291
FXUS61 KOKX 032010
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
410 PM EDT Sat Aug 3 2024
.SYNOPSIS...
-- Changed Discussion --
Low pressure and a frontal boundary remain in the vicinity through
Sunday night. A cold front then approaches on Monday and passes
through late at night. The front then stalls nearby through
Tuesday night before pushing just south and east of the area
Wednesday into Wednesday night as a weak area of low pressure
passes south of the area. The frontal boundary and remnants from
a tropical system slowly approach from the south through the
end of the week.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --
A flood watch and severe thunderstorm watch continue for this
afternoon and evening for portions of the forecast area.
Shortwave lift and instability will continue to produce showers and
thunderstorms into this evening. Most of the forecast area stands a
good chance of seeing some rainfall by the end of tonight, but
parts of SE CT and eastern LI could end up dry for the night as
the shortwave exits NE and instability diminishes as the night
wears on. The late night hours should then be dry for most
areas.
Shear is just strong enough for severe wind gusts and large hail
in the strongest convection. Meanwhile, MLCAPEs range from
1500-2500 J/KG over approx the western half of the forecast
area. Isolated to scattered instances of severe thunderstorms
are possible from Nassau and Fairfield Counties to points west.
As such, a severe thunderstorm watch is in effect for these
areas through 9pm this evening.
Another concern is flash flooding. Flow through the mid levels
will be unidirectional and aligned with the orientation of the
stalled boundary in the vicinity of the northern/western zone.
So although the forward motion of the cells won`t be very slow,
training is a possibility. Combined with PWATs 1.75-2.00
inches, hourly rainfall rates of 1-2 inches per hour and locally
briefly higher are possible. HREF probabilities show a 40-60%
chance of hourly rainfall rates of at least an inch per hour
this afternoon and evening in some areas. A flood watch for
flash flooding has therefore been issued for this afternoon
through midnight for NYC, Lower Hudson Valley, and NE NJ where
the combination of potential rainfall amount/rates and flash
flood guidance warrant a watch.
Otherwise, heat advisories remain unchanged into this evening
and muggy conditions continue overnight with lows mostly in the
70s.-- End Changed Discussion --
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/...
-- Changed Discussion --
A somewhat similar setup for Sunday as the frontal boundary will
still be over the area. A 500mb trough axis is progged to pass
through during the afternoon to evening hours, providing some lift
along with a 60-70kt jet streak region in the upper levels. There
will be a chance of showers and thunderstorms in the morning, but
they will become more likely starting in the afternoon. Training is
less of a concern this time, but the steering flow will be a little
weaker. PWATs still high enough however for the threat of isolated
flash flooding. The flooding threat should become a little more
clear after seeing how much rain falls through tonight. The rain
threat then diminishes along with the instability and lift in the
evening, with dry conditions everywhere by midnight. With weaker
shear and lower instability, the severe weather threat will be very
limited.
The frontal boundary dissipates just offshore and leaves us with
weak high pressure over the area during Monday. A cold front will
approach, bringing a chance of showers and thunderstorms during the
afternoon, mainly north of the city. The flooding threat looks to be
limited due to the relatively quick forward motion of any cells that
develop, and enough CAPE and shear introduces a low chance of strong
to severe wind gusts.
850mb temps are progged at 18-19C. There should be enough sunshine
and SW flow for mid 90s in the normally warmest spots with mostly
upper 80s to lower 90s elsewhere. Wind direction and low enough
boundary layer RH should allow for surface dewpoints to mix out a few
degrees during peak heating, so max heat indices will be generally
in the lower and middle 90s. With neither 100 degree heat indices on
Monday, nor 2-day criteria of 95+ indices, no heat advisories are
anticipated.-- End Changed Discussion --
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
-- Changed Discussion --
A cold front will be draped across the area Monday night. A weak
area of low pressure along the frontal boundary over the Central
Plains states will move east along the boundary, passing south of
the Great Lakes during the day Tuesday, then just south of the
forecast area by Wednesday morning. As the low pushes east, it may
help to push the front just south of the area Wednesday afternoon
and night. Unsettled conditions are expected Monday night through
Wednesday with the front in the vicinity, then low pressure moving
nearby. However, the best chances for any showers and thunderstorms
will be with the low Tuesday night into Wednesday.
Chances for precipitation then drop off, and may drop off further
with more model runs if high pressure nudges more into the forecast
area than is currently forecast. However, given uncertainty in this
time frame onward, did not veer too far from NBM. Thereafter, even
more uncertainty in the forecast given the location of the remnants
of the potential tropical system and its interaction with the
frontal boundary leading to uncertainty in placement of any
potential for heavy rain during this time frame, so again stuck
close to the NBM. Therefore, unsettled weather is possible from the
middle of the week through the beginning of next weekend.
