NYC Office Forecast Discussion

047
FXUS61 KOKX 160027
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
727 PM EST Tue Jan 15 2019

.SYNOPSIS...
High pressure gives way to an approaching cold front over the
Great Lakes, which passes across the area Wednesday night. High
pressure then quickly passes to the north on Thursday followed
by a frontal system Thursday night into Friday. A stronger
frontal system will likely impact the region Saturday into
Sunday night. Arctic high pressure builds into the region Monday
and Tuesday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Temps were lowered a few degrees for NYC with the 645 pm temp
at Central Park only 1 degree off from the fcst low.
Otherwise,the fcst is on track.

Weak high pressure passes to the east tonight as a cold front
tracks across the Great Lakes. Light winds will back to the W/SW
and gradually pick up toward daybreak as the pressure gradient
tightens between low pressure moving across eastern Canada and
high pressure offshore. Other than a few high clouds this
evening ahead of a mid level short wave, skies will become
mostly clear.

Lows will be near seasonable, if not a couple a degrees above as
weak low-level warm advection develops. Readings will range
from the teens to lower 20s in outlying areas, to around 30 NYC
metro.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/...
A cold front moves out of the Lower Great Lakes Region Wednesday
morning and then passes across the area in the evening. This
will be a dry frontal passage preceded by a gusty W/SW flow up
to 25 mph. There is some uncertainty with the extent of cloud
cover on Wednesday with subsident westerly flow, however model
time-height cross sections indicate a moist layer between
900-850 mb. At the very least, would suspect partly cloudy skies
to perhaps mostly cloudy.

Skies clear behind the cold front Wednesday night with mid and
high levels clouds increasing late Thursday ahead of an approaching
frontal system.

Temperatures will be near seasonable levels Wednesday and Wednesday
night, but then turning much colder on Thursday with highs
struggling to reach freezing.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Zonal flow across the northeast and into the mid Atlantic will
see a weak southern stream shortwave pass through the mid
Atlantic Thursday night and Friday. A weaker shortwave will be
moving through the northern stream, however, at this time there
is no phasing of these systems, with the northern stream lagging
behind the southern wave. Enough cold air will be in place as
high pressure will be passing to the north. Snow will begin
around 00Z Friday across the region and continue into Thursday
night. Then warmer air ahead of the low will allow a transition
to rain and snow along the coast, going over to all rain Friday.
There is no cold air damming in place so at this time freezing
rain is not expected. However, the cold air does remain in place
inland, across portion of the lower Hudson Valley. All snow is
expected there. This will be a light QPF event, however, there
is the potential for advisory level snow across portions of the
lower Hudson Valley. The NAM was an outlier, keeping cold air,
and an all snow event across the region.

Near zonal flow remains Friday night into Saturday and there
will be only a brief period of dry weather before the next
system begins to impact the area Saturday afternoon. The
shortwave energy associated with this system will be coming
onshore of the Pacific northwest Wednesday night into Thursday.

Guidance remains fairly consistent with a deepening and
significant low impacting the area Saturday into Sunday night.
There has been a slight trend toward a more inland track, and a
warmer solution. With increased confidence in the storm have
continued with likely and categorical probabilities. There does
remain some uncertainty with precipitation type. So along the
coast began as all rain with a brief possibility of light snow
Saturday evening before strong warm advection sets in. Again,
there is no blocking high to the north and no cold air damming.
However, there is a trend toward more phasing of some northern
stream energy and the southern shortwave. With a deep moisture
feed from the Gulf of Mexico there is the potential for
significant precipitation. Mainly a rain event, except well
inland. More uncertainty comes as the low deepens and departs
Sunday afternoon and Sunday night. There is uncertainty as to
how quickly cold air wraps back into the system and how much QPF
will be on the back of the low. So, rain transitions back to
snow, and possibly some freezing rain, although confidence in
this is low. Arctic air moves in behind the system with wind
chills become a factor Sunday night into Monday.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
High pressure centered well to the southwest of the region will
provide VFR conditions through the TAF period.

