091
FXUS61 KOKX 112059
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
359 PM EST Tue Feb 11 2025
.SYNOPSIS...
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Low pressure passes well south of the area tonight into early
Wednesday morning. Another low pressure and its associated frontal
system move across the area Wednesday night into Thursday.
Strong high pressure then builds in through Friday night. High
pressure moves out into the Atlantic on Saturday. A low pressure
system develops and approaches thereafter through the rest of
the weekend. An associated strong low moves across Sunday into
Sunday night. High pressure returns thereafter, gradually building
in for early next week.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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Winter Weather Advisory in effect for Nassau and Suffolk
Counties 9pm this evening through 7am Wednesday morning.
Low pressure beginning to develop over the southeast this
afternoon and will push ENE off the southern Middle Atlantic
this evening into tonight. The region will continue to lie on
the northern periphery of the precip shield. The latest model
trends all support a bump up in liquid equivalent with around a
few hundredths well inland, around a tenth southern portions of
the Lower Hudson Valley and coastal CT, 0.15-0.20" in the NYC
metro, and around 0.25" across Long Island. The NAM still
appears to be the wettest of the guidance across the area,
especially across the southern half with as much as 0.3" in NYC
and near 0.4" across eastern Long Island. The 18z NAM has
lowered QPF just slightly, but overall remains consistent with
its last several cycles. Most of the 12z CAMs have come into
better agreement with the rest of the model consensus. The HRRR
is one of the drier models, but have noted it be to dry at times
in previous events when the region is on the northern
periphery.
There are also several key ingredients that support the trend
upward in liquid equivalent and resulting snow accumulation
including a stronger 700mb frontogenesis signal combining with
strong upper divergence from a 170-190 kt departing polar jet
streak to our north. Models do tend to struggle with the
combination of these features and have seen several past events
over perform with lift accompanying a strong upper jet. The
other factor is the majority of the model suite is indicating
enhancement of the precip shield from Southern NJ up into the
area at least the southeast portion of the area tonight as the
coastal low emerges off the coast. Thermal profiles are also
supporting an all snow event. Soundings indicate deep ice
saturation within the dendritic growth zone for several hours
tonight, especially across Long Island and portions of the NYC
metro. The strongest lift appears to occur between 10pm and 2am
with a decrease the rest of the night.
The snow will begin to overspread from the south tonight between
7-9pm, becoming steady and continuing through the early morning
hours. There is a period between about 10pm and 2am where
snowfall rates could run between 0.25-0.50" per hour. There is
even a low probability snowfall rates could briefly approach 1"
per hour across Long Island from around 11pm-1am as the
strongest forcing and deepest moisture combine. Snowfall rates
will drop off from west to east from 3am to 5am. Some flurries
may linger towards day break, but accumulating snow should end
before sunrise.
Snow to liquid ratios look higher with this event given we are
on the northern periphery of the low and soundings show more of
an ice saturation signal over one with deeper supercooled water
saturation signal. For these reasons have gone closer to a
12-13:1 ratio.
Updated snow totals are around 3 inches with potential of a few
spots approaching 4 inches across Long Island. Elsewhere across
the NYC metro and much of NE NJ and coastal CT, generally 1-2
inches are forecast. Locations closer to the south shore in
Staten Island and southern Brooklyn and southern Queens could
see up to 3 inches. More locations could see closer to 3 inches
in the NYC metro and NE NJ if a wetter and further north trend
continues. Amounts across the interior will be lower and
generally less than an inch as this area is closer to subsidence
from the high building in from the north.
A Special Weather Statement for areas outside the advisory where
amounts over an inch are expected to account for potential of
slick conditions tonight.
Lows generally in the upper 20s along the coast and lower to mid 20s
interior.-- End Changed Discussion --
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/...
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The offshore low pressure moves further out into the Atlantic
Wednesday morning. Heights aloft along the eastern seaboard
will rise through the day in response to an amplifying upper
trough over the Plains. High pressure will briefly build down
across New England from southeast Canada. Another strong upper
jet streak will pass over New England so mid and high level
clouds are likely to persist through the day. The day time hours
are expected to be dry as subsidence from the high pressure to
the north dominates. High temperatures range from the lower and
middle 30s inland to the middle and upper 30s near the coast.
The next low pressure and its associated frontal system fast
approach Wednesday night. Warm advection precip north of the
warm front will expand across the region Wednesday evening and
Wednesday night. SW flow aloft will increase helping to drive
warmer air over the region. The latest model trends have
indicated an overall warmer solution with a brief window for a
wintry mix of snow/sleet changing to liquid overnight. There is
still potential for some freezing rain across the interior late
at night into early Thursday morning. For the NYC metro and Long
Island, warmer air at the surface and aloft will change any
brief snow to plain rain late in the evening and night.
Snow/sleet accumulations look light and generally a coating near
the NYC metro to around an inch well inland. Ice accumulations
for the interior could be several hundredths.
