National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
375
FXUS61 KOKX 150603
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
203 AM EDT Tue Oct 15 2019

.SYNOPSIS...
A dry cold frontal passes east overnight, followed by building
high pressure through Tuesday. A frontal system will approach on
Wednesday, with a rapidly intensifying coastal low tracking
just southeast of the area Wednesday Night, and into the
Canadian Maritimes Thursday into Thursday Night. High pressure
builds in for next weekend. Another frontal system approaches
for early next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Cold front extends across the east end, and passes east
overnight. High pressure over the Ohio Valley then builds east
through the night.

Patchy fog over astern LI should scour out as the front passes
east and a light north wind develops. Otherwise, mainly clear
skies are anticipated.

Overnight lows will be right around normal, generally in the
40s, except around 50 for the NYC metro.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
Shortwave ridging between one departing upper low over eastern
Canada and an amplifying trough over the upper Midwest into the
Great Lakes, will result in dry, seasonably cool conditions. Any
clouds will be on the increase late Tuesday night as a frontal
system approaches from the west.

A light northerly flow in the morning will become onshore in
the afternoon as surface high pressure works offshore.

Highs on Tuesday will top out in the lower 60s. Lows Tuesday
night will likely vary considerably due to good radiational
cooling, from the lower 50s in metro NY, to the mid 30s to
lower 40s elsewhere. With a light onshore flow and increasing
low-level moisture, fog may be a possibility as well as frost.
Guidance still showing dew point depressions significant enough
to leave mention of fog out at this time.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Main story during this period will be a strong frontal
system/developing coastal low affecting the region late Wednesday
into Thursday.

Main features will be a strongly amplifying northern stream
shortwave digging through the US/Canada border of the Rockies this
afternoon. This feature will develop a closed upper low that slides
into the upper Great lakes Tue/Tue Night, then phases with the
southern stream Wednesday morning. The phasing and deepening closed
low will approach the region Wednesday, and then pivoting through
the area Wed Night into Thu morning and up the New England coast
into the Canadian maritimes Thu afternoon thru Thu Night. At the
surface, low pressure associated with the northern stream closed low
will track east through the Great lakes Tue into Wed, with its
associated strong cold front pushing towards the region late
Wednesday. At the same time, phasing jet energy will begin to
intensify a southern wave of low pressure tracking ne ahead of the
front off the Mid-Atlantic coast; tracking just SE of LI Wed night.
This will become the primary intense low pressure by Thursday
morning as it tracks up the New England coast.

There is good general model agreement in the above scenario, but
still some spread on intensity of the developing coastal low as it
tracks se of LI and into New England, and to a lesser extent spread
in how close or over the area the low tracks. The sensitivity of
this appear to be with evolution of a Central PAC closed low, and
downstream amplification of west coast ridging and northern stream
shortwave, and then the eventual phasing with southern stream. The
main implication for our area would be modest, in terms of
amount/axis of rain and strength of winds ahead and behind system.
This should come into better focus over the next 24-48 hrs.

Strong deep layer forcing with this system and a deep subtropical
PAC and Gulf moisture connection (+1 1/2-2 std PWATS) point towards
a heavy rain event late Wed through Wed Night. Strong forcing,
closed low/vort energy moving through aloft, and weak surface
instability point to potential for some deeper convection and
embedded thunder. This brings likelihood for 1 to 2 inches of
rain, with locally 2-4" inches of rain possible. Rain should
quickly taper off late Wed night as trough axis pivots east.
Deep cyclonic flow on Thursday will result in considerable cloud
cover with scattered showers/sprinkles, particularly interior.
Can`t even rule out a wet snow flake or two across the far NW
hills in any heavier showers as cold pool moves through aloft
and coolest airmass of the season works in.

In terms of winds, ahead of the low a period of E/SE winds 20 to 25
mph gusts 30-35 mph (peak winds 25-30 gusts to 40 mph possible
across eastern LI) likely along the coastal plain Wed
afternoon/evening. Then in the wake of low pressure W/NW winds of 20
to 30 mph and gusts to 40 to 45 mph likely late Wed Night into
Thursday. There is potential for wind advisory 30-35 mph and gusts
to 50 mph if stronger low development verifies. Windy
conditions will continue into Thursday Night, although gust
potential likely decreases with decreased instability.

