Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1051 PM EDT Sat Sep 20 2014
high pressure off the New England coast and extending into the
middle Atlantic will weaken tonight through Sunday Sunday as low
pressure passes offshore. A cold front will move across Sunday
night. High pressure will build in on Monday...and remain in
control through Saturday.
Near term /until 6 am Sunday morning/...
clouds beginning to build north over Long Island and Queens this
evening. Expect these clouds to continue building north overnight.
Have adjusted sky grids to follow this trend.
Adjusted pop overnight as well to account for slower trend in
isolated/scattered showers in association with low to middle level warm air advection and a
weak middle level shortwave passing across. Still forecast showers to
develop mainly in/near NYC metropolitan late tonight. Patchy drizzle is
also possible late with dry middle levels and moist low levels.
Instability increases aloft late but mostly after deeper moisture
and better lift have moved east.. so no mention of thunder at this time.
Lows tonight are on the warmer side of MOS guidance given warm air advection
taking place...with near 70 at LGA...middle and upper 60s most
elsewhere...and around 60 well inland and over The Pine Barrens of
Short term /6 am Sunday morning through Sunday night/...
scattered showers should be around mainly in the am...with isolated thunder
also possible over eastern Long Island and southeast CT...as a weak non-
tropical low passes just to the southeast of Long Island.
Heaviest precipitation with this low should be associated with warm air advection on
its eastern flank and well offshore...so do not expect heavy
rainfall at this time. Should see some clearing by afternoon via
subsidence in the wake of this low...which along with warm air advection ahead of
an approaching cold front should allow high temperatures to reach the
lower 80s in many places except eastern Long Island and southeast CT where
clouds and showers will be slower to depart...and in the higher
Precipitation should be light with the cold frontal passage Sunday night...with low
chance pop northwest of NYC and slight chance pop elsewhere. After frontal passage
expect some clearing late at night...with lows generally 55-60
inland...and 60-65 in NYC metropolitan and along the coast.
There is a moderate risk of rip currents at Atlantic Ocean facing
Long term /Monday through Saturday/...
an upper trough will still be across the northeast at the start of
the period with a surface cold front likely just to the east of the
area. The upper trough axis is forecast to pass east of the area
late Monday. As of now will continue with the dry forecast to start
Monday with the front east of the region and downsloping
northwesterly wind aiding in drying the lower levels. However...if
the front slows there is a chance that a few showers may linger
across extreme southeastern Connecticut into the Twin Forks early
A strong ridge builds over the region Monday night into Tuesday the
remains nearly stationary through Saturday. At the surface a cool
Canadian air mass build in Monday and then remains through Saturday.
Monday through Wednesday will be cooler than normal...then a warming
trend sets up for Thursday through Saturday as the air mass modifies.
Aviation /03z Sunday through Thursday/...
a weak coastal low moves to east of the North Carolina coast by
Sunday morning...and south of Cape Cod by early Sunday afternoon.
A cold front passes Sun night.
MVFR conditions continue to develop tonight. Have restricted IFR to
eastern terminals overnight/early Sunday morning where appears
best chance of -shra and/or drizzle. Conditions should improve to
VFR at all but gon by around midday Sunday. A few -shra possible
with the front Sun night...but mainly VFR expected at this time.
Southeast-east-southeast winds under 10 knots tonight...with inland terminals becoming
light and variable. Southeast flow continues Sun morning...then veer to the
SW in the afternoon. Winds shift to the northwest behind the front Sun night.
Outlook for 00z Monday through Thursday...
Sunday night...mainly VFR. Scattered -shra possible.
Monday-Monday night...VFR. Northwest winds g20kt possible...becoming north
seas were remaining in the 3 to 4 feet range and the wind over the
waters has diminished for now. With the approach of a coastal low
the wind will increase once again. Not confident that seas will
build to small craft overnight and holding off on an advisory.
Better chance for Small Craft Advisory conds Sunday night as swells associated
with the low passing to the southeast arrive.
A cold front will be moving east of the forecast waters early Monday
with high pressure building from the west. Seas on the ocean waters
will continue at small craft levels Monday morning...and some gusts
during Monday on all the forecast waters may reach 25 knots at times.
As the high builds over the waters Monday night wind...gusts...and
seas are expected to have fallen below small craft. High pressure
remain over the waters into at least Friday with wind and seas below
less than 1/4 inch of rain expected tonight through Sunday night
as a low passes offshore...followed by a cold frontal passage Sunday night.
Then dry Monday through Sat.