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Area forecast discussion 
National Weather Service New York New York
1005 am EST Monday Jan 26 2015

Synopsis...
a Nor'easter develops off the Delaware-Maryland-Virginia coast this afternoon and
tracks slowly north tonight as it intensifies reaching just east of
Montauk Point by Tuesday night. The storm weakens as it moves east
to the Gulf of Maine on Wednesday. High pressure on Thursday is
followed by a clipper low passing across Thursday night into early
Friday. Cold high pressure builds in for the weekend.

&&

Near term /until 6 PM this evening/...
surface low pressure was located near Jefferson NC at 9am...and
will move off the coast this morning and develop into a
Nor'easter.

Light snow has developed across the County Warning Area and periods of snow will
continue through the afternoon. Forecast of 1-3 inches is still on track...but
did lower visibility in the grids to around 3/4sm.

The onset of heavy snow was moved back to 6 PM...although this may
even be too late as MDT-heavy snow could be occurring over Li by 2
PM and by 4 PM over CT. The 12z NAM lends support to this.

Temperatures. Will only be in the lower and middle 20s
inland...to the upper 20s and lower 30s closer to the coast.

&&

Short term /6 PM this evening through 6 PM Tuesday/...
a life threatening...potentially historic winter storm expected
from late today into Tuesday...

Nwp guidance has shown a little more spread than one would like to
see at such a short range. Much of the 00z guidance lowered quantitative precipitation forecast
amounts for much of the region...which would mean lower snow
totals. However...the 00z European model (ecmwf) remained very consistent with its
previous runs. It did lower quantitative precipitation forecast slightly...but the overall evolution
of the system remained similar to its 12z run. Did not want to make
drastic changes to the expected snow amounts and headlines with
just one model cycle. In fact...the latest 06z NAM has come into
closer agreement with the 00z European model (ecmwf). The 21z and 03z sref means
remained similar to the 00z European model (ecmwf) and 06z NAM.

The 00z GFS appears to be a fast NE outlier. It may also be
suffering from convective feedback as the surface low follows quantitative precipitation forecast
maximum offshore...and does not seem to get fully captured by the
upper low.

Still anticipate the low to undergo rapid intensification as the
parent upper low cuts off aloft near the middle Atlantic coast
tonight. The low stalls southeast of Montauk late tonight into Tuesday. A
prolonged period of moderate to heavy snow is expected on the northwest
flank of the low...in the deformation zone. The middle level low
centers and intense middle level frontogenesis will promote heavy
snow bands...but it is impossible to predict their location this
far out. Models also have a tendency to not spread the best lift
far enough northwest in intense cyclones.

With all of this in mind...did lower snow totals slightly in
collaboration with surrounding offices and wpc...but we are still
expecting an overall 18 to 24 inches...locally higher where best
mesoscale snow banding sets up. Snowfall rates of 2-4 inches per
hour expected late tonight into Tuesday morning.

In addition...the deep low pressure combined with strong high
pressure to the north and west and heavy falling/blowing snow will
create blizzard conditions across the entire region. A Blizzard
Warning remains in effect...with potential for sustained winds up
to 35 miles per hour on Long Island...and wind gusts ranging from 40 miles per hour
inland...to 45-50 miles per hour most elsewhere. Gusts up to 60 miles per hour cannot be
ruled out across far eastern Long Island.

With the low nearly stalling near Cape Cod on Tuesday...light to
occasionally moderate snow is possible in mesoscale
bands...especially late Tuesday morning into early afternoon.

Temperatures during the storm will generally be in the 20s...except
falling to 15-20 tonight inland. Wind chills will be mostly in
the single digits to middle teens...but could get close to zero across
southern CT. Temperatures on Tuesday will only be in the lower to
middle 20s.

&&

Long term /Tuesday night through Sunday/...
the Nor'easter begins to fill and pull away Tuesday night. Light
snow ends from west to east with an inch or less of additional
accumulation. Winds also diminishing and have removed mention of
blowing snow.

