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000
FXUS61 KOKX 170227
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
927 PM EST Sat Feb 16 2019

.SYNOPSIS...
High pressure builds in through Sunday morning, then passes east
Sunday afternoon. Weak low pressure will approach from the west
Sunday night, then pass just south and east late Sunday night into
Monday. High pressure will then return for Tuesday, followed by
another low pressure system for mid week. High pressure builds
back Friday into Saturday, with another low pressure system
possible for the end of the weekend into early next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Forecast on track as high pressure will continue to build and
nose in over the region tonight. A northern stream shortwave
departs through the Canadian maritimes tonight, while a southern
stream shortwave tracks east, well to the south. Cloud cover
with both disturbances should remain well north and south of the
region. With the the low level flow veering to the north, any
moisture from the Great Lakes should shut off for NW zones.
Therefore mainly clear skies should continue through the night
and into Sunday morning.

Diminishing winds will result in only a light northerly flow
and clear skies, with far outlying areas decoupling completely.
Therefore, with polar high influence and advection diminishing
overall should see some spread with temperatures, with teens in
outlying rural locations and mainly 20s in the more urban areas.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Sunday morning should start off mainly clear, followed by increasing
afternoon cloud cover as SW flow aloft gets better established. This
will be in response to an upper level low across the high plains and
Midwest. This will increase the warm advection in the upper levels
in advance of the next storm system which is slated for late Sunday
evening through Monday morning.  Right now there is very good model
agreement with the large scale features as ejecting upper level
energy under the base the of the Midwest trough will get sheared due
to the progressive nature of the southern branch.  The model
agreement is there with the surface reflection as well as weak low
pressure will drive into the Central Appalachians towards WV, then a
surface low is expected to develop along the Delaware, Maryland
coast for Sunday night into Monday morning and eject quickly to the
east-northeast.  12Z model QPF is not very impressive with this
system with a general consensus of 0.1 to 0.3 inches, with a couple
of outliers like the NAM showing a bit more QPF.  The NAM warm
tongue may be overdone, which is a typical bias of the model, but
not totally discounting it.  Based on the overall pattern and
teleconnections the argument can be made that the low level cold air
(cold air below 3kft) may not be that easy to erode and push out.
There are hints of minor blocking, or a lack of overall progression
over Eastern Canada with an upper level low near the 50 Lat 50 Lon
position.  The thinking now is that snow should begin close to 0z
Mon for the city and western areas, with the snow starting a couple
of hours late for the late evening perhaps across eastern and
northeastern sections.  Initially the profile should be cold enough
for all snow at the onset, however the discrepancies are always in
the details with NWP.  The difficult aspect is to ascertain how much
of an easterly flow will get established in the low levels, and for
how long.  There is not a whole lot of room for warm advection below
freezing in the mid levels, therefore a change to a wintry mix
is a high likelihood, with southwestern sections going over to
light rain into early Monday morning. Another aspect that has
discrepancies is a potential lack of moisture in the snow growth
region for locations cold enough for mainly snow, especially as
getting closer to 6 and 9z Mon. This could very well lead to a
period of light freezing rain and drizzle for areas that remain
below freezing at the surface. The likelihood for this will
increase further north, and northeast across the region based on
latest BUFKIT profiles, which is supported with closer
proximity for northeast zones to the departing surface high
pressure.

With warm advection burst done into Monday morning anything that
falls should be very light with lack of overall moisture depth.
Where low level sub-freezing cold air holds light mixed
precipitation and / or freezing drizzle may linger into the
early afternoon. Overall it looks like a 1 to 2 inch type event
at this time which is still enough to make for some hazardous
travel, especially with the potential for freezing rain /
freezing drizzle for Monday morning across at least portions of
the region, and possibly down to parts of the Connecticut coast.
High pressure will then build in later in the day with dry
conditions returning into Monday night.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
A confluence of weak mid-level northern and southern stream
shortwave energy moves east across the region on Monday. At the
surface, associated low pressure to the se of LI Monday morning will
slide steadily offshore through the day. Deep moisture/lift axis
slides offshore by morning, but a lingering surface trough, onshore
flow and mid level lift will be enough to have lingering light
precip through the day. With mid-level drying, ice nucleation is
unlikely to occur aloft close to the city/coast, but could be
marginally cold enough across interior for ice nucleation. Temps
will likely hover near freezing Sun Night into early Monday morning
for city and LI before warming above, with coastal CT and points
just NW slowly warming above freezing through the mid to late
morning, while interior and CT river valleys will likely struggle to
get above freezing through the afternoon. So wintry precip Sunday
Night, could briefly transition to freezing rain early Monday
morning, before transition to mainly light rain/drizzle for city and
LI. For coastal CT and just NW of NYC light freezing rain/sleet/snow
likely change to light snow, rain and drizzle during the mid to late
morning, but a mixture of light freezing rain/light snow still
possible across interior into the afternoon. Although ice
accumulation should be minimal, a trace of ice is possible away from
south coast of LI and much of NYC/NJ metro to a few hundredths of an
inch across interior, making for a treacherous morning commute
across untreated surface for these areas. The late afternoon/evening
commute could still be locally treacherous for untreated surface
across the interior, with black ice even becoming an issue down to
the coast in the late evening.

