000
FXUS61 KOKX 092316
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
716 PM EDT Wed Aug 9 2023
.SYNOPSIS...
Weak high pressure shifts offshore tonight, followed by a wave
of low pressure and its associated frontal system for Thursday
afternoon and evening. High pressure then quickly follows late
Thursday night into Friday and should last into at least part of
Saturday before another frontal system impacts the area into
early Sunday. High pressure briefly settles in again before
frontal system moves in late Monday to Tuesday timeframe.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
-- Changed Discussion --
Minor adjustments were made to account for temperatures
slightly warmer than forecasted in parts of CT and to account
for the diminished rain chance in parts of the Lower Hudson
Valley. Otherwise, forecast remains on track for tonight.
The slight chance of an isolated shower or t-storm across
western and northwestern sections this evening has now
diminished. Look for mainly clear skies into tonight as weak
high pressure will be in control. The winds will shift later
tonight so look for it to be not quite as cool as the previous
night. A wind shift more to the SW and eventually S towards Thu
morning will lead to dew points beginning to creep up. High
clouds begin to increase after midnight from west to east, with
mid clouds approaching toward daybreak, especially further west.
Lows tonight will be mainly in the lower to upper 60s, with
perhaps the NYC metro right around 70.-- End Changed Discussion --
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Clouds increase quickly Thursday morning as a warm frontal boundary
approach from the west and southwest. Look for showers to develop
mainly from west to east towards noon, and spread eastward during
the afternoon hours. Elevated instability is progged with the
approaching boundary, thus showers should pick up in intensity
during the afternoon with rumbles of thunder. Severe weather is not
expected initially with a lack of sfc based CAPE, but higher
instability lower down is expected to approach and arrive into the
very late afternoon and early evening. The convective allowing
models (CAMs) are suggesting a healthy rain event, along with a
potential squall line. The squall line poses a concern as far as
severe weather potential. A QLCS cannot be ruled out, and with a
higher helicity and lower level lapse rates towards the evening
commute, cannot rule out severe weather as SPC has a marginal risk
for a portion of the area, which may get expanded or even upgraded
at some point. This would especially be the case if the surface low
tracks further north. Have heavy rain and gusty wind enhanced
wording for the afternoon, then further east into the early and mid
evening further east. With Integrated water vapor transport (IVT)
increasing further east into the evening with theta-e values going
up and higher lower level lapse rates which could act upon any lower
level helicity, some rotating storms with an isolated tornado cannot
be ruled out.
As far as the heavy rain goes, WPC has upgraded the entire area from
a marginal to slight risk of excessive rainfall. High mean RH, warm
cloud layer to around 11 kft, and PWAT values getting close to 2
inches does suggest some flash flood risk. Due to the progressive
nature of the system, have held off on any Flood Watches for the
time being, but with this latest package consensus QPF amounts have
more than doubled. For most of the area the current thinking is 1 to
1.5 inches of rain, with certainly locally higher amounts of closer
to 3 inches possible due to the convective nature. The HREF PMM is
rather loud, with even higher totals locally. However, this output
has been overdone at times this season, so not quite ready to go
there yet, especially with the progressive nature of the system.
Repeating rain over the same area(s) are driving the excessive rain
/ flood risk and thus the WPC ERO upgrade.
Later Thursday evening the system gets further east with any
activity quickly ending and the line of convection offshore of
eastern areas, likely by midnight. In its wake drier air comes in on
a WNW flow. Clearing should set in fairly quickly later Thu night
with a subtle drop in dew points towards daybreak.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
A general trough will be situated overhead to start Friday as it
tracks east into NE CAN, dragging a cold front with it, leaving us
with north winds and drying dewpoints. Should see plenty of sunshine
with temperatures near or slightly below average for Friday. Some
radiational cooling possible Friday night with light winds and
mostly clear skies.
Saturday starts off with weak ridging early in the morning before a
weak trough settles in later in the day. Onshore flow returns as the
ridge exits, increasing moisture. A weak cold front that pushes in
late Saturday into early Sunday along with the 12Z GFS and 0Z ECMWF
showing some areas of MUCAPE and SBCAPE between 1000-2000 J/kg. With
ingredients in place, left a slight chance for thunderstorms
along with scattered showers for late Saturday, early Sunday.
A deep trough and associated low pressure builds to our west on
Sunday and tracks east towards us on Monday, passing Tuesday. This
will bring with it the chance for showers and thunderstorms. While
the timing is still less confident in this system, it appears best
timed for late Monday into Tuesday.
&&
.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
High pressure pushes off the Southeast coast tonight. Low pressure
then approaches from the west late tonight into early Thursday
morning.
VFR through tonight. MVFR or lower conditions by very late in the
TAF period as low pressure affects the area.
A W to WNW flow of 10 to 15 kt diminishes this afternoon and
evening, with gusts diminishing to 15 to around 20 kt. KJFK may hang
on 20-25 kt gusts over the next hour or so. Gusts should end around
or just before 00Z.
Tonight, the flow becomes light and turns more southerly. Winds
increase a bit on Thursday morning, with some occasional gusts
possible by late morning. Winds may turn more SE later in the
morning. There is a great deal of uncertainty with wind direction,
speed, and gusts due to uncertainty in strength and track of the low
pressure.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Gusts may diminish and end slightly earlier than forecast.
OUTLOOK FOR 18Z THURSDAY THROUGH SUNDAY...
Thursday: MVFR to IFR with Isolated thunderstorms possible. S to SE
wind gusts 15-20 kt. There is a great deal of uncertainty in wind
direction, speed, and gusts due to uncertainty in strength and track
of low pressure.
Thursday Night-Friday: Showers end early Thursday night, then VFR. W
wind gusts 15-20 kt on Friday.
Saturday-Sunday: Mainly VFR. Chance of showers late Saturday into
Sunday.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
The winds will be relatively light with a relatively weak pressure
gradient tonight. The winds will turn SW tonight, then more directly
out of the S towards Thu morning. Seas climb to about 4 ft for much
of the ocean waters later Thu afternoon as a frontal system
approaches. A period of marginal sustained small craft gusts will
become likely, especially further east on the ocean towards evening.
Otherwise sub small craft conditions prevail for the majority of the
time. A line of showers and thunderstorms may contain some stronger
gusts for the evening, before pushing to the east later Thu night.
The winds will then turn more WNW late Thu night behind the frontal
boundary.
Sub-SCA conditions are expected to persist Friday through Monday.
&&
.HYDROLOGY...
WPC has placed the entire CWA in a slight risk of excessive rainfall
on Thursday. The progressive nature of the storm system will likely
preclude widespread flooding from heavy rain, but some localized
flooding is possible in areas where repeated heavy rain takes place
in association with any thunderstorms for Thu afternoon and
evening.
&&
.TIDES/COASTAL FLOODING...
There is a moderate risk for rip currents on ocean beaches Thursday
and Friday.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Rip Current Risk until 9 PM EDT this evening for NYZ075-
080-081-178-179.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JE/BR
NEAR TERM...JE/BR
SHORT TERM...JE
LONG TERM...BR
AVIATION...JP
MARINE...JE/BR
HYDROLOGY...JE/BR
TIDES/COASTAL FLOODING...