The warm front and associated weak secondary low lift north over
the area on Thursday. It is always difficult to forecast the
exact placement of these features. However, the guidance has
been trending warmer with a much stronger parent low passing
well to our northwest Thursday. This should be able to scour out
some of the low level cold air across the interior by Thursday
morning. The bulk of any remaining precip occurs in the morning
with drier air beginning to move in late in the day as the
associated cold front moves through. Latest model consensus
indicates highs in the 40s. With potential of dew points in the
40s as well, there may some fog around with lingering melting of
the recent snow pack. This is something that may need to be
added into the forecast in future updates.-- End Changed Discussion --
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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The key feature of the long term will be the evolution of a
strong quite deep mid and upper level cutoff low in Southern
Canada. The mid and upper level pattern is expected to be more
amplified as a result. The active upper jet stream remains
across the region much of the long term period with more periods
of strong meridional SW flow.
The overall forecast trend, POPs went up this weekend compared to
previously forecast and temperatures on average cooled compared to
previously forecast. Forecast followed NBM but did blend in
consensus of raw model data for temperatures this weekend. For the
precipitation, greater weight was given to utilize a precipitation
type from thickness method for Saturday night into Sunday using the
GFS with some manual cooling of layers.
Dry conditions expected with strong high pressure building in
Thursday night through Friday night. Lows at night are forecast to
be near normal and highs forecast on Friday are slightly below
normal.
Precipitation event, this weekend, warm front followed by strong
low and associated occluded front. The strong low moves across
Sunday into Sunday night along with its occluded front. Warm air
advection makes for plain rain for entire region pretty much
all of Sunday afternoon.
However, with onset (Saturday) and tapering off of precipitation
(Sunday night), snow will be probable for all of the region. In
between, mainly Saturday night into Sunday, warming aloft in
advance of the strong low will present a potential transition
to a wintry mix, including freezing rain across the interior.
There is uncertainty and subsequent forecasts may have northward
or southward shifts with this wintry mix and snow line and its
timing.
Too much uncertainty at this point for any exact rain, snow and/or
ice amounts.
Behind this front, strong cold air advection is expected with jet
max south of the region. Coldest temperatures of the forecast period
are expected for Monday and Tuesday of next week. Forecast highs
struggle to approach the freezing mark and are well below
normal.-- End Changed Discussion --
&&
.AVIATION /21Z TUESDAY THROUGH SUNDAY/...
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Low pressure passes south of the terminals tonight.
VFR through about 00Z. Cigs and vsbys then lower to MVFR then
IFR in snow after 00-02Z tonight for the NYC and LI terminals.
A period of SN is possible between 03-06Z with vsbys reduced to
1/2SM. Conditions start to improve after 09-12z, however
conditions may remain MVFR through midday Wednesday.
SW winds aob 10kts this afternoon. Flow weakens and becomes
light and variable this evening before becoming NE late at
night.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments are likely for the timing of flight category changes
in light snow this evening into the overnight period. Snowfall
amounts of 1-2 inches expected with locally up to 3 inches.
.OUTLOOK FOR 18Z WEDNESDAY THROUGH SATURDAY...
Wednesday: MVFR likely early. VFR possible into the afternoon. ENE
gusts 15-20 kt at the coastal terminals in the afternoon.
Wednesday Night-Thursday: Snow/wintry mix developing Wednesday
evening with IFR/LIFR. At the coast, wintry mix for a brief period
before becoming plain rain. Further north, Wintry mix becoming plain
rain Thursday morning. E gusts 15-20 kt Wednesday night.
Friday: VFR. NW wind gusts 15-20 kt during the day.
Saturday: VFR early. MVFR or lower possible with rain/snow mix near
coast and snow inland late. Becoming all rain at the coast by early
evening, and a bit later at the inland terminals.
Sunday: MVFR for much of the day in rain; winds SW 5-10kts.
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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Conditions will remain below SCA levels on all waters tonight.
E/NE winds on Wednesday with marginal SCA gusts and seas likely
in the morning then higher confidence in winds and seas at SCA
levels in the afternoon and at night. Winds will also increase
to SCA levels on the LI Bays and eastern Sound Wednesday night.
SCA conditions likely linger on the ocean Thursday and could
also expand to the Sound, Bays, and Harbor.
SCA conditions are probable on the local waters Thursday night
into Friday. Sub-SCA conditions then probable Friday night
through Saturday night. SCA conditions potentially return for
Sunday and Sunday night.-- End Changed Discussion --
&&
.HYDROLOGY...
There are no hydrologic concerns through early next week.
&&
.TIDES/COASTAL FLOODING...
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With full moon on Wednesday and SCA easterly flow Wed Night into
Thu AM ahead of approaching frontal system, there is potential
for scattered areas of minor coastal flooding with Thu morning
high tide for vulnerable areas along Jamaica Bay, western Great
South Bay and western LI Sound, and more isolated along NY/NJ
harbor.
Some beach flooding and escarpment possible during the Thu AM high
tide with elevated water levels and e to w sweep of 4 to 6 ft
breaking surf, but dune erosion threat appears limited at this
point.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None.
NY...Winter Weather Advisory from 9 PM this evening to 7 AM EST
Wednesday for NYZ078>081-177-179.
NJ...None.
MARINE...Small Craft Advisory from 6 PM Wednesday to 6 AM EST Thursday
for ANZ332-340-345.
Small Craft Advisory from 6 AM Wednesday to 7 PM EST Thursday
for ANZ350-353-355.-- End Changed Discussion --
&&
$$
SYNOPSIS...JM/DS
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...JM
AVIATION...DBR
MARINE...JM/DS
HYDROLOGY...JM/DS
TIDES/COASTAL FLOODING...