000
FXUS61 KOKX 140005
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
805 PM EDT Sun Aug 13 2023
.SYNOPSIS...
A cold front shifts east of the region into this evening. High
pressure briefly builds in thereafter Monday, before a frontal
system impacts the area Monday night through Tuesday. High
pressure returns for Wednesday and Thursday, with a frontal
system impacting the region Thursday night into Friday. High
pressure returns Saturday.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Surface cold front continues to advance through the eastern
forecast region this evening. A few showers developed along
the3 frontal boundary, but have dissipated at the time of this
update. Behind the front, winds have shifted westerly in its
wake, allowing for drying conditions under a mix of clear skies
and scattered cu. Only minor changes have been made to the
current forecast to account for current observations and trends.
Weak high pressure briefly builds in tonight with a zonal flow
aloft. Dry conditions with mostly clear conditions this evening,
then maybe some cirrus sneaks in overnight as temperatures
bottom out in the 60s to around 70 in the urban metro.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
Surface high pressure shifts offshore Monday, but should be able to
maintain dry conditions into the afternoon. Clouds thicken more
noticeably in the afternoon as a frontal boundary approaches from
the south and west. Ahead of this, a seasonable mid August afternoon
is expected, with temperatures in the 80s.
Meanwhile, a digging H5 trough swings into the Great Lakes, with
associated surface low pressure tracking into the Midwest, and its
warm front lifting north through the Mid-Atlantic. A secondary
low center may form along this boundary as it approaches, and
the frontal wave moves through the local region overnight into
Tuesday morning, with the primary low and attendant cold front
moving through Tuesday night.
The primary concern with this system is the potential for flash
flooding. Models show anomalously deep moisture through the column,
PWATs exceeding 2 inches, about as high as they go locally per SPC
sounding climatology, shifting in Monday night into Tuesday morning.
WPC has expanded the slight risk of excessive rainfall to now
include almost the entirety of the forecast area. Total QPF has
nudged upwards from the previous forecast as well, with a widespread
1 to 1.5 inches, and locally heavier amounts.
Some uncertainty remains regarding the severe weather potential. CSU`s
12z MLP paints a 15% risk for severe wind across NE NJ, NYC, and the
lower Hudson Valley, with a 5% to 15% elsewhere. While speed and
directional shear will be present as the front lifts through,
instability will be a limiting factor, MLCAPE values remain largely
under 1000 J/kg per 12z HREF, though with the increased low level
helicity, 0 to 1 km values exceeding 100 m2/s2, can`t rule out
isolated severe weather, mainly a damaging wind gust or brief
tornado. CSU`s 12z MLP paints a 15% risk for severe wind across
NE NJ, NYC, and the lower Hudson Valley, with a 5% to 15%
elsewhere. SPC has maintained a marginal risk into Tuesday AM
for all but southern CT.
The steadiest, heaviest rain looks to occur overnight into Tuesday
morning when moisture convergence is maximized as the frontal wave
tracks over the region. Localized rainfall rates of 1 to 2 inches
is possible during this period. The exact placement of the
synoptic features though will determine where the axis of
heaviest rainfall sets up, and this will need to be fine tuned
over the next day. Given this uncertainty, have held off on any
flood headlines for the time being.
Behind the moisture slug early Tuesday morning, a lull likely
develops over the region until the attendant cold front and
daytime instability is able to instigate scattered convection
in the afternoon and early evening. Once again, isolated strong
to severe thunderstorms will be possible, and could produce
locally heavy rainfall on top of what falls earlier.
The cold front moves through late Tuesday evening, and drier
air begins to advect into the region behind it as high pressure
returns.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
A mid-level ridge continues to build into the area Wednesday into
Thursday while high pressure builds in at the surface, keeping the
region dry with less cloud cover. Temperatures look to sit near or
just below seasonal as the ridge is not particularly strong.
Another shortwave digs into the Great Lakes and upper midwest
Thursday night into Friday. A cold front will pass with this
feature, with likely enough lift to produce isolated to scattered
showers, with some diurnal convection possible, though signals do
not look particularly strong for it. It will also depend on what
time the front ultimately passes.
High pressure builds to the south Friday night into Saturday and
with a west to southwest flow temperatures and dew points will be
increasing through next weekend.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
High pressure will build in from the west tonight into Monday. A
warm front approaches late Monday.
VFR conditions through 00z Tuesday. After 00z, a chances of MVFR
or lower in showers will be possible.
Winds become light and westerly tonight with wind speeds less
than 10 kts. Some terminals will have variable wind direction
with wind speeds 5 kts or less tonight. A more southerly flow
develops Monday afternoon near 10 kt.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of the winds turning south on Monday may be off by an
hour or two.
OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY...
Monday night through Tuesday: Showers, possibly heavy at times.
A chance of thunderstorms. MVFR or lower possible at times.
Tuesday night: Chance of showers and thunderstorms, mainly in the
evening, especially east of NYC terminals. MVFR or lower possible at
times.
Wednesday through Thursday: VFR. Chance of showers late Thursday
night with MVFR or lower possible at times. S-SW wind gusts 15-20 kt
Thursday afternoon.
Friday: MVFR or lower possible at times. A chance of showers. Slight
chance of thunderstorms afternoon into early evening. W gusts near
20 kt.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Weak pressure fields will keep conditions on forecast waters below
SCA thresholds through Monday.
Persistent southerly flow develops Monday night into Tuesday
ahead of a cold front, and may allow ocean seas to build to near
5 feet late Tuesday into early Wednesday before subsiding.
Winds and seas remain below SCA levels across the forecast
waters Wednesday and Thursday. On Friday, winds will remain
below SCA criteria, but waves may reach 5 feet on ocean waters.
&&
.HYDROLOGY...
A widespread 1 to 1.5 inches of rainfall is forecast late Monday
through Tuesday, with locally higher amounts likely. Coupled
with wet antecedent conditions, moderate to heavy rainfall may
lead to scattered areas of flash flooding, particularly late
Monday night into Tuesday morning.
From Wednesday through the end of the week, no hydrologic impacts
are expected.
&&
.TIDES/COASTAL FLOODING...
There is a low risk for rip currents on Monday for NYC and Nassau
ocean beaches with a moderate risk farther east along Suffolk
ocean beaches.
A moderate risk for rip currents follows on Tuesday for all ocean
beaches.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...BR/DR
NEAR TERM...BR/DR
SHORT TERM...DR
LONG TERM...BR
AVIATION...BC
MARINE...BR/DR
HYDROLOGY...BR/DR
TIDES/COASTAL FLOODING...