Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 240957
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
457 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/...
A strong coastal low about 80 miles south of Long Island this
morning has resulted in a wintry mix across western portions of
the Lower Hudson Valley with mainly rain elsewhere. The steadiest
precipitation is coming to an end as the best dynamics and thermal
forcing lift north of the area.

The 60-70 kt low-level jet passing to the east this morning will
allow for gradually diminishing winds. Wind advisory currently set
to expire across CT and LI by 6 AM.

N-NE flow has helped to maintain a shallow cold pool across the
area with most locations in the 30s, but a few spots were around
freezing in the Lower Hudson Valley, in particular Orange County.
Vertical temperature profiles in these areas are marginally cold
enough for a wintry mix with reports of 1-2 inches of sleet in
spots. Warmer air aloft wrapping in off the Atlantic should
provide a strong enough warm nose for a transition to all rain.
The greatest uncertainty though resides in the near surface
temperatures which at this time are forecast to get up into the
mid and upper 30s inland. There is the possibility that some
lingering freezing rain could hang on past the advisory expiration
time. Confidence is low at this time and will have to see how
temperatures trend the next couple of hours before any extension.

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 /09Z 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.
The strongest gusts will occur early this morning, with gusts to 30-
35 kts at the city and coastal terminals.

MVFR ceilings will prevail across the region this morning as the
heaviest rain continues to taper off from south to north. While the
steadiest rain will come to an end early this morning, periods of
light rain and drizzle will continue throughout the day. As the
heaviest rain moves out, IFR ceilings are expected to develop late
this morning from KJFK and KLGA east across the coastal terminals.
Ceilings then gradually improve to VFR early Wednesday morning.

All precipitation today will be in the form of rain with the
exception of KSWF, where rain will mix with sleet at times early
this morning and again tonight.

...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.

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...
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
the storm and gale warnings across the waters likely to be
converted to SCA later this morning.

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...
One more round of minor to moderate coastal flooding in the southern
and eastern bays of Long Island this morning. 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. As winds back to
N/NE, could see water levels fall on the lower end of guidance.

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...Wind Advisory until 6 AM EST early this morning for CTZ006>008-
     010>012.
NY...Coastal Flood Warning until 11 AM EST this morning for
     NYZ079>081-179.
     Wind Advisory until 6 AM EST early this morning for NYZ078>081-
     177-179.
     Winter Weather Advisory until 7 AM EST this morning for NYZ067-
     068.
     Coastal Flood Advisory until 8 AM EST this morning for NYZ074-
     075-178.
NJ...Winter Weather Advisory until 7 AM EST this morning for NJZ002.
     Coastal Flood Advisory until 8 AM EST this morning for NJZ006-
     106-108.
MARINE...Gale Warning until 6 AM EST early this morning for ANZ330-335-
     338-340-345.
     Storm Warning until 6 AM EST early this morning 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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