Becoming sunny on Wednesday with 15-20 miles per hour winds. Temperatures forecast below
MOS with snow cover. Wind chills on Wednesday are in the lower
teens.

Continue to undercut MOS through the period with the new snow cover.

Clipper system still on tap for Thursday night into Friday morning.
This looks like a "typical" clipper with 1-3" in an all snow event.

High pressure builds back in on Saturday with below normal
temperatures continuing.

The active pattern reaching the limits of predictability by Sunday.
Suggestion of a southern stream system sometime late this weekend
into early next week. With gefs looking very chaotic...hard to say
much as to what might happen with this next system.

&&

Aviation /15z Monday through Friday/...
** high impact snow and wind event expected from late today into
Tuesday night **

Low pressure develops east of the middle Atlantic coast this
morning...then tracks south and east of the region tonight.

Mainly IFR conditions in snow through 18z...then LIFR conditions by
18-21z from west to east. Blizzard conditions expected at
kjfk/klga/kisp/kgon by late this evening. 1-3" of snow expected by
00z...then 2-4 inch an hour rates develop from southeast to northwest starting
around midnight.

North winds veer to the NE early this morning. Winds become gusty by
late morning with gusts up to 25-30kt by middle-late afternoon. Winds
back to the north-northeast late tonight...with gusts increasing to 25-40kt
lowest far west terminals and strongest far east terminals.

Moderate icing is likely below fl180. Moderate turbulence between
surface-fl390 with local severe possible fl210-340. Refer to zny meteorological impact statement for
more information.

New York 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: conditions may briefly drop to LIFR before 18z
in snow bands. 1-3 inches of snow expected through 00z. After
00z...heavy snow with rates of 2-4 inches per hour likely.

Klga fcster comments: conditions may briefly drop to LIFR before 18z
in snow bands. 1-3 inches of snow expected through 00z. After 00z...heavy
snow with rates of 2-4 inches per hour likely.

Kewr fcster comments: conditions may briefly drop to LIFR before 18z
in snow bands. 1-3 inches of snow expected through 00z. After
00z...heavy snow with rates of 2-4 inches per hour likely.

The afternoon kewr haze potential forecast is yellow...which implies
slant range visibility 4-6sm or greater outside of cloud.

Kteb fcster comments: conditions may briefly drop to LIFR before 18z
in snow bands. 1-3 inches of snow expected through 00z. After
00z...heavy snow with rates of 2-4 inches per hour likely.

Khpn fcster comments: timing of gusts may be off by an hour or two.
Conditions may briefly drop to LIFR before 18z in snow bands. 1-3
inches of snow expected through 00z. After 00z...heavy snow with
rates of 2-4 inches per hour likely.

Kisp fcster comments: conditions may briefly drop to LIFR before 18z
in snow bands. 2-3 inches of snow expected through 00z. After
00z...heavy snow with rates of 2-4 inches per hour likely.



Outlook for 12z Tuesday through Friday...
Tuesday and Tuesday evening...LIFR or lower conditions with
blizzard conditions. NE-north winds g35-50 knots.
Late Tuesday night...becoming VFR. Northwest winds g25-35kt.
Wednesday...VFR. Northwest winds g25-30kt possible.
Wednesday night-Thursday...VFR.
Thursday night...MVFR or lower conditions in light snow.
Friday...chance MVFR in light snow in the am. VFR with northwest winds g25-30kt in
the afternoon.

&&

Marine...
no changes to the marine headlines with this forecast package.
Have made minor adjustments to winds and seas.

Winds and seas increase across all waters on today ahead of
approaching low pressure. Gale force easterly wind gusts expected
on the ocean waters during the day...ramping up tonight as winds
back northerly to minimal hurricane force on the eastern ocean
waters late Monday night into Tuesday morning...and storm force elsewhere
and also on eastern Long Island Sound and the bays of Long Island.
The eastern ocean waters may also see sustained storm force winds
during this time.

Winds and seas start subsiding Tuesday night. Expect to be below
gales before morning and below Small Craft Advisory levels in the early evening
Tuesday.

