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Area forecast discussion 
National Weather Service New York New York
1157 am EDT Friday Mar 27 2015

Synopsis...
a cold front will push farther offshore today. Low pressure will
develop offshore tonight...and track towards the Maritimes
Saturday. An upper level disturbance moves across Saturday and
moves east of the region Saturday night. High pressure builds in
thereafter. For the new work week...a series of clipper lows will
be moving across.

&&

Near term /until 6 PM this evening/...
most of the showers have tapered off over the area...but several
shortwaves continue to pass through the region through this
afternoon. There are some radar returns moving towards the
northeast...but there are not many surface observation confirming precipitation
reaching the ground. Will lower probability of precipitation to slight chance for the
afternoon...as showers will be spotty.

Northerly winds will slowly advect colder air into the
region...not allowing temperatures to rise much from morning lows. Cloud
cover will keep temperatures a few degrees below seasonable in the middle to
upper 40s. Around 50 NYC/New Jersey metropolitan.

&&

Short term /6 PM this evening through Saturday night/...
deep upper trough gradually pivots to the East Coast tonight into
Saturday night...with potential closed low tracking over the tri-
state to middle-Atlantic vicinity Saturday night.

At the surface...low pressure tracks NE along the cold front well southeast
of the region tonight into Sat night. Operational models and
respective ensemble are in fairly good agreement with the low
staying far enough offshore to keep the heaviest precipitation from this
low offshore. But the majority of solutions...except for
operational European model (ecmwf)...do spread western edge of light precipitation shield
into eastern Li/southeast CT tonight into Sat night. Sunysb sensitivity
analysis depicts a slight spread in ensemble members on west side
of low track...depicting a low probability of slightly farther west
solution if the trough digs a bit deeper. This would increase
precipitation potential for Li/CT.

At the same time...several models have been signaling a weak
inverted trough hanging back over the region tonight into Sat as
closed middle-level low approaches. The track/intensity of the middle-
level closed low and associated surface trough location will be
key to potential development of any steadier and more widespread
precipitation Friday night into Sat night. The strength/position of this
feature has wavered from model run to model run from southern New
England to northern middle Atlantic over the last several
days...inspiring little confidence on where this feature sets up.
For locations that do not fall under the inverted trough or
western edge of precipitation shield...there will be an isolated/scattered threat
for mainly diurnal shower activity across the area on Saturday
under combo of middle-level vorticity energy and cold pool instability.
With the above mentioned uncertainty and precipitation potential have
maintained an west to east gradient of chance probability of precipitation tonight into Sat
night.

Thereafter...models in general agreement with the upper trough
sliding east and surface high building towards the region late
Saturday night with gradual tapering of precipitation across eastern tri-
state.

In terms of p-type...cold air advection tonight into Sat should allow precipitation to
mix with/change to wet snow late tonight. If precipitation is
steady/heavy enough a mainly wet snow would be expected on
Saturday based on thermal profile aloft...but if it is very light
and scattered in nature a rain/snow mix would be likely due to
inability to cool boundary layer sufficiently.

Most likely scenario at this point is 1-2 inches or less of wet
snow Friday night into Sat night across eastern Li/southeast CT...with a
coating to nothing further west. If inverted trough develops over
the region...or offshore low tracks a bit farther west...an
advisory level wet snow would be possible across mainly
Li/CT...with a light coating to inch farther west. This latter
scenario is a low probability at this time.

Temperatures on Sat/Sat night will likely run about 10 to 15 degrees
below seasonable under the upper trough and cold pool.

&&

Long term /Sunday through Thursday/...
high pressure builds into the area at the surface on
Sunday...with the center of the high passing well to the
south...while at the same time there will be ridging aloft.
Thicknesses quickly build on Sunday as the high pushes off the
southeast coast late in the day...which means warmer temperatures
as compared to Saturday...mainly for NYC...northeast New Jersey...and
lower Hudson Valley. Long Island and southern CT may see only
slightly warmer temperatures as winds shift to more of a southerly
direction during the day. This onshore flow off the cold ocean
waters will keep temperatures cooler than inland areas.

