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957
FXUS61 KOKX 231743
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
143 PM EDT Fri Sep 23 2016

.SYNOPSIS...
A cold front will approach from the north today, then move across
the Tri-state this evening. Strong high pressure then builds in
from south-central Canada through Sunday night, then slides
offshore Monday. A slow moving frontal system could impact the
area from Monday night through Thursday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Upper level features the southward shift of a longwave trough and
jet stream across the Northeast.

The SW-W flow, while light, will lead to a warm day. Temperatures
will climb into the 70s and 80s, with the warmest locations acrossthe
NYC metro area.

There is a possibility for isolated showers and thunderstorms late
this afternoon across interior locations ahead of the cold front.

There is a moderate risk of rip current development at Atlantic
Beaches today.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Aloft, the upper level trough and jet stream move farther south into
the region with associated height falls.

At the surface, the cold front moves across tonight from north to
south during the evening hours. Showers are confined to along the
boundary and behind the front, lingering out east perhaps through
much of tonight while a more brief period is possible for western
sections. In addition, multiple models show some negative Showalter
indices moving across just behind the cold front. Therefore, this is
suggesting some thunderstorms will be possible. With limited
instability however, kept these isolated in coverage. Showers will
be isolated to scattered, greater coverage farther east in the
region. Without much of moisture sources to draw from, total
rainfall is expected to remain quite light.

Strong high pressure builds in behind the cold front. A northerly
flow takes shape behind the front which will bring cold and dry
air advection. This will allow for a cooler and drier airmass to
build in for late tonight and Saturday. The lows tonight though
will be limited though due to the lingering clouds which will
mitigate radiational cooling. ECS guidance was used for lows
tonight.

For Saturday, the northerly flow continues with dry weather
returning that morning through the rest of the day. There could be a
few showers remaining out east during the early morning but
otherwise expecting a dry day. It will also be remarkably cooler
with highs only in the upper 60s to mid 70s, closer to normal
than recent days. MET guidance was used for this to depict some
southern coastal locations getting downslope flow and relatively
higher temperatures.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
The region will be under northwest flow aloft Saturday night-Sunday
night as it remains in between a cutoff low slowly lifting through
the Canadian Maritimes and a deep layered ridge moving into the
Great Lakes and Ohio Valley. It should be dry with minimal cloud
cover as a result.

Lows Saturday night were based on a blend of MAV/MET/ECS guidance
and NAM 2-meter temperatures, weighed towards the coolest guidance
outside of urban areas to reflect likelihood of decent radiational
cooling conditions (did adjust normal cold spots down a tad more
than the blend above would suggest). Lows should be generally around
5-10 degrees below normal.

Highs on Sunday were based on a blend of MAV/MET guidance, NAM 2-
meter temperatures and a mix down from 875-825 hPa per BUFKIT
soundings. Highs should be around 5 degrees below normal. Lows
Sunday night were based on a blend of MEX/MEN/ECE/ECM/EKD/WPC
guidance and NAM 2-meter temperatures weighed towards the coolest
guidance outside of urban areas. Lows should be around 5-10 degrees
below normal.

The deep layered ridge axis builds over the area on Monday, keeping
things dry. Cloud cover should be minimal until maybe late in the
day, when some high clouds could begin to build into far western
zones.

The models continue to differ greatly in their handling of the Omega
block over the country early next week and the developing cutoff low
that should come down from central Canada towards the middle of next
week. The CMC is the strongest with the ridging in the middle of the
block and keep things dry until Tuesday night, the ECMWF is weakest
with the ridge and brings in precipitation Monday night, with the
GFS in between. Noting that multiple cutoff lows are involved with
this pattern, there likely will be quite a bit of model spread for
several more days.

Even though the ECMWF has been fairly consistent over the past 3
runs in how it has handled the system, it is likely too progressive
given the relatively high amplitude of the forecast Omega block
and the fact that multiple cutoff lows are involved. Both of
these factors typically favor a less, not more progressive
movement of systems.

