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Area forecast discussion 
National Weather Service New York New York
637 am EST Friday Jan 30 2015

Synopsis...
low pressure and an associated cold front will move through this
morning. An Arctic cold front will follow this afternoon as the
low rapidly deepens off the New England coast. High pressure will
build in tonight into Saturday...then pass to the south Saturday
night. Another cold front will move through on Sunday...and low
pressure will pass to the south on Monday. High pressure will
return through middle week.

&&

Near term /until 6 PM this evening/...
weak low pressure and cold front is poised to move through the
area. This incipient weak low will go on to become a strong ocean
storm east of New England. Bands of snow and rain showers have
developed along and ahead of the front and look to spread mainly
across Long Island and southern CT this morning. This would bring
an additional coating to an inch of accumulation on top of any
prior light accumulation overnight. Any isolated rain showers may
result in some light icing. Again this is expected to be isolated.

The Arctic cold front was approaching central PA/NY...and may
also be accompanied by scattered snow showers as it moves through this
afternoon. Northwest winds will also increase after Arctic frontal passage and
start to usher in much colder air...with high temperatures in the
Lower/Middle 20s dropping quickly into the 20s.

&&

Short term /6 PM this evening through 6 PM Saturday/...
multiple wind/cold hazards will exist during this time frame.
First...the higher elevations and the NYC metropolitan urban heat island
should be the first areas to see northwest winds gusting as high as 45-50
miles per hour tonight via the combo of strong cold air advection and a rapidly tightening
pressure gradient as the low to the east bombs out S of Nova
Scotia into the 980s. These strong winds should spread to the rest
of the area late tonight.

The combo of sustained winds 15-25 miles per hour...a little higher than MOS
guidance...and temperatures falling through the teens and into the
single digits inland...colder than the coldest of GFS/NAM MOS
guidance lows by a couple of degree...will result in hazardous wind
chills of 15 to 20 below from late tonight into Sat morning for
most inland sections...and around 10 below for NYC and urban
sections to the west...Long Island and far southeast CT.

Sat should be a very cold day despite sunshine...with highs
struggling to reach 20 in NYC and Long Island...and remaining in
the teens elsewhere.

&&

Long term /Saturday night through Thursday/...
gusty northwest winds abate Saturday night as deep low pressure moves to
the Canadian Maritimes. High pressure builds to the south as a cold
front approaches from the northwest early Sunday.

Attention then turns toward low pressure that is expected to develop
around the middle Mississippi Valley ahead of northern stream trough.
At this time...models have shifted slightly north as they track the
low from around West Virginia Sunday night to off the middle Atlantic
coast Monday morning. It appears that the low tracks south of the
area...then just southeast of the 40n/70w benchmark Monday afternoon.

Still plenty of uncertainty as main energy just moving into western
Canada...and run to run shifts in track have been observed.
However...will boost probability of precipitation into the likely category for much of the
County Warning Area...with highest probability of precipitation southern portion...lower to the north. European model (ecmwf)
and GFS output at least a half inch of measurable. Based on this
model run...agree with previous forecast of a general 4 to 8 inches
of snow in this progressive storm...although may up that by an inch
or two on the low and high end...perhaps 5 to 10. However...any
shift to the south...which is certainly possible...will result in
lower snow amounts/chances for precipitation.

Thereafter...Arctic air moves in behind the low as high pressure
that originates from the Canadian prairies builds across middle west
and toward the eastern Seaboard by Tuesday.

Dry weather returns with much uncertainty for middle to late week. The
question is whether or not southern stream phases with northern
stream trough sometime Wednesday night or Thursday. This would result in
clipper type front approaching from the west with possible low pressure
development well to the south tracking off the East Coast.
Again...European model (ecmwf) and GFS differ with timing and strength...so will cap
probability of precipitation at chance for now late Wednesday through Thursday.

Temperatures were a gridded MOS/mav and met blend Sat night and
Sunday...with gridded MOS and wpc next week. Overall...cold weather
will prevail with below or much below normal temperatures on average.

&&

Aviation /12z Friday through Tuesday/...
low pressure passes through the region this morning and intensifies over
the western Atlantic waters.

Snow is tapering off as it approaches the northeast...but cannot
rule out a few lingering light snow showers. Will tempo MVFR conds
as the cold front swings through the region.

Any sub-VFR conds lift by early afternoon.

