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

Synopsis...
high pressure over the area this morning will slide offshore
today. An area of low pressure will approaches from the west
Thursday evening...then crosses the area late Thursday night and
Friday...immediately followed by an Arctic cold front. Low
pressure deepens as it departs to the east Friday night. High
pressure builds Saturday. A weak cold front moves through on
Sunday. Low pressure moves out of the Mississippi Valley and
tracks to the south Monday. High pressure follows into middle week.

&&

Near term /until 6 PM this evening/...
the ridge was moving offshore as middle and high clouds continue to
push east with the advance of low pressure to the west. The wind
was generally light and slowly shifting to the south. The
combination of very weak warm advection and sunshine was allowing
for temperatures to rise a little more quickly...especially along
the coast. Dew points were slower to rise...however...a slow
upward trend will continue this afternoon.

&&

Short term /6 PM this evening through 6 PM Friday/...
fairly high confidence in the short term as a clipper system moves
across the region tonight and Friday.

There is some uncertainty with temperatures. Thinking that latest
mav/met guidance is a bit too warm...so cut temperatures a degree or
two...especially with a snowpack across the much of the area. Will
continue to go with snow just about everywhere - though expect a wet
snow for the coast. Snowfall totals will range from 1 to 2 inches
across the entire County Warning Area. 1 inch closer to the coast and 2 further
north and west of NYC.

The clipper pulls an Arctic front across the region with a massive
drop in temperatures during the late afternoon. It will become windy
by late afternoon...dropping wind chills into the single digits over
western zones and teens and lower 20s over eastern zones.

&&

Long term /Friday night through Wednesday/...
global models are in general agreement on trough closing off as it
traverses just to the east Friday night.

Not a lot of change in the upper flow as closed low remains over
Hudson Bay...with deep trough over the Atlantic. Mean trough remains
from the central states eastward. Ridge out west flattens somewhat
in time.

At the surface...low pressure deepens over the Gulf of Maine as
it moves slowly east. High pressure moves out of the Upper Middle
west toward the Ohio Valley Friday night. In between...very tight
pressure gradient is in place across the northeast. The high moves
well to the south...with a weak front between another high to the
north. This front moves through sometime Sunday...with little
fanfare.

Then attention turns to low pressure that tracks across the lower
miss valley Sunday. Analysis of various model tracks would put the
low off the Middle Atlantic States sometime Monday...with ggem much
slower.

Solutions from run to run continue to waffle and uncertainty exists.
Various sources of energy in the short term do not reach western
Canada until Friday...so it may take until at least late Friday
for possible solutions to converge hopefully. Will thus not stray far
from previous forecast...but will introduce probability of precipitation Sunday night and
continue into Monday.

Cold air will prevail. Dangerously cold Friday night courtesy
of strong cold air advection and strong northwest winds. In fact...winds
may reach advisory criteria for portions of the area...and these
winds along with plummeting temperatures will yield below zero wind chill
readings. Northwest zones likely approach Wind Chill Advisory criteria of
-15.

Another round of dangerously cold temperatures arrives behind the Monday
night system. Leaned toward wpc numbers...with some weight to
previous forecast.

&&

Aviation /18z 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
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".

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".

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".

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

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".

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".

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 just under 1".

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...
sub-Small Craft Advisory conditions continue this afternoon as the high was moving
off the northeast to middle Atlantic coast. Winds shift around to
the south as the high moves east. Winds and seas start to increase
late tonight in response to a tightening pressure gradient. Expect
small craft advisories on the ocean water tonight starting at 6z.

A clipper system moving north of the waters will drag an Arctic
front across the waters on Friday. Winds rapidly increase late
Friday. Expect gale force gusts to start to develop after 18z
Friday.

As low pressure deepens to the east and high pressure builds to the
west...strong gales are expected Friday night into Saturday morning.
In fact...some gusts could approach storm force. Overall though
gusts of 35 to 45 knots are expected.

Very cold temperatures will result in freezing spray Friday night into
Saturday.

Winds diminish slowly later Saturday and Saturday night as high
pressure passes well south and a weak front approaches from the
north. Another area of low pressure is expected to approach late
Sunday and move just south of the waters Monday. Winds increase
behind this low.

Rough seas Friday night and Saturday will gradually subside with
the diminishing winds. Seas build again Monday.

&&

Hydrology...
no significant precipitation is expected through Friday...though
some light snow is expected tonight into Friday...with no
hydrologic impact expected.

There is the potential for significant precipitation in the form
of snow...of at least 1/2 inch liquid equivalent Sunday night and
Monday. However...much uncertainty exists as the storm may pass
far enough to the south for little or no precipitation. Stay
tuned.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Gale Warning from 1 PM Friday to 6 am 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...BC/pw
near term...BC/met/pw
short term...British Columbia
long term...precipitable water
aviation...Goodman/maloit
marine...BC/pw
hydrology...BC/pw

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