Region then transitions into a confluent upper flow Tue into Wed,
between upper ridging south of Bermuda and polar low sliding across
central Quebec. At the surface, Canadian high pressure builds into
the region Monday Night and overhead on Tuesday.

Region comes more under the influence of the southern stream
midweek, as early week SW US trough shears eastward towards the
Great Lakes and New England, while SW troughing is reinforced once
again. In the SW flow aloft, weak southern stream energy lifts up
towards the region Tue Night into Wed, with associated southern low
gradually approaching Wed and tracking near the region Thu. At this
point, forcing with this system does not look to be too strong with
another light precip event likely. Thermal profiles appear cold
enough to start as all snow Wed/Wed eve, then gradually
transitioning to wintry mix interior and all rain coast Wed Night
into Thu morning, before gradually tapering off late Thu as mid-
level shortwave passes.

Thereafter, generally zonal PAC influenced upper low for late week
into the weekend, lending to slightly above seasonable temps. Next
chance of significant precip possible for late weekend into early
next week as northern and southern stream show signs of
interacting.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
High pressure builds across the terminals through Sunday
morning, then offshore in the afternoon. Low pressure approaches
Sunday evening.

VFR through early Sunday evening. Conditions will lower to MVFR
as a wintry mix develops after 00z Monday.

Winds veer to the N tonight as they weaken below 10 kt. The
winds at city terminals may not fall below 10 kt until after
06z. Winds continue to veer to the NE Sunday morning and then E
to SE in the afternoon, remaining less than 10 kt.

.OUTLOOK FOR 00Z MONDAY THROUGH THURSDAY...
.Sunday night-Monday...IFR in wintry mix changing over to
rain at the coast early Monday morning.
.Tuesday...VFR. NW winds G20-25kt.
.Wednesday...Snow possible with MVFR or lower conditions
in the afternoon and evening, changing to a wintry mix at
night.
.Thursday...MVFR or lower in a wintry mix.

&&

.MARINE...
High pressure will build across the waters tonight through
Sunday with sub SCA conditions through Sunday night.

Low pressure passes to the south and east Sunday night. Marginal
SCA conditions possible on the ocean waters Monday into Monday
night, specifically for seas Monday, and more likely for SCA
gusts Monday Night. Conditions fall below SCA Tuesday into
Wednesday as high pressure builds in.

The next chance for SCA conds will likely be Wed Night into Thu
Night with next low pressure system moving over or south of the
waters.

&&

.HYDROLOGY...
There are no hydrologic concerns through the middle of next
week.

&&

.TIDES/COASTAL FLOODING...
A low pressure system tracking to the south of the region Sunday
Night into Monday, and approaching full moon on the 19th, will
bring potential for minor coastal flooding during the Monday
morning high tide. At this point it appears to be a low-end
event across the most vulnerable locales of the south shore bays
of Queens and Nassau County, W LI sound, and a few spots in
lower NY/NJ Harbor.

1 to 1 1/2 ft of surge, locally 2 ft, are need for for minor flood
thresholds to be reached during Monday morning high tide.

&&

.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...JE/NV
NEAR TERM...JE/NV
SHORT TERM...JE
LONG TERM...NV
AVIATION...DS
MARINE...JE/NV
HYDROLOGY...JE/NV
TIDES/COASTAL FLOODING...
EQUIPMENT...