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Area forecast discussion 
National Weather Service New York New York
1005 am EST Thursday Feb 11 2016

Synopsis...
an upper level system will pass through the region today. High pressure will
drift across the area on Friday. An Arctic cold front will approach
Friday night...and pass through late Friday night into Sat morning
while low pressure passes southeast of Long Island. Strong high pressure will
then build from the west later Sat into Sunday night...then pass east on
Monday. A warm front will approach Monday afternoon and night...then low
pressure will move up the coastal plain Tuesday into Tuesday night...and pass
to the NE on Wednesday.

&&

Near term /through tonight/...
scattered snow showers have exited to the east this morning with
mostly sunny skies across the most of the area. This will be
short-lived though with steep low-level lapse rates and deep
cyclonic flow. Stratocu will fill in through the morning with the
development of scattered snow showers along and ahead of an approaching
surface trough. Highs will top out in the upper 20s...which is 10 to 12
degrees below normal.

Increasing middle level winds will also allow for gusts up to 35 miles per hour.
Brief periods of hazardous travel possible in snow and wind.

Lapse rates ease tonight with subsidence in the wake of the upper
trough. As a result will dry things out quickly this evening with
clearing skies overnight.

&&

Short term /Friday/...
fair weather to start with a surface hi pressure ridge over the
area...then the ridge is weakened by low pressure passing offshore and
an approaching Arctic front. The data seems to be trending faster
with approaching upper trough and cold front...so went close to the 3z
sref for timing across western zones. The GFS produces some light snow
across eastern areas on the periphery of the low. Bumped up the dry
probability of precipitation in the sref across eastern zones too slight chance for this. Any westward
trend could bring a dusting by dark eastern CT and Li. A blend of
guidance was used for temperatures with readings over 10f blw average.

&&

Long term /Friday night through Wednesday/...
an Arctic cold front approaches Friday night along with a
shortwave from the north. At the same time...shortwave energy
moves off the middle Atlantic coast. The combined energy should
initiate surface cyclogenesis along a baroclinic zone to our south
with the low passing well southeast of the 40n/70w benchmark late at
night. Chance of snow directly associated with this low looks high
enough to raise pop to likely for eastern Long Island...with chance
pop across most of southern CT and Long Island...with only minor accums
expected as strongest forcing with the low remains well offshore.
Elsewhere could see isolated-scattered snow showers with the approaching
Arctic front via decreasing stability and cyclonic flow aloft.

An anomalously cold air mass then pours in behind the cold front for
the weekend...with winds likely approaching advisory criteria in NYC
metropolitan...Long Island and perhaps the higher elevations inland.
Another shortwave arrives alongside the core of cold air aloft
during Sat/Sat evening. The atmospheric column dries...however
there may still be a chance of flurries during this period.

As for temperatures Sat and Sat night...the calendar day high temperature on
Sat will probably occur at midnight as temperatures cool off overnight
and then stay down through the day via strong cold air advection. Temperatures may
recover a little on Sat to the upper teens and lower 20s...but
strong northwest winds during this time should keep wind chills at or
below zero through the day. Models continue to show 850mb temperatures
dropping to -30c during the night before rising a few degrees
toward daybreak. Based on a similar synoptic setup last Feb with
warmer temperatures aloft...went near or slightly below the low temperatures
forecast by European model (ecmwf) MOS...with lows close to zero in NYC and zero to 5
below elsewhere. The cold air combined with winds would produce
wind chills that would warrant an advisory during Sat night into
Sunday morning...and a warning for the northern suburbs and Long
Island.

Remaining cold but dry Sunday/Sunday night as high pressure
builds in...with highs only in the teens...and lows in the teens
NYC metropolitan and single digits elsewhere.

Models then in disagreement with the timing of the next system to
potentially affect the region. High pressure shifts offshore on
Monday...with possibility of overrunning light snowfall reaching
parts of the area by late day. A longwave trough then shifts
through the eastern states...with its axis prognosticated to move
through late Tuesday night. This then helps strengthen a surface low
moving up the vicinity of the eastern Seaboard. Low confidence in
the evolution...track and timing of this system...and consequently
precipitation type late Monday night into Tuesday morning. With a leading warm
front approaching late Monday night and temperatures warming aloft...think
snow will transition to mixed precipitation late Monday night and then rain
during Tuesday morning. After that...heavy rain looks like a good bet
Tuesday into Tuesday night ahead of the low.

&&

Aviation /15z Thursday through Monday/...
a low pressure trough moves through this afternoon.

VFR. Chance sub-VFR with -shsn this afternoon. Probability of prevailing
snow or pinpointing a particular hour of tempo snow for at least a
half hour is too low to include in tafs. -Shsn nevertheless still
possible at any given terminal this afternoon.

West-northwest winds...prevailing south of 310 magnetic...with gusts around
30 knots today. Winds subside this evening.

..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: chance -shsn with 1-2sm visibilities within the 17-20z
time frame. Frequent gusts may drop below 30kt by 22-00z.

Klga fcster comments: chance -shsn with 1-2sm visibilities within the 17-20z
time frame. Frequent gusts may drop below 30kt by 22-00z.

Kewr fcster comments: chance -shsn with 1-2sm visibilities within the 17-20z
time frame. Frequent gusts may drop below 30kt by 22-00z.

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

Kteb fcster comments: chance -shsn with 1-2sm visibilities within the 17-20z
time frame. Occasional gusts 30-33kt possible until 22z.

Khpn fcster comments: chance -shsn with 1-2sm visibilities within the 17-20z
time frame. Occasional gusts 30-33kt possible until 22z.

Kisp fcster comments: chance -shsn with 1-2sm visibilities within the 18-21z
time frame. Occasional gusts 30-33kt possible until 22z.

Outlook for 12z Thursday through Monday...
Thursday night...VFR. Diminishing northwest winds.
Friday...VFR.
Friday night and Saturday...sub-VFR possible in brief -shsn. Northwest
winds around 20 knots with gusts up to 30 knots during the day.
Sunday-Monday...VFR.

&&

Marine...
winds will increase out of the west today with gale conditions expected.
Gale Warning remains up through tonight...then winds decrease through the
day on Friday.

Winds then increase to Small Craft Advisory levels late Friday night as low pressure
passes to the southeast...and gales are likely Sat into Sat night on all
waters after an Arctic cold frontal passage...continuing into
Sunday morning on the ocean. The gales combined with SST in the
lower 40s and air temperatures in the 20s on Sat...single digits Sat
night and teens on Sunday will lead to freezing spray problems...
with moderate to heavy accretion possible especially Sat night
into Sunday morning.

Quiet conds eventually return Sunday afternoon/night as high
pressure builds in.

&&

Hydrology...
liquid equivalent of less than a tenth of an inch is expected through
Friday...and 1/10 inch or less Friday night into Sat morning.

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/fcst minimum...record low maximum/forecast high
for 2/14 for 2/14

NYC...........2 (1916) / 1.............17 (1979) / 17
LGA...........1 (1979) / 4.............15 (1979) / 18
JFK...........4 (1979) / 2.............17 (1979) / 19
isp...........7 (2015) / -3.............26 (1987) / 15
ewr...........0 (1979) / 0.............15 (1979) / 18
bdr...........3 (2015*) / -3.............18 (1979) / 15

*in 1979 as well

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Gale Warning until 6 am EST Friday for anz330-335-338-340-345-
350-353-355.

&&

$$

Synopsis...jmc/Goodman
near term...jmc/dw
short term...jmc
long term...Goodman
aviation...BC/jc
marine...jmc/Goodman/dw
hydrology...jmc/Goodman
climate...//

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