Area Forecast Discussion
Issued by NWS Upton, NY

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211
FXUS61 KOKX 171149
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
649 AM EST Tue Jan 17 2017

.SYNOPSIS...
A warm front slowly approaches from the southwest through tonight.
This passes just south of Long Island late tonight into Wednesday
with a small area of low pressure moving across. The low moves east
of the region Wednesday. High pressure builds into the region on
Thursday as offshore low pressure gradually moves east. The high
weakens on Friday followed by a weak wave of low pressure passing
to the south Friday night. High pressure returns this weekend
before the next low pressure and associated frontal system impacts
the area early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Still dry across the region with any weak echoes evident on radar
being mainly over Orange County where temperatures are in the low
to mid 30s. The freezing or below temperatures may be more
isolated with associated freezing drizzle areas. Window should be
brief as more warming is anticipated by late this morning allowing
for all precip to be plain rain.

The main focus will be temperatures and approaching precipitation
ahead of a warm front. This will be associated with increasing
isentropic lift, maximizing this afternoon into tonight with
an increasing SE low level jet. Upper level subtropical jet will
be approaching with its left front quad, enhancing lift late today
through tonight.

For temperatures today took the HRRR/NAM12 average and tonight took
a blend of MAV/MET/ECS. SW flow leading into this morning and
lowering and thickening clouds should keep temperatures nearly
steady with a slight rise late this morning through the afternoon.

Freezing rain/freezing drizzle just expected across Orange County
with not much expected elsewhere with plain rain or plain drizzle
being the precipitation mode. Other interior locations may have
some isolated locations experiencing sub-freezing conditions with
therefore some isolated freezing rain or drizzle, not enough to
include in a freezing rain advisory.

Questionable forecast data seen in Bufkit NAM and GFS about this
afternoon into tonight with temperatures near 2kft as they show them
cooling off by a few degrees to below freezing. The RAP and HRRR
show the cooling too but keep temperatures near 2kft above freezing.
Too much uncertainty and without much dynamic cooling or efficient
wet bulb cooling expected, kept plain rain late today through
tonight. With moisture laden boundary layer, also put in patchy
fog for tonight into early Wednesday.

&&

.SHORT TERM /WEDNESDAY/...
For Wednesday, took a blend of MAV/MET/ECS for temperatures. Light
rain continues behind the low as 500mb vort max passes south of the
region with associated PVA. This will become more of a shower mode
by afternoon, mainly across eastern sections.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Active jet stream pattern will continue into early next week. The
latest global models and ensemble means are in overall good
agreement with just some timing differences. Above normal
temperatures will be the theme with NYC likely not falling below
freezing through at least early next week.

Offshore low will gradually move further east over the Atlantic
Wednesday night into Thursday. High pressure settles over the region
Thursday into Friday as ridging builds aloft. High temperatures both
days will be in the middle and upper 40s for most locations and near
50 degrees in the NYC and NE NJ metro.

Active southern branch of the jet will bring the approach of the
next system on Friday. And upper low over the Plains will open up on
Friday and energy will get driven under building ridging over the
eastern States. Models and ensembles have come into better agreement
with this system weakening as it approaches Friday night. The weak
surface reflection should largely stay to the south of the Tri-
State, with potential for some precipitation to graze the region.
Confidence is low in the coverage of precipitation since the system
is weakening as it moves nearby and lift and moisture are limited.
850 mb 0C line on the GFS, GEFS mean, ECMWF, and ECMWF EPS mean lies
across northern New England so snow is not a concern. Inland surface
temperatures would be the only concern if precipitation were to make
it that far north, and at this time thinking it should be above
freezing everywhere for just plain rain.

Anomalous ridging aloft continues this weekend and surface high
pressure will build down from SE Canada. The active southern branch
of the jet will continue as the next system organizes across the
central States on Sunday. Global models and ensembles continue to
show a strong cut-off low lifting towards the Ohio Valley Sunday
night into Monday. Its associated frontal system will gradually
approach early next week. Confidence in specific details is low at
this point since this is about a week out, but the signals are there
for a significant rainfall event.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
A warm front slowly approaches from the southwest through early this
evening as low pressure moves through the eastern Great Lakes
region. Another low will develop on a triple point across central
New Jersey this evening and track south of Long Island tonight.

VFR through this morning. MVFR conditions develop around 17Z with
light rain. Conditions lower to IFR late this afternoon into early
this evening. IFR conditions then remain through 12Z Wednesday with
light rain and fog.

Winds will be SW to W less than 10 KT to light and variable early
then becoming SE this afternoon and then e late this afternoon into
this evening. Winds will mainly be 5 to 8 KT.

There is uncertainty to the timing and direction of the winds and
will be dependent on the movement of the warm front and timing and
placement of the developing low this evening.


   ...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: Amendments possible as MVFR ceilings could
develop before 17Z and visibilities may remain MVFR. Winds may also
become SE before 17Z.

KLGA TAF Comments: Amendments possible as MVFR ceilings could
develop before 17Z and visibilities may remain MVFR. Winds may also
become SE before 17Z.

KEWR TAF Comments: Amendments possible as uncertainty with the
timing of MVFR ceilings developing this afternoon. May be +/- 1-2
hours of 17Z.

The afternoon KEWR haze potential forecast is green...which implies
slant range visibility 7SM or greater outside of cloud.

KTEB TAF Comments: Amendments possible as uncertainty with the
timing of MVFR ceilings developing this afternoon. May be +/- 1-
2hours of 17Z.

KHPN TAF Comments: Amendments possible as MVFR ceilings could
develop before 17Z and visibilities may remain MVFR. Winds may
also become SE before 17Z.

KISP TAF Comments: Uncertainty with the timing of MVFR ceilings
this afternoon and may be sooner than 17Z, and developing IFR
conditions may be before 21Z.


.OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY...
.Wednesday...IFR early, improving to MVFR, in rain and fog. Rain
ending in the afternoon with visibilities improving, ceilings MVFR.
.Wednesday night...Becoming VFR.
.Thursday-Friday...VFR.
.Friday night-Saturday...Chance of MVFR or lower with light rain
developing.

&&

.MARINE...
Conditions remain mostly below SCA on the waters with the
pressure gradient remaining weak enough today through early Wednesday.
The only exception would behind a low Wednesday afternoon, in
which ocean waters east of Moriches Inlet could potentially reach
SCA criteria.

Winds on the ocean will gradually diminish Wednesday night, but some
SCA gusts are still possible east of Moriches inlet. Easterly swells
from offshore low could bring ocean seas to SCA levels Wednesday
night into Thursday. Winds and seas on all waters are forecast to be
below SCA levels Thursday night into the weekend.

&&

.HYDROLOGY...
No hydrologic impacts are anticipated with around a half inch of
precipitation Tuesday through Wednesday morning.

Potential exists for a significant precipitation event early next
week.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Freezing Rain Advisory until 10 AM EST this morning for NYZ067.
NJ...None.
MARINE...None.

&&

$$
SYNOPSIS...JM/DS
NEAR TERM...JM
SHORT TERM...JM
LONG TERM...DS
AVIATION...MET
MARINE...JM/DS
HYDROLOGY...JM/DS



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