Sub Small Craft Advisory on Thursday into early Friday morning. Then Small Craft Advisory winds return
as a clipper system deepens well off shore.

&&

Hydrology...
a major snowstorm expected from Monday into Tuesday night...with liquid
equivalent amounts of 1.5 to 2.25 inches.

Liquid equivalent precipitation amounts for the system moving
through Thursday night into Friday is currently forecast to be
light...mostly in the form of snow.

Ice on the Wallkill and Yantic rivers is causing minor
fluctuations in river levels at this time.

&&

Tides/coastal flooding...
coastal Flood Watch continues as it remains uncertain if we will see
widespread coastal flooding.

The Nor'easter is expected to produce moderate coastal impacts
for parts of region overnight into early Tuesday morning high
tide. There's the potential for flooding of vulnerable shore roads
and/or adjacent properties due to height of storm tide and/or wave
action.

The uncertainty with the surge is in how quickly winds turn from
the NE to north. An earlier veering of winds to the north ahead of high
tide typically reduces surge in our region.

The most likely surge for coastal areas is:

- western Long Island Sound is 3 to 4 feet of surge with potential for
up to 4 1/2 feet.

- Eastern Long Island Sound is 2 1/2 to 3 1/2 feet of surge with
potential for up to 4 feet.

- New York Harbor and the South Shore bays 2 1/2 to 3 1/2 feet of
surge with potential for up to 4 feet.

Beach erosion and washovers are expected along ocean facing barrier
beaches of Long Island due to 7 to 12 feet waves and the high storm
tide. A few exposed water front structures may be damaged.

High waves and high storm tide will also cause beach erosion along
north facing shorelines of Long Island Sound and along the Twin
Forks. A few exposed water front structures may be damaged.
Coastal Flood Watch continues as it remains uncertain if we will see
widespread coastal flooding. This morning extra-tropical storm surge
models have lowered the surge forecast...so the threat is somewhat
diminished. The tide of concern is the one overnight...this
afternoon's high tide is not expected to cause coastal flooding.

&&

Climate...
this blizzard has the potential to produce the largest single-
storm snowfall in NYC history. Here are the current top ten
snowfalls for the city...



Amount dates

26.9 Feb 11-12 2006
25.8 Dec 26-27 1947
21.0 Mar 12-13 1888
20.9 Feb 25-26 2010
20.2 Jan 7-8 1996
20.0 Dec 26-27 2010
19.8 Feb 16-17 2003
19.0 Jan 26-27 2011
18.1 Jan 22-24 1935 and March 7-8 1941
18.0 Dec 26 1872

&&

Okx watches/warnings/advisories...
CT...coastal Flood Watch from late tonight through Tuesday morning
for ctz011-012.
Blizzard Warning from 1 PM this afternoon to midnight EST
Tuesday night for ctz005>012.
Coastal Flood Watch from late tonight through Tuesday morning
for ctz009-010.
New York...coastal Flood Watch from late tonight through Tuesday morning
for nyz079-081.
Blizzard Warning from 1 PM this afternoon to midnight EST
Tuesday night for nyz067>075-078>081-176>179.
Coastal Flood Watch from late tonight through Tuesday morning
for nyz071-073-078-176-177.
Coastal Flood Watch late tonight for nyz074-075-080-178-179.
New Jersey...Blizzard Warning from 1 PM this afternoon to midnight EST
Tuesday night for njz002-004-006-103>108.
Marine...Small Craft Advisory until 6 PM EST this evening for anz345.
Storm Warning from 6 PM this evening to 6 PM EST Tuesday for
anz330-340-345-353-355.
Gale Warning from 6 PM this evening to 6 PM EST Tuesday for
anz335-338.
Gale Warning until 6 PM EST this evening for anz350-353-355.
Hurricane force wind warning from 6 PM this evening to noon
EST Tuesday for anz350.

&&

$$
Synopsis...ds/tongue
near term...jmc/ds
short term...ds
long term...tongue
aviation...mmd
marine...ds/tongue
hydrology...ds
tides/coastal flooding...precipitable water
climate...

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