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Area forecast discussion 
National Weather Service New York New York
729 am EST Friday Feb 12 2016

Synopsis...
high pressure slides offshore today. A low pressure system will
track southeast of the region tonight. In its wake an Arctic cold
front will approach tonight...and pass through towards daybreak
Saturday. Arctic high pressure then builds in from the
west...settling right across the region Sunday night. High
pressure over the region slides east on Monday as a developing low
pressure system well west of the region approaching. This next low
moves across the area Tuesday and Tuesday night. Another cold
front moves across Wednesday with high pressure starting to build
thereafter.

&&

Near term /until 6 PM this evening/...
polar upper low slowly drops southeast from the Canada...with a
shortwave rounding its base towards the region in the evening. At
the surface...high pressure slowly moves offshore of the middle
Atlantic.

A tranquil but cold day...with highs in the lower to middle 20s.
Increasing high clouds this afternoon ahead of approaching
shortwave.

&&

Short term /6 PM this evening through Saturday night/...
polar low continues to descend into the northeast through Saturday
night with a short lived but dangerous to potentially life
threatening Arctic intrusion Sat into sun.

Leading up to this...shortwave energy rounding the base of the
polar low will approach the region this evening and cross tonight
into early Saturday morning. This will coincide with the approach
of the Arctic front late tonight and crossing early Sat morning.
Meanwhile a Pacific shortwave dives to the southern middle Atlantic coast
this evening...spawning low pressure that will track well southeast of
the region tonight.

Scattered snow showers/flurries expected ahead of approaching
shortwave energy this evening...with potential for even a period
of light snow across eastern Li/southeast CT with initial onshore flow
and then fringe impacts from offshore low. Scattered snow showers
expected once again ahead of/along Arctic frontal passage late
tonight into Sat morning. Overall potential for a dusting in most
spots...with up to an inch or two across far eastern Li and
possible southeast CT.

Arctic intrusion begins early Sat morning in wake of Arctic front
with northwest of 20 to 30 miles per hour with gusts to 45 miles per hour. Potential for a few
gusts to 50 miles per hour Sat after/evening based on more favorable momentum
Transfer. There is potential for Wind Advisory conditions to be
met for both marginal sustained winds and gusts along the New Jersey/NYC
metropolitan...coast and higher elevations. Winds will be slow to
subside Sat night with strong gradient between Arctic high and
Canadian Maritimes low.

Dangerously cold air mass advects into the region Sat morning in
the wake of Arctic front. Highs will likely be reached ahead of
the front in the morning in the teens. Then temperatures should steadily
falling into the single digits and lower teens through the
afternoon...with wind chills falling to 10 to 20 degrees below
zero. Heart of cold enters Sat night into Sunday morning...with
temperatures likely to fall to around zero for NYC/New Jersey metropolitan and
coast...and 5 to 10 below zero across interior portions of the
tri-state. Combined with slow to diminish winds...dangerous to
potentially life threatening wind chills of 20 to 30 below
expected. High enough confidence for a rare windchill warning
across northern zones...and windchill advisory for city/coast.
Windchill watch remains for coastal CT...with temperatures on borderline
for advisory vs warning.

With upper low approaching in the after/evening and residual lake streamer
moisture...scattered instability cumulus and scattered flurries possible from late
morning into evening. Across Twin Forks of Li...maybe enough of a
fetch over Long Island Sound and instability for scattered snow
showers/flurries Sat after into Sat evening. Clearing skies late Sat
night on backside of upper low.

&&

Long term /Sunday through Thursday/...
one of the coldest days of the season will occur on Sunday as the
polar vortex remains over the region. Early morning temperatures
will be in the single digits across northeast New Jersey...NYC...and Long
Island. Across the interior...temperatures will start the morning in
the 0 to -10 degree range. With mostly sunny skies on
Sunday...expect temperatures to rise into the teens for daytime
highs. With windy conditions early Sunday morning...expect wind
chills in the -15 to -25 range. These wind chills likely do not
rise above 0 until the early to middle afternoon.

The upper level trough...and cold surface high pressure over the
region will slide east late Sunday into Sunday night...allowing
temperatures to moderate through the first part of the new week.
Expect temperatures Sunday night to remain somewhat steady with
temperatures in the teens. By Monday...temperatures slowly rise
through the 20s and into the lower 30s.

A trough moving out of the middle of the country will approach on
Monday. Expect clouds to thicken and lower through the day...with
probability of precipitation gradually increasing through the afternoon. With temperatures
still below freezing...expect precipitation to start as snow.

Southerly flow out ahead of the low pressure system will result in
warm air advection continuing Monday night and Tuesday. As
temperatures rise through this period...expect precipitation to
gradually change from snow to rain. The transition from snow to rain
will occur from the southeastern portion of the County Warning Area...to the
northwestern. By middle morning on Tuesday...it is expected that
temperatures warm enough everywhere for just plain rain across the
entire County Warning Area. Highs on Tuesday climb into the upper 40s and lower 50s.

00z forecast guidance in decent agreement with the low pressure
system...and associated cold front moving across the region Tuesday
night into Wednesday morning...with most of the precipitation ending
early Wednesday. The models do however differ on the exact placement
of the low...and the track it takes across the region. For
now...expecting rainfall amounts between 1 and 2 inches...with at
least some of that quantitative precipitation forecast...starting as a period of snow. See
additional details on quantitative precipitation forecast in the hydrology section.

High pressure builds into the region behind the cold front Wednesday
night through Friday...with mostly dry conditions. Highs on Thursday
will be in the lower 40s...with 30s expected on Friday.

