Area Forecast Discussion
Issued by NWS Upton, NY

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921
FXUS61 KOKX 160931
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
431 AM EST Sat Dec 16 2017

.SYNOPSIS...
Weak low pressure passes to the north today bringing a cold
front south of the region. High pressure builds in for tonight
and Sunday. Then a series of lows will pass through the area
through mid week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Heights will be slowly rising through the day as northern stream
trough lifts out to the northeast. A weak shortwave and
associated vort max rotates through the trough, with much of
the energy passing to the north. At the surface a weak low will
pass through New England. A cold front does come through late
this afternoon and into early this evening. However, the front
is rather weak, and will be more reflected by a wind shift.
Precipitation will be minimal, and have lowered probabilities
across the region as the NAM and HRRR show light precipitation,
mainly across the northern and western areas of the CWA. Also,
will be more convective in nature, so keeping snow showers
wording. Only a tenth or two of snow will be possible, with
accumulations mainly across the lower Hudson Valley.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
A few flurries may be lingering into the early evening hours if
the cold front is slower to push through. At this time will keep
the evening dry. After 03Z heights will continue to rise through
Sunday as the flow becomes more zonal. A dampening shortwave
will be moving into the weak upper ridge late Sunday and Sunday
night, and pass through Sunday night.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
A weakening shortwave passes through Sunday night into Monday.
Have lowered the probabilities slightly as the shortwave is
weakening and flat, with little moisture. Warmer air will be
pushing into the region, and as the warm air lifts north of the
cold surface air a period of freezing rain, some ice pellets and
snow will be possible. Too early for specific details on this
light precip event.

Thereafter, models in fairly good agreement with the broad bu
shallow northern stream trough approaching the region on
Tuesday and sliding through during the midweek. At the surface,
the primary low pressure system rides through Quebec/Ontario
with trailing cold front approaching the region Tuesday Night.
Overall, appears to be mainly a light qpf event for the Monday
night into Tuesday evening period, due to limited interaction
between northern and southern stream. Thermal profile suggests
precip would be mainly liquid, but could be dealing with
freezing rain across interior Monday night as cold air
typically has a tough time scouring our in this setup.

Upper trough swings through the NE Tue Night into Wed with a
glancing shot of modifying arctic air in the wake of the cold
front for Wed/Thu.

Upper flow flattens and even becomes a bit ridged for Thursday
ahead of the next northern stream trough digging into the Upper
Plains, which should allow for a moderation in temps ahead of
next potential frontal system.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
Weak low pressure tracks across New England today dragging a
cold front through this evening.

VFR into mid morning or so with CIGS between 3-5 KFT developing from
late morning through the afternoon. Local MVFR or IFR conditions
cannot be ruled out in isolated rain or snow showers late in
the day mainly N and W of NYC terminals.

Westerly winds 5 to 10 kt continue early this morning. Occasional
gusts to around 20 kt are possible, mainly across NYC metro
terminals. After 12-14Z, westerly winds increase to 15 to 20 kt,
with gusts 20 to 30 kt. Gusts become less frequent after 20-21Z.

By evening, winds turn to the NW and diminish.

.OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY...
.Late tonight...VFR.
.SUN...VFR during the day. Chance MVFR in a mix of -RA/-SN towards
midnight.
.MON...Low chance MVFR in -RA for coastal terminals, light wintry
mix inland. Improvement as the day progresses.
.TUE...MVFR possible with a slight chance of showers.
.WED...VFR. NW winds G20-30KT.

&&

.MARINE...
Gusty small craft winds will be likely across all the forecast
waters today into early this evening as a rather tight pressure
gradient moves through the waters as low pressure moves into the
Atlantic and high pressure builds to the west. So, will continue
with the small craft advisory as posted. Gusty winds may linger
into this evening on the ocean waters. Ocean seas may remain
around small craft levels into Sunday evening as well. So, the
advisory remains into this evening on the ocean.

The next chance for SCA conditions will be late Tuesday/Tue eve
ahead of approaching cold front, but higher likelihood of
widespread SCA Tuesday Night through Wednesday night with tight
pressure gradient and strong caa in wake of cold front. Gales
are possible during this time frame.

&&

.HYDROLOGY...
No significant hydrologic impacts expected.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the
air for an extended period of time.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ330-
     335-338-340-345.
     Small Craft Advisory until 1 AM EST Sunday for ANZ350-353-355.

&&

$$



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