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Area forecast discussion 
National Weather Service New York New York
407 am 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 am this morning/...
high pressure over the region this morning...slides offshore
through the day. Expect dry conditions. Expect an increase in middle
and high level clouds moving in from the west today...as a low
pressure system and associated middle level shortwave approaches from
the west.

High temperatures today climb into the upper 20s to lower 30s.
Stayed close to a MOS blend today.

&&

Short term /6 am this morning 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 develops over the SW
states...tracking 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 /09z Thursday through Monday/...
a high pressure ridge will move overhead today...then slide to the
east tonight as developing low pressure approaches.

VFR through much of the day...then there is increasing potential
for MVFR ceilings to develop after 21z across NYC/New Jersey and western
terminals. IFR conds as possible in light snow as early as 00z...
with increasing probabilities thereafter through 06z.

North winds under 10 knots will become vrb around 5 knots middle to late
morning...then mainly southeast flow under 10 knots will develop and last
into evening. A period of gusts close to to 20 knots is possible
city/coast.

..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: high confidence through this afternoon.

Klga fcster comments: high confidence through this afternoon.

Kewr fcster comments: high confidence through this afternoon.

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

Kteb fcster comments: high confidence through this afternoon.

Khpn fcster comments: high confidence through this afternoon.

Kisp fcster comments: high confidence through this afternoon.

Outlook for 06z Friday through Monday...
late tonight-Friday morning...IFR conditions likely in light snow.
Snow accumulation of about an inch likely...perhaps up to 2 inches
at khpn/kswf.
Friday afternoon...still a chance of light snow with MVFR conds.
Northwest winds increasing to 15g20-25 knots as the low begins to intensify
while moving off the New England coast.
Friday night-Sat...VFR. Northwest winds 20-25g30-35kt...diminishing late in
the afternoon.
Sat night-Sunday...VFR with high pressure passing ohd.
Sunday night-Mon...chance of snow with IFR conds as low pressure
passes to the south.

&&

Marine...
sub-Small Craft Advisory conditions expected today. 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 kts 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 Thursday night 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...British Columbia
short term...British Columbia
long term...precipitable water
aviation...Goodman
marine...BC/pw
hydrology...BC/pw

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