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fxus61 kokx 171220 
afdokx

Area forecast discussion
National Weather Service New York New York
720 am EST sun Dec 17 2017

Synopsis...
high pressure moves over the region today, then drifts east
tonight. A weak low tracks west and north of the area tonight
and Monday with a warm front passing to the north. Another low
passes to the north Tuesday into Wednesday. High pressure builds
in late in the upcoming work week. A frontal system approaches
by the start of next weekend.

&&

Near term /until 6 PM this evening/...
the band of mid clouds across the lower Hudson Valley, into
northern New Jersey, and most of Long Island were beginning to
erode. However, unsure how much this will continue to occur.
Also, higher clouds were beginning to move into the region well
in advance of the next system to affect the region. So, will
keep area mostly cloudy through the day.

Only minor adjustments to the temperatures and dew points were
made through today.

Heights slowly rise through the day as the upper flow becomes
more zonal. A shortwave moving out of the Southern Plains will
weaken as this wave moves into the mid Atlantic. At the surface
a weak open low will track to east of the Great Lakes with a
weak warm front developing to the south of the area. Will keep
precipitation out of the region through today.

&&

Short term /6 PM this evening through 6 PM Monday/...
an open wave low will pass to the west and north as the northern
stream remains nearly zonal and progressive. A weak warm front
approaches tonight and moves north early Monday. There will be
little forcing or moisture with the frontal boundary, and
widespread precipitation is no longer expected. Precipitation
more scattered and light. With warm air pushing into the cold
air north of the warm front tonight, thermal profiles still
indicating a possibility of a snow, rain, and freezing rain mix
ahead of the warm front. Freezing rain will be brief and light,
maybe more drizzle. With the uncertainty, brief timing, and low
chance of occurrence, will not Post any headlines at this time.

Once the front moves north precipitation comes to an end. There
is some uncertainty as to the timing of the warm frontal
passage Monday morning, especially across the eastern zones.

&&

Long term /Monday night through Saturday/...
the northern stream remains nearly zonal into the beginning of
the week as a couple of weak shortwaves moves through the flow.
Then Tuesday a deeper northern stream trough digs into the
Great Lakes and moves into the northeast. Much of the energy and
lift with this system will remain to the north. And as a cold
front drops south Tuesday and Tuesday night, there will be
little moisture. So have removed the probabilities of
precipitation Tuesday and Tuesday night.

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. Upper flow flattens and even becomes a bit ridged
for Thursday ahead of the next northern stream trough digging
into the upper plains. At the surface, high pressure builds in
from the west Wed and across Thu, with dry and seasonably cold
conditions.

Models in general agreement with a pattern shift to a more
longitudinally oriented upper flow heading into the weekend, as
several pieces of northern stream energy begin to dig a deep
longwave trough into the western/central US. This may bring the
coldest air of the season into the central US by around
Christmas. Meanwhile, energy rounding this trough appears to
send a frontal system through the region during the Fri night-
Sat night time period.

&&

Aviation /12z Sunday through Thursday/...
high pressure over New England will move east through tonight as
a warm front approaches from the SW.

VFR through at least 03z tonight. Scattered-broken clouds ranging between
4-7kft expected into the aftn. Most guidance is indicating low
clouds move into the area tonight (some hi-res guidance is only
available through 04z attm), but have varying times. MVFR ceilings
may develop several hours than forecasted in 12z tafs.

Light northerly winds become light and vrb this aftn and
tonight (or a very light NE-east flow at NYC terminals aft 00z) as
high pressure slowly builds eastward. There could be a few
flurries or an isold light snow shower aft 03z tonight, which
may temporarily drop conds to MVFR. Probability isn't high
enough to include in the forecast attm.

Outlook for 12z Monday through Thursday...
Mon...VFR returning in the morning.
Tue...MVFR ceilings possible during the aftn. SW winds 10-15g20-30kt
possible.
Wed-Thu...VFR. Northwest winds g20-30kt probable Wed/Wed night.

&&

Marine...
seas at buoy 44097 (se of block island) were 5.2 feet at 1100z
and seas at buoy 44017 were likely below small craft levels, so
the advisory was allowed to expire.

A period of tranquil conds will prevail on all waters through
Mon night with a weak pressure gradient in place.



The next chance for Small Craft Advisory conditions will be late Tue/Tue eve in
SW flow ahead of approaching cold front, with high likelihood of
widespread Small Craft Advisory Tuesday night through Wednesday with tight
pressure gradient and strong caa in wake of cold front. Marginal
gale gusts are possible during this time frame.

Conditions then should fall back below Small Craft Advisory heading into Thu as
high pressure builds towards the waters.

&&

Hydrology...
no significant hydrologic impacts expected.

&&

Equipment...
NYC National oceanic and atmospheric administration weather radio station kwo-35 (162.55 mhz) is off the
air for an extended period of time.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.

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