discussion on 2024-02-12

000
FXUS61 KOKX 120950
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
450 AM EST Mon Feb 12 2024

.SYNOPSIS...
-- Changed Discussion --Weak high pressure across the area today will give way to a
storm system approaching from the southwest. Deepening low
pressure moves into the Tennessee Valley tonight with a
secondary forming near the Delmarva region Tuesday morning. The
coastal low will deepen while passing to the south and east of
Long Island during the day Tuesday. High pressure will return
from Wednesday into Thursday before an Alberta Clipper low
passes through Thursday night into Friday. Another low may
impact the region next weekend.-- End Changed Discussion --

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --Weak high pressure will remain across the area today as the
forecast area resides on the northern edge of high clouds
associated with a storm system over the southern states. The
latter of which will become a big player in the forecast late
tonight into Tuesday. Skies may vary between mostly cloudy
across LI/NYC metro, to partly/mostly sunny inland. It will be
another mild day with highs in the upper 40s. This is about 5 to
8 degrees below normal.-- End Changed Discussion --

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...

-- Changed Discussion --* Major winter storm to impact area late tonight into Tuesday.

* Guidance has trended colder the last 24h with the potential
for 6+ inches across coastal locations. The Connecticut coast,
southern Westchester, and portions of interior NE NJ have been
included in a Winter Storm Warming. For Long Island, NYC, and
adjacent areas of NE NJ, there is a Winter Storm Watch.

* Confidence is high across CT, the Lower Hudson Valley, and
interior NE NJ for 6+ inches of snow. There is medium
confidence for the watch area with high confidence of 3+
inches

* The greatest uncertainty is across the NYC metro area and Long
Island for the timing of rain changing over to snow. At this
time, this looks to be around 7-8am Tuesday.

Overall model guidance in recent says has been pretty good with
respect to the track of low pressure that will impact the area
late tonight into Tuesday, Where there has been uncertainty is
with the rain/snow line across the area with only a marginally
cold airmass in place. However, the last 24h specifically, from
the 18Z cycle and beyond, there has been enough of a southward
trend of the low to expand the potential for 6+ inches down to
the coast. The southward trend has also placed the area in a
favorable area of deformation/frontogenetic forcing with the 85h
and 50h low to the south of the area. Thus, the potential for
heavy banded snow to the north and west of the low track.

There is good agreement with 1-1.25 inches of liquid equivalent
with the possibility of locally higher amounts. Interior locations
and even down to coastal CT may see some brief rain at the
onset, but this is largely an all snow event for these locations.
Even across LI and NYC, with the changeover occurring near daybreak,
there could be 0.75 to 1" of liquid equivalent that is snow.
SLRs at the coast will likely be low at the onset, but then
increase as the snow becomes heavy and low-level winds become
more northerly. For thermo profiles, used a blend between the
colder NAM and warmer GFS. This should result in temperatures at
the height of the heaviest snow in the lower 30s. For snowfall
totals, expecting 8 to 12 inches in the warning area and the
potential of 5 to 8 inches in the watch area. SPC HREF showing
high probabilities of more than an inch an hour inland with even
50-60% probs some hours at the coast. There could be some
hours, especially inland of 2 to 3 inches an hour.

Much of the precipitation moves in during the early morning
hours Tuesday, becoming heaviest toward daybreak into early
afternoon. Snow ends from west to east in the afternoon. In
addition, NE to N winds at the height of the storm will gusts 25
to 35 mph, strongest along the coast. There could even be a few
higher gusts up to 40 mph. This will further restrict visibilities.
However, with the wet nature of the snow any blizzard-like
conditions are expected to be of short duration.

NW winds on the backside of the low gradually subside Tuesday
night with clearing skies. Lows will be close to normal and
mainly in the 20s.-- End Changed Discussion --

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --There has not been too much change to the forecast thinking
Tuesday night into next weekend.

*Key Points*

* Temperatures look to be below normal with mainly dry
conditions this period.

