Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
736 am EDT Tuesday Sep 23 2014
high pressure will build into the northeast through tonight and
then east on Wednesday. A weak low pressure wave will drift up
towards the region for the middle week and then out to sea for late
week. High pressure builds back in for the weekend into early next
Near term /until 6 PM this evening/...
shortwave shortwave energy will continue to slide east through southeast
Canada today...with high pressure building in from the west.
North/northwest flow this morning will subside...with potential for late day
seabreeze along immediate coast.
Deep northwest flow should limit cloud cover to just few-scattered instability cumulus
Temperatures will run a few degrees below seasonable with mixing limited
under subsidence inversion and recent shot of Canadian air. Temperatures
generally upper 60s to lower 70s.
There is a moderate rip current risk at the ocean beaches this
morning due to residual southeast swells. The threat likely transitions
to low through the afternoon as swells subside.
Short term /6 PM this evening through 6 PM Wednesday/...
weak upper ridging builds into the region tonight into
Wednesday...but with a cutoff southern upper low shearing NE around
western Atlantic upper ridging on Wednesday.
At the surface...high pressure will slide over the NE tonight. Good
radiational cooling conds for first half of tonight...with lows
well down into the 40s across interior and Pine barrens...and
lower to middle 50s elsewhere. If NE gradient remains weak until
after daybreak...a few upper 30s possible across interior/Pine
Surface high pressure continues to slide just east of the New
England coast on Wednesday...with models in good agreement with a southern
coastal trough/weak low drifting up the coast toward the middle Atlantic.
Conditions should be mainly dry for the region under high pressure
on Wednesday...but increasing high cloudiness is likely ahead of this
disturbance. Based on model trends there is a low probability that light
rain could work into southern portions of the tri-state by late day
Wednesday. A strengthening NE gradient is likely between the low to the
south and high pressure to the NE resulting in a strengthening
onshore flow...particularly along the coast.
Temperature guidance may be a bit too high based on model trends...with
temperatures potentially running slightly below seasonable with onshore
flow and increasing cloudiness. Have undercut mav/met blend
Long term /Wednesday night through Monday/...
a broad area of high pressure remains over much of the northeast at
the start of the long term with the center shifting just off the
Maine coast. At the same time...the surface low from the south
slowly makes its way north.
Uncertainty exists around this low in regards to timing and
intensity...and associated precipitation. Latest guidance looks to be
wetter and farther north with this low. GFS/CMC are
fastest/wettest with rain overspreading the area on Thursday.
European model (ecmwf)/NAM keep the low suppressed to the south with rain not
beginning till late Thursday. The real question will be if the
high pressure can hold off the rain and until when. For now...did
put slight chance/chance probability of precipitation Wednesday night through Friday morning which
is a change from the previous forecast. Not confident enough to go
any higher than that at this time.
As the low approaches...the gradient tightens and NE winds increase
Wednesday night into Thursday. Gusts up to 20-25 miles per hour possible on Long
Island and southeast CT.
Large difference in temperature guidance for Thursday as well depending on
how the low pressure plays out. Will take a Middle Range of values
for Thursday with highs in the upper 60s to lower 70s...cooler than
previously forecast. For the rest of the long term...a general
gmos/wpc blend was used with temperatures a few degree above normal through
High pressure and a broad upper ridge encompassing much of the
eastern United States then takes control of the weather for the
weekend and into the beginning of the week. Dry weather and mostly
sunny skies are expected.
Aviation /12z Tuesday through Saturday/...
high pressure will build over the area through tonight...then settle over
northern New England on Wednesday.
VFR through the taf period.
Light northwest flow becomes vrb by 16-18z...with local sea breeze development
along the coasts in the afternoon.
Some variability in wind direction can be expected through 16-18z.
..NY 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: no unscheduled amendments expected.
Klga fcster comments: no unscheduled amendments expected.
Kewr fcster comments: no unscheduled amendments expected.
The afternoon kewr haze potential forecast is green...which
implies slant range visibility 7sm or greater outside of cloud.
Kteb fcster comments: no unscheduled amendments expected.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 12z Wednesday through Saturday...
Wed-Thu...low pressure tracks up the coast. Chance MVFR or lower at
times. East winds Wednesday becoming north on Thursday. Speeds 10-15kt potentially
stronger depending on the track of the low.
Friday...becoming VFR with north winds 10-15kt.
Sat...VFR with light winds.
southeast swells and northwest winds continue to subside this morning with sub
Small Craft Advisory conds expected through tonight as high pressure controls the
Model trends have been for a wave of low pressure to track farther
northward for the the midweek period. This will result in a
strengthening east/NE gradient on Wednesday with potential for Small Craft Advisory conds
by late in the day on the ocean waters. Small Craft Advisory ocean seas likely
through Thursday and possibly into Friday depending on the timing
of the surface low as it moves north. Gusts above 25kt will also
linger through Thursday until the gradient slackens with high
pressure building back in for Friday. Cannot rule out gusts of
30-34kt as well Wednesday-Thursday but confidence is low at this point.
Potential for seas to build in excess of 10 feet Wednesday night/Thursday if
stronger winds materialize.
Sub Small Craft Advisory winds and seas then expected to return for the weekend as
high pressure builds in.
mainly dry conditions expected through Wednesday.
A surface low will track north and possibly impact the area Wednesday
night-Fri. A high amount of uncertainty exists on how far north
and quickly the precipitation shield gets. At this time...confidence is
increasing in light precipitation amounts Wednesday night/Thu...with
potential for a significant rainfall.
persistent NE flow and new moon will bring potential for minor
coastal flooding with Thursday morning/after high tide cycle...mainly along
vulnerable New York Harbor...NYC/western Li Back Bay and western sound
With the higher water levels...minor beach erosion likely with 2 day
duration of rough surf sweeping downshore from east to west.