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Area forecast discussion 
National Weather Service New York New York
412 PM EST Thursday Jan 29 2015

Synopsis...
low pressure and an associated cold front approach from the west
tonight with the cold front passing through late tonight into
early Friday morning. An Arctic cold front will follow Friday
afternoon as the low deepens off the northeast coast. High
pressure builds in Friday night and Saturday.

A wintry pattern will persist through the middle of next
week...with frigid cold on Sat and chances for snow Sun night into
Monday...and again around Wednesday.

&&

Near term /until 6 am Friday morning/...
ridge of high pressure continues to move offshore as a clipper
system approaches from the west. A shortwave embedded in a digging
upper trough will provide lift for light snow to develop this
evening. Have categorical probability of precipitation by later tonight. Warm advection
ahead of the low was raising boundary layer
temperatures...however...profile should remain cold enough for all
snow. Warm air moving in over the waters will allow for rain and
snow over the waters and a slight chance that enough warm air may
move in across the very far eastern zones for a mix of rain and
snow. Temperatures will hold nearly steady or only fall a few
degrees tonight. Followed closer to the colder NAM temperatures
and trends.

&&

Short term /6 am Friday morning through Friday night/...
the clipper low move through during the morning with an associated
cold front. Meanwhile the upper trough continues to dig and become
negatively tilted. A strong vorticity maximum rounds the base of the trough
Friday afternoon allowing for the low to rapidly deepen off the
northeast coast. An Arctic front moves through Friday afternoon as
the low deepens. Northwest wind will increase and become gusty as
Arctic air flows in. Late Friday afternoon and Friday night
sustained wind and gusts are expected to fall just below advisory
levels...with the highest wind along the coast. The combination of
cold air and gusty wind will produce wind chills well below zero
Friday night...with wind chills at advisory levels by late Friday
night. Being late third period into fourth period will hold off on
a Wind Chill Advisory.

&&

Long term /Saturday through Thursday/...
980s low spinning near Nova Scotia will keep gusty northwest flow locked in
on Sat...producing wind chills mainly at or below zero for most of the day.
As winds slacken late...wind chills will likely rise into the single
digits. 850 mb winds in the GFS are around 55-60kt at 12z Sat...so
there is the potential for Wind Advisory early with gusts in the 45-50
miles per hour range. Subsidence on the western fringe of the system should aid in the
gust potential...while at the same time clearing out the skies.

Weak hi pressure ridge Sat night so much lighter winds into sun.

Models lining up with the next system for Sun night and Monday. The 12z GFS
and European model (ecmwf) are virtually the same with respect to the track and intensity. At 18z
Monday the low centers were approximately 60 miles apart and about 130
miles S of the benchmark. Most of the GFS ensemble members were
clustered on this solution.

Extensive area of middle level moisture with the system...so with high slr/S
at least light-MDT accums possible. Based on the progressive
nature...it looks like a 4-8 inch potential at this time. This of course can
change...in fact a southern track could leave the County Warning Area with just flurries.
As an aside...the 12z mex has Cat 8 snowfall for all sites.

Hi pressure Monday night and Tuesday. Sunny on Tuesday as a result.

The Gulf opens up midweek potentially in tandem with another northern
stream upper trough. European model (ecmwf) forecasts low pressure heading towards Cape Cod. This
reflects the idea of low pressure exhibited in the 00z run. The GFS is
less organized. Included 30 probability of precipitation for precipitation Wednesday.

&&

Aviation /21z Thursday through Tuesday/...
high pressure slides offshore this afternoon. Low pressure approaches
from the west this evening...crosses the area overnight and Friday
morning...then exits to the east as it deepens Friday afternoon.

VFR this afternoon. MVFR likely develops around/just after
midnight with the onset of light snow...then IFR in light snow
from 5-8z from northwest to southeast through 11-15z from northwest to southeast...when should
return to MVFR with scattered snow showers for remainder of taf
period. Generally expecting 1-2 inch snowfall with highest amounts
at northern terminals.

Note there is a low chance of freezing rain/rain at far eastern terminals
late tonight before the onset of steady snow.

Light and variable winds become southeast at less than 10 knots at
city/coastal terminals this afternoon. Winds then veer to the S this
evening...remaining light and variable inland. Winds shift SW-W-NW
Friday morning (11-15z city terminals)...with gusts to around 20-25
knots by early afternoon.

High confidence in occurrence of winds. Moderate to high
confidence in snow and associated MVFR/IFR conditions. Confidence
in exact timing is lower.

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: timing of changes in wind speed and
direction and changes in flight categories could be off +/- 2-3
hours. Most likely snow accumulation is around 1 inch.

Klga fcster comments: timing of changes in wind speed and
direction and changes in flight categories could be off +/- 2-3
hours. Most likely snow accumulation is around 1 inch.

Kewr fcster comments: timing of changes in wind speed and
direction and changes in flight categories could be off +/- 2-3
hours. Most likely snow accumulation is around 1 inch.

Kteb fcster comments: timing of changes in wind speed and
direction and changes in flight categories could be off +/- 2-3
hours. Most likely snow accumulation is around 1 inch.

Khpn fcster comments: timing of changes in wind speed and
direction and changes in flight categories could be off +/- 2-3
hours. Most likely snow accumulation is 1-2 inches.

Kisp fcster comments: timing of changes in wind speed and
direction and changes in flight categories could be off +/- 2-3
hours. Most likely snow accumulation is around 1 inch.

Outlook for 18z Friday through Tuesday...
Friday afternoon...most likely VFR...MVFR in isolated -shsn a low
possibility. Northwest wind g20-30 knots likely.
Friday night-Saturday...VFR. Northwest winds g30-40kt likely.
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...
high pressure was moving through the waters as low pressure
approaches from the west. An increasing southerly flow ahead of the
low tonight will allow for seas on the ocean to build to small
craft levels. In addition some southerly wind gusts...mainly over
the outer forecast waters...may reach small craft levels. As low
pressure passes through the waters late tonight into early Friday
the wind will diminish and will likely fall below small craft for
a few hours. Then as the low and associated cold front move
through wind shifts to the northwest and increase as the low
deepens. An Arctic cold front crosses Friday afternoon. The
deepening low and strong cold advection will allow the wind over
the waters to gust to gale force Friday afternoon into Saturday.
The Small Craft Advisory remains as posted...and the Gale Warning
was extended through Saturday.

Gales will wind down Sat night as low pressure passes north of Nova Scotia.
Seas may be close to 5 feet on the extreme eastern ocean sun...elsewhere
winds and waves will be blw Small Craft Advisory levels. Small Craft Advisory winds likely Monday as low
pressure deepens east of the waters. Improving conditions on Tuesday as hi pressure
builds over the region.

&&

Hydrology...
one to two tenths of an inch of liquid equivalent is expected from
late tonight into Friday afternoon with the precipitation falling
as snow.

Low pressure Sun night and Monday will bring the potential for less than an
inch of liquid equivalent. Precipitation likely to be all snow.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Gale Warning from 1 PM Friday to 6 PM EST Saturday for anz330-
335-338-340-345-350-353-355.
Small Craft Advisory from 1 am to 1 PM EST Friday for anz350-
353-355.

&&

$$
Synopsis...jmc/met
near term...met
short term...met
long term...jmc
aviation...maloit
marine...jmc/met
hydrology...jmc/met

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