000
FXUS61 KOKX 131148
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
748 AM EDT Wed Sep 13 2023
.SYNOPSIS...
A cold front and wave of low pressure along it approach today,
moving through tonight. High pressure then builds in on Thursday,
remaining centered to the west through Friday, before weakening over
the weekend. At the same time, Hurricane Lee is forecast to pass
offshore to our east. A weak frontal system impacts the region
early next week.
Monitor https:/www.weather.gov/okx/tropical or
https:/www.nhc.noaa.gov for the latest NHC forecasts on Hurricane
Lee.
&&
.NEAR TERM /THROUGH TONIGHT/...
A closed low upper trough axis swings east through the Great
Lakes today. The primary surface low tracks into SE Canada as
an attendant cold front and weak surface wave approach the
local region. Along and ahead of this, showers and thunderstorms
will move into the area, continuing intermittently through this
evening.
First round of showers and embedded thunderstorms is entering
NE NJ and NYC as of daybreak, and this will spread east into
the remainder of the region through the morning hours. Locally
heavy downpours may lead to reduced visibilities and hazardous
travel conditions for the morning rush. There may be breaks in
the wet weather by late morning or early afternoon, allowing
additional convection to retire through the early evening.
The primary threat from this system is the potential for heavy
rainfall leading to flooding. Layer precipitable waters over 1.5
inches and parallel flow evident from low to upper levels may lead
to training of showers and thunderstorms. While typical nuisance
flooding of urban and poor drainage areas is likely, areas of flash
flooding also cannot be ruled out. The wet antecedent conditions
have lowered 1 hr FFG values, with some parts of NE NJ under an
inch. Given this, and the elevated potential to exceed this in
the abundantly moist environment, maintained the regionwide
Flood Watch into this evening. See hydro section for additional
details.
While instability is relatively weak, modest speed and directional
shear allowing for increased helicity in the low levels brings
at least the potential of a few strong or severe thunderstorms.
Isolated damaging wind gusts, and even a weak tornado or two,
would be the main hazards. SPC kept a 2% tornado risk outlined
for much of the forecast area.
Forecast highs are on the cooler side with the rain and clouds,
only ranging from the low to mid 70s. Surface features should
clear east of Long Island after midnight, with the region drying
out overnight as temperatures fall into the 50s and 60s.
&&
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
Dry conditions return Thursday as a 1022 mb surface high builds into
the Great Lakes on Thursday, setting up a NW flow over the local
region. This advects a much drier air mass into the region, and dew
pts plummet into the lower 50s by the afternoon, a refreshing change
from the recent regime. BUFKIT soundings prog 850mb temps around 9
or 10C, and with a well-mixed BL, afternoon temperatures should
average near or just a hair below normal in the low to mid 70s.
Abundant sunshine prevails.
Clear skies persist Thursday night, and temperatures bottom out in
the 50s for most. Parts of interior CT and the lower Hudson Valley
could fall into the 40s by daybreak, particularly if the flow
lightens enough. Largely followed a superblend of guidance for this
update.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
For Fri, high clouds in advance of Lee will be on the increase,
otherwise temps/dewpoints look similar to those for Thu. Northerly
winds between inland high pressure and Lee will also be on the
increase to 15G25mph as the pressure gradient increases between
inland high pressure and the outer circulation of Lee.
Strongest winds associated with Lee should arrive Fri night and
continue into Sat, with winds backing NW on Sat as the hurricane
passes well east. The hurricane`s wind field will be expanding in
size as it moves northward, and winds especially across coastal SE
CT and eastern Long Island could become strong, sustained 25-30 mph
with gusts up to 40 mph possible. Can`t rule out tropical storm
force winds in those areas right near the shoreline in areas with a
good NW-N exposure.
NBM PoP still clips eastern CT/Long Island on the periphery of Lee,
with only light rainfall amounts expected, at most.
WAA starts early next week, with slight chance for showers and
possibly a thunderstorm Mon/Tue.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
A cold front approaches and moves across the terminals
Wednesday afternoon into Wednesday night.
SHowers have moved through NYC terminals this morning with a few
thunderstorms north and west of city terminals. There is a
chance of thunderstorms with briefly heavy rain and gusty
winds 17Z-0Z this afternoon and evening; conditions may lower
to MVFR. Timing of the redevelopment of showers and
thunderstorms was pushed back a few hours from earlier
thinking. Lower confidence for thunder after 16/17Z, and storms
may be more isolated, however, went with a TEMPO group for the
chance. Showers end mid to late afternoon west, and not til
after 00Z Thursday east. The chance for showers and
thunderstorms are also included with PROB30s for later timing
near 00Z with MVFR conditions at times.
