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fxus61 kokx 142024 
afdokx

Area forecast discussion
National Weather Service New York New York
324 PM EST Thu Dec 14 2017

Synopsis...
high pressure builds across the area tonight then quickly shifts
offshore on Friday as an area of low pressure develops off the
mid Atlantic coast. Low pressure quickly departs eastward on
Saturday, with high pressure briefly building in again in its
wake. A series of weak low pressure and frontal systems will
pass through mid week.

&&

Near term /through tonight/...
the pressure gradient will initially remain tight between the
departing low and building high pressure, maintaining breezy
conditions and subsequent wind chill values that will fall into
the teens and single digits by tonight. Dry advection on the
back side of the departing low and the loss of diurnal heating
will allow the stratocu to dissipate, leading to mostly clear
skies overnight and favorable radiational cooling as the
pressure gradient gradually begins to relax with time.
The remaining snow pack should aid in cold low temperatures in
the single digits to teens, generally about 10 to 15 degrees
below climatological normals.

&&

Short term /Friday through Friday night/...
the persistent blocking pattern will gradually begin to break
down on Friday with a subtle eastward shift to a large scale
East Coast upper trough, while upstream low pressure flattens a
dominant ridge on the West Coast.

Phased vorticity maximums will push eastward, allowing a surface
low to intensify off the Carolina coast before ejecting
eastward. Across the area, temperatures will remain below
normal, largely below freezing, with increasing cloud cover
through the day as the phased vorticity maximums approach.
Although the heaviest snowfall will remain well south of the
area, mid-upper level saturation will gradually increase into
the evening, with any developing precipitation aloft
subsequently saturating low levels enough to produce at least a
dusting of snow along the coast.

Cloud cover decreases again Friday night as the system pushes
east of the area, while winds gradually increase as the pressure
gradient increases ahead of building high pressure. Low
temperatures are already forecast to be well below normal, but
could drop further depending on the exact timing of clearing
skies and increasing winds.

&&

Long term /Saturday through Thursday/...
a progressive pattern in place across the country for the long term
period. High pressure builds to the south on Saturday as a coastal
low remains well to the southeast of the area. As the low exists, west-
northwest winds increase, especially across Long Island and coastal CT
where the low level jet moves across. Below normal temperatures,
combined with gusty winds, will keep wind chill values in the low
20s during the day.

The forecast becomes more uncertain on Sunday night into Monday as a
weak warm front moves towards the region. While models are in good
agreement regarding upper level energy, there is still disagreement
amongst precipitation amounts. However, with winds shifting to the
SW expecting a period of rain/mixed precipitation overnight into
Monday. Confidence still remains low based on the differences in
model guidance.

By Monday temperatures return to near seasonal norms for mid
December.

Thereafter, models in fairly good agreement with a northern stream
trough approaching the region on Tuesday, but differences exist in
the amount of interaction with southern stream energy/moisture.
Primary low pressure system appears to ride through Quebec/Ontario
with trailing cold front approaching the region, but precip
coverage amounts will be dependent on the aforementioned
southern stream interaction. Thermal profile suggests precip
would be a wintry mix transitioning to rain, but predictability
at this point is low.

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 midweek.

&&

Aviation /19z Thursday through Tuesday/...
VFR as high pressure builds in from the west through Friday
morning. Low pressure develops off the Delmarva Friday
afternoon.

Northwest wind gusts diminish this evening.

New York 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: direction averages 310-320 magnetic this
afternoon with +/- 20 degrees of variablity. High confidence
forecast. Gusts could extend an hour later than fcst especially
on the itws.

Klga taf comments: direction averages 320-330 magnetic this
afternoon with +/- 20 degrees of variablity. High confidence
forecast. Gusts could extend an hour later than fcst.

Kewr taf comments: direction averages 310-320 magnetic this
afternoon with +/- 20 degrees of variablity. High confidence
forecast. Gusts could extend an hour later than fcst.

Kteb taf comments: no unscheduled taf amendments expected.

Khpn taf comments: taf amendments not scheduled.

Kisp taf comments: high confidence forecast.

Outlook for 18z Friday through Tuesday...
Friday aftn/ngt...VFR. Chance flurries in the afternoon and evening.
Sat...VFR. West-northwest winds g20-25kt daytime.
Sun...VFR.
Monday...chance MVFR -ra, -rasn inland early.
Tuesday...becoming MVFR. Chance -ra.



&&

Marine...
both winds and seas will remain at Small Craft Advisory-levels on the ocean
waters through this evening as low pressure departs and high
pressure builds across the area. Winds may occasionally gust to
near Small Craft Advisory-levels elsewhere, but in general winds and seas will
begin to subside overnight on all waters as high pressure builds
and the pressure gradient begins to relax.

Tranquil conditions will then persist into Friday, before winds
and seas increase to Small Craft Advisory-levels again Friday night with the
departure of a low pressure system to the south and east. These
conditions will persist into Saturday night, followed by a
better chance of Small Craft Advisory or possible gales in the wake of a midweek
system.

&&

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.
Marine...Small Craft Advisory until midnight EST tonight for anz355.
Small Craft Advisory until 6 am EST Friday for anz350-353.

&&

$$
Synopsis...cb/MD/NV
near term...Maryland
short term...Maryland
long term...cb/NV

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