000
FXUS61 KOKX 070107 CCA
AFDOKX
Area Forecast Discussion...CORRECTED
National Weather Service New York NY
807 PM EST Sat Jan 6 2024
.SYNOPSIS...
Low pressure will pass south of Long Island overnight, and east
of the region on Sunday. High pressure moves east of the area
on Monday. Low pressure strengthens and passes west of the
region Tuesday into Wednesday. The low will then move northeast
and weaken Wednesday into Thursday. Weak high pressure then
returns thereafter through Friday.
&&
.NEAR TERM /THROUGH SUNDAY/...
-- Changed Discussion --
The challenge of this forecast will be for areas just inland of
the coast the next several hours, particularly interior NE NJ
and the CT coast. A strengthening east flow will gradually warm
the boundary layer, however, with liquid equivalent rates of .1
to .2"/hr moving up from the south, those areas could see brief
snowfall rates of 1 to 2"/hr before mixing with or going over
to rain. Inland areas will also see an increase in intensity of
the snow the next couple of hours, from SW to NE. Even a slight
change in distance north and west will make a difference. For
example, KEWR has gone over to plain rain at 37F/34F, while KNYC
is right around the freezing mark. Latest dual pol CC from KDIX
and KOKX shows lower CC values (marking mixed pcpn going over to
rain) near KEWR and along the south shore of LI. This area should
advance north with a changeover to all rain across LI and the NYC
metro the next 1 to 2 hours. However, model soundings for
locations just north and west of NYC, such as KTEB are pointing to
a prolonged period of heavy wet snow before the mid levels dry
out and an elevated warm layer moves in aloft. At that time,
precipitation would transition over to a drizzle or light rain,
but the bulk of the heavy precipitation would have fallen as snow.
Also, seeing very similar soundings along the CT coast. However,
the strengthening easterly flow off the LI Sound is a significant
warming factor for the boundary layer. If the wind could stay a
bit more north of east the potential is there for higher
accumulations. This will have to be watched carefully over the
next couple of hours, but for the time will stay the course with
the hazards and snowfall amounts.
Otherwise, models remain in agreement that low pressure passes
to our south tonight and just NW of the 40N/70W benchmark Sunday
morning. Bulk of the precip will occur through tonight, but PVA
aloft interacting with a surface trough on the backside of the
storm brings additional, but lighter precip during the day
Sunday.
Still looks like an all-snow event for a good portion of the
northernmost zones, but not out of the question that as the mid-
levels dry out late tonight a brief period light freezing rain
occurs. A warm nose near 850mb tonight introduces a wintry mix
farther south to the coast. Then between the warm nose and
sufficient boundary layer warmth on an easterly wind off the waters,
mainly rain for LI and NYC metro.
Winds ramp up tonight with gusts mostly 30-40mph for the
coastal areas. Still looks as if we`ll fall short of advisory
criteria, but there may be a stray gust or two that gets over 45
mph across parts of eastern Long Island during the overnight
hours.
Flooding does not appear to be a factor with this system. For the
locations where precip is expected to be primarily rain, flash flood
guidance combined with expected rainfall amounts and the progressive
nature of the storm should preclude flash flooding/river flooding.
Across parts of NE NJ, it won`t take as much for a chance of
flooding, but at the same time, some of this will be falling in the
form of snow.
Stuck fairly close to the previous forecast regarding temperatures
through the event, which is a little cooler than NBM.-- End Changed Discussion --
&&
.SHORT TERM /SUNDAY NIGHT/...
Clearing skies due to subsidence and a dry airmass building in.
Gusty NW flow as the low pulls away, especially LI surrounded
by the warm water. Across the interior, fresh snowpack could
allow for decoupling and possibly temps below the NBM fcst.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
*Key points*
* A potentially significant storm system will impact the region
Tuesday into Wednesday.
* A period of heavy rain, and river and coastal flooding are all
possible with this system.
* Strong winds with the potential for gusts of 45 to 60 mph, highest
along the coast, Tuesday night into early Wednesday, are also
possible.