Easterly flow develops during this time frame, and in addition to
clouds and rain, this will lead to cooler conditions. Highs during
this time frame may will average below normal, and may not go above
80 for much of the region Wednesday, with slightly warmer, but still
below normal temperatures on Thursday. Conditions will still be
humid, but not like the extremely humid conditions we have been
experiencing as of late.
Low pressure over southeastern Canada, will slowly trek northeast
into the Canadian Maritimes by this evening. This will allow a cold
front to slowly approach today, moving through late in the
afternoon into the evening.-- End Changed Discussion --
&&
.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --
Weak low pressure will remain in the vicinity with a front lingering
into Sunday.
Mainly VFR expected into this evening. TSRA becoming more numerous
north and west of the NYC terminals into this evening. Thunderstorms
may produce gusty winds into the evening. TSRA/SHRA dissipate after
1Z with mostly dry conditions expected overnight. Low stratus may
develop overnight with MVFR conditions possible after 06-09Z and
into Sunday morning. MVFR cigs may linger into late morning/early
afternoon (15-18Z). Another round of TSRA is possible Sunday, mainly
from 19-23Z for the NYC and northwestern terminals.
A S/SW flow 10-15 kts with sea breeze enhancement through the
evening. A few gusts of 20-25 kt are possible, especially at
coastal terminals. Winds lessen and remain out of the SW tonight
through Sunday morning.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments possible with TSRA into this evening. Timing of MVFR cigs
late tonight may be off by an hour or two.
OUTLOOK FOR 21Z SUNDAY THROUGH THURSDAY...
Sunday: Chance of MVFR or lower in afternoon/evening in any
SHRA/TSRA.
Monday: VFR.
Tuesday-Wednesday: MVFR or lower possible in SHRA/TSRA.
Thursday: Mainly VFR. Chance of MVFR or lower in SHRA/TSRA.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
-- Changed Discussion --
Sub-SCA conditions expected for non-ocean waters through Monday
night. For the ocean, southerly fetch and swell will maintain seas
of at least 5 ft through Sunday evening. Have extended the SCA west
of Fire Island Inlet to go through midnight Sunday night, and
extended the SCA through all of Sunday night farther east. Sub-SCA
conditions follow for Monday.
Waves build on the ocean waters Monday night into Tuesday as low
pressure approaches and moves over the waters. Waves diminish
Tuesday afternoon as the low pushes east of the region. Waves
increase again later in the week with building long period
southerly swells from a tropical cyclone. Refer to latest
forecast information from the NHC.-- End Changed Discussion --
&&
.HYDROLOGY...
-- Changed Discussion --
Rainfall rates of 1-2 inches per hour and locally higher will be
possible into this evening. Given 1 and 3-hour flash flood guidance,
isolated to scattered instances of flash flooding will be possible
during this time, then generally dry conditions overnight.
Another round of showers and thunderstorms is anticipated Sunday
afternoon, potentially lasting into the evening. The extent of
potential flash flooding will partly depend on what occurs
through this evening, but it appears at least isolated flash
flooding can occur. No hydrologic issues are expected after
early evening Sunday through Monday night.
There is the potential for heavy rainfall Tuesday into Wednesday as
a weak area of low pressure moves along a stalled frontal boundary
in the vicinity of the forecast area. However, there remains a good
deal of uncertainty in exactly where the axis of heavy rain will set
up.
Another round of heavy rainfall is possible for the end of the week
into the beginning of next weekend with the remnants of the
tropical system. There is even more uncertainty with this feature.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
-- Changed Discussion --
A high risk of rip currents continues into this evening and is
expected to continue all the way through Monday evening. This is
due to southerly swells of around 5 feet.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...Air Quality Alert until 11 PM EDT this evening for CTZ005-006-
009-010.
Heat Advisory until 7 PM EDT this evening for CTZ005>011.
NY...Air Quality Alert until 11 PM EDT this evening for NYZ069>075-
078>081-176>179.
Heat Advisory until 7 PM EDT this evening for NYZ067>075-078-
080-176>179.
Flood Watch until midnight EDT tonight for NYZ067>075-176-178.
High Risk for Rip Currents through Monday evening for NYZ075-080-
081-178-179.
NJ...Heat Advisory until 7 PM EDT this evening for NJZ002-004-006-
103>108.
Flood Watch until midnight EDT tonight for NJZ002-004-006-
103>108.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ350-353.
Small Craft Advisory until midnight EDT Sunday night for
ANZ355.-- End Changed Discussion --
&&
$$
SYNOPSIS...JC/JP
NEAR TERM...JC
SHORT TERM...JC
LONG TERM...JP
AVIATION...MW
MARINE...JC/JP
HYDROLOGY...JC/JP
TIDES/COASTAL FLOODING...