Area Forecast Discussion
Issued by NWS Upton, NY

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833
FXUS61 KOKX 230538
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1238 AM EST Mon Jan 23 2017

.SYNOPSIS...
A stationary front will remain off the southern Mid Atlantic
coast overnight with areas of weak low pressure moving along the
front. Meanwhile, a strong southern low will track through the
southern states overnight and then northward to the mid Atlantic
coast Monday. The low will intensify into a major coastal storm
and track northward along the coast Monday night into Tuesday.
High pressure will build in the wake of the storm on Wednesday. A
series of weak mainly dry cold fronts will move southeast around
low pressure north of New England through late week Sunday.

&&

.NEAR TERM /THROUGH TODAY/...
With little to no precipitation in the area as weak ridging
builds in from the north, updated probabilities to remove and
lower across the forecast area. Fog will not be an issue until
toward Monday morning as strong and gusty winds develop with cold
advection.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/...
Intense coastal storm expected late tonight into Tuesday with
high winds, heavy rain, wintry mix NW of NYC, and coastal impacts.

A closed low over the Gulf states will continue to intensify
tonight and then negatively tilt up the east coast Monday into
Tuesday. The result will be a strong surface low over the
Southeast states tonight tracking to the coast Monday, reaching a
position just south of Long Island Mon Night into Tuesday
morning. The low will interact with high pressure building south
from Quebec to produce a very tight pressure gradient and long
easterly fetch from south of Newfoundland.

Models have trended even slower and a bit farther se than 24 hrs
prior...but are well clustered with intense low pressure slowly
tracking to the southeast of LI Mon Night into Tuesday, with the
strongest winds expected Monday afternoon through the first half
of Monday night.

Strong Winds...Coastal areas continue with high wind warning for
high confidence in sustained 30-40 mph with gusts 55-70 mph mon
aft/eve. A wind advisory for interior southern CT, Westchester,
Rockland, and into portions of NJ where winds gusts could reach 50
mph. Highest winds are expected across Long Island, particularly
on the east end and along the south shore. This based on excellent
potential for downward momentum transfer of a 65-70 kt 950-975 mb
LLJ via both mixing in either a well-mixed or moist absolutely
unstable boundary layer. The storm also presents high potential
for a gravity wave event to unfold and enhance downward momentum
transfer, as a highly unbalanced/ageostrophic upper level flow
develops in the exit region of an intense upper jet streak moving
up the coast, with large duct function values present in the low
levels over and just south of the CWA.

Heavy Rain...PW of 3-4 standard deviations above avg in tropical
connection continues to be signaled. Coastal front development
over e li/se ct and orographic lift over eastern faces of hilly
terrain will be favored for the heaviest rainfall. Embedded
convection not out of the question late Monday/Mon eve ahead of
approaching closed low and with warm conveyor belt feeding into
the region. Based on ensemble/operational output, expect rainfall
of 1-3 inches with locally higher amounts (4+ inches).

Wintry Mix...Models continue to signal strong low-level CAD under
an H7-8 warm nose late tonight through Monday evening over the
region. Based on strong dynamics and a deep enough cold layer well
NW of NYC Mon, should see a prolonged mix of sleet and rain and
interior NE NJ...Lower Hud...and SW CT...with period of just snow
and sleet across Orange/Putnam/W Passaic. This will bring
likelihood for 1 to 3 inches of sleet and snow in the NW
hills...highest amount in highest elevations. ECMWF and GFS are
indicating enough dynamic cooling for even a period of heavy snow
late Mon/Mon eve well nw of NYC...but this may be due to under-
estimation of the h7-8 warm nose as shown in the NAM. If the warm
nose can be overcome or is weaker...there is a low potential for 3
to 6 inches of heavy wet snow across the NW Hills.
Additionally...temps hovering around the lower 30s will present
potential for a light glaze of freezing rain across NW hills as
well...but overall not an efficient setup for heavy ice accum. A
winter wx advisory has been issued to address the winter wx threat
across Orange/Putnam/W Passaic for Mon aft/eve. Elsewhere...sleet
could mix in briefly at the coast Mon aft/eve.

