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Area forecast discussion 
National Weather Service New York New York
647 am EST Thursday Dec 18 2014

Synopsis...
low pressure over Nova Scotia will slowly track eastward through
Friday as high pressure builds in from the west. A weak trough of
low pressure will move across the area Saturday night and Sunday.
Low pressure will develop over the southeast coast Monday and move
northeast passing southeast of Long Island early Tuesday. A strong
low pressure system will approach the area on Wednesday passing
west of New York City.

&&

Near term /until 6 PM this evening/...
forecast is generally on track. Have extended isolated
sprinkles/flurries for an additional hour...based on latest radar
trends. Also have adjusted winds as they have been gusting
slightly higher than forecast.

Otherwise...low pressure over Nova Scotia early this morning will meander
about the Canadian Maritimes today. The local area will be caught
between this system and high pressure over the upper Midwest which
will result in a gusty west/northwest flow.

Potent vorticity maximum currently moving through the region early this
morning is producing flurries/sprinkles. This activity will cease by
12z as the energy slides to the east.

Cloudy skies early on will give way to mostly sunny skies with high
near normal levels.

&&

Short term /6 PM this evening through Friday night/...
the low in the Maritimes will slowly depart to the east through Friday
night as anomalous ridge near James Bay builds towards New England.
The pressure gradient will relax with winds gradually veering to the north.
Dry weather continues with subsidence increasing although some
moisture could become trapped under an inversion with stratocu
developing. Any lake effect streamers tonight and Friday are not
expected to make it to northwest zones. Temperatures will remain near normal
levels through the short term.

&&

Long term /Saturday through Wednesday/...
prepare for periods of unsettled weather...with a chance of light
rain/snow Sat night-Sunday...chance of a weak Nor'easter late Monday-early
Tuesday...then a potential high impact storm with heavy rain and strong
winds on Wednesday/Christmas evening.

Sat night-Sunday...a weak negatively tilted short WV trough is forecast
to mv NE across the area aided by weak low level warm air advection.
Lowered chances of precipitation as high pressure over northern New England
remains dominant and limits lift. Can not rule out a chance of light
snow/rain for Sat night into early Sunday then a chance of light rain
Sunday afternoon. A dusting is possible.

Sun night-early Tuesday...a synoptic scale trough is forecast to develop
across the central U.S. Aiding in cyclogenesis off the southeast coast by
early Monday. This will increase chances for a weak Nor'easter mainly
Monday afternoon-night with a widespread rainfall of 1/2-1 inch and sub
advisory NE winds. Because a new moon is predicted on Sunday...
astronomical tides will be higher than average with at least a chance for
widespread minor tidal flooding late Monday-early Tuesday.

Wednesday...good agreement among the global models continue for a strong middle
week storm tracking west of the area with the development of a southeast
wind swept heavy rain followed by strong winds during the day on
Christmas. Low pressure is forecast to rapidly deepen across the Tennessee/Ohio
valleys Tuesday night into Wednesday...wrapping up over the Great Lakes Wednesday
night into Thursday with pressures approaching 960 mb. This track would
keep the forecast area in the warm sector of the storm with the
potential for convection and even strong winds. The caveat here is
that the storm is about a week away with a lot of time for change in
track and timing. In addition...the fast Pacific flow would lead one to
believe that there are going to be timing issues with the southern
branch short wave energy.

&&

Aviation /12z Thursday through Monday/...
deepening low pressure will drift through the Canadian Maritimes
through the taf period. Scattered-broken 035-050 ceilings and gusty winds prevail
today with winds decreasing tonight.

Isolated rain/snow showers into early morning near kgon.
Otherwise...mainly VFR through taf period with possible MVFR
ceilings today.

Winds...direction mainly 290-300 degrees with speeds of 15-20 knots
gusts near 25 knots. There could be some variation with gusts being
intermittent for a brief period of time.

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: moderate confidence forecast. Wind gust timing
could be off by a few hours.

Klga fcster comments: moderate confidence forecast. Wind gust timing
could be off by a few hours.

Kewr fcster comments: moderate confidence forecast. Wind gust timing
could be off by a few hours.

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

Kteb fcster comments: moderate confidence forecast. Wind gust timing
could be off by a few hours.

Khpn fcster comments: moderate confidence forecast. Wind gust timing
could be off by a few hours.

Kisp fcster comments: moderate confidence forecast. Wind gust timing
could be off by a few hours.

Outlook for 12z Friday through Monday...
Fri-Sat...VFR.
Sat night...MVFR or lower with light rain/snow. Mainly snow at kswf
and mainly rain.
Sunday...MVFR or lower...with light rain/snow changing to plain rain
throughout.
Monday...chance of wintry mix interior for the morning with
otherwise chance of rain. MVFR or lower possible.

&&

Marine...
a tight pressure gradient across the waters will result in marginal
Small Craft Advisory wind gusts on the non-ocean waters today and Small Craft Advisory level winds and
seas on the ocean waters into tonight. Conds on the ocean may fall
below Small Craft Advisory levels shortly after midnight...but will keep the end time
as 11z. Sub-advsy conds will then prevail through Friday night with the
gradient relaxing as high pressure builds from the west.

Saturday through Sunday night...winds and seas are forecast to
remain tranquil under high pressure.

Monday through Tuesday...as low pressure develops over the southeast coast and
moves NE toward the coastal waters...increasing NE winds of 15-20 knots
will cause seas to build to Small Craft Advisory levels by Monday
night.

Potential for minor tidal flooding...will increase Monday based on a
predicted new moon for Sunday as both NE winds increase and an
easterly fetch increases ahead of a developing coastal low.

&&

Hydrology...
no measurable precipitation through Friday.

Sat night-Sunday...chance of light snow/rain with amounts of less
than one-tenth of an inch. No Hydro impacts are forecast.

Monday afternoon-Monday night...increasing chance of a widespread 1/2-1inch
liquid equivalent rainfall. Localized minor urban flooding is
possible. Precipitation will be mixed with wet snow west and north of NYC.

Wednesday...increasing chance of a wind swept heavy rain of 1-2 inches
with potential significant impacts to mass transit.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory until 6 PM EST this evening for anz330-
335-338-340-345.
Small Craft Advisory until 6 am EST Friday for anz350-353-355.

&&

$$
Synopsis...jc/dw
near term...maloit
short term...jc
long term...dw
aviation...jm
marine...jc/maloit/dw
hydrology...jc/dw

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