&&

Aviation /13z Friday through Tuesday/...
weak high pressure will move across today. Low pressure will pass
well to the south tonight. An Arctic cold front will move through
just before daybreak on Sat.

VFR. Medium to high confidence in wind forecast. Winds generally
west-northwest 5-10 knots will back SW this afternoon. Occasional g15-20kt possible
at the NYC metropolitan terminals this afternoon...especially kewr.
Winds shift northwest and become gusty after Arctic frontal passage late tonight.

Scattered snow showers with brief local IFR visibility are possible tonight
as the Arctic front approaches and as the offshore low makes its
closest approach...which could leave a coating of accumulation on
runways. Probabilities are still low and as such are handled via
prob30 this far out in time.

..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: occasional g15-20kt possible this afternoon.

Klga fcster comments: occasional g15-20kt possible this afternoon.

Kewr fcster comments: high confidence in winds.

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

Kteb fcster comments: occasional g15-20kt possible this afternoon.

Khpn fcster comments: occasional g15-20kt possible this afternoon.

Kisp fcster comments: high confidence in winds.

Outlook for 12z Sat through Tuesday...
Sat...scattered early morning snow showers with brief MVFR visibility still
possible mainly kisp/kgon...otherwise VFR. Northwest winds 20-25 knots with
gusts 35-40 knots...highest at the NYC metros and kisp.
Sunday...VFR. Northwest winds 15-20g25kt in the morning.
Monday...VFR.
Monday night...IFR conds likely. Snow changing to rain by late
evening NYC metros/kisp...and around/shortly after midnight
khpn/kbdr/kgon...and cold ground could make for a period of freezing
rain on runways despite air temperatures rising above freezing.
Snow mixing with or changing to freezing rain around midnight
at kswf.
Tuesday...rain likely with IFR conds. Southeast-S winds g30-35kt and low level wind shear.

&&

Marine...
winds will continue to subside as high pressure builds in this
morning. Seas will take until middle morning hours to subside across
eastern ocean.

Thereafter...sub Small Craft Advisory conditions expected today as SW winds
develop ahead of an approaching Arctic cold front. A few gusts to
around 20 knots likely on the ocean this afternoon/evening.

The relatively tranquil conditions will be short lived...with
Arctic frontal passage forecast around daybreak Sat with northwest gales
developing soon thereafter. Gales expected on the ocean...and
likely for rest of the waters Saturday and Saturday night. Gales
prevail into early Sunday before decreasing to 20-30 knots during the
day. These winds should build ocean seas to 7 to 11 feet...and 3 to
6 feet on central and eastern Li sound. With Arctic air mass
overspreading the waters...moderate to heavy freezing spray
expected Saturday into Saturday night for most of the waters.

Some left over gales may prevail into early Sunday before decreasing
to 20-30 knots during the day. Freezing spray is also possible on
Sunday at least the ocean waters. Weak pressure gradient Sunday
night through Monday night will lead to below Small Craft Advisory conditions.
Conditions build back to Small Craft Advisory levels ahead of the next low pressure
system Tuesday and Wednesday.

&&

Hydrology...
liquid equivalent of less than a tenth of an inch is forecast
tonight into Saturday morning in the form of snow showers.

Low pressure moving up the coast has potential to produce liquid
equivalent quantitative precipitation forecast at least 1 to 2 inches. Part of this will fall as
snow initially...but then runoff via melting snow and heavy rain
Tuesday into Tuesday night could cause at least Urban and Small
Stream flooding problems. It is too early to say if main Stem rivers
would be affected.

&&

Climate...
with the extremely cold air mass forecast Saturday into
Sunday...record minimums and record low maximums may be reached.
Here are the records and forecasts...

Station......record/forecast minimum
for 2/14

NYC...........2 (1916) / 1
LGA...........1 (1979) / 2
JFK...........4 (1979) / 1
isp...........7 (2015) / 1
ewr...........0 (1979) / 0
bdr...........3 (2015*) / -1

Station......record low maximum/forecast high
for 2/14

NYC.............17 (1979) / 17
LGA.............15 (1979) / 17
JFK.............17 (1979) / 18
isp.............26 (1987) / 15
ewr.............15 (1979) / 17
bdr.............18 (1979) / 16

*in 1979 as well

&&

Okx watches/warnings/advisories...
CT...wind chill warning from 4 PM Saturday to noon EST Sunday for
ctz005>008.
Wind chill watch from Saturday afternoon through Sunday
morning for ctz009>012.
New York...Wind Chill Advisory from 4 PM Saturday to noon EST Sunday for
nyz072>075-078>081-176>179.
Wind chill warning from 4 PM Saturday to noon EST Sunday for
nyz067>070.
Wind chill watch from Saturday afternoon through Sunday
morning for nyz071.
New Jersey...Wind Chill Advisory from 4 PM Saturday to noon EST Sunday for
njz004-006-104>108.
Wind chill warning from 4 PM Saturday to noon EST Sunday for
njz002.
Wind chill watch from Saturday afternoon through Sunday
morning for njz103.
Marine...gale watch from late tonight through Sunday morning for anz330-
335-338-340-345.
Heavy freezing spray watch from Saturday evening through
Sunday morning for anz330-335-338-340-350-353-355.
Freezing spray advisory from 4 am to 6 PM EST Saturday for
anz330-335-338-340-350-353-355.
Gale Warning from 4 am Saturday to 7 am EST Sunday for anz350-
353-355.
Small Craft Advisory until 10 am EST this morning for anz350.

&&

$$
Synopsis...BC/NV
near term...Nevada
short term...Nevada
long term...British Columbia
aviation...Goodman
marine...BC/NV
hydrology...BC/NV
climate...

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