Winds and heavy precip should fall off late Mon Night into early
Tue morning from west to east as the LLJ moves NE...but how
quickly is still in question.

The slow moving storm will pass on Tuesday. With the associated
upper level low remaining over the region, will continue to
mention likely/cat PoP mainly in the morning.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Tuesday until Midnight...Light precipitation will end from west to
east as low pressure moves east of coastal New England. The highest
chc for mixed precip will be across our far west zones and across
higher elevations NW of NYC. However, we are not anticipating any
significant accumulations.

Wednesday and Thursday...A weak ridge of high pressure will move
quickly east across the region early Wednesday followed by a long
wave of low pressure thru the day Thursday. No sensible weather is
forecast as temps cont to avg above normal in SW flow.

Friday through Sunday...signals a weather pattern change as a ridge
builds across western North America and a trough develops across the
Eastern U.S. This will bring colder temps across the area to close
out January.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
A deep low centered over the southeastern states will track slowly
to the east to northeast overnight, and becomes a coastal low off
the mid Atlantic states by 00Z Tuesday. The low then tracks slowly
northward along the coast Monday night.

Winds will be the main issue overnight through Monday night with
east to northeast winds 15 to around 20 KT with gusts 25 to 30 KT,
increasing to gusts near 40 KT by 12Z Monday.

MVFR ceilings likely lower to IFR before 12Z, and there is a
low chance MVFR fog develops before morning.

As rain develops Monday conditions will become IFR and at time LIFR.
A mix of rain, snow and sleet is likely at KSWF, with periods of
heavy snow and sleet in the afternoon. Snow amd sleet could total 1
to 2 inches by late Monday. By late in the afternoon there is a
chance of sleet at KHPN.

East to northeast winds continue to increase during Monday, peaking
at around 30 KT with gusts to around 50 KT late in the day. There is
a chance of occasional gusts to near 60 KT along the coast late in
the afternoon int the early evening. Winds will begin to slowly
diminish after 00Z Tuesday.

.OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY...
.Late Monday Night...IFR in rain and fog with rain, snow and sleet at
KSWF. E-NE wind 20-30 KT G30-40 KT.
.Tuesday-Tuesday night...Rain ending late in the day Tuesday into
Tuesday evening. Conditions improving during the evening to
VFR southwest to northeast. Winds NE backing to NW during Tuesday.
.Wednesday and Thursday...VFR. SW Winds 15-25 kt.
.Friday...VFR. W 15-25 kt.

&&

.MARINE...
An intensifying storm moving up the coast will bring hurricane
force wind gusts to the ocean waters Monday into Monday evening
and possibly even the eastern Sound/bays Mon evening. On the non-
ocean waters, storm warnings remain in effect. Expect peak winds
50-60 kt where storm warnings remain. Before then, gales are
likely to develop quickly tonight, followed by storm force winds
developing from south to north through the day on Monday.

Max seas could peak at 20-22 ft on the ocean, 9-12 ft from Orient
Point east, and 8-9 ft on central Long Island Sound, per combo of
WaveWatch/NWPS guidance and wind/wave climatology.

Marine Long Term...
.Tuesday through Wednesday Afternoon...Seas will gradually
subside as winds become SW at 15-20kt by Wednesday Afternoon.
.Wednesday Night...Winds and seas decrease below Small Craft
Advisory levels.
.Thursday and Friday...Winds and seas increase to SCA on the Ocean
with the approach and passage of a cold front.

&&

.HYDROLOGY...
QPF late tonight into Monday will likely be in the 1-3 inch
range, with locally higher swaths possible with the heaviest
rainfall Mon afternoon/eve. If high end rainfall amounts are
realized, this will bring a threat for moderate urban flooding
and minor small stream flooding in NE NJ and the Lower
Hudson Valley. This will be exacerbated by coincidence of high
tide with heavy rain Mon eve along coastal waterfront and
shoreline roads...including along tidally affected rivers.
Potential for minor flooding on larger rivers is slight.

