Area Forecast Discussion
Issued by NWS Upton, NY-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KOKX 280244
Area Forecast Discussion
National Weather Service New York NY
1044 PM EDT Tue Sep 27 2016
A weakening cold front will remain offshore through Wednesday
night while high pressure builds in from the Canadian Maritimes. A
nearly stationary low pressure system over the Ohio Valley and Mid
Atlantic regions, with an associated warm front remaining to our
south due to strong high pressure over New England and the
Canadian maritimes, will then bring an extended period of
unsettled weather from Wednesday night into the weekend. The low
will weaken and move slowly northeast early next week.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Satellite shows low clouds across eastern Long Island, while
radar shows isolated showers over the coastal waters, both
associated with the offshore front. Bumped PoP up over eastern
sections to account for these showers. Also bumped low temps down
slightly elsewhere as these areas remain under mostly clear skies
for a good portion of the night.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
The weather continues to become more unsettled during this
For Wednesday through Wednesday Night, the region will remain
between a southward shifting large cutoff upper level low going
towards the Tennessee Valley and the upper level shortwave in the
Canadian Maritimes. There will be continued ridging between the
two upper level features. However, at the surface, the center of
high pressure remains strong and centered more towards Southeast
Canada. There will be a low pressure area well southwest of the
region that will be approaching. There is evident too from the
model MSLP fields an inverted trough that will be approaching
ahead of the surface low. Aloft, there will be increasing
isentropic lift especially Wednesday afternoon through Wednesday
night. This goes along with the SW flow in the mid to upper levels
setting up warm air advection aloft.
At the surface, a persistent pattern with high pressure in Southeast
Canada and the local region being on the SW periphery of this
high. This will give the region increasing NE flow and with the
high being strong centered in the Canadian Maritimes, a steep
pressure gradient will setup, resulting in winds becoming gusty.
Model precipitation fields are showing some very light
precipitation amounts across the region Wednesday and increasing
towards the western portions of the region Wednesday night. This
all conveys here a situation with moisture getting trapped under
an inversion. This low level moisture will increase Wednesday and
eventually materialize as drizzle or light rain to start with and
a higher chance of rain Wednesday night when it will increase in
intensity, coverage, and become more steady. At that time, the
atmospheric column becomes more moist as well.
Regarding temperatures Wednesday, used the ECS guidance and
slightly adjusted downward. NE flow and increasing clouds points
to a cooler than normal day on average out east while farther west
highs are forecast to be near normal. Wednesday night features
lows from a MAV/MET blend with again not much of a spatial range,
mostly mid 50s to near 60 across the area.
.LONG TERM /THURSDAY THROUGH TUESDAY/...
NWP guidance is in remarkably good agreement on the big picture
through the weekend, with a large upper low completely cutting off
from the westerlies and stalling over the Ohio Valley from Thu
through Sat, then lifting across the Great Lakes on Sunday and
weakening into an upper trough that slides across the Northeast on
Monday. Meanwhile, as a strong upper high builds over the Western
Atlantic, upper level confluence to its north where it meets the
westerlies will maintain strong surface high pressure over
northern New England and the Canadian Maritimes,that should nose
down into our area and keep a warm front to our south. This
combination will keep us in an unsettled weather pattern through
at least the weekend, with periods of moderate to heavy rain. The
first of these is likely to come Thu night into Fri morning via
strengthening easterly low level Atlantic inflow, moistening mid
levels via deep southerly flow aloft, a mid level vort max riding
up the coast, and increasingly difluent flow aloft. Another bout
of heavy rain may come to Long Island and southern CT on Saturday
as another mid level impulse rides up the coast and as a weak wave
of low pressure forms along the front just to the south. In
between these bouts of heavier rain skies should remain overcast,
with periods of intermittent light rain. An exception to this may
take place Thu afternoon, when some guidance indicates the high
may build down strongly enough from the north to shut off precip
for a time across the interior. Some elevated instability will be
present Sat into Sat night, with some rumbles of thunder possible.
As the upper low lifts into the Great Lakes on Sunday, an
associated weak triple-point low and/or occluded front should
slowly lift across, with precip becoming more showery in nature.