KLGA/KJFK/KTEB have been experiencing an unusual sea breeze
from the NNE to NE off Long Island Sound. Think this will
dissipate this evening as the overall flow turns WSW overnight.

Winds on Wed should be WSW 5-10 kt during the AM push, then
increase a little further to just over 10 kt with gusts either
side of 20 kt from late AM into the afternoon.

 ...NY Metro Enhanced Aviation Weather Support...

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

KJFK TAF Comments: No unscheduled AMD expected.

KLGA TAF Comments: No unscheduled AMD expected.

KEWR TAF Comments: No unscheduled AMD expected.

KTEB TAF Comments: No unscheduled AMD expected.

KHPN TAF Comments: No unscheduled AMD.

KISP TAF Comments: No unscheduled AMD expected.

.OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...
*** HIGH IMPACT WEATHER LIKELY SATURDAY NIGHT INTO SUNDAY ***
.Thursday...VFR.
.Thursday night and Friday morning...Lowering to MVFR and IFR
in light snow, changing to rain in the morning except at KSWF.
Runway accumulations about 3 inches at KSWF, 1-2 inches at KHPN,
about an inch elsewhere.
.Friday afternoon through Saturday morning...VFR.
.Saturday afternoon...Becoming IFR at KSWF with chance of snow,
MVFR at the NYC metros with chance of rain.
.Saturday night...IFR conds developing throughout. Most likely
precip types: Rain at KLGA/KJFK/KISP, snow changing to
rain/sleet after midnight at most other terminals, all snow at
KSWF. Too early to give specific runway accumulations. LLWS
possible late.
.Sunday...IFR. Possible mixed precip early at KSWF/KHPN,
otherwise precip changing back to snow with some additional
accumulation in the afternoon, then tapering off at night. LLWS
possible in the morning. NW winds G20kt afternoon and at night.

&&

.MARINE...
Marginal SCA seas are possible through early this evening,
otherwise a brief period of sub-SCA conditions overnight as
light NW winds back to the W/SW. Gradient winds increase toward
daybreak Wednesday as a cold front approaches from the Great
Lakes and high pressure builds offshore. SCA conditions are
likely to develop on the ocean, eastern Sound, and southern and
eastern bays. Winds and seas will then gradually diminish
overnight Wednesday behind the cold front with high pressure
passing to the north on Thursday.

Winds and seas are expected to remain below SCA levels across
all the forecast waters Thursday through Saturday as a weak
frontal system moves through the waters Thursday night and
Friday.

As another frontal system approaching and the pressure gradient
increases Saturday night into Sunday, SCA level wind gusts will
be possible. Then as the frontal system passes to the east and
deepens late Sunday into Sunday night, gale conditions will be
possible on the ocean waters, with SCA level winds and gusts on
the remainder of the forecast waters.

&&

.HYDROLOGY...
No hydrologic issues anticipated through Thursday.

Around 1/3 of an inch of liquid equivalent QPF is forecast
Thursday night into Friday. Some of this will fall as snow,
thus no hydrologic issues are expected.

There remains the potential for a heavy precipitation event
Saturday through Sunday night across the northeast and mid
Atlantic. With good consistency in the forecast at this time,
confidence is increasing.

&&

.EQUIPMENT...
NYC Central Park winds are out of service until further notice.
Loss of data is due to a severed cable. Parts are on order.

NYC NOAA Weather Radio Station KWO35 (162.55 MHz) will remain off
the air for an extended period of time.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 6 AM Wednesday to 1 AM EST Thursday
     for ANZ330-340-345.
     Small Craft Advisory from 6 AM Wednesday to 6 AM EST Thursday
     for ANZ350-353-355.

&&

$$
SYNOPSIS...MET/DW
NEAR TERM...JMC/DW
SHORT TERM...DW
LONG TERM...MET
AVIATION...BC/Goodman
MARINE...MET/DW
HYDROLOGY...MET/DW
EQUIPMENT...

NWS OKX Office Area Forecast Discussion