000
FXUS61 KOKX 231447
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1047 AM EDT Sat Mar 23 2024

.SYNOPSIS...
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Low pressure approaches tonight into early Saturday, moving
across Saturday afternoon into early Saturday evening.
Thereafter, the low moves northeast of the region for the
remainder of Saturday night. High pressure builds Sunday, and
ridges down from the north Monday into Tuesday. A weakening warm
front approaches Tuesday night into early Wednesday. A frontal
system then pushes through slowly on Thursday with low pressure
forming along the boundary to the south and pushing offshore
into Friday. Weak high pressure attempts to build in afterwards.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Low pressure and an upper level trough approach tonight. Cloud
coverage becomes overcast as clouds lower into early Saturday
morning, with rain starting overnight and into daybreak
Saturday.

Depending on exact start time, there could be a wintry mix for
some parts of the interior but expect any accumulations of snow
to stay under an inch without any measurable ice accumulation.
There will be a possibility of some freezing rain for parts of
the interior, particularly for Orange County NY.

Precipitation type expected to be all rain after 5AM Saturday.

Lows will be established by late evening lower 30s for interior
to mid 30s to near 40 along the coast. Temperatures across
interior hold nearly steady overnight while closer to the coast,
they will gradually rise.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
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Flood watch extended for NE NJ, Lower Hudson Valley, and
Southern CT, same start time, 8AM Saturday but it goes until 8AM
Sunday. This extension is because some of the area rivers and
streams could still above their banks late Saturday night and
this could linger into early Sunday morning.

Flood watch remains in effect from 8AM Saturday through late
Saturday night, ending 2AM Sunday for Long Island and NYC.

Models with their axis of heaviest rainfall have some
variations but overall shows the higher amounts generally
between 2.5 and 4 inches from SW to NE from Northeast NJ
northeastward through Southwest CT.

Low pressure continues to approach the region Saturday with an
increase in SE flow. The trough will continue to approach as well
aloft with an associated increase in precipitable water. getting
above normal for this time of year. According to SPC OKX sounding
climatology, it will be above 90th percentile and near the max for
late March with perceptible waters forecast to get to near 1.2
inches. This will lead to a greater moisture potential with this
approaching system as a low level jet from the south increases.
Aloft, upper levels will have increasing jet as well and the local
region will be near right rear quad, increasing divergence and
increasing synoptic lift during the day.

Rain light in the morning, becomes steady. The rain picks up and
becomes heavy late morning into the afternoon. Heavy rain lingers
for eastern areas Saturday evening while to the west, rain will be
lighter and eventually taper off. Late Saturday night, rain
tapers off for eastern areas. The low pressure late Saturday night
will be moving northeast of the region towards the Canadian
Maritimes with high pressure starting to build in from the SE
Canada and into the Great Lakes. This will increase cold air
advection with gusty northerly flow Saturday night. Some of the
precipitation before totally ending could be a mix of rain snow
for some areas but this is a low chance and would be mainly across
the interior portions.

Winds pick up Saturday, will be higher within convective
elements. Winds become gusty everywhere Saturday night with
increase in pressure gradient between low moving northeast of the
area and high pressure to the west. Gusts up to 30 to 35 mph
during day Saturday, with gusts near 40 mph more likely Saturday
night, especially along the coast. Thunderstorms could produce
brief wind gusts to near 45 mph.

Concerning flood impacts, NE NJ and into Rockland appears to have
lowest amounts of rain needed for flash flooding, 1 to 1.5 inches
in a 3 to 6 hour window. That seems to be the general area where
flooding could more easily take place. See hydrology section for
more details.

The ensemble river forecasts depict a large majority of the area
rivers going into flood with this upcoming event, especially
taking the GEFS and NAEFS ensembles into account.

CAMs depict a large aggregate of heavy rainfall entering the
region from SW to NE Saturday afternoon. Eventually as this area
shifts NE towards Lower Hudson Valley and Southern Connecticut the
CAMs are indicating a squall line developing for the coastal
areas, parts of NYC through Long Island and Southern Connecticut
for the early evening hours. Here is where there could be
localized torrential downpours with chances for 1 inch per hour
rainfall rates as well as a fraction of the low level jet getting
mixed down via downward momentum of the heavy rain and within any
thunderstorms. This will be manifested as a downburst of winds
with wind gusts up to near 40 to 45 mph for brief periods of time.
CAMs are coherent in their reflectivity signatures but vary in
size and individual intensities.

Regarding thunderstorms, there are some mesoscale model
depictions of MUCAPE moving across parts of the coastal areas
Saturday afternoon and also within point selections on BUFKIT,
some narrow elevated CAPE. The timing shown however is more
during the afternoon and not as much during the early evening.
It appears the strongest vertical forcing and vorticity are
occurring afternoon into early evening along with increasing low
level frontogenesis. Chances for thunderstorms along southern
Long Island and ocean late Saturday afternoon into Saturday
evening are forecast. Slight chances of thunderstorms to the
north across the rest of the area are also forecast.
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&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
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The latest guidance is showing better agreement in getting precip
offshore and clear of far eastern sections Sunday AM. High pressure
to the north in Southern Canada slowly builds out of the northwest
on Sunday. Clearing takes place from west to east during the morning
and into the early afternoon. There remains some question as to how
much clearing takes place, especially further east. The second half
of the weekend however does appear to remain dry. As the offshore
low spins and rotates bands of showers well offshore, a few could
get close to far eastern areas but all in all the chance for showers
looks fairly remote, thus covered with only a slight chance /
minimal PoPs for far eastern areas Sunday night into early Mon AM.