Model guidance/ensembles continue to show above-average consistency
in the extended advertising a potent low pressure system to impact
the area midweek. Weak upper ridging on Monday gives way to a
strengthening trough and jet diving south out of the Northern Plains
on Tuesday. This feature heads into the Great Lakes on Wednesday,
and into New England by Thursday. This places the local area on the
eastern side of the system, in the vicinity of the left front quad
of the upper jet Tuesday night into early Wednesday.
At the surface, deepening low pressure Tuesday afternoon induces a
fetch with a connection to the Gulf. Moisture advection commences as
a result into the area, with PWATs nearing 1.25" by Tuesday evening.
This would be close to, or just over, the max PWAT values for OKX
per the SPC sounding climatology. As the surface low heads northeast
into Great Lakes Region by late Tuesday, precipitation will begin to
overspread the area ahead of a warm front. Given the area resides on
the eastern side of the system, am expecting an all rain event. The
one exception may be at the onset across the Lower Hudson Valley,
where residual cold air may allow for some light snow before quickly
changing over. Rain becomes steadier, and heavier, into the Tuesday
overnight as the cold front approaches before finally waning early
on Wednesday. Given the moisture fetch, enhanced forcing from the
upper jet and frontal approach, the ingredients are in place for a
period of heavy rainfall. NBM continues to advertise a widespread 2-
3" event, with highest amounts across northern NJ and the lower
Hudson Valley, where WPC maintains the moderate risk of excessive
presentation. See the hydrology section for additional details.
Then there are the winds associated with the LLJ as the system
approaches. Model soundings continue to show a period of 65-70 kts
at 950mb with a weakly inverted to mostly neutral PBL as the LLJ
approaches after 00Z Wednesday. Have shaved some off of the NBM wind
values given its performance of overpredicting for the past few high
wind events. This yields a widespread 30-40 mph sustained with 45-
60mph gusts, with highest values across the coast.
Weak ridging builds in thereafter for Thursday and Friday.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
Low pressure approaches from the south, passing east of Long Island
tonight into Sunday.
Currently, MVFR to IFR conditions are being reported for most
terminals, except KGON where precipitation has yet to begin.
Conditions will continue to lower to IFR or lower overnight.
Gradual improvement to MVFR through Sunday afternoon, with a
return to VFR around 00Z Monday.
Precipitation will continue to become more widespread over the
next few hours and become more intense. A changeover to rain has
already occurred across KJFK, KEWR, and KISP, though a
changeover back to snow or a rain/snow mix is possible at times
over the next hour or two, though unlikely. The rain/snow line
will move north through the night, with a changeover to rain
possible as far north as KHPN. KSWF will likely remain all snow,
but even here a wintry mix is possible, and freezing rain may
mix in after 06Z. Did not include this in the TAF as there is
some uncertainty with it actually mixing in. There may be a
brief lull in the precipitation just before and during daybreak
Sunday morning. However, as the low passes east of the region,
precipitation will move back into the area with the rain/snow
line will moving southeast and a changeover to all snow is
possible Sunday morning. However, it is more uncertain for
western terminals as precipitation will be tapering off as the
colder air moves in here.
E-ENE winds 10-15 kt increase to around 20 kt along the coast
tonight with gusts 25-30 kt here into early Sun AM. Flow lightens
after 12Z Sun, close to 10 kt, as direction backs northerly,
then NW. Isolated gusts of 30-35 kt are possible.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments likely through the TAF period with timing of category
changes and precipitation onset/ending.
OUTLOOK FOR 00Z MONDAY THROUGH THURSDAY...
Sunday PM: MVFR Becoming VFR. N/NW winds around 10 kt.
Monday: VFR.
Tuesday: VFR early becoming MVFR or lower. Rain during the
afternoon. E winds 15-20kt with gusts 25-30kt in the afternoon. SE
winds increasing Tuesday night to 25-35kt, gusting 40-45kt, highest
winds along the coast. LLWS likely at night.
Wednesday: MVFR or lower with rain in the morning. Rain ending late
in the day with conditions improving. S-SW wind 20-25kt gusting 35-
45kt. Gusts decrease afternoon into the night.
