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Area forecast discussion 
National Weather Service New York New York
408 PM EST Friday Feb 12 2016

Synopsis...
an Arctic cold front approaches from the northwest this
evening...then crosses the tri-state late late tonight and
Saturday morning...as a coastal low tracks well to the southeast.
Arctic high pressure then builds in through Sunday night before
sliding offshore on Monday. A low pressure system develops across
the southeast Monday night and tracks up the eastern Seaboard
Tuesday into Tuesday night. A cold front moves through Wednesday
followed by high pressure for the remainder of the week.

&&

Near term /until 6 am Saturday morning/...
most guidance suggests that as the 700-500 hpa trough axis
approaches tonight...it should be able to pull enough moisture northwest
from the coastal low well offshore to bring the chance of some
light snow to the region tonight...with light snow likely over the
S Fork of Long Island. There is also a low chance for snow squalls
right ahead of the Arctic front. Expect generally a dusting to
less than 1 inch of snow at most locations...though the South Fork
could see an inch maybe two. The main threat from any snow squall
would be a rapid reduction in visibility and gusty winds with its
passage.

After a relatively tranquil evening...wind increase ahead of
then...behind the Arctic front. Lows will occur very late
tonight/early Sunday morning...behind/with the Arctic front.

Blended NAM 2-M temperatures with met/ecs/mav guidance for lows.
Values should be around 10-15 degrees below normal.

&&

Short term /6 am Saturday morning through Sunday/...
Arctic air pours in to the region Saturday/Saturday night...with
850 temperatures plunging to 25-30 below late Saturday night
(depending on model of choice). Expect highs to occur Saturday
morning...mainly in the 10s...then temperatures slowly fall
during the day. Will see a more rapid drop off Saturday evening
with loss of solar heating and strongest low level cold advection.
Winds increase out of the northwest 15-30 miles per hour with gusts to 35-45 miles per hour by
middle Saturday morning...and remain about that strong into Saturday
evening. This is just below advisory criteria...cannot not rule
out a few gusts to 40kt/sustained winds of 27kt. Regardless...wind
issues will be addressed in the west-southwest product. Winds do diminish
late Saturday night to 10-25 miles per hour with gusts of 30-40 miles per hour. Lows
Saturday night generally from near 0 across Long Island/NYC metropolitan
to 5-10 below across northern interior zones. Lows based on blend
of NAM/GFS/ECMWF 2-meter temperatures and MOS guidance - weighed
towards colder NAM values...noting generally under forecast of
extreme cold by most guidance.

As for wind chills...should fall below zero Saturday morning...to
around 10-15 below by Saturday evening...then to advisory (15-24
below)/warning (25-30 below) levels late Saturday night into
Sunday morning. Did convert most of the wind chill watch to an
advisory...with the exception of S New London where 25 below wind
chills were most likely.

Sunday should be dry with northwest flow aloft. Highs should be around 25
degrees below normal...consistent with a blend of mav/met/ecs
guidance...NAM/ECMWF 2-meter temperatures...and a mix down from
925 hpa per BUFKIT soundings. With diminishing winds...wind
chills in the afternoon should range from 5 below to 5 above zero.

&&

Long term /Sunday night through Friday/...
Sunday night...brunt of the Arctic mass will have modified by Sunday
night as 850 hpa temperatures warm to around -10c. However...the surface
high settles right over the tri-state which will allow for good
radiational cooling conditions as winds will be light. The only
potential drawback is from some high clouds which may begin to
stream overhead as a 500 hpa shortwave lifts across the Great Lakes
region. Low temperatures will range from the low single digits
inland to the upper single digits and lower teens closer to the
coast. Wind chills will be close to actual air temperature with
light winds.

Monday through Tuesday...high pressure will move offshore on Monday
allowing for a return flow to set up with low level warm advection
commencing during the day. Aloft...amplifying ridging on across
western North America sends several pieces of energy into a digging
trough across the central states. This is where uncertainty in the
forecast greatly increases and models diverge in the handling of
this energy. This is not surprising as this energy is emanating from
the North Pacific. It will not be until Sunday morning that this
energy moves over land with better sampling. Low pressure will
develop across the southeast late Monday into Monday night as this
energy amplifies the middle and upper level trough. Warm advection
and increasing moisture ahead of this low should allow for
precipitation to break out Monday afternoon and evening...with
thermal profiles mainly supporting snow. It is after this time that
uncertainty greatly increases as the low intensifies and tracks along
the coast or just inland Tuesday. Deterministic and ensemble models
show quite a large spread with the track and intensity of this low
pressure Monday night into Tuesday. This will ultimately determine
exact thermal profiles and how much precipitation we end up seeing
across the area.