The low will meander offshore through early Tuesday with the upper
level ridge axis approaching late Mon and likely passing through by
Tue AM. At the same time in the low levels high pressure ridges down
from the north along the northeast coastal plain. This should keep
the low levels dry and with sinking motion to the west of the
offshore low and frontal boundary expect a good deal of sunshine on
Tuesday. Some high clouds should start to push in for the afternoon
and evening in advance a warm front which draws closer Tuesday
night. For now kept Tue night dry as higher heights along the
eastern seaboard should slow down the advancement of lower clouds
and precip from the west. Heights lower for mid week and by
Wednesday the flow aloft becomes more cyclonic and thus introduced
chance PoPs, with some low end likely PoPs late in the day and at
night. Questions remain for Thursday with much of the global
deterministic guidance more to south and eventually to the east with a
wave of low pressure forming along a slow moving occluded / cold
frontal boundary for Thursday into Friday. Went a bit below
consensus / NBMEXP PoPs Thursday and Friday and kept chance to low
end chance PoPs in place for this timeframe with overall confidence
below average late in the period.

Temperatures will average a few degrees below normal Sunday through
Monday night, followed by slightly milder and near normal
temperatures for the remainder of the week.
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&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
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Low pressure approaches today and moves over the terminals this
afternoon.

IFR with occasional MVFR or LIFR is expected with rain today
through 22Z-00Z. Periods of +RA across most terminals,
especially on or around 19Z. Isolated TS not out of the
question Sat afternoon and evening. Have included TS at all
terminals, expect for KSWF, though the chance for occurrence is
still in question. Rainfall rates near 1" per hour possible
through this afternoon and/or early evening.

Winds are expected to shift S-SE in the next few hours for most
terminals 10-20kt with gusts 20-30kt. Some stronger wind gusts
likely to work down to near the surface during the day on
Saturday especially NYC terminals east where brief gusts to 40kt
possible during the afternoon and evening points east.
Immediately behind the low, winds shift to the N in the
afternoon for Western terminals. Wind shifts to N-NE as the low
passes Long Island late in the day.

LLWS for KNYC terminals and points east this morning and
afternoon, with 40-50kts of flow at 2kft, and guidance showing
around 40kts of shear through the layer. Highest potential
across LI and SE CT.

    NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

Amendments likely for changing CIGs and VSBY on Saturday. High
confidence in +RA potential Sat aft and evening NYC east. Low
confidence in TS potential.

OUTLOOK FOR 15Z SUNDAY THROUGH WEDNESDAY...

Sunday: VFR. N-NE wind gusts around 25kt.

Monday: VFR. NE gusts 20-25kt.

Tuesday and Wednesday: VFR.

Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
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&&

.MARINE...
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Sub-SCA conditions tonight. SCA for non-ocean Saturday but
brief gale force gusts possible with heavy rain and any possible
thunderstorms late afternoon. Low level jet will be closer to
the region so the ocean goes from SCA gust conditions in the
morning to gales in the afternoon. Gales expected for all waters
Saturday night, continuing into Sunday morning.

Gales should give way to small craft conditions from west to
east on Sunday, with gales possibly lingering out on the eastern
ocean into a portion of Monday. Otherwise small craft
conditions will remain in place through Monday night for much of
the coastal waters with ocean seas remaining quite elevated.
Perhaps more marginal small craft conditions will remain for the
western non-ocean waters. Small craft seas will remain in place
for the ocean waters through Tuesday, with small craft gusts
perhaps only remaining for the far eastern waters into Tuesday
afternoon.
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&&

.HYDROLOGY...
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Total rain forecast, 2.5 to 3.5 inches with locally higher
amounts possible. This will give a chance for flooding,
especially Saturday afternoon into Saturday evening, when flash
flooding will be possible as well. There could be some residual
flooding with elevated rivers and streams after rain ends
Saturday night which could linger into early Sunday morning. NE
NJ into Rockland seems especially prone, where there is some of
the lowest flash flood guidance for 3 to 6 hours. Low-lying,
poor drainage and urban areas will also be prone to flooding.

MMEFS indicates potential, especially from GEFS, for some
moderate to possibly even localized major flooding for some
rivers, particularly for the Saddle River at Lodi. The moderate
flooding risk is if more than 3 inches of rain occurs within a 6
to 12 hour period and the major flooding risk is if more than 4
inches of rain occurs within a 6 to 12 hour period.

No hydrological impacts are anticipated in the long term Sunday
through Friday.
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&&

.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Flood Watch from Saturday morning through Sunday morning for
     CTZ005>012.
NY...Flood Watch from Saturday morning through Sunday morning for
     NYZ067>071.
     Flood Watch from Saturday morning through late Saturday night
     for NYZ072>075-078>081-176>179.
NJ...Flood Watch from Saturday morning through Sunday morning for
     NJZ002-004-006-103>108.
MARINE...Small Craft Advisory from 6 AM to 6 PM EDT Saturday for ANZ331-
     332-335-338-340-345.
     Gale Warning from 6 PM Saturday to noon EDT Sunday for ANZ331-
     332-335-338-340-345.
     Gale Warning from 6 AM Saturday to noon EDT Sunday for ANZ350-
     353-355.
-- End Changed Discussion --

&&

$$

SYNOPSIS...JE/JM
NEAR TERM...JE/JM
SHORT TERM...JM
LONG TERM...JE
AVIATION...JP
MARINE...JE/JM
HYDROLOGY...JE/JM