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FXUS61 KOKX 121907
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
207 PM EST Wed Dec 12 2018

.SYNOPSIS...
High pressure builds in from the north through tonight. A weak
upper level disturbance passes on Thursday. A frontal system and
associated low pressure will then impact the area over the
weekend before high pressure builds in for early next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Forecast once again updated to reflect cloudier conditions
across the lower Hudson Valley, portions of NJ, NYC, western
Connecticut and Long Island. These clouds may continue to
advance eastward in northwest flow. There remains uncertainty on
whether the clouds will be able to clear, and with a subsidence
inversion strengthening it is more likely moisture will remain
beneath around 3000-4000 ft.

Upper level shortwave departs today while at the surface, high
pressure builds in from the north. Cold air advection behind the
front will mean a continuation of the below normal temperatures
the area has been seeing as of late. Highs will top out in the
middle 30s to near 40. Conditions will be mostly clear as
subsidence from high pressure limits cloud formation.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Conditions remain dry through tonight as surface high pressure
remains centered over southeastern Canada/northern New England
and an upper level ridge moves through the Northeast. Low
temperatures tonight will be problematic, especially for the
outlying areas as clouds start to increase late tonight ahead of
an approaching weak upper level low over the eastern Great
Lakes region. Currently, the forecast is for temperatures to
drop early in the night, but as the clouds move in, temperatures
will remain steady or rise. However, if clouds move in later,
temperatures will likely drop in the outlying areas, but if the
clouds come in earlier, temperatures will remain steady or rise
earlier than is currently forecast.

The upper low will track near central or southern New York by
Thursday afternoon. There will be a slight chance for
precipitation for western areas during the late morning, with a
slight chance for the entire area by the afternoon hours.
However, the upper low will be weakening as it approaches and
only very light amounts of precipitation are expected.

As for precipitation type, precipitation could start off as all
snow for most places. Much of New York City will start off as a
rain/snow mix transitioning to all rain as the boundary layer
warms up. By the afternoon, plain rain is expected across Long
Island, New York City, and much of northeast New Jersey. The one
concern will be the possibility of freezing rain across western
Passaic and interior portions of the Lower Hudson Valley during
the middle to late afternoon time frame. Soundings indicate the
possibility of ice crystals NOT being present, while at the
surface it will be at or below freezing, so any precipitation
will fall as liquid and freeze on contact in these areas.

Precipitation amounts will be very light, only looking at a
couple of hundredths of an inch. If snow does accumulate, it
will be limited to north and west of New York City, and only a
couple of tenths of an inch, in other words a dusting. Again,
the one concern would be the ice across the aforementioned
interior locations. If this does end up happening, a Winter
Weather Advisory would likely be needed. Do not have any ice
accumulation in the forecast, but even a widespread trace amount
of freezing rain would warrant an advisory. Will continue to monitor
the situation.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
While any lingering showers or flurries should be offshore by
Thursday night, the combination of light east-southeast flow and
lingering low level moisture will result in the chance of patchy
drizzle and/or freezing drizzle generally north and west of NYC. The
best chance for any freezing drizzle appears to be across Orange,
Putnam, and western Passaic counties, where moisture will linger the
longest and temperatures will be several degrees below freezing.

Thereafter, attention then turns to the frontal system progged to
impact the region over the weekend. Models remain in good agreement
with both the surface and upper level evolution of the system
through early Saturday morning as low pressure slowly traverses the
Lower Mississippi Valley. Thereafter, models diverge significantly,
with the 00Z GFS allowing the closed low to drift much farther
north, which has implications for the duration of precipitation over
the area through the weekend. These differences are related to how
the southern stream system interacts with numerous northern stream
shortwaves, which will become better resolved as the energy comes
onshore in the coming days.

For now, the majority of the daylight hours on Friday look to remain
dry as surface high pressure initially over the area drifts
offshore. Rain then overspreads the area Friday night and continues
into Saturday morning before beginning to taper off Saturday
afternoon. At least a chance of rain could linger into Saturday
night and Sunday, especially if the more northern low track comes to
fruition.

Dry weather then returns for the start of the next work week as high
pressure builds in behind the departing low.

Temperatures will be 5-10 degrees above normal on Friday and
Saturday ahead of the system before falling back to near to slightly
below normal for the remainder of the long terms period.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
High pressure builds in through tonight. A weak disturbance
moves across the area on Thursday.

Mainly VFR today. clouds have moved into the western half of the
CWA with cigs around 3-4kft. Unsure how long these clouds will
last. They may dissipate after 21z or 22z, similar to yesterdays
stratus. Additional higher clouds move in from the west tonight
as low pressure slowly approaches from the west.

MVFR cigs develop early Thursday morning with some light snow
possible. Conditions may lower to IFR by mid morning. For the
City terminals, the light snow should change over to a rain/snow
mix around 15z, however further north, the precipitation should
remain snow a bit longer.

NW winds 10-15 kt are expected, with a few gusts 15-20 kt this
afternoon. Winds lighten later today and tonight as they veer
to the NE. Winds then become easterly during the day
Thursday.


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: Winds right around 310 true through much of the
afternoon. Gusts should be less frequent.

KLGA TAF Comments: Winds right around 310 true through much of the
afternoon. Gusts should be less frequent.

KEWR TAF Comments: Winds right around 310 true through much of the
afternoon. Gusts should be less frequent.

KTEB TAF Comments: Winds right around 310 true through much of the
afternoon. Gusts should be less frequent.

KHPN TAF Comments: No unscheduled amendments are expected.

KISP TAF Comments: No unscheduled amendments are expected.

.OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY...
.Thursday...MVFR with local IFR possible in light rain or snow.
.Friday...MVFR to start, then MVFR/IFR conditions likely late
in rain.
.Saturday...IFR likely in rain.
.Sunday and Monday...MVFR possible in rain.

&&

.MARINE...
SCA has been cancelled as winds and seas gradually begin to
subside with high pressure building in from the north. Winds
and waves will then remain below SCA tonight and Thursday.

A frontal system and associated low pressure will approach the area
Friday night through Saturday. SCA may be needed starting on
Saturday as winds and seas increase in response to the passing
system. Ocean seas then appear to remain elevated into at least
Sunday, although significant uncertainty remains in the evolution of
the system during the second half of the weekend.

&&

.HYDROLOGY...
No significant widespread liquid equivalent amounts expected
through Friday.

Rainfall amounts Friday night into Saturday will range from 0.5 to 1
inch across the region. This could result in minor flooding in poor
drainage areas, otherwise the recent dry conditions should limit any
flooding potential.

&&

.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...None.

&&

$$
SYNOPSIS...FEB/JP
NEAR TERM...MD/JP
SHORT TERM...JP
LONG TERM...FEB
AVIATION...BC
MARINE...FEB/MD/JP
HYDROLOGY...FEB/JP
EQUIPMENT...
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