Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 220738
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
238 AM EST Sun Jan 22 2017

.SYNOPSIS...
A low pressure system will approach the Tennessee River and Ohio
Valleys from the southern plains today, reaching the southern Mid
Atlantic region by Monday morning. Meanwhile, high pressure builds
southeast into the Canadian Maritimes. The low will intensify into
a significant coastal storm as it moves up the coast toward the
area Monday through Tuesday. High pressure builds for Wednesday as
the coastal low departs towards New England. A cold front slowly
approaches the area from the west, moving through late Thursday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Widespread dense fog was across the region as a saturated low
layer under an inversion remains into early morning. At the upper
levels weak ridging moves east. Winds will be near calm amd with
little advection temperatures and dew points are likely to remain
near steady early on.

This saturation is depicted in NARRE/HRRR and NAM profiles. A
dense fog advisory remains in effect.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY NIGHT/...
Significant coastal storm expected late tonight into Tuesday with
potential high wind...heavy rain...and coastal impacts.

Upper level system closes off over the southern plains and then
negatively tilts up the east coast Monday into Tuesday. The
result will be strong low pressure tracking through the southern
states today...towards the Mid Atlantic Mon morning...with a
coastal low developing and tracking s/se of LI Mon into Mon Night.
Models in better agreement with the synoptic fields...with reduced
but still some spread in the track/timing of the closed upper low
as it moves up the coast...which is playing out in model spread on
track/speed of the approaching surface low Mon/Tue. This is
particularly seen in the timing/location of coastal low
development late Mon and then SE of the region Mon Night...and how
quickly the strong easterly jet moves ne of the region. GFS/NAM
have trended quicker with ECMWF trending a bit slower...which
leaves uncertainty in how quickly winds and precip taper off late
Mon/Mon eve. Have maintain slower previous forecast timing based
on this wavering and blocky pattern development.

Potential continues for multiple impacts of strong winds, heavy rain
(period of wintry mix NW) and minor to locally moderate coastal
flooding, with likelihood of occurrence in that general order.

Strong Winds...high confidence in wind advisory of 30 to 40 mph
with gusts 50-60 mph for the coast Mon...with moderate potential
for high wind gusts of 60-65 mph with an easterly jet 5-6 std
above climo and peaking around 70-75 kt at 925 hpa. Farther
north/west, wind gusts will likely approach or exceed wind
advisory criteria, reaching 40- 50 mph, particularly higher
terrain. High wind watch remains in effect for coast. Peak winds
could begin as early as mid Mon morning and linger well into Mon
eve.

See coastal flood sections for potential coastal impacts.

Heavy precip...PWATs of 3-4 stds above normal continue to be
signaled as the system taps into tropical connection to the
Caribbean and Eastern Pacific. Coastal front development (E LI/SE
CT?) and orographic lift over western faces of hill terrain will
be favored for heaviest rainfall amounts in anomalously moist and
strong easterly flow. 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...likelihood for 1 to 3 inches of qpf
with higher amounts possible.

NAM/GFS indicating low-level cold air damming signature
undercutting 750-850 hpa warm nose tonight through Monday aft
over the region. Based on strong dynamics and deep enough cold
layer well N&W of NYC Mon...sleet could mix in briefly at the
coast...with more prolonged rain/sleet or even plain sleet across
NW hills Mon morn/aft. A light sleet accumulation is possible
across interior portions of NE NJ...Lower Hud...and Southern
Ct...particularly the NW hills.

Winds and heavy precip should fall off Late Mon/Mon Night from sw to
e as llj moves ne...but how quickly is still in question.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Slow moving coastal storm passes Tuesday. With the Upper trough
and associated upper level low remaining over the region, will
continue to mention likely POPs through the day, before gradually
ending Tuesday night.

Generally looking at mostly dry conditions Wednesday through
Saturday. A cold front will bring cooler conditions for the end of
the long term period.

Expect highs Tuesday through Thursday in the middle and upper 40s, a
good 10 degrees above normal. Friday and Saturday, high temperatures
fall back to near normal, with high in the upper 30s and lower
40s.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
Widespread IFR to LIFR conditions will remain through the
early morning hours as a saturated low layer remains under an
inversion.

Winds will be light and variable to calm early this morning.

A wave of low pressure passes to the south today. A large low
pressure system moves from the lower Mississippi Valley into the
Tennessee River Valley during the day, and into the Ohio Valley
tonight.

