Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 011759
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1259 PM EST Wed Mar 1 2017

.SYNOPSIS...
Deep low pressure tracks from the Great Lakes to the Canadian
maritimes through Thursday. An associated warm front moves to
the north this afternoon, with a cold front crossing the Tri
state tonight. An Alberta Clipper approaches Thursday night and
moves across the area Friday. High pressure builds in from the
west Friday night through Saturday night, eventually moving off
the Southeast coast Sunday. A large frontal system approaches
from Southeast Canada late this weekend into early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A warm front has been slow to move north and is expected to move
north this afternoon. Visibilities have increased with local to
patchy areas of dense fog remaining. Have allowed the dense fog
advisory to expire.

With the warm frontal passage and a brief break in the cloud
cover this afternoon still expecting destabilization. There area
remains in a slight risk for severe thunderstorms and will
continue with the enhanced wording into this evening, around
03Z. With the approach of the cold front and the pre frontal
tough moving east probabilities quickly lower late this evening
into late tonight, and adjusted probabilities through tonight.

The flow is mainly unidirectional aloft, but there is some
veering from the surface to 500 hPa. As a result, while the main
mode should be convective line segments, could see some bowing.
Thus the main threat is from straight line winds. If bowing
segments occur, then the risk of weak tornadoes cannot be
completely ruled out.

Record highs still possible today, see the climate section of
the AFD for details. There is also some potential that some
locations could have a record high minimum temperature for the
calendar day. The achievement of this record likely will not be
determined until midnight, as the rate at which cold air comes
in behind the cold front could serve as a limiting factor over
western zones.

&&

.SHORT TERM /THURSDAY/...
With near dry adiabatic lapse rates progged through 850 hPa
Thursday and 850 hPa winds progged to 40-50kt Thursday (actually
starting late tonight). Have issued a wind advisory CWA wide for
likelihood of wind gusts of 45 to 50 mph from 6z-23z Thursday.
Also, there is some potential for coastal areas to have
sustained winds reach the threshold of 31 mph.

Otherwise a northern stream shortwave passes to the north
Thursday, but dry low levels and strong downsloping boundary
layer flow should keep things dry.

It will be noticeably cooler Thursday, with highs in the 40s,
some 15-25 degrees cooler than today.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
The upper level jet will be situated south of the region Thursday
night through early Saturday along with there being a deep upper
level trough within the Northeast. The trough will lift out of the
region Saturday night through Sunday with ridging taking place. This
will continue through Tuesday. The upper level jet will not be as
strong and will be moving across the region and eventually north of
the region early next week.

A much colder airmass Thursday night will prevail through Saturday
night. Colder than normal temperatures can be expected with cold air
advection from a gusty NW flow Thursday evening. Winds will diminish
going into Friday. An Alberta Clipper will be arriving Friday,
providing a chance of snow across the region with wet bulb cooling
as falling snow aloft will cool the column down to below
freezing after a short time. Forecast POPs could go up with
subsequent forecasts as most GEFS members were showing
precipitation across the region on Friday. NAM is strongest with
the clipper showing a deeper low and more precipitation while
ECMWF shifts the clipper more to the south of the region, only
grazing the region with very little precipitation, while the CMC
is basically dry. Kept mention of a chance of light snow
Friday.

The liquid equivalent amounts were mostly less than a quarter of an
inch and with temperatures being above freezing initially, not much
in accumulation is expected at this time, keeping snow at a few
tenths of an inch accumulation. There is the possibility though
of getting around 2 inches of snow with any colder trend to
temperatures as well as any higher trend in moisture content and
precipitation.

Conditions dry out Friday night into Saturday with another
blast of cold air delivered on another round of gusty NW flow
with an area of high pressure building to the west of the
region. The flow aloft becomes more progressive with ridging
aloft and the airmass will moderate Sunday into Monday. The
winds decrease Saturday night along with continued dry
conditions as the ridge of high pressure moves across. The high
moves off the Southeast coast Sunday and further shifts south
Monday. A large frontal system traveling through Southeast Canada
will be approaching late this weekend into early next week. The
associated warm front moves across Monday with a cold front moving
in on Tuesday.

Temperatures will return to being above normal Sunday night through
Tuesday. Concerning precipitation Sunday night into early next week,
some rain and snow showers are a low probability Sunday night into
Monday with rain shower possibilities thereafter with the
aforementioned frontal system approaching.

&&

.AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
Conditions across the forecast area vary from VFR/MVFR west of
NYC and IFR/LIFR east of NYC.

An area of rain showers moving across the eastern terminals
should push east by 19z. Some improvement is expected after
19Z.