The signals are there for a rapidly intensifying low to move from
the middle Atlantic region Tuesday morning to northern New England
and southeast Canada by Tuesday night. The 12z GFS takes the low across
Long Island and Connecticut while its ensemble mean is a little
further west...moving it across New York City and up the lower
Hudson Valley. The 12z European model (ecmwf) appears to be on the western edge of
the guidance with the low tracking across central PA. This would put
the entire area in the warm sector. The 12z European model (ecmwf) is also one of the
most amplified of the guidance as it shows the energy at 500 hpa
cutting off...which the other models do not indicate as the system
is quite progressive. The 12z CMC is further east and faster...with
the low moving across eastern Long Island/southeast CT. There is also large
spread in the ensembles showing variety of these solutions mentioned
above.

Have followed a consensus forecast due to this uncertainty. Have also
continued with likely probability of precipitation for this time period. This brings snow
changing to rain at the coast Monday night...with a wintry mix
changing to rain inland late Monday night into Tuesday. Temperatures
may take a little longer to warm above freezing inland...so a period
of freezing rain is possible Monday night...before changing to rain
Tuesday morning. Rain...possibly heavy at times...is expected on
Tuesday with temperatures well into the 40s. Timing and amounts
remain uncertain at this time...but a general range of 1 to 3 inches
of total quantitative precipitation forecast is forecast in the consensus of the models. See Hydro
section for more information. It could also become quite breezy
Tuesday...but this again will ultimately be determined by the exact
track and intensity as the low moves across the area. Much of the
precipitation should end Tuesday night as the low moves well NE of
the area.

Wednesday through the end of the week....a trailing shortwave may
swing through on Wednesday...so have left probability of precipitation in the low chance
range. A cold front also moves through on Wednesday. Temperatures
will be near normal in the lower 40s. Temperatures should fall back
below normal levels Thursday as high pressure builds over the
region. The high is currently prognosticated to move offshore Friday as
another frontal system approaches.

&&

Aviation /21z Friday through Wednesday/...
weak high pressure into this evening. A cold front moves through
late tonight.

VFR into this evening. SW winds around 10kt.

Outlook for this overnight...scattered shsn could potentially leave a
coating of snow on the runways.

..NY metropolitan enhanced aviation weather support...

Detailed information...including hourly taf wind component forecasts
can be found at: http:/www.Erh.NOAA.Gov/zny/n90 (lower case)

Kjfk fcster comments: no unscheduled amendments expected.

Klga fcster comments: no unscheduled amendments expected.

Kewr fcster comments: occasional gusts around 15kt possible until 22-
23z.

Kteb fcster comments: no unscheduled amendments expected.

Khpn fcster comments: no unscheduled amendments expected.

Kisp fcster comments: no unscheduled amendments expected.

Outlook for 18z Sat through Wednesday...
Sat...VFR. Northwest gusts around 35kt.
Sun...VFR. Northwest gusts 20-25kt in the morning.
Monday...VFR am. Chance afternoon snow with sub-VFR.
Monday night...IFR conditions likely. Snow changing to rain by late
evening NYC metros/kisp...and around/shortly after midnight
khpn/kbdr/kgon...and cold ground could make for a brief period of
freezing rain on runways despite air temperatures rising above freezing.
Snow mixing with or changing to freezing rain after midnight at
kswf. Southeast gusts around 25kt late.
Tuesday...rain likely with IFR conditions. Southeast-S winds g30-35kt and low level wind shear.
Wednesday...mostly VFR. Chance rain/snow shower and brief sub-VFR.

&&

Marine...
sub-Small Craft Advisory conditions on most waters this evening...then Small Craft Advisory
conditions develop on the coastal ocean waters overnight...so have
issued an Small Craft Advisory there. There also could possibly be Small Craft Advisory gusts late
on the East Sound/bays of Long Island...but confidence in this is not
high enough for a headline at this time.

