Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 241237
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
737 AM EST Tue Jan 24 2017

.SYNOPSIS...
Strong low pressure just south of Long Island this morning will
track slowly northeast through tonight and up into the Canadian
Maritimes on Wednesday. High pressure builds in briefly for
Wednesday. Low pressure moves across the Great Lakes Wednesday
night and deepens as it moves into southeast Canada, remaining
nearly stationary through the upcoming weekend. This low will send
a series of cold fronts through the area, one on Thursday and then
again over the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Winter Weather Advisory has been extended both in time and area
across the Lower Hudson Valley and interior Southwest Connecticut.
The advisory was expanded to include Northern Fairfield in
Connecticut and Northern Westchester and Rockland Counties in New
York.

A shallow dome of cold air, which models are having a tough time
handling, has been a bit colder and deeper. There has been little
ground truth overnight, but mesonets and recent public reports
have indicted 1-2 inches of sleet. There is still a fair amount
of uncertainty as to how quickly temperatures will rise this
morning on the backside of a strong coastal low as winds become
even more northerly. Latest mesoscale models support nearly steady
temperatures or slight rises across the interior. For now, have
extended the advisory through noontime. This may have to be
extended into the afternoon. Warmer air aloft wrapping in off the
Atlantic should provide a strong enough warm nose for a transition
to all liquid.

In addition, the wind advisory has expired as the 60-70 kt low-
level jet has lifted north and of the area.

The steadiest precipitation has ended as the best dynamics and
thermal forcing have lifted north of the area. Expect mainly
light precipitation this morning.

As the negatively tilted closed upper low lifts to northeast
today, models are keying in on a deformation zone on its west side
with the potential for banded moderate rain this afternoon, mainly
impacting NYC metro and points north and west. There is some
uncertainty as to where this will exactly set up. An additional
quarter to half inch of rainfall is possible with this band with
lesser amounts elsewhere.

Temperatures will be slow to rise to today, with many locations
holding nearly steady, ranging from the mid 30s inland to the
lower 40s at the coast. Gusty North winds up to 30 mph will be
possible into this afternoon.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
The vertically stacked low moves slowly along the New England
coast tonight with the chances of precipitation slowly lowering
from the southwest to the northeast. Heights begin to rise late
at night as weak ridging builds to the west.

Some of the rain on the backside of this system could transition
over to sleet or freezing rain briefly before coming an to end
tonight. Overnight lows will drop to around freezing inland, and
in the mid and upper 30s at the coast.

High pressure and sunny skies will be on tap for Wednesday.
Building heights aloft and winds backing to the west will result
in a much warmer day, with highs in the mid and upper 40s. This
is about 10 degrees above normal.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The next shortwave trough moves across the Great Lakes Wednesday
night and swings across the region on Thursday. The GFS and some
of its ensemble members indicate potential for showers as the cold
front associated with this shortwave moves through Thursday. Other
models and ensembles are drier. This appears to be due to the
amplitude of H5 energy and moisture return. Will cap pops off at
30 percent at this time.

Cold front moves offshore Thursday afternoon and evening. This front
signifies a return to more seasonable temperatures, potentially a
few degrees below normal. There is also good agreement among the
models and ensemble means with a hemispheric pattern change with
deep ridging across Western North America and mean troughing over
the east. Dry forecast into the weekend although there is enough
energy aloft within cyclonic flow that a few snow showers may reach
interior sections.

Late in the weekend into early next week, there are signals the mean
trough across the east may sharpen up, but it is a bit early to say
if there any impacts to sensible weather.

&&

.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
Low pressure will stall south of Long Island today, then track
northeast into the Gulf of Maine tonight.

Gusty northeast flow will continue this morning before beginning to
decrease and back to the northwest late this afternoon into tonight.
Gusts this morning will generally top out at around 25 kts, with
a few 30 kt gusts possible over the next couple hours at the coast.

