000
FXUS61 KOKX 271940
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
340 PM EDT Thu Apr 27 2023
.SYNOPSIS...
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High pressure slowly pushes offshore tonight and into Friday as a
low pressure system approaches from the southwest into Friday night.
The low pressure moves through on Saturday followed quickly by a
stronger low pressure impacting the area Sunday into early
Monday. The low then meanders over the northeast into the middle
of next week.-- End Changed Discussion --
&&
.NEAR TERM /THROUGH FRIDAY/...
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Any isolated light showers will dissipate along with a general
thinning of the cloud cover as we progress into this evening with
the upper level shortwave moving east and the surface high pressure
filling back in briefly tonight. This will result in a dry and
partly clear night. Lows are expected to be in the 40s. Some
interior spots may drop into the upper 30s, especially if any
clearing occurs.
Upper level ridging amplifies over the area on Friday with surface
high pressure retreating to the east and a strengthening complex low
pressure system developing to the west and southwest. Much of the
day should remain dry as high pressure to the northeast should
prevent moisture from infiltrating the area until the late
afternoon. An increasing pressure gradient with the approach of
the developing low to the southwest will result in increasing SE
flow into the afternoon and evening. By late afternoon, rain
will gradually move into the area from southwest to northeast,
especially after sunset. Highs on Friday will be in the upper
50s to near 60.-- End Changed Discussion --
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
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SE flow continues to increase into Friday night with rain
overspreading the entire area as low pressure remains positioned
just south of the area. Widespread rainfall continues to
intensify overnight, becoming moderate at times, especially into
the early morning Saturday.
Low pressure positioned to the south of the area will slow its
northeastward progression but allow for widespread rainfall during
much of the day on Saturday. There are some indications that some
elevated instability develops for eastern portions of the area which
may result in isolated embedded thunder, though the chance remains
low. Strong SE flow may result in gusts along the coast upwards
of 35 to 40 mph. Overall, the rainfall totals from this first
event should be a widespread 1 to 1.5 inches of rain, with
greater totals expected along the coast.
A bulk of the rainfall should gradually push northeastward into
Saturday evening and overnight with a lull in the rain expected
overnight at some point. While widespread rainfall should diminish,
there may be scattered showers overnight Saturday into early Sunday
ahead of a secondary low pressure system moving into the area.-- End Changed Discussion --
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
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An unsettled weather pattern will persist for the second half of the
upcoming weekend into next week.
A warm front will lie nearby to Long Island to start the day on
Sunday. Initial shortwave will continue to move northeast of the
area. Attention quickly turns to a highly amplified synoptic pattern
with a southern stream shortwave over the Gulf States and a large
upper low over the Great Lakes. The larger upper low is going to
force the southern stream wave northeast and Sunday. The southern
stream then quickly phases into the upper low which becomes dominant
over much of the eastern US Sunday night into Monday. Surface low
pressure will rapidly deepen as it moves out of the southeast
towards the northeast on Sunday. The latest 12z model suite has the
low tracking from the Carolinas to somewhere over the northeast by
Sunday night. The low will then become vertically stacked with the
larger upper low later Monday into Monday night.
There will likely be a brief lull in widespread showers Sunday
morning with coverage increasing rapidly during the afternoon and
evening. It still appears that the core of the low level jet will
pass just off to our south and east. However, if the surface low
tracks a bit further west, then there is a chance for the low level
jet to end up overhead or nearby bringing deeper moisture. If the
low tracks more over Long Island (still within the ensemble spread),
then the low level jet and deepest moisture would end well offshore.
Despite the uncertainty with the low level jet, a period of moderate
to locally heavy rain is possible across much of the area late
Sunday into Sunday night. Strong large scale lift from falling
heights aloft along with PWATs 1.25-1.50 inches support this
potential. There is some elevated instability and have included
slight chance of thunder Sunday evening and night. Strong onshore
flow should limit surface instability.
This looks like a long duration rainfall event with some locally
heavy rainfall at times. The latest NBM 24 hour probability of
seeing greater than 1" of rain from 12z Sunday to 12z Monday is
about 50 to 70 percent. The latest NBM 24 hour probability of seeing
greater than 2" of rain during the same time period has increased in
recent runs to around 15 to 25 percent. However, the NBM probability
of seeing greater than 1 inch in any 6 hour period from 12z Sunday
through 12z Monday is low and less than 10 percent. This supports
the idea of a longer duration rainfall, but with minor impacts from
nuisance/urban flooding. Cannot completely rule out isolated flash
flooding in any heavier convection Sunday night.
Showers should taper off late Sunday night as a dry slot works its
way over the region. The low will lift north Monday before
meandering over the northeast into Wednesday and could even be
nearby on Thursday.