Gale conditions develop rapidly Saturday and last through
Saturday night on all waters. Gales will linger into Sunday
morning over the coastal ocean waters and eastern sound/bays. As
a result have converted the existing gale watch to a Gale Warning
for the non-ocean waters...and synched up with existing one on the
ocean to cover Saturday/Saturday night. The Gale Warning was
extended for the coastal ocean waters and eastern sound/bays
through Sunday morning. A Small Craft Advisory will be needed once gale conditions
have ended on all waters for a period of time on Sunday.

The combination of gales and cold temperatures will produce at
least moderate freezing spray on all but the South Shore bays
(forecast waves are too low for significant spray there) Saturday
into Sunday...with heavy freezing spray forecast Saturday night on
the sound/New York Harbor/East bays...and into Sunday morning for the
eastern sound/bays.

Sub-Small Craft Advisory conditions forecast Sunday night through Monday as high
pressure moves over the waters. Then...developing low pressure
across the southeast tracks up the eastern Seaboard Monday night into
Tuesday. This will increase seas well above Small Craft Advisory levels on Tuesday
and bring the likelihood of Small Craft Advisory winds across all waters. There is
also a chance for gale force gusts...at least on the ocean...on
Tuesday. The low moves well NE of the waters Tuesday night into
Wednesday with...but conditions should at least remain above Small Craft Advisory
levels through Wednesday.

&&

Hydrology...
less than a tenth of an inch of liquid equivalent quantitative precipitation forecast is forecast
through Saturday. It should be dry Saturday night and Sunday.

A developing low pressure system moving near or along the coast
Monday night into Tuesday had the potential to produce 1 to 3 inches
of liquid equivalent precipitation. Some of this will fall as frozen
precipitation Monday night...but then runoff via melting snow and
heavy rain Tuesday could cause at least Urban and Small Stream
flooding problems. It is too early to say if main Stem rivers would
be affected due to uncertainty in where the heaviest rainfall will
occur as well as the exact track and intensity of the low pressure.

&&

Climate...
with the extremely cold air mass forecast Saturday into
Sunday...record minimums and record low maximums may be reached.
Here are the records and forecasts...

Station......record/forecast minimum
for 2/14

Central Park.....2 (1916) / 0
LaGuardia........1 (1979) / 1
jf Kennedy.......4 (1979) / 2
Islip............7 (2015) / 1
Newark...........0 (1979) / 0
Bridgeport.......3 (2015*) / -1

Station......record low maximum/forecast high
for 2/14

Central Park....17 (1979) / 14
LaGuardia.......15 (1979) / 15
jf Kennedy......17 (1979) / 16
Islip...........26 (1987) / 14
Newark..........15 (1979) / 14
Bridgeport......18 (1979) / 14

*in 1979 as well

&&

Okx watches/warnings/advisories...
CT...Wind Chill Advisory from 4 PM Saturday to noon EST Sunday for
ctz009>011.
Wind chill warning from 4 PM Saturday to noon EST Sunday for
ctz005>008-012.
New York...Wind Chill Advisory from 4 PM Saturday to noon EST Sunday for
nyz071>075-078>081-176>179.
Wind chill warning from 4 PM Saturday to noon EST Sunday for
nyz067>070.
New Jersey...Wind Chill Advisory from 4 PM Saturday to noon EST Sunday for
njz004-006-103>108.
Wind chill warning from 4 PM Saturday to noon EST Sunday for
njz002.
Marine...Gale Warning from 6 am Saturday to noon EST Sunday for anz330-
340-345-350-353-355.
Heavy freezing spray warning from 6 PM Saturday to noon EST
Sunday for anz330-335-340.
Freezing spray advisory from 4 am to 6 PM EST Saturday for
anz330-335-338-340.
Heavy freezing spray warning from 6 PM Saturday to 6 am EST
Sunday for anz338.
Gale Warning from 6 am Saturday to 6 am EST Sunday for anz335-
338.
Small Craft Advisory from 11 PM this evening to 6 am EST
Saturday for anz350-353-355.
Freezing spray advisory from 4 am Saturday to 6 PM EST Sunday
for anz350-353-355.

&&

$$
Synopsis...maloit/ds
near term...maloit
short term...maloit
long term...ds
aviation...jc
marine...maloit/ds
hydrology...maloit/ds
climate...

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