Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kokx 161327 
afdokx

Area forecast discussion
National Weather Service New York New York
827 am EST Tue Jan 16 2018

Synopsis...
high pressure continues to move offshore today, allowing low
pressure to approach from the west, passing just north of the
area tonight. Meanwhile, a developing coastal low will develop
and pass just east of Montauk during the day Wednesday, then
moves up the coast into the Canadian Maritimes Wednesday night.
High pressure will then build to the south through Friday,
moving into the western Atlantic this weekend. Low pressure will
then approach from the west early next week.

&&

Near term /until 6 PM this evening/...
high pressure continues to push offshore today. This will allow
weak low pressure and associated cold front to approach from
the west. While 00z forecast model guidance were fairly good
agreement keeping much of the region dry today, have updated
pop based on spotter report on Orange County indicating a trace
of new snow on the ground. Most of the light snow today should
be to just the far northwestern portion of the County Warning Area. As such,
have backed up the start time of the Winter Weather Advisory for
portions of New Jersey and the lower Hudson Valley til 4 PM. Otherwise,
expect cloudy skies today. Temperatures today climb into the
lower and mid 30s, warmer closer to the coast.

&&

Short term /6 PM this evening through 6 PM Wednesday/...
winter weather advisories in effect for northeast New Jersey,
the lower Hudson Valley, southern Connecticut and the northern
portion of NYC for late this afternoon through Wednesday.

Low pressure and associated cold front approach the western
portion of the County Warning Area tonight, with the low passing just north of
the region. Meanwhile, a second area of low pressure develops
south of Long Island tonight, and passes east of Montauk early
Wednesday afternoon. The combination of these two system will
bring precipitation to the region. Highest confidence for snow
is north and west of NYC, while the potential for mixed p-types
reduces confidence for the city into Long Island and coastal
Connecticut. Expecting the precipitation to remain mostly all
snow through midnight, then as the developing low approaches, it
should bring some warmer air into the area to change
precipitation over to rain or a rain/snow mix across much the
Long Island, NYC and portions of coastal CT. The changing p-type
has made forecasting snowfall amounts somewhat difficult,
especially right along the rain/snow line. For now, thinking the
highest snowfall totals will be across the lower Hudson Valley
and southern CT, with the exception of southern New London
County. These areas have 4-6 inches of snow forecast. Across NE
New Jersey and the northern portions of NYC, looking at 3-4 inches. The
southern portion of NYC and Nassau, 2-3 inches are expected. And
across Suffolk County on Long Island, up to 1 inch. The
heaviest precipitation is expected to fall Tuesday night into
Wednesday morning, then taper off from west to east during the
mid to late afternoon and early evening. 16/00z forecast
guidance has come into better agreement with the track of the
low, however a shift to the west, would increase the chance for
more rain across NYC and CT and potentially increase snowfall
amounts across the interior. A track farther offshore, would
increase snowfall amounts closer to the coast.

Lows tonight fall into the middle and upper 20s across the
interior, while coastal locations fall into the lower 30s. On
Wednesday, highs climb into the lower 30s across the interior,
with middle 30s closer to the coast.

&&

Long term /Wednesday night through Monday/...
on the heels of an upper trough passing offshore early Thursday, a
progressive southern branch of the polar jet will become dominant
across the lower 48, with a a gradual warmup as the air mass
transitions to Pacific origin. Daytime highs on Thursday will be or
just above near freezing, rising to the upper 40s and lower 50s by
Sunday/Monday.

Conditions will be mainly dry as a large area of high pressure over
the lower Mississippi Valley translates slowly east and passes to
the south through the week and offshore this weekend.
A southern branch storm system then approaches late in the weekend
into early next week, with a surface low forecast to track up into
the Great Lakes. The trailing cold front moves through Monday night.
This is likely to be a rain event with a deep layered southerly flow
preceding the system, but with cold sfc air initially there could be
some mixed precip inland late Sunday night/Monday morning inland northwest
of NYC.

&&

Aviation /14z Tuesday through Saturday/...
high pressure retreats to the northeast today. An area of low
pressure approaches from the south into tonight, then tracks to near
Cape Cod by early Wednesday afternoon.

Mainly MVFR, except some low end VFR ceilings at kgon to today, with
conditions becoming MVFR there by 23z. Conditions should then become
IFR at all terminals after midnight.

