discussion on 2024-02-13

000
FXUS61 KOKX 131130
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
630 AM EST Tue Feb 13 2024

.SYNOPSIS...
Deepening low pressure near the Delmarva will pass south of
Long Island this morning, and then well out to sea this
afternoon into tonight. High pressure will then build in from
the west through Thursday before an Alberta Clipper low passes
through Thursday night into Friday. A series of weak lows may
pass across during the weekend before high pressure returns
Monday.

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --*Winter Storm Warnings remain up across the entire forecast
area.

*Snowfall totals have dropped with a continued southward trend
of the low track. Expect 5-8 inches on average with locally
higher amounts.

Radar filling back in across the NYC metro and LI, which should
allow for a changeover to all snow in the hours and strong upper
lift and banded precipitation forms to the north and west of
deepening low pressure near the Delmarva. Reports across
portions of the Lower Hudson Valley of 2 to 4 inches in heavier
band that went through that area. Focus is expected to start
shifting to the south and east of this area over the next few
hours.

The biggest change to the forecast was a southward trend in the
low track the last 24h, but based on latest hires and 06Z NAM
and GFS this trend appears to have stopped. Generally looking at
widespread 5 to 8 inches across the area, which remains under a
winter storm warning. Locally higher amounts are possible in
any persistent banding.

This will be a quick moving storm that rapidly deepens while
passing south of LI this morning. The forecast areas resides in
a favorable zone for heavy banded snow with the 50h and 80h
lows passing to the south creating deformation/frontogenesis
across the area. Expect a 5-6 hour window this morning into
early this afternoon with 1"/hr rates and possibly 2" at times.
Snow ends from west to east this afternoon and shuts down
completely across far eastern areas by early this evening.
Temperatures at the height of the storm will right around
freezing, then may warm a bit in the afternoon as the snow comes
to an end.

With the southward trend of the storm track, winds have also
backed off a bit, but still see the potential of NE-N gusts of
20 to 30 mph, highest along the coast. A few higher gusts will
be possible across LI.-- End Changed Discussion --

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
NW winds on the backside of the low will gradually subside
tonight as the low pulls away out into the Atlantic with
clearing skies. Lows will be close to normal, in the 20s.

High pressure will gradually build toward the eastern seaboard
on Wednesday. NW winds on Wednesday will gust up to 30 mph. The
ridge axis will be over the area Wednesday night before
shifting offshore on Thursday. Temperatures during this time
will average several degrees below normal with highs in the 30s
Wednesday and lows Wednesday night in the upper teens inland
and 20s elsewhere.

.LONG TERM /THURSDAY THROUGH MONDAY/...
No major changes have been made to the long term Wednesday
through early next week.

Key Points:

* Temperatures look to be below normal through the weekend
before a slight warming trend early next week.

* A fast moving clipper system passes across the northeast
Thursday night followed by another potential fast moving
system early in the weekend.

A fast moving Alberta Clipper low continues to be signaled on
the guidance for Thursday night. The latest consensus takes the
surface low north of our area, which introduces slightly warmer
air. Moisture is still limited, but there is a brief window
Thursday night for enough lift to raise PoPs to high chance. NBM
precip probabilities continue support predominately snow
showers inland, but mainly rain with some wet snow mixed in
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. This is a fast moving system which
limits the amount of precip that could fall.

High pressure briefly returns Friday before modeling diverges
Friday night into the weekend. Another fast moving northern
stream shortwave approaches and could bring another clipper type
low. It is beginning to look like the northern stream will be
more suppressive and force any southern energy well south of the
area. It is still about 6 days out so the evolution could still
change. PoPs on the model consensus remain low with just a
chance of snow showers Friday night into Saturday. Uncertainty
increases further on Sunday as there could be another piece of
northern stream energy passing through, but moisture right now
looks very limited. High pressure may return early next week.

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
*Significant winter storm to impact the terminals Tuesday.

Low pressure approaches from the southwest overnight, passing south
of the area towards midday, before moving away late in the afternoon
and evening.

Precip will be mainly snow at the start for northern most terminals,
with a brief period of rain or a rain/snow mix at the more southern
terminals. Precip then changes to all snow with IFR conditions for
the more southern terminals by 10-12z. A low end chance remains that
some ice pellets mix in during the transition from rain to snow, but
confidence of occurrence is not high enough and duration not long
enough to warrant including in the TAF. Snow then continues through
the early afternoon, and will be heavy at times during the morning
with VLIFR visibilities. The snow tapers in the afternoon, with dry
conditions and VFR returning by late afternoon.