&&

.TIDES/COASTAL FLOODING...
Minor coastal flooding expected along the western great south bay
with Mon Am high tide along with the Southern bays of Long Island.
With a slower onset of strong winds...the threat for minor coastal
flooding has decreased for the NY Harbor and Western Li Sound.

Primary attention is for the late Monday afternoon/evening high
tide cycle. Moderate coastal flooding expected along southern and
eastern bays of LI...Staten Island...low-lying north and east
facing coastlines along Western LI Sound...and the Atlantic
beachfront due to combo of elevated water levels and wave
action. There is a low potential for major flood thresholds to be
reached in the most vulnerable Great South Bay communities such
as Lindenhurst and Freeport. A coastal flood warning has been
issued to address this flood threat. Elsewhere minor to locally
moderate coastal flooding expected.

Minor to locally moderate coastal flooding could linger for the
southern and eastern bay areas for the Tuesday morning high tide
cycle as well.

An ensemble of guidances is showing potential for surge to build to
2 to 2 3/4 ft Mon am...and 3 1/2 to 4 1/2 ft by Monday evening.
The Mon evening expected surge is in line with surges seen during
a March 13th 2010 with similarities in wind/wave forcing.

The other concern will be for widespread dune erosion and localized
washovers at Atlantic ocean beaches from elevated waters levels
and an east to west sweep of 8 to 14 ft surf Mon into Tue.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...High Wind Warning until 1 AM EST Tuesday for CTZ009>012.
     Flood Watch from this afternoon through late tonight for
     CTZ009.
     Wind Advisory until 1 AM EST Tuesday for CTZ005>008.
     Coastal Flood Advisory from 5 PM this afternoon to 11 PM EST
     this evening for CTZ009>012.
NY...High Wind Warning until 1 AM EST Tuesday for NYZ071>075-
     078>081-176>179.
     Coastal Flood Warning from 3 PM this afternoon to 11 PM EST
     this evening for NYZ079>081-179.
     Winter Weather Advisory from 1 PM this afternoon to 7 AM EST
     Tuesday for NYZ067-068.
     Flood Watch from this afternoon through late tonight for
     NYZ069>075-176>179.
     Wind Advisory until 1 AM EST Tuesday for NYZ069-070.
     Coastal Flood Advisory from 3 PM this afternoon to 9 PM EST
     this evening for NYZ072-075-178.
     Coastal Flood Advisory from 5 PM this afternoon to 11 PM EST
     this evening for NYZ073-176.
     Coastal Flood Advisory until 8 AM EST this morning for NYZ080-
     179.
     Coastal Flood Warning from 7 PM to 11 PM EST this evening for
     NYZ071-078-177.
     Coastal Flood Warning from 3 PM this afternoon to 7 PM EST
     this evening for NYZ074.
NJ...High Wind Warning until 1 AM EST Tuesday for NJZ006-106-108.
     Winter Weather Advisory from 1 PM this afternoon to 7 AM EST
     Tuesday for NJZ002.
     Flood Watch from this afternoon through late tonight for
     NJZ004-006-103>108.
     Wind Advisory until 1 AM EST Tuesday for NJZ004-103>105-107.
     Coastal Flood Advisory from 3 PM this afternoon to 9 PM EST
     this evening for NJZ006-106-108.
MARINE...Storm Warning until 1 AM EST Tuesday for ANZ330-335-338-340-
     345.
     Hurricane Force Wind Warning from 1 PM this afternoon to 1 AM
     EST Tuesday for ANZ350-353-355.

&&

$$
SYNOPSIS...BC/GC/NV
NEAR TERM...BC/MET/NV
SHORT TERM...BC/NV
LONG TERM...GC
AVIATION...FEB/MET
MARINE...BC/MET/NV
HYDROLOGY...BC/NV
TIDES/COASTAL FLOODING...



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