Cyclonic flow will be slow to relent through the day Friday. NW
winds will be weakening, but still a a breezy day. Another below
seasonable day with sct-bkn afternoon strato-cu.

Then a gradual moderation to seasonable and then above seasonable
temps and fair weather this weekend as upper ridging build in and
high pressure builds to the south of the region.

Next chance of rain looks to be some time early next week, as
another deep trough develops over the central US, with an
increasingly moist and active flow deep SW flow developing into the
Eastern US. indication are a slow moving frontal system or systems
approaching for Monday/Tuesday.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
High pressure builds in through the TAF period. VFR conditions
are expected for all terminals.

For NYC terminals, winds will be relatively higher going into
Tue AM with N-NW flow of 10-15 kt decreasing to near 10 kt.
Winds then eventually shift to more of a SW direction at 5-10 kt
Tue afternoon with sea breeze circulations developing.

Otherwise, rest of terminals have an initial NW wind of 5-10 kts
that will eventually become more SW during Tue afternoon at
nearly the same wind speed with developing sea breeze for
coastal terminals.

.OUTLOOK FOR 06Z WEDNESDAY THROUGH SATURDAY...
.Late Tuesday night...VFR. Winds become more SE.
.Wednesday...Rain developing. Conds quickly lowering to IFR
late afternoon/evening, lingering past midnight at KGON.
SE winds G25kt. LLWS also possible along the coast late
afternoon/evening, mainly at KISP/KGON.
.Thursday...VFR. NW winds G25-35kt.
.Friday...VFR. NW winds G20-25kt mainly AM.
.Saturday...VFR.

&&

.MARINE...
The pressure gradient remains relatively weak during the short
term through Tuesday night. Conditions are expected to remain
below SCA across all local waters.

SE winds increase across the waters on Wed ahead of an
approaching cold front and developing low pressure. SCA
conditions expected on all waters by early Wed afternoon into
Wed evening. A brief period of SE gales likely on the ocean
waters east of Moriches inlet as the low approaches, and
possible for the rest of the ocean waters and the eastern
Sound/bays.

Winds expected to shift to the NW Wed evening, with W-NW gales
likely on the ocean waters late Wed night, and on all waters for
Thursday. Gale conditions should fall to SCA Thu Eve/night,
with SCA wind gusts likely subsiding Friday morning into
afternoon. Ocean seas will rapidly build Wed aft/eve, but should
fall below SCA Fri afternoon as winds weaken as they will be
wind wave dominant.

&&

.HYDROLOGY...
A significant rainfall of 1-2 inches is likely Wednesday
afternoon into Wednesday night, with localized swaths of 2-4
inches possible. The bulk of the rainfall is expected in a 6-9
hr period late Wednesday afternoon through Wednesday evening.

Urban, poor drainage, and low lying flooding is expected. There
is a low probability of flash flooding along a few of the fast
responding small rivers and streams in NE NJ and the Lower
Hudson Valley if the higher rainfall amounts are realized.

Additionally, localized flash flooding will also be an issue
for coastal roads if heaviest rain coincides with the Wed Night
high tides.

&&

.TIDES/COASTAL FLOODING...
Tidal departures of generally 2 to 2 1/2 ft above astronomical
are needed for minor flooding during the times of high tide late
Wed Eve into Wed night. There is quite a bit of spread in the
ensemble guidance, partly due to some differences in the
potential strength of low pressure wind fields, and equally so
due to timing of a wind shift from E-SE winds to NW as low
pressure moves by. At this point, model consensus would
indicate potential for widespread minor coastal flooding, with a
low probability for localized moderate impacts where wave
action combines with elevated water levels.

If the heaviest rain coincides with the Wed night high tide,
more widespread flooding could be experienced than would
normally be expected.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO35 (162.55 MHz) remains off the
air.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$
SYNOPSIS...NV/DW
NEAR TERM...NV/DW/PW
SHORT TERM...DW
LONG TERM...NV
AVIATION...JM
MARINE...NV/DW/PW
HYDROLOGY...NV/DW
TIDES/COASTAL FLOODING...
EQUIPMENT...