Conditions begin to improve around 14Z, with MVFR conditions
possible by around 16Z. Timing is uncertain at this time, and there
is a chance IFR conditions remain into the afternoon. With the
approach of the low from the south, rain becomes likely around 23Z
or shortly after. Winds become east to northeast, 5 to 10 KT this
morning after 12-14Z, and increase through the day, to near 15 KT
with gusts 20-25 KT by late in the afternoon into the early evening.
There is a chance the low approaches more slowly, then rain and
gusty winds would be delayed.

.OUTLOOK FOR 06Z MONDAY THROUGH THURSDAY...
.Late tonight...MVFR TO IFR in rain and fog. At KSWF light sleet AND
RAIN likely toward 08Z. E-NE wind 20-30 KT G35-45 KT.
.Monday-Monday Night...IFR in rain and fog. LLWS. Rain and sleet at
KSWF. E-NE wind 25-35 KT G40-50KT, occasional higher gusts near the
coast.
.Tuesday-Tuesday night...Rain tapering off by afternoon with
improving ceilings into the evening. NW winds G25-35KT, highest in
the morning.
.Wednesday and Thursday...VFR. SW Winds 15-25 kt.

&&

.MARINE...
Seas on the outer ocean water south of Montauk Point were running
around 4 feet with a long period southeasterly swell. Made minor
adjustments to the ocean seas early on.

Dense fog remains across the forecast waters through the morning.

An intensifying storm moving up the coast Monday into Monday
night will bring storm force gusts to all waters late tonight
into Monday night. Easterly wind gusts 50-60 kt are expected
mainly daytime Mon into Mon evening on the ocean, and beginning a
little bit later Mon morning on the remaining waters. Strongest
winds will be on the ocean, there is even a low prob of a brief
period of hurricane force gusts (65+ kt) per 18Z NAM, which
predicts 950-975 mb winds that strong and a well-mixed low-level.

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.

Winds start to diminish on Tuesday, however seas will take a while
to fall below 5 ft. Expect a prolonged period of small craft
conditions on the area ocean waters.

&&

.HYDROLOGY...
Likelihood of 1 to 3 inches, with locally higher swaths possible
with a coastal storm tonight into Monday...with heaviest rainfall
Mon aft/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/Lower Hud Valley. This would be exacerbated by
coincidence of high tide with the heavy rain Mon eve. Rises on
larger rivers would be likely...but at this point the potential
for minor flooding appears slight.

&&

.TIDES/COASTAL FLOODING...
A strong coastal storm will impact 2 successive high tide cycles of
at least minor coastal flooding. The first tide cycle to be impacted
is late tonight into early Monday morning. Minor coastal flooding is
expected in spots as astronomical tides run a little higher than the
late afternoon/evening tides. East/northeast winds are increasing
during this time, but will not be quite at their peak.

Expect the lower NY Harbor areas to experience minor coastal
flooding, along with the South Shore and eastern bays of Long
Island, and western Long Island Sound.

Then, attention turns toward the next high tide cycle late Monday
afternoon/evening. Potential for moderate coastal flooding for
southern and eastern bays and beachfront communities of LI with this
Monday evening high tide, and widespread minor coastal flooding
elsewhere.

The moderate coastal flood potential will increase if the slower
coastal low movement (stronger E/NE winds Mon evening) comes to
fruition...with even a low potential for major flood thresholds to
be reached in the most vulnerable communities such as Lindenhurst
and Freeport. A coastal flood watch has been issued to address this
moderate flood threat. Minor 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 3 ft Mon am...and 3 1/2 to 4 1/2 ft by Monday evening.

The highest threat for coastal impacts will be for flood prone
locales along the south shore bays of LI/NYC...eastern bays of
LI...lower NY/NJ harbor including tidally affected rivers...and
western LI Sound.

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 12 ft surf Mon into Tue.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Dense Fog Advisory until 10 AM EST this morning for CTZ005>012.
     High Wind Watch from late tonight through late Monday night
     for CTZ009>012.
NY...Dense Fog Advisory until 10 AM EST this morning for NYZ067>075-
     078>081-176>179.
     Coastal Flood Watch from Monday afternoon through Monday
     evening for NYZ079>081-179.
     High Wind Watch from late tonight through late Monday night
     for NYZ071>075-078>081-176>179.
NJ...Dense Fog Advisory until 10 AM EST this morning for NJZ002-004-
     006-103>108.
     High Wind Watch from late tonight through late Monday night
     for NJZ006-106-108.
MARINE...Dense Fog Advisory until 10 AM EST this morning for ANZ330-335-
     338-340-345-350-353-355.
     Storm Warning from 1 AM Monday to 1 AM EST Tuesday for ANZ330-
     335-338-340-345-350-353-355.

&&

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



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