A mix of MVFR and IFR conditions to start. Where they are not
already IFR, ceilings will fall to IFR at most of the city and
coastal terminals through the morning hours. Ceilings then begin
to improve this evening, eventually becoming VFR by Wednesday
morning.

While the steadiest rain has moved north of the area, periods of
light rain and drizzle will continue throughout the day. Most
terminals will see plain rain, however KSWF will see a mix of
rain, sleet, and freezing rain this morning. Sleet may also mix in
for a brief period this morning at KHPN. Steadier rain may return
in and around the city terminals this afternoon, although exactly
where any more persistent rain sets up remains in question.

     NY Metro Enhanced Aviation Weather Support...

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

KJFK TAF Comments: Amendments possible this morning for changes in
ceiling and visibility.

KLGA TAF Comments: Amendments possible this morning for changes in
ceiling and visibility.

KEWR TAF Comments: Amendments possible this morning for changes in
ceiling and visibility.

The afternoon KEWR haze potential forecast is YELLOW...which implies
slant range visibility 4-6SM outside of cloud.

KTEB TAF Comments: Amendments possible this morning for changes in
ceiling and visibility.

KHPN TAF Comments: Amendments possible this morning for changes in
ceiling and visibility. Sleet may briefly mix with rain this
morning.

KISP TAF Comments: Amendments possible this morning for changes in
ceiling and visibility.

.OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY...
.Wednesday and Thursday...VFR. NW winds become W-SW Wednesday near
10 kt. SW-W winds Thursday 10-15 kt gusts to near 20 kt.
.Friday...VFR. W winds 10-15 kt gusts to 20 kt.
.Saturday...VFR. W winds 10-15 kt.

&&

.MARINE...
Storm warning on the ocean waters has been downgraded to a gale,
while the remaining waters are under an SCA.

Low pressure just south of the waters this morning will track
slowly northeast today and up into the Canadian Maritimes on
Wednesday. Winds are forecast to subside quickly this morning with
SCA conditions likely on all waters by afternoon.

The low continues to pull away tonight with a tight enough
pressure gradient for SCA conditions to continue with NW gusts
25-30 kt.

Winds diminish on all waters Wednesday with a weakening pressure
gradient as high pressure settles over the waters. Ocean seas
should also subside below 5 ft by evening.

SCA conditions are likely on all waters on Thursday with a
steepening pressure gradient with a cold front passage. These
conditions may continue into Friday and possibly into Saturday,
especially on the ocean waters.

&&

.HYDROLOGY...
An additional quarter to half inch of rainfall is possible today
as a band of moderate rain develops on the backside of departing
low pressure. The exact placement is uncertain, but likely from
from around the NYC metro to points north and west. These amounts
should not pose any hydrologic issues.

&&

.TIDES/COASTAL FLOODING...
Added western LI sound to the cstl flood advisory based on
trends.

One more round of minor to moderate coastal flooding in
the southern and eastern bays of Long Island this morning. Major
cstl flooding near lindenhurst.

Elsewhere mainly localized minor coastal flooding. Will maintain
current headlines.

An ensemble of guidances is showing surge of 2 1/2 to 3 ft early
this morning but with a higher astro tide.

The other continuing 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.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory until noon EST today for CTZ005.
     Coastal Flood Advisory until 11 AM EST this morning for CTZ009-
     010.
NY...Winter Weather Advisory until noon EST today for NYZ067>070.
     Coastal Flood Advisory until 11 AM EST this morning for NYZ071-
     078-177.
     Coastal Flood Warning until 11 AM EST this morning for
     NYZ079>081-179.
NJ...Winter Weather Advisory until noon EST today for NJZ002.
MARINE...Small Craft Advisory until 6 AM EST Wednesday for ANZ330-335-
     338-340-345.
     Gale Warning until noon EST today for ANZ350-353-355.

&&

$$
SYNOPSIS...DW
NEAR TERM...DW
SHORT TERM...DW
LONG TERM...DS/DW
AVIATION...FEB
MARINE...DW
HYDROLOGY...DW
TIDES/COASTAL FLOODING...pw



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