* A fast moving clipper system passes across the northeast
Thursday night.

* Forecast confidence lowers next weekend as there are some
indications of another low pressure moving near the region.

High pressure builds towards the eastern seaboard on Wednesday.
The ridge axis will be over the area Wednesday night before
shifting offshore on Thursday. The deterministic and ensemble
means are in good agreement on this scenario. A fast moving
Alberta Clipper low continues to be signaled on the guidance for
Thursday night. A general consensus has the surface low passing
over New England. Overall moisture is limited, but there should
be a brief period of lift to continue with chances of
precipitation. NBM precip probabilities support predominately
snow showers inland, but a mix of rain and snow showers to the
coast. The more northern track of the clipper low would
introduce slightly milder air towards the coast. If the low were
to trend further south, colder air and higher chances of a
period of snow showers could occur across the entire area. It is
important to note this is a fast moving system which limits the
amount of precip that could fall.

The modeling diverges Friday into the upcoming weekend. Another
fast moving northern stream shortwave may approach next Saturday
and could have some interaction with a southern stream system.
Other guidance hints that the northern stream may be suppressive
limiting any precip chances and low pressure development. It is
still much too early for any details on p-types and impacts as
each scenario seems plausible. For now NBM slight chance PoPs
Saturday into Saturday night look reasonable.-- End Changed Discussion --

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --High pressure remains in control through this evening. Low pressure
approaches the region from the southwest tonight passing south of
the area on Tuesday.

VFR conditions expected today and into the first half of tonight.
MVFR or lower conditions expected around or just after 06Z Tuesday
as precipitation begins to move in for the metro terminals.
Precipitation likely starts as all rain, changing to a rain/snow mix
beginning between 10-12z Tuesday morning and into early Tuesday
morning as colder air moves into the area for the NYC terminals.
There is a low end chance that some ice pellets mix in during the
transition from rain to snow, but this should be brief and
confidence is not high enough to include in the TAF. Further north,
(KSWF) it will be cold enough for this to be an all snow event.

Light winds are expected through mid morning. Winds turn more
towards the south remaining under 10 kt late this morning into the
afternoon. Winds become more easterly tonight, and increase through
the night. Towards the end of the TAF period, winds will be from the
NW.

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

No unscheduled amendments expected through 00z Tuesday.

OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY...

Tonight...IFR or lower conditions likely. At KSWF/KHPN,
precipitation is expected to start and remain all snow. At KBDR and
KGON, precipitation may start off as a rain/snow mix, then changing
to all snow late Monday night. Elsewhere, rain possibly mixing with
snow or sleet towards daybreak. NE winds 10-15 G20-25 kt late,
highest NYC metro/coast.

Tuesday...IFR or lower cond likely. Any rain changes to all snow
through the morning. Some sleet may mix in early in the morning.
Snow tapering off from W-E during the afternoon, with cond possibly
becoming VFR late. NE-N winds 15-20 G25-30kt, becoming NW in the
afternoon.

Tuesday night through Wednesday night...VFR. NW winds 10-15G20kt
daytime, and 10-15G20kt at night.

Thursday: VFR.

Thursday night: Chance of MVFR and snow showers. NW winds 10-15G20-
25kt late.

Friday: VFR. NW winds 10-15G20-25kt.

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

.MARINE...
-- Changed Discussion --Quiet conditions today with weak high pressure across the waters.

NE winds increase tonight ahead of an approaching deepening low
pressure system from the southwest. The low then passes just
south and east of the ocean waters on Tuesday. This will allow
winds to reach gale force on the ocean on Tuesday, with a gale
warning now in effect. A few gusts to 35 kt may also be
possible on the eastern Sound and the bays of Long Island, with
SCA cond elsewhere.