The winds increase into the morning push, and will probably be
strongest towards the tail end, or just after the AM push, with
sustained winds around 20kt and gusts around 30kt from 13z-17z from
the NE, then N. Winds back toward the NW late Tues aftn with gust
still 20-25kt. Gusts likely momentarily end Tue evening.

Forecast Airport Snowfall Totals:

KJFK/KLGA/KEWR/KTEB/KSWF: 5-8 inches

KISP/KHPN/KBDR/KGON: 6-10 inches

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

Amendments will be needed for flight category changes and probably
precip type timing adjustments approaching the morning push. Precip
at onset may be all snow at some of the terminals instead of a
rain/snow mix or all rain.

OUTLOOK FOR 06Z WEDNESDAY THROUGH SATURDAY...

Tuesday night through Wednesday night...VFR. NW winds G20-25kt
during the nighttime and around 30kt daytime Wed.

Thursday: VFR.

Thursday night: Chance of MVFR and snow showers or mixed rain/snow
showers. NW winds G25kt late.

Friday: VFR. NW winds G25-30kt.

Saturday: Chance of MVFR/IFR with snow showers.

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

.MARINE...
Gales Warning continues for the ocean waters today as NE winds
back around to the N as deepening low pressure passes to the
south of the waters. SCA elsewhere. Winds have been adjusted
slightly downward from previous forecasts as the low track has
trended southward. Winds on the waters will weaken late this
afternoon into tonight with SCA cond continuing mainly on the
ocean.

A steepening pressure gradient Wednesday will lead to SCA
conditions on all waters with potential for marginal gale force
gusts on the ocean. Winds begin to weaken on the waters
Wednesday night, falling below SCA levels Thursday before
potentially reach SCA levels Thursday night into Friday. Ocean
seas will be elevated through Wednesday night before briefly
subsiding below 5 ft Thursday. Elevated seas are briefly
possible Friday but should be below SCA levels next Saturday.

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

.TIDES/COASTAL FLOODING...
* Widespread minor to locally moderate coastal flooding with
the Tuesday morning/midday high tides.

* Minor coastal flooding likely Tuesday Night for the south
shore of Nassau County and coastal Westchester and Fairfield

Forecast is based on 50th percentile Stevens NYHOPS, ETSS, and
ESTOFS blend guidance, which tends to do well with these NE to N
system. PETSS guidance appears to be too high based on this
setup.

Winds quickly ramp up to NE gales early Tuesday morning,
backing to the N through the time of high tide. Widespread
moderate flooding (2 to 2 1/2 ft agl) expected for southern
Nassau Tue AM, with widespread minor elsewhere. Locally moderate
coastal flood impacts possible for Jamaica Bay and SW Suffolk
due to tidal piling accentuated on north facing shores, as well
as north facing shorelines of LI and twin forks due to 2 to 4
ft wave actions.

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.

For the ocean beach front, 3 to 6 ft breaking surf will likely
cause beach flooding and beach escarpment during the morning
and night high tides. Dune erosion impacts area expected to be
localized and minor.

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...Winter Storm Warning until 6 PM EST this evening for
CTZ005>012.
Coastal Flood Advisory from noon today to 4 PM EST this
afternoon for CTZ009-010.
Coastal Flood Advisory from 11 AM this morning to 4 PM EST
this afternoon for CTZ011-012.
NY...Winter Storm Warning until 6 PM EST this evening for
NYZ067>075-078>081-176>179.
Coastal Flood Advisory from noon today to 4 PM EST this
afternoon for NYZ071-073-078-176-177.
Coastal Flood Advisory until noon EST today for NYZ072-074-075-
178.
Coastal Flood Advisory until 5 PM EST this afternoon for
NYZ079>081.
Coastal Flood Warning until 3 PM EST this afternoon for NYZ179.
NJ...Winter Storm Warning until 6 PM EST this evening for NJZ002-
004-006-103>108.
Coastal Flood Advisory until noon EST today for NJZ006-106-108.
MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ331-
332-335-338-340-345.
Gale Warning until 6 PM EST this evening 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...DS/DW
TIDES/COASTAL FLOODING...