As a result only bring slight chance pops into the NW 1/3 of the CWA
late Monday night. With decent overlap in precipitation coverage
between the ECMWF and GFS on precipitation coverage 12-18z on
Tuesday over roughly western 1/2 of the CWA - do have chance pops
there. Otherwise have slight chance pops CWA wide from Tuesday-
Thursday. Though there is at least moderate confidence that there
will be some rain over the entire area in this time frame,
confidence in exactly when any rainfall will occur is too low at
this time to warrant higher pops.

Temperatures Monday-Thursday were based on the Superblend and start
out below normal Monday, then generally run within a few degrees of
either side of normal from Monday night-Thursday.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
A cold front approaches from the north late this afternoon. The
front passes through this evening with some SCT -SHRA (with a very
low CHC for TS) mainly N and E of the NY Metro in its wake.

VFR conditions are anticipated through most of the forecast
period. Behind the front, MVFR ceilings are expected after
midnight into the early morning Saturday.

W to SW winds will lighten as the cold front approaches by
evening. Timing of cold frontal passage with distinct wind shift
to the NNE may be 1-2 hours sooner than forecast this evening.

A few gusts to 20 KT are possible from time to time.

     NY Metro Enhanced Aviation Weather Support...

Detailed information...including hourly TAF wind component fcsts
can be found at: http:/www.weather.gov/zny/n90

KJFK TAF Comments: S winds will lighten before the cold front
moves through. Timing of wind shift to the N/NE could be off an
hour or two.

KLGA TAF Comments: Winds shift to the S by 19-20z. Then timing of
wind shift to the N/NE could be off an hour or two this evening.

KEWR TAF Comments: SW winds will lighten before the cold front
moves through. Timing of wind shift to the N/NE could be off an
hour or two.

KTEB TAF Comments: W winds will lighten before the cold front
moves through. Timing of wind shift to the N/NE could be off an
hour or two.

KHPN TAF Comments: W winds will lighten before the cold front
moves through. Timing of wind shift to the N/NE could be off an
hour or two.

KISP TAF Comments: S winds will lighten before the cold front
moves through. Timing of wind shift to the N/NE could be off an
hour or two.

.Outlook for 18Z Saturday through Wednesday...
.Saturday afternoon-Monday...VFR. NW-N winds diminish during this
time.
.Monday night...VFR with possible showers developing.
.Tuesday-Tuesday night...Mainly VFR. Chance of showers at times.
.Wednesday...Any showers end. VFR.

&&

.MARINE...
Light winds today, with swells producing 3 to 4 ft seas on the
coastal ocean waters. The pressure gradient increases tonight, and
remains fairly tight into Saturday. This coupled with cold
advection behind a passing cold front tonight, should bring gusts
to around 25 kt on all waters after midnight, so have an issued an
SCA for all waters starting at midnight.

Frequent gusts to 25 kt or likely to come to an end around
sunrise, so end the SCA on the non-ocean zones at 10z. However,
the gusty winds combined with a SE swell should produce seas to
around 5 ft across the coastal ocean waters through the day on
Saturday - so have the SCA on those waters valid through 22z.

A light to moderate pressure gradient over the waters Saturday
night- Tuesday will keep sustained winds to 15 kt or less and
gusts less than 25kt. It is possible, depending on exact strength
of winds and the extent of swells on Saturday night-Sunday that
the coastal ocean waters could see seas up to 5 ft. Otherwise,
seas and waves are expected to be below Small Craft Advisory
thresholds Saturday night through Tuesday as well.

&&

.HYDROLOGY...
Generally less than a quarter of an inch of rain tonight/early
Saturday. Otherwise, it will be mainly dry through Saturday.

It should also be dry from Saturday night through at least Monday
evening.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from midnight tonight to 6 AM EDT
     Saturday for ANZ330-335-338-340-345.
     Small Craft Advisory from midnight tonight to 6 PM EDT
     Saturday for ANZ350-353-355.

&&

$$
SYNOPSIS...JM
NEAR TERM...JM
SHORT TERM...JM
LONG TERM...Maloit
AVIATION...PW
MARINE...Maloit/JM
HYDROLOGY...Maloit/JM