Gusty SE winds are expected Sunday night, especially across the
eastern portion of the area. The magnitude of the winds will be tied
to the exact track of the low, with a further west track bringing
potential for stronger winds further inland. Gusty SW-W winds are
then expected on Monday as the low lifts to the north.
Gusts 25-35 mph are possible Sunday night and then 20-30 mph on
Monday.
There are some differences with the handling and speed of the upper
low through the week, but the cyclonic flow aloft supports below
normal temperatures and varying degrees of cloud cover each day.
Energy within the upper low and some daytime heating could provide
some showers, especially inland Tuesday through Thursday.-- End Changed Discussion --
&&
.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
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A frontal boundary will remain stalled near the region through
tonight. Low pressure approaches from the southwest on Friday.
Generally looking at VFR or MVFR at the area terminals. These
conditions are expected through much of the TAF period, with better
chances of VFR conditions tonight and Friday. Rain chances increase
late in the 30-hour TAFs. Will include a PROB30 after 21z to account
for this.
Winds under 10 kt through the TAF period. Winds should be light and
variable across the interior, with more of a S or SE flow at the
coastal terminals.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
VFR potentially prevails the day at some terminals. Timing of MVFR
onset and ending may be off by a few hours.
OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY...
Friday afternoon-Friday Night: Mainly VFR during the day, then MVFR
or lower with increasing chances of rain at night. Rain becomes
likely late at night for NYC terminals and terminals to the north
and west. ESE- E wind gusts 15-20 kt.
Saturday: Rain with MVFR or lower. E wind gusts near 20-25 kt.
Sunday and Sunday night: MVFR or lower. Rain, mostly in the
afternoon and night. SE wind gusts 20-25 kt at night.
Monday: MVFR possible with a chance of rain showers. Wind direction
switches from more SE to eventually more WSW. Wind gusts 20-25 kt.
Tuesday: MVFR possible in showers. SW winds 10-15kt. Gusts up to
20kt possible.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
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Sub-SCA conditions are expected through much of the day on Friday
with light winds. The pressure gradient increases ahead of an
approaching low pressure system Friday night which will result in
SCA SE gusts to 25 kt on the ocean and NY Harbor as early as
22Z Friday. SCA SE gusts of 25-30 kt overspread the rest of the
waters by 6Z and linger through the day on Saturday. A Gale
Watch is in effect for the ocean waters beginning 10Z Saturday
as SE winds may approach 35 kt through much of the day as the
low is positioned just south of the area. Waves heights on the
ocean increase to 8-10 feet on Saturday as well.
Winds decrease quickly on Saturday night with sub-SCA conditions
expected for all sheltered waters. SCA conditions continue on the
ocean with wave heights remaining well above 5 ft.
Seas on the ocean remain elevated on Sunday with a SE swell, so SCA
conds will continue through the rest of the weekend. Winds ramp up
Sunday night with a low pressure center approaching from the Mid-
Atlantic with SCA probably on all waters, with winds probably still
gusting to 25 kt on Monday on the backside of the storm. Winds
should fall below SCA levels Monday night, but ocean seas will
likely remain elevated above 5 ft into Tuesday.-- End Changed Discussion --
&&
.HYDROLOGY...
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A storm system brings a widespread inch to inch and a half of
rainfall late Friday through Saturday. With moderate to locally
heavy rain at times, nuisance flooding will be possible,
particularly in vulnerable urban locales.
An additional inch to inch and a half of rainfall is possible during
mainly late Sunday into Sunday night. Again, mainly minor
nuisance/urban flooding would be the extent of hydrologic
impacts.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
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A strong SE flow due to a deepening low pressure on Sunday may bring
high tide levels Sunday evening to minor flood benchmarks. The main
concern at this time appears to be for the south shore Back Bays and
SW CT coast along the Western Long Island Sound. Tides are
relatively low astronomically, so approximately 2 to 3 ft surge is
needed to bring water levels to minor flooding at these locations
Sunday evening.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 2 AM to 6 PM EDT Saturday for ANZ331-
332-335-340-345.
Small Craft Advisory from 6 PM Friday to 6 PM EDT Saturday for
ANZ338.
Small Craft Advisory from 6 PM Friday to 6 AM EDT Saturday for
ANZ350-353-355.
Gale Watch from Saturday morning through Saturday afternoon
for ANZ350-353-355.-- End Changed Discussion --
&&
$$
SYNOPSIS...DS/MW
NEAR TERM...MW
SHORT TERM...MW
LONG TERM...DS
AVIATION...BC
MARINE...DS/MW
HYDROLOGY...DS/MW
TIDES/COASTAL FLOODING...