland may lead to MVFR or IFR cigs/vsbys into
mid morning. Embedded thunderstorm possible with this activity.
Thereafter, the boundary shifts farther west, resulting in
continued scattered SHRA at times late this morning and early
afternoon over the NYC metro, NE NJ, and the LoHud. Eastern
terminals (KISP, KBDR, KGON) may remain mostly dry during this
time.

Heavier showers are possible in the afternoon and early evening, and
chances for TSRA increase in this window at NYC terminals, KHPN, and
KSWF, but timing and coverage is fairly uncertain. Another lull
likely develops by the evening hours, before coverage of
showers and possible thunderstorms return overnight, mainly
after 6Z Sat, with conditions potentially lowering toward IFR.
This may persist thru late Sat AM or early afternoon before
gradual improvement and return to VFR.

Light flow becomes predominantly southerly with speeds
generally increasing to 10 kt. Gusts up to 20 kt will be
possible in the afternoon, mainly for coastal terminals. Gusts
end in the early evening, with 10 kt or less southerly flow
persisting into early Saturday.

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

Timing of categorical changes could be off by several hours.

Low confidence in TSRA coverage and timing today and tonight.

Gusts this afternoon may be more occasional.

OUTLOOK FOR 15Z SATURDAY THROUGH TUESDAY...

Saturday: MVFR or lower with showers/thunderstorms early in the day.
Improvement to VFR by afternoon.

Sunday: VFR.

Monday and Tuesday: Mainly VFR. A chance of afternoon into early
evening showers and thunderstorms with MVFR possible, mainly north
and west of NYC terminals.

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

&&

.MARINE...
No changes to winds and seas at this time. Only minor changes
were made to the probabilities of rain through this afternoon.

Ocean seas remain elevated today into tonight with south to
southeast swells, so the SCA was extended through tonight and
may even need to be extended through Saturday night as
conditions will be marginal. Not enough confidence to extend it
that far out yet, but it at least appears that sub-advisory
condition will prevail on Sunday.

Winds and seas will then largely remain below SCA criteria
early to mid next week. Ocean seas may begin to approach 5 ft
late Wednesday ahead of an approaching front.

&&

.HYDROLOGY...
Rainfall today through Saturday afternoon is expected to range
mostly 1-2 inches in the areas currently with a Flood Watch, with
locally higher amounts possible. Timing of the greatest threat so
far appears to be this afternoon through Saturday morning, but
flooding will still be possible in the afternoon. Additionally,
a threat of minor flooding includes the morning primarily for NE
NJ and NYC. Mostly small stream and minor urban/poor drainage
flooding are anticipated, but isolated to scattered instances of
flash flooding will be possible during this time.

Given an abundantly moist air mass in place, any thunderstorms that
develop early to mid next week will have the potential to produce
locally heavy downpours that result in nuisance flooding,
particularly in urban and poor drainage areas.

&&

.TIDES/COASTAL FLOODING...
There is a high risk of rip current development along all ocean
beaches today through Saturday.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch through Saturday afternoon for CTZ005-009.
NY...Flood Watch through Saturday afternoon for NYZ067>075-176>179.
     High Risk for Rip Currents through Saturday evening for NYZ075-080-
     081-178-179.
NJ...Flood Watch through Saturday afternoon for NJZ002-004-006-
     103>108.
MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ350-353-
     355.

&&

$$

SYNOPSIS...JC/DR
NEAR TERM...JC/MET
SHORT TERM...JC
LONG TERM...DR
AVIATION...
MARINE...JC/DR/MET
HYDROLOGY...JC/DR
TIDES/COASTAL FLOODING...