Spotty snow showers are possible at northwest terminals this morning.
Otherwise, expect any precipitation to hold off until after sunset,
except at kswf where could see some light snow in the afternoon.
Expect all snow at lower Hudson Valley and New Jersey terminals and kbdr.
Will see a snow/rain mix, possibly changing to all rain at kgon/kisp
and possibly rain mixing in with the snow at klga and kjfk
overnight.

There is a chance that kisp and kgon and a low chance that klga and
kjfk could change completely to rain overnight/Wednesday morning,
but the confidence in this is too low to reflect in the tafs at this
time.

Light and variable winds become southeast at less than 10 kt at city
terminals this afternoon, then light and variable again this
evening, before becoming NE at less than 10 kt tonight.

New York Metro enhanced aviation weather support...

Detailed information...including hourly taf wind component fcsts can
be found at: http:/www.Weather.Gov/zny/n90

Kjfk taf comments: timing in changes to wind speed and direction
could be off +/- 1-2 hours. High confidence in wind speeds less than
10 kt. Spotty IFR ceilings possible this morning. Snow totals
around 3 inches through Wednesday.

The afternoon kjfk haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.

Klga taf comments: timing in changes to wind speed and direction
could be off +/- 1-2 hours. High confidence in wind speeds less than
10 kt. Spotty IFR ceilings possible this morning. Snow totals
around 3 inches through Wednesday.

The afternoon klga haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.

Kewr taf comments: timing in changes to wind speed and direction
could be off +/- 1-2 hours. High confidence in wind speeds less than
10 kt. Spotty IFR ceilings possible this morning. Snow totals
around 3 inches through Wednesday.

The afternoon kewr haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.

Kteb taf comments: timing in changes to wind speed and direction
could be off +/- 1-2 hours. High confidence in wind speeds less than
10 kt. Spotty IFR ceilings possible this morning. Snow totals
around 3 inches through Wednesday.

Khpn taf comments: timing in changes to wind speed and direction
could be off +/- 1-2 hours. Snow totals around 4 inches through
Wednesday.

Kisp taf comments: timing in changes to wind speed and direction
could be off +/- 1-2 hours. Spotty IFR ceilings possible this
morning. Snow totals around 1 inch or less through Wednesday.

Outlook for 12z Wednesday through Saturday...
Wednesday...IFR likely, with LIFR possible. Light snow expected,
expat rain or a rain/snow mix at Long Island/eastern CT terminals
and possibly kjfk/klga. Conditions improve to VFR late at western
terminals.
Wednesday night-Thursday...VFR. Northwest-west-northwest winds g15-25kt possible.
Thursday night-Saturday...VFR. West-southwest-west winds g15-20kt possible
Thursday night-Friday.



&&

Marine...
Small Craft Advisory in effect for the ocean waters as seas remain 4-5 ft. Ocean
seas increase a bit more tonight. Flow returns to a northwest direction
and begins to gust late on Wednesday, continuing into Thursday
night. Small craft wind gusts and marginal seas will be likely
on the ocean waters through Thursday night with a chance of
small craft gusts across eastern Long Island Sound and the
eastern Long Island bays. Friday through the weekend winds and
seas will be below Small Craft Advisory levels as high pressure builds to the
south and a weaker pressure gradient resides across the forecast
waters.

&&

Hydrology...
no significant hydrologic impacts are expected.

&&

Equipment...
NYC National oceanic and atmospheric administration weather radio station kwo-35 (162.55 mhz) is off the
air for an extended period of time.

&&

Okx watches/warnings/advisories...
CT...Winter Weather Advisory from midnight tonight to 6 PM EST
Wednesday for ctz005>012.
New York...Winter Weather Advisory from 4 PM this afternoon to 4 PM EST
Wednesday for nyz067>070.
Winter Weather Advisory from midnight tonight to 6 PM EST
Wednesday for nyz071>073.
New Jersey...Winter Weather Advisory from 4 PM this afternoon to 4 PM EST
Wednesday for njz002-004-103-105-107.
Winter Weather Advisory from midnight tonight to 6 PM EST
Wednesday for njz006-104-106-108.
Marine...Small Craft Advisory from midnight tonight to 6 PM EST
Wednesday for anz355.
Small Craft Advisory until 6 PM EST Wednesday for anz350-353.

&&

$$
Synopsis...BC/Goodman
near term...British Columbia
short term...British Columbia
long term...Goodman

National Weather Service Glossary of Abbreviations