A second round of showers and possible thunderstorms are
expected between 20z-00z. Unsure just how much thunder we get,
for now, will carry VCTS in the tafs where there is some higher
confidence of thunder occurring. Elsewhere, will carry a SHRA
in the forecast.

After 00Z, drier conditions are expected with a return to VFR.
Some of the forecast guidance is hinting at some low cigs
tonight. Confidence low on this occurring, and will leave out
of the tafs, however will monitor the potential for this to
occur.

As for winds, South to Southwest winds gradually increase
through the taf period, with gusts into the 20-30kt range
tonight and 30-40kt range on Thursday. Winds veer to the west
overnight.

...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: Timing of start of wind gusts may be delayed
up to a few hours. Improvements to visibility and ceilings may
be off up to 2 hours. Amendments likely.

KLGA TAF Comments: Timing of start of wind gusts may be delayed
up to a few hours. Improvements to visibility and ceilings may
be off up to 2 hours. Amendments likely.

KEWR TAF Comments: Timing of start of wind gusts may be delayed up
to a few hours. Improvements to visibility and ceilings may be off
up to 2 hours. Amendments likely.

KTEB TAF Comments: Timing of start of wind gusts may be delayed
up to a few hours. Improvements to visibility and ceilings may
be off up to 2 hours. Amendments likely.

KHPN TAF Comments: Timing of start of wind gusts may be delayed
up to a few hours. Improvements to visibility and ceilings may
be off up to 2 hours. Amendments likely.

KISP TAF Comments: Timing of start of wind gusts may be delayed
up to a few hours. Improvements to visibility and ceilings may
be off up to 2 hours. Amendments likely.

.OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY...
.Thursday Afternoon...VFR. W-NW winds G25-35KT.
.Friday...MVFR/IFR possible with a chance of light snow. NW
winds G20-25KT.
.Saturday...VFR. NW G20-25KT.
.Sunday...VFR. Chance of rain. SW winds G20KT.
.Monday...VFR.

&&

.MARINE...
Visibilities have slowly improved as a warm front moves into the
ocean waters. The dense fog advisory has been cancelled.

A small craft advisory remains in effect this afternoon through
tonight as ocean seas remain at 4 to 5 feet. Winds were below
small craft advisory levels, however, winds will be increasing
to small craft this afternoon and continue through tonight.
With deep mixing and strong low level cold advection Thursday,
all waters should see gusts to Gale Force, so have issued a Gale
warning for Thursday for all marine zones.

Gales dropping off to SCA level winds (mainly over the ocean
and eastern waters) Thursday evening with ocean seas remaining
in SCA Thursday night. Winds diminish late Thursday night.
Friday features below SCA conditions. Behind the clipper system,
a return to SCA conditions is forecast for Friday night through
much of the first half of the weekend as the pressure gradient
tightens between high pressure building from the west and low
pressure strengthening as it moves farther offshore. Gales will
be possible at times Saturday and Saturday night for all waters
with the cold air advection. High pressure being relatively
closer for the second half of the weekend with a weaker pressure
gradient will allow for SCA conditions to drop off.

&&

.HYDROLOGY...
Rainfall through tonight is expected to average 1/3 to 1/2 of an
inch, with locally higher amounts possible. While the
possibility is low, stronger convection could cause isolated
minor flooding of poor drainage/urban areas.

No hydrologic impacts expected from any precipitation late this week
through Monday.

Melting of the snow pack in Vermont and Massachusetts has caused
significant rises along the Connecticut River.

&&

.CLIMATE...
Record highs for Wednesday March 1

Location.......Record High/Year Set.....Forecast High

Newark..................75/1972...............72
Bridgeport..............59/1972...............61
Central Park............73/1972...............69
LaGuardia...............68/1972...............68
J F Kennedy.............58/2004*..............65
Islip...................60/2004...............62

* = and in previous years

Record high minimum temperatures for Wednesday March 1

Location....Record High Min/Year Set.....Lowest Temperature during 24 hour day

Newark..................43/1976...............51
Bridgeport..............41/1976...............44
Central Park............45/2004...............47
LaGuardia...............44/2004...............51
J F Kennedy.............42/1974*..............48
Islip...................39/2016...............48

* = and in previous years

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory from 1 AM to 6 PM EST Thursday for CTZ005>012.
NY...Wind Advisory from 1 AM to 6 PM EST Thursday for NYZ067>075-
     078>081-176>179.
NJ...Wind Advisory from 1 AM to 6 PM EST Thursday for NJZ002-004-
     006-103>108.
MARINE...Small Craft Advisory until 6 AM EST Thursday for ANZ330-335-
     338-340-345-350-353-355.
     Gale Warning from 6 AM to 6 PM EST Thursday for ANZ330-335-338-
     340-345-350-353-355.

&&

$$


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