The upper low will continue to weaken and move east, but not clear
our area until Tue morning, so forecast carries at least slight
chance PoP until then.
High temps in this regime will be slightly below average Thu-Fri,
with a return to near average Sat into Mon, and then slightly
below average on Tue as Canadian high pressure starts to return.
Low temps meanwhile should be mostly warmer than average until Mon
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --There is a band of some mid level clouds impacting the eastern
terminals this evening, otherwise VFR.
Forecast transitions over to a prolonged period of sub-VFR
conditions starting on Wednesday and likely persisting into the
first half of the weekend.
High pressure builds south from eastern Canada and noses into the
area late tonight into Wednesday. At the same time, low pressure
will drop south across the Great Lakes and into the Ohio Valley
states. This will result in a strengthening NE flow with overrunning
clouds and possible light rain.
Widespread MVFR conditions are forecast to develop from east to
west, as early as 09Z at KGON, and as late as 16Z across the Lower
Hudson Valley. There is the possibility for these ceilings to move
in earlier than forecast, as well as drop into the IFR category,
especially for the coastal terminals. Light rain is a
possibility, but not expecting restrictions to visibility at this
time. Another potential wrinkle in the forecast is the magnitude
of the high building in from the north. Should the high build a
bit farther south, this could improve conditions for a time.
Light and variable winds this evening becoming NE around 10 kt
early Wednesday morning. By mid to late morning, NE winds
increase to 10-15 kt and become gusty at times, as high as
20-25 kt at the coast.
.Outlook for 00Z Thursday through Sunday...
.WED NIGHT...Widespread MVFR ceilings, possibly IFR. NE winds
G20-25KT at the coastal terminals.
.THU-SAT...IFR/MVFR in showers. NE winds 15-20 kt with gusts
25-30 kt possible THU-FRI.
.SUN...Mainly VFR but MVFR possible with a chance of showers. N
winds 10-20 kt.
-- End Changed Discussion --
Latest obs still show 5-ft seas at 44017 and 6-ft seas at 44097,
the combination of 2-ft wind waves and 3-4 ft southerly swell.
Combined seas may come down a little overnight, but decided to
start SCA for the eastern ocean waters now rather than wait until
Then Wednesday into Wednesday Night, SCA looks more probable
across all waters especially on the ocean. There will be a tight
pressure gradient setting up between a Southeast Canada high and
low pressure southwest of the region. Think max gusts reach near
30 kt, mostly Wednesday night.
Then as the pressure gradient tightens further, easterly gales
appear likely from Thu into Fri morning mainly on the ocean, but
perhaps also on the nearby bays of eastern Long Island and eastern
Long Island Sound, with SCA conds on the harbor and western Sound.
Issued gale watch for the ocean for Thu into Thu night.
SCA conds are likely to continue thereafter on all waters into
Fri, on the eastern Sound/bays into Fri night, and on the ocean
Any rain Wednesday through Wednesday night will be light, with
rainfall totals less than 1/4 inch.
The heaviest rainfall amounts with a nearby low pressure system
should fall to our west, but there could still be some periods of
heavier rain Thu night into Fri morning, also Fri night into
Saturday. Total basin average rainfall from Thu through Sat
should range from 1 to 2 inches, highest east, with potential for
local amounts of 2-3 inches across parts of Long Island and
southern CT. This is not expected to cause major
A persistent moderate easterly flow during mid to late week may
combine with increasing astronomical high tides associated with
the new moon on Friday to cause minor to locally moderate coastal
flooding. The high tide cycles from Thu night into Fri morning
appear to be of most concern.
-- Changed Discussion --CT...None.
MARINE...Small Craft Advisory from noon Wednesday to 6 AM EDT Thursday
Gale Watch from Thursday morning through late Thursday night
Small Craft Advisory from 6 AM Wednesday to 6 AM EDT Thursday
Small Craft Advisory from 10 AM Wednesday to 6 AM EDT Thursday
Small Craft Advisory until 6 AM EDT Thursday for ANZ350.
-- End Changed Discussion --