SW 10 knots or less will shift to the northwest (around or just to the right
of 310 mag) in the afternoon and increase to around 15 knots with gusts
around 25 knots. Tonight through Saturday morning...winds increase
further to 20-25 knots with 35-40 knots gusts.

..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: amds likely for timing of wind shift and
timing of wind speeds...which may be off by an hour or so. Amds also
likely for timing of -sn and timing of conds improving to VFR.

Klga fcster comments: amds likely for timing of wind shift and
timing of wind speeds...which may be off by an hour or so. Amds also
likely for timing of -sn and timing of conds improving to VFR.

Kewr fcster comments: amds likely for timing of wind shift and
timing of wind speeds...which may be off by an hour or so. Amds also
likely for timing of -sn and timing of conds improving to VFR.

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

Kteb fcster comments: amds likely for timing of wind shift and
timing of wind speeds...which may be off by an hour or so. Amds also
likely for timing of -sn and timing of conds improving to VFR.

Khpn fcster comments: amds likely for timing of wind shift and
timing of wind speeds...which may be off by an hour or so. Amds also
likely for timing of -sn and timing of conds improving to VFR.

Kisp fcster comments: amds likely for timing of wind shift and
timing of wind speeds...which may be off by an hour or so. Amds also
likely for timing of -sn and timing of conds improving to VFR.

Outlook for 12z Saturday through Tuesday...
Saturday...VFR. Northwest winds 35-40 knots...diminishing late.
Saturday night...VFR. Northwest wind g 20-30kt possible early.
Sunday...VFR. Northwest wind g15-20kt possible.
Sunday night-Monday..chance of snow with IFR conditions. NE-north
wind g25-35kt possible.
Monday night...becoming VFR from west to east as any snow comes to an
end. North-northwest wind g20-25kt possible.
Tuesday...VFR.

&&

Marine...
Small Craft Advisory conds developing on the ocean at this time in SW flow ahead of weak
low pressure and an associated cold front will increase to northwest
gales on all waters by late afternoon following an Arctic cold
frontal passage. Gusts on the ocean could approach storm force late tonight
into Sat morning. The combo of strong winds and cold water temperatures
from the middle 30s to lower 40s will also result in at least
moderate freezing spray during this time frame. There is a chance
for heavy freezing spray on Li sound...New York Harbor and the near
shore ocean waters where SST is only in the middle/upper 30s...and a
heavy freezing spray warning may eventually be required for those
waters.

Gusty winds will diminish Saturday night into Sunday. Seas will
respond by subsiding through this time frame. Some 5-footers may
clip the easternmost ocean waters S of Montauk into Sunday...but
sub Small Craft Advisory conditions are likely across the waters Sunday.

However...this will be brief as winds increase again ahead of low
pressure Sunday night and Monday. The low is expected to pass to the
south Monday...moving well to the east Monday night. High pressure
builds in Tuesday.

Strong Small Craft Advisory conditions Monday will improve by Tuesday as the high
builds.

&&

Hydrology...
total quantitative precipitation forecast of 1-2 tenths of an inch liquid equivalent expected
through this afternoon...with most of the precipitation falling
as snow.

Low pressure Sunday night and Monday will bring the potential for
quantitative precipitation forecast of 1/2 to 1 inch liquid equivalent...all in the form of snow.

&&

Okx watches/warnings/advisories...
CT...Wind Advisory from 4 PM this afternoon to 4 PM EST Saturday
for ctz005>012.
Wind Chill Advisory from midnight tonight to noon EST Saturday
for ctz005>007-009-010.
New York...Wind Advisory from 4 PM this afternoon to 4 PM EST Saturday
for nyz067>075-078>081-176>179.
Wind Chill Advisory from midnight tonight to noon EST Saturday
for nyz067>071.
New Jersey...Wind Advisory from 4 PM this afternoon to 4 PM EST Saturday
for njz002-004-006-103>108.
Wind Chill Advisory from midnight tonight to noon EST Saturday
for njz002-004-103-104.
Marine...freezing spray advisory from 6 PM this evening to 6 PM EST
Saturday for anz330-335-338-340-345-350-353-355.
Gale Warning from 1 PM this afternoon to 6 PM EST Saturday for
anz330-335-338-340-345-350-353-355.
Small Craft Advisory until 1 PM EST this afternoon for anz350-
353-355.

&&

$$
Synopsis...Goodman/pw
near term...Goodman/pw
short term...Goodman
long term...precipitable water
aviation...mps/NV
marine...Goodman/pw
hydrology...Goodman/pw

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