A cold front then approaches the area Sunday night...and moves
through late Monday into Monday night. Some light precipitation
is possible out ahead of the front Sunday night. There is limited
moisture to work with however...so only slight chance probability of precipitation. Warm
air advection ahead of the front will mean precipitation in the
form of rain showers for much of the area. However...there may be
some snow showers well inland. Any snow will change to rain during
the morning on Monday.

Pattern becomes rather progressive as the upper level
flow is pretty zonal. At the surface...weak high pressure builds
in for Tuesday. A quick moving clipper system moves through on
Tuesday night...departing the area on Wednesday. Again...much of
the area should be warm enough for rain...with the possibility of
some flakes mixing in Tuesday night across southern CT as colder
air moves in behind the low.

A warm front approaches the area on Wednesday night...moving through
on Thursday...followed quickly by the associated cold front.

&&

Aviation /16z Friday through Tuesday/...
weak high pressure will gradually build in today. Will see mainly
VFR conds...but could see on-off MVFR conditions/light rain
showers through the day.

Winds north-north-northwest around 10 knots...backing northwest and diminishing slightly
this afternoon.

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: brief MVFR ceilings possible at any time before
20z.

Klga fcster comments: brief MVFR ceilings possible at any time before
20z.

Kewr fcster comments: brief MVFR ceilings possible at any time before
20z.

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

Kteb fcster comments: brief MVFR ceilings possible at any time before
20z.

Khpn fcster comments: no unscheduled amend.

Kisp fcster comments: brief MVFR ceilings possible at any time before
21z.

Outlook for 12z Sat through Tuesday...
Sat...chance of MVFR conds with any rain or snow showers.
Northwest winds g20-25kt.
Sat night. VFR. Northwest winds g25kt.
Sunday...VFR.
Monday...VFR. West winds g25kt.
Tuesday...VFR. Northwest winds g20kt.

&&

Marine...
marginal Small Craft Advisory winds this morning with Small Craft Advisory ocean seas today as high
southerly swells only slowly subside. Marginal Small Craft Advisory conds expected
on ocean tonight into Sat morning with gusty northwest flow...caa...and
residual southerly swells. Better chance of Small Craft Advisory conds on ocean and
possibly all waters will be Sat night in wake of departing
offshore low and as high pressure builds in from the west.

Waves diminish to sub Small Craft Advisory on Sunday...but build to above Small Craft Advisory
criteria on a southerly flow late Sunday night into Monday ahead of
an approaching warm front. Winds mainly over the ocean waters will
gust to 25 knots late Sunday night into Monday night. Winds and waves
will diminish on Tuesday as the pressure gradient relaxes with weak
high pressure building in. Waves quickly build again to above Small Craft Advisory
criteria Tuesday night in response to southerly flow ahead of an
approaching clipper system...then diminish on Wednesday as the
system departs the region.

&&

Hydrology...
an additional tenth of an inch or so of quantitative precipitation forecast through this
afternoon.

No significant widespread precipitation expected through this
weekend into next week.

Rivers and streams are expected to remain below bank full...but
increased river/stream flow across the lower Hudson Valley and
southern Connecticut will continue ice breakup and movement into
this weekend. Isolated ice jams are possible...which if they
occur...could result in localized flooding. Since ice jam flooding
is unpredictable and sudden...interests along ice covered rivers
should monitor National Weather Service forecasts for the latest information.

For details on specific area rivers and lakes...including
observed and forecast river stages and lake elevations...please
visit the advanced hydrologic prediction service /ahps/ graphs on
our web site.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory until 6 PM EDT Saturday for anz350-353-
355.

&&

$$
Synopsis...jp/NV
near term...mps
short term...Nevada
long term...jp
aviation...jc/Goodman
marine...jp/NV
hydrology...jp/NV

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