Scientific Forecaster Discussion
fxus61 kokx 140559
Area forecast discussion
National Weather Service New York New York
159 am EDT Mon Oct 14 2019
weak low pressure passes just southeast of Long Island overnight,
followed by building high pressure Monday into Tuesday. Low
pressure and a cold front will affect the region Wednesday and
Wednesday night. The low moves to the northeast Thursday as high
pressure begins to build to the southwest. High pressure will
then dominate Friday into next weekend.
Near term /until 6 am this morning/...
made some adjustments to pops for rain, cloud coverage,
temperatures and dewpoints to better match observed trends.
Models indicated that the majority the rain passes south of the
region, just brushing Long Island overnight. The rain is
spreading across much of eastern Long Island, with the heaviest
primarily remaining offshore.
The forcing for this rain is coming from increasing cyclonic
flow aloft along with a southern stream jet streak passing just
off to our southeast overnight. This will help develop a weak surface
low that will pass just southeast of Long Island. Lows overnight
expected to range from the upper 40s to upper 50s.
Short term /6 am this morning through 6 PM Tuesday/...
there will be a chance of lingering rain during the first half
of Monday morning over Li and southeast CT. Otherwise, dry weather and
diminishing clouds on Monday with highs above normal across the
tri-state area. The flow aloft Monday night through Tuesday
becomes more zonal and surface high shifts towards US through
the period with its axis moving offshore Tuesday afternoon.
Rain-free conditions therefore continue, and temperatures will
return closer to seasonable levels.
Long term /Tuesday night through Sunday/...
a progressive northern stream will dominate the weather through the
long term period with a relatively amplified pattern.
The beginning of the long term will be tranquil as ridging moves
into the western Atlantic and a significant shortwave amplifies into
the Great Lakes region. The forecast as been consistent, and
confidence increasing, for a deep coastal low to develop Wednesday
afternoon and the upper trough closes off and becomes negative. An
impulse moving into the base of the trough emerges off the mid
Atlantic late Wednesday with a coastal low expected to develop along
the cold front, and along a thermal ridge, and quickly deepen
Wednesday night. There will be a lot of lift with the low along with
elevated instability and elevated cape. Precipitable water vales
quickly increase to 1 1/2 inches during this time. A brief period of
moderate to heavy rainfall is likely late Wednesday afternoon into
the evening with embedded convective elements in the rain. A rumble
of thunder is a possibility at that time as well. There is also a
flood threat. See the hydrology section for details. The low tracks
quickly along the New England coast Wednesday night and
precipitation then ends. With wrap around moisture Thursday, and
some energy rotating around the west side of the upper low, there is
a slight chance of a few showers across the far interior zones
Temperatures Tuesday night will not be diurnal as strong warm
advection develops. Lows will most likely occur Tuesday evening,
then temperatures will rise through the night, especially across the
Strong and gusty westerly winds develop behind the low Thursday,
mainly near the coast. Winds and gusts are expected to remain below
advisory levels at this time.
Tranquil weather returns as an amplified ridge builds into the area
Thursday night through the upcoming weekend. Next weekend
temperatures are likely to be above normal.
Aviation /06z Monday through Friday/...
an area of low pressure will move off the Delmarva Peninsula and
track south of Long Island. High pressure builds in early
Monday, then a cold front passes through Monday evening.
MVFR ceilings are moving into the Metro terminals as well as
kisp and khpn, with a low chance of IFR in a few locations
toward Monday morning. These conditions will spread a bit
farther north and east as the night progresses. Kswf may remain
VFR the entire night. Rain chances will be confined to eastern
terminals and off the coast, and therefore only indicated vcsh
at kisp and kgon. VFR conditions return mid morning into the
Winds generally light and variable through the overnight and
into early Monday morning. Winds then become west to SW 5 to 10 kt.
Outlook for 00z Tuesday through Friday...
Wednesday...MVFR/IFR likely developing in rain. Chc southeast gusts
around 25 kt.
Thursday...VFR. Northwest gusts 25 to 35kt.
Friday...VFR. Northwest winds, diminishing gusts.
a weak pressure gradient will prevail over the waters through
Tuesday. Sustained winds for much of this period are expected to be
at 10 kt or less, but may briefly approach 15 kt Monday night. Seas
should remain below 5 ft.
High pressure over the forecast waters Tuesday moves offshore
through Tuesday night as a deepening low, and associated cold front,
approaches from the Great Lakes. A coastal low is expected to
develop south of Long Island Wednesday afternoon and track along the
New England coast Wednesday night.
Conditions will be sub Small Craft Advisory levels Tuesday into Wednesday morning.
Wednesday afternoon Small Craft Advisory conditions develop. Wind gusts increase
Wednesday night into Thursday as the low moves away and a strong
west to northwest flow develops. Gale force gusts are likely
Wednesday night on the ocean waters, and across all the forecast
waters Thursday, possibly into early Thursday evening.
Winds subside Thursday night into Friday, along with ocean seas.
no hydrologic impacts for any rainfall that occurs overnight
into early Monday morning.
A significant rainfall of 1 1/2 to 2 inches is likely Wednesday and
Wednesday night, with locally higher amounts possible. The bulk of
the rainfall is currently expected Wednesday afternoon into
Wednesday evening. Urban, poor drainage, and low lying flooding is a
significant threat. There is a possibility of flash flooding with a
few of the smaller, and fast responding, rivers and streams
NYC National oceanic and atmospheric administration weather radio station kwo35 (162.55 mhz) remains off the