Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
811 am EDT sun Sep 21 2014
a low pressure system off the southeast coast will pass east of the
region today. A cold front will move across the area tonight. High
pressure will build in on Monday...and remain in control through the
end of the week.
Near term /until 6 PM this evening/...
heavy rain banding has been disrupted as low level jet and axis of sub-
tropical moisture has moved east and low level convergence
boundary has washed out. Overnight rainfall amounts ranged from
0.50 to 1.50 with some locally higher amounts.
Otherwise...an area of low pressure will pass south and east of
Long Island today. As a result...scattered showers will move
across the region through the morning hours. The majority of the
precipitation will fall across the Long Island and southern CT.
There may also be an isolated rumble of thunder or two...however
the chances are low and will leave out of the forecast for now.
The heaviest of the rain associated with the passing low will
remain far enough offshore not to impact the area.
We should see some clearing by afternoon...with some slightly drier
weather. The only exception will be across the far western sections
of the County Warning Area...where some showers could be possible with an
approaching cold front.
High temperatures are forecast to reach the upper 70s and lower 80s
in many places except far eastern Long Island and far southeast CT where clouds
and showers will be slower to depart...and in the higher interior
There is a moderate risk of rip currents at Atlantic Ocean facing
Short term /6 PM this evening through 6 am Monday/...
a cold front will move across the region tonight. 00z model guidance
indicating the front will come through mostly dry. Will keep some
chance/slight chance probability of precipitation through midnight from western Long Island
and western CT points west. Across the eastern section...thinking
the showers will not make it out this far. Expect clearing after the
frontal passage...with temperatures falling into the 55-60
inland...and 60-65 in NYC metropolitan and along the coast.
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.
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 /12z Sunday through Thursday/...
a weak coastal low tracks NE...just southeast of the area today...with a
cold frontal passage tonight.
Widespread MVFR to IFR ceilings this morning expected to gradually
improve through MVFR to VFR this morning into early
afternoon. Timing of improvement is a bit uncertain...with slower
improvement in ceilings expected for eastern terminals. Kgon likely
remains MVFR or lower for much of the day.
Scattered rain showers/thunderstorms and rain threat through this afternoon mainly
kisp/kgon...isolated threat elsewhere.
This evening/tonight...mainly VFR conds expected at western
terminals. Isolated -shra possible across western terminals...with
cold front. Brief MVFR or lower conds possible at kisp/kbdr late
aft/eve...likely MVFR or lower conds at kgon...until cold frontal
passage between 04z and 08z from west to east.
Light east/southeast flow across terminals this morning. Flow should become
S/southeast for coastal terminals this afternoon...SW for kswf and
possibly kewr/kteb. Light SW flow this evening for all terminals
ahead of cold front...shift to the northwest 8 to 12 knots behind the front
Outlook for 12z Monday through Thursday...
Monday-Monday night...VFR. Northwest winds g20kt possible...becoming north
seas on the ocean waters are between 4 and 5 feet. Wavewatch guidance
has seas reaching Small Craft Advisory levels early this morning...then subsiding for
a brief period this afternoon before increasing once again tonight
and Monday. As a result...have put up a Small Craft Advisory for
hazardous seas on the the ocean waters through Monday.
Seas increase tonight 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...and some gusts during
Monday on all the forecast waters may reach 20-25 knots at times. Seas
will subside Monday night as the high builds over the waters.
High pressure will remain over the waters into at least Friday with
winds and seas below Small Craft Advisory levels.
scattered shower activity through this afternoon.
Less than 1/4 inch of rain expected through tonight. Then dry Monday
Marine...Small Craft Advisory for hazardous seas until 6 PM EDT Monday
near term...British Columbia
short term...British Columbia