Thursday: VFR. WSW winds 10-15kt.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
Gales develop tonight on all waters with low pressure approaching,
then passing through or just south of the ocean waters late tonight
into Sunday morning. No changes with this update regarding the
end time of the gale warnings. SCA will likely be needed for the
western waters after the warning expiration Sunday morning.
Same for the eastern waters Sunday afternoon. Sub-advisory
conditions for the non ocean waters starting Sunday afternoon
into evening. Ocean seas will remain elevated, so advisory
conditions prevail Sunday afternoon and night.
Lingering 5 to 6 ft waves are expected on the ocean waters on
Monday. Otherwise, quiet conditions on the waters expected until
late Tuesday. Strong low pressure will then track to the west and
impact the area through Wednesday. Gale force wind gusts look likely
on all waters, as well as the potential for storm force gusts for a
period early Wednesday. In addition, waves on the ocean waters may
reach 15 to 20 ft. Continued mention of gales and storm force gusts
in the HWO.
&&
.HYDROLOGY...
No hydrologic impacts are expected through Monday.
Thereafter, significant hydrologic impacts are likely. A period
of heavy rainfall Tuesday night into Wednesday will likely
result in flooding across the region. Any total runoff would be
enhanced inland with melted snowfall, especially across the
interior. The Weather Prediction Center has a segment of the
area in a moderate risk for excessive rainfall within parts of
Northeast NJ and expanded the risk further into the Lower Hudson
Valley. The rest of the forecast region in a slight risk for
excessive rainfall. River levels across northeastern NJ and the
Lower Hudson Valley, where the heaviest rainfall is expected to
fall, are expected to rise.
&&
.TIDES/COASTAL FLOODING...
E/NE gales tonight into Sunday morning will produce a surge of
about 2 to 3 ft, resulting in widespread minor coastal flooding
during the morning high tide cycle Sunday. Localized moderate is
a possibility across the south shore back bays of Nassau and
southwest Suffolk counties. Isolated dune erosion expected
during the Sunday morning high tide, overwashes not expected.
There is the chance for a significant coastal flood event with
the Wed AM high tide. Potential for SE gale to storm force winds
Tuesday Night, bringing potential for widespread moderate to
locally major coastal flooding. Early guidance from Steven`s
NYHOPS ensemble is producing surge values of 3 to 4 ft. This
will also coincide with increasing astronomical tides with a new
moon on Jan 11. Along the oceanfront, potential for 15-20 ft
surf causing widespread dune erosion and scattered overwashes.
Localized dune inundation/breaches possible where dunes have
been compromised by earlier storm events. More details on this
event early next week.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Storm Warning until 6 PM EST Sunday for CTZ005>008.
Winter Weather Advisory until 11 AM EST Sunday for CTZ009.
Coastal Flood Advisory from 4 AM to 10 AM EST Sunday for
CTZ009>012.
Winter Weather Advisory until 6 PM EST Sunday for CTZ010>012.
NY...Winter Storm Warning until 6 PM EST Sunday for NYZ067>070.
Winter Weather Advisory until 11 AM EST Sunday for NYZ071.
Coastal Flood Advisory from 4 AM to 10 AM EST Sunday for
NYZ071-078-177.
Coastal Flood Advisory from 2 AM to 11 AM EST Sunday for
NYZ079-081.
Coastal Flood Advisory from 1 AM to 10 AM EST Sunday for
NYZ080-179.
NJ...Winter Storm Warning until 6 PM EST Sunday for NJZ002-103.
Winter Weather Advisory until 11 AM EST Sunday for NJZ004-104-
105-107.
MARINE...Gale Warning until noon EST Sunday for ANZ331-332-340-345-350-
353.
Gale Warning until 5 AM EST Sunday for ANZ335-338-355.
&&
$$
SYNOPSIS...JC/DBR
NEAR TERM...JC/DW
SHORT TERM...JC
LONG TERM...DBR
AVIATION...JP
MARINE...JC/DBR
HYDROLOGY...JC/DBR
TIDES/COASTAL FLOODING...