Light southerly flow continues before showers arrive in the
morning, with light and variable winds outside of the NYC metro
terminals. Winds gradually become SW ahead of the front, and
then W to N/NW behind the front. Winds remain rather light with
the passage of the front, and gusts are not expected.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments will be needed for timing of showers/thunderstorms,
and for lowering conditions. High confidence that showers and
thunderstorms occur, and moderate confidence with timing.
The John F. Kennedy International afternoon haze forecast for
this evening is MODERATE.
OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...
Wednesday night: VFR at the NYC terminals and west, showers,
with MVFR possible east, ending by late evening, 02Z, becoming
VFR.
Thursday - Friday: VFR. Northerly wind gusts around 15 to 20 kt
Thursday night through Friday night.
Saturday: Mainly VFR. NW wind gusts around 20 to 25 kt.
Sunday: VFR. West winds with gusts 15-20kt.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Ocean seas with long period swells continue to build. Have
extended the SCA on the ocean through 10Z Fri -- though this
will need further extension.
Non-ocean waters remain below SCA threshold through Thursday.
Ocean seas should continue to build on Thu, reaching 5-8 ft by late
day Thu, 8-12 ft Fri morning, and peaking at 9-14 ft Fri evening.
Seas will then actually start to slowly decrease Fri night into Sat
as strong offshore flow counteracts incoming swell, down to 8-12 ft
by daybreak Sat, 6-8 ft Sat evening, then below 5 ft by Sunday
afternoon.
Sustained N-NW winds or frequent gusts from Lee could peak at
tropical storm force (35 to 40 kt) Fri night into Sat, mainly
on the eastern ocean waters/sound. Elsewhere, SCA conditions
likely from Fri into Sat, with a few gusts up to 35 kt possible
Fri night/Sat AM.
&&
.HYDROLOGY...
Showers and thunderstorms into this evening will bring a widespread
1 to 2 inches of rainfall to the region, with locally 2 to 3
inches. Rainfall rates could reach 1 to 2 inches per hour in
heavier downpours.
This brings the possibility of flooding,especially in low
lying, poor drainage and urban areas. With recent rains, it
will not take much more than an inch in one hour to produce
flash flooding. A Flood Watch is in effect for the entire region
today -- until 6 PM for NE NJ, NYC, the lower Hudson Valley, SW
CT, and western Long Island, and until 2 AM for New Haven,
Middlesex, and New London counties, as well as Suffolk on Long
Island.
Thereafter, no hydrological issues are expected through early next
week.
&&
.TIDES/COASTAL FLOODING...
A High Surf Advisory is in effect today for Nassau and Suffolk
county beaches, and for all the ocean beaches Thursday, as surf
heights increase from 4 to 8 ft today to around 6 to 9 ft on
Thursday. Hazardous surf should continue into Saturday, and may
peak over 10 ft on Friday, similar to the fcst wave heights at
the offshore buoys. In combination with higher water levels due
to the new moon which occurs on Thursday, beach erosion may
also become a problem on Friday.
A high rip current risk statement is in effect for all beaches
through Friday, and will likely have to be extended into at
least Saturday based on the current fcst track and intensity of
Hurricane Lee.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch until 6 PM EDT this evening for CTZ005-009.
Flood Watch through late tonight for CTZ006>008-010>012.
NY...Flood Watch until 6 PM EDT this evening for NYZ067>075-176>179.
Flood Watch through late tonight for NYZ078>081.
High Risk for Rip Currents through Friday evening for NYZ075-080-
081-178-179.
High Surf Advisory from 9 PM this evening to 10 PM EDT
Thursday for NYZ075-178.
High Surf Advisory until 10 PM EDT Thursday for NYZ080-081-179.
NJ...Flood Watch until 6 PM EDT this evening for NJZ002-004-006-
103>108.
MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ350-353-355.
&&
$$
SYNOPSIS...BR/DR
NEAR TERM...DR
SHORT TERM...DR
LONG TERM...BR
AVIATION...BR
MARINE...BR/DR
HYDROLOGY...BR/DR
TIDES/COASTAL FLOODING...