discussion on 2024-03-22

000
FXUS61 KOKX 222008
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
408 PM EDT Fri Mar 22 2024

.SYNOPSIS...
-- Changed Discussion --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/...
-- Changed Discussion --Low pressure and an upper level trough approach Friday night. For
Friday night, cloud coverage will eventually become overcast
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/...
-- Changed Discussion --Flood watch remains in effect from 8AM Saturday through late
Saturday night, ending 2AM Sunday.

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.
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.

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.

Thunderstorms, there is 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 to strongest vertical
forcing and vorticity are occurring late afternoon into early
evening. For Southern Connecticut, NYC and Long Island as well as
surrounding waters, will mention the possibility of thunderstorms.-- End Changed Discussion --

.LONG TERM /SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --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.-- End Changed Discussion --

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Low pressure approaches early Saturday and moves over the
terminals Saturday afternoon.

VFR into tonight with lowering ceilings. MVFR in -RA for the
Sat AM push, with the onset after 06Z Sat. 18z-03z IFR or lower
likely. Periods of +RA across most terminals. Isolated TS not
out of the question Sat afternoon and evening. Have included TS
at KJFK and may expand to KISP where the highest probability of
exists. Rainfall rates near 1" per hour possible for a time
late in the day NYC eastward.

Winds then shift more S-SE this evening into early Saturday and
increase to around 15-25kt late morning Saturday and continuing
in the afternoon. 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 after 18z Western terminals. Wind shifts to
N-NE as the low passes Long Island late in the day.

LLWS starting around 12Z for KNYC terminals and points east,
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.Timing
of LLWS onset early Saturday may be +/- an hour or two. High
confidence in +RA potential Sat aft and evening NYC east. Lower
confidence in TS potential KJFK and KISP.

OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY...

18z Saturday: IFR or lower in rain. Rain heavy at times into
evening. SE wind gusts 20-25kt during the day with LLWS possible
city east, becoming N all areas with gusts 30-35kt at night.

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

.MARINE...
-- Changed Discussion --Sub-SCA 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.-- End Changed Discussion --

.HYDROLOGY...
-- Changed Discussion --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. 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.

No hydrological impacts are anticipated in the long term Sunday
through Friday.-- End Changed Discussion --

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...Flood Watch from Saturday morning through late Saturday night
for CTZ005>012.
NY...Flood Watch from Saturday morning through late Saturday night
for NYZ067>075-078>081-176>179.
NJ...Flood Watch from Saturday morning through late Saturday night
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...JM
SHORT TERM...JM
LONG TERM...JE
AVIATION...IRD
MARINE...JE/JM
HYDROLOGY...JE/JM