Winds on the waters will weaken somewhat Tuesday night as the
storm system departs. This will be short-lived as high
pressure builds in from the west Wednesday increasing the
pressure gradient. SCA winds are likely on all waters and there
is even a chance for gale force gusts on the ocean. Winds begin
to weaken on the non-ocean waters Wednesday night could remain
near SCA levels on the eastern Bays and easter LI Sound with
ocean still 25-30 kt. Winds should fall below SCA levels
Thursday before potentially reach SCA levels Friday behind a
departing Clipper low pressure. Ocean seas will be elevated
Tuesday night through Wednesday night before briefly subsiding
below 5 ft Thursday. Elevated seas are possible to end the week.-- End Changed Discussion --

.HYDROLOGY...
There are no hydrologic issues expected at this time.

.TIDES/COASTAL FLOODING...
-- Changed Discussion --* Minor coastal flooding is likely during times of high tide through
tonight.

* Widespread minor and some moderate coastal flooding becoming
more likely with the Tuesday morning/midday high tides.

Forecast continues to be heavily based on Stevens NYHOPS guidance,
which has been performing reasonably well over the past 24 hours.

Have decided to leave the coastal flood statement for coastal
Fairfield/Westchester running through early this afternoon with the
expectation of minor thresholds just being reached at the Stamford
and Bridgeport gauges. A better chance of more widespread coastal
flooding will be possible tonight, so have gone ahead and issued a
coastal flood advisory for tonight`s high tide cycle.

A coastal flood advisory remains in effect for the south shore of
Nassau County for the high tide cycles today and tonight. Further
west, most of the guidance has the high tides falling just short of
reaching minor thresholds.

Depending on how some of the tides behave with todays high tide
cycles, a statement or advisory may be needed tonight. Areas that
might eventually need an advisory include southwestern Suffolk,
southern Queens, southern Brooklyn, Lower NY Harbor and parts of
western Long Island Sound. Nassau County already has an advisory up.

Have not change any headlines for Tuesday, there`s enough confidence
in moderate flooding to put up a coastal flood watch for Southern
Nassau County. Localized moderate coastal flooding is possible for
Southwestern Suffolk County. Otherwise, widespread minor coastal
flooding is looking more probable for all but along the eastern
Sound and along Peconic/Gardiners Bays. Just like Monday night,
there`s still time to gain more confidence in the extent of minor
flooding before issuing headlines. Timing of a wind shift from NE to
N on Tuesday brings some uncertainty on how quickly some drainage
help could occur as well as the amount of time the north shore of
Long Island is exposed to a more direct onshore flow.-- End Changed Discussion --

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...Winter Storm Warning from 1 AM to 6 PM EST Tuesday for
CTZ005>012.
Coastal Flood Advisory from 11 PM this evening to 2 AM EST
Tuesday for CTZ009.
NY...Winter Storm Warning from 1 AM to 6 PM EST Tuesday for
NYZ067>071.
Coastal Flood Advisory from 11 PM this evening to 2 AM EST
Tuesday for NYZ071.
Winter Storm Watch from late tonight through Tuesday afternoon
for NYZ072>075-078>081-176>179.
Coastal Flood Advisory from 8 AM this morning to 10 AM EST
Tuesday for NYZ179.
Coastal Flood Watch from Tuesday morning through Tuesday
afternoon for NYZ179.
NJ...Winter Storm Warning from 1 AM to 6 PM EST Tuesday for NJZ002-
004-103>105.
Winter Storm Watch from late tonight through Tuesday afternoon
for NJZ006-106>108.
MARINE...Small Craft Advisory from 5 AM to 6 PM EST Tuesday for ANZ331-
332-335-338-340-345.
Gale Warning from 6 AM to 6 PM EST Tuesday for ANZ350-353-355.-- End Changed Discussion --

SYNOPSIS...DS/DW
NEAR TERM...DW
SHORT TERM...DW
LONG TERM...DS
AVIATION...BC
MARINE...DS/DW
HYDROLOGY...DW
TIDES/COASTAL FLOODING...//