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000 
FXUS61 KOKX 110906
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
406 AM EST Wed Dec 11 2019

.SYNOPSIS...
A weak wave of low pressure passes offshore this morning. 
Arctic high pressure then builds across the region late today
into Thursday. The high shifts offshore Thursday night. A low 
pressure system approaches from the south Friday. Rainfall 
becomes likely late Friday and overnight with an all day rain 
event expected through Saturday. The low exits to the northeast
late Saturday into Sunday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Precipitation shield continues to overspread the region early
this morning. The rain/snow line appears to lie across north
shore of Long Island to the NYC metro with mostly snow being
observed to the north. However, the intensity of the snow so far
has been light. In fact, some of the returns on radar across
western Orange County are not reaching the ground. 

500 mb shortwave energy continues to provide PVA aloft in
combination with upper divergence from a 170-180 kt jet streak
to our NW. The region will lie in the right entrance of the jet,
which favors large scale lift and supports the precipitation we
are currently observing. Have been monitoring the trends in the
last several runs of the HRRR and the model seems to be 
handling the current situation fairly well. Thinking its 
projection of several bands of snow within the larger precip 
shield early this morning looks on target. The snow will be 
quickest to end across the lower Hudson Valley and interior NE 
NJ, but will linger through the morning commute across NYC, Long
Island and southern Connecticut. HRRR soundings indicate 
significant lift in a saturated dendritic growth zone especially
across Long Island and southeast Connecticut. This is the area 
where higher snow amounts look more likely. 

One question continues to revolve around how far NW across the 
interior of the Lower Hudson Valley and Northeast New Jersey 
accumulating snow will reach. Low level dry air seems to be 
impacting snow reaching the ground. If this trend continues even
as a surge of lift aloft moves north from the Middle Atlantic, 
then snow amounts may be too high across those locations. 
 
The snowfall forecast has not changed too much. Still 
anticipate bands of snow to impact the morning commute for much 
of the region, with the moderate to possibly locally heavy snow 
across portions of Long Island and southeast Connecticut. The 
city and urban NE NJ into the Hudson River Corridor and SW 
Connecticut should see accumulating snow during the morning 
commute as well, but the duration will likely not be as long as 
further east. 

No changes were made to the Winter Weather Advisory. Despite
amounts not reaching criteria for much of the advisory area, 
impacts to the morning commute are still expected. 1-2 inches 
still looks likely in the advisory area, but there could be 
higher amounts closer to 3 inches across Long Island and 
southeast Connecticut in the banding mentioned above. 
Accumulation on roads may be limited if the snow intensity does 
not increase during the morning commute. However, temperatures 
will be falling and some slick spots could still develop on the 
roads. An SPS has been issued to the NW of the advisory to 
account for the potential of slick roads even if there is 
limited snowfall that way. A wet snow is expected, but with 
temperatures dropping to the low 30s as the snow intensity 
increases, slick conditions should develop on roads as well. 
Most of the snow accumulation should be on grassy surfaces, but 
within moderate to heavy snow bands roads could become snow 
covered despite a warmer ground temperature. 

The snow tapers off from west to east and should be over around
midday across eastern portions of the area. Clouds will
gradually clear into the afternoon, but some locations
especially near the coast may remain mostly cloudy. Highs will
generally be in the middle and upper 30s. 

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
A strong arctic high pressure builds into the region tonight and
will settle over the northeast on Thursday. Most models have the high 
around 1040 mb as it settles overhead on Thursday. Upper trough
axis swings across New England tonight with heights gradually 
rising on Thursday. NW winds will increase and gust 20-25 mph 
Wednesday night with clearing skies. Dry and cold conditions
Wednesday through Thursday. Lows will fall into the teens inland
and lower and middle 20s near the coast tonight. Wind chills
will be in the teens. For Thursday, highs will be in the lower
and middle 30s. Winds will be light with the high pressure
overhead. 

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Surface high continues to shift offshore Thursday night allowing for 
southerly winds to advect in moisture and comparatively warmer 
conditions headed into the latter part of the week. Overhead 
cloudiness returns to the Lower Hudson Valley and temperatures rise 
into the mid 40s for the day Friday.. There is a slight chance of 
warm frontal showers in the late morning with rain chances 
increasing into the late afternoon and overnight hours. These 
showers are associated with a deepening low pressure system off the 
Carolina coast. Southwest to northeast upper level flow over the 
eastern seaboard will spur this low north off the coast of Long 
Island through the overnight hours Friday into Saturday. Model 
soundings show the sub-tropical airmass has precipitable water 
values between 1.00-1.20 inches which will provide ample moisture 
for the expected rainfall. Timing has the majority of the rain 
falling for the NYC metro and surrounding areas in the 
overnight hours then lingering through the day Saturday. 
Rainfall totals around 1 to 2 could cause some instances of 
nuisance flooding in pour drainage areas.

Upper level trough axis pivots across New York state Sunday as 
a drier and more stable airmass moves into the region. Clouds 
clear out and temperatures are again the in mid 40s. Though 
overnight with the northwest winds, lows will fall near freezing
around the city with areas north expected to be in the upper 
20s prior to sunrise. High pressure builds Monday with more 
clear skies. This is short lived as an upper level jet stream of
150 kts over New England quickly transits the ridge axis 
eastward. The next low pressure system of note enters the Ohio 
River valley Tuesday morning. Global models show the possibility
of mixed precip ahead of the system, but regardless could 
likely see another all day rain event for Tuesday.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
A cold front has move southeast of the area with some left over 
precipitation expected this morning. High pressure builds into the 
region this afternoon.

The rain/snow line continues to move across portions of the area 
this morning. The only places still observing all rain are southern 
Long Island and KGON.  As the precipitation changes from rain to 
snow (from NW to SE), conditions become MVFR and eventually IFR. The 
snow will end from NE to SE between 11-16Z. A brief period of 
moderate to locally heavy snowfall is possible in the morning if any 
banding sets up. Runway accumulations will generally range from 1-2 
inches, with slightly higher accumulations possible for some Long 
Island and southeast Connecticut terminals. 

Conditions improve to VFR Wednesday afternoon once the snow
ends.

Winds will be from the NW around 5-10 kt to start. Winds then 
shifting back to the W and increasing in speed towards the end of 
the TAF period. A few gusts to 20-25 kt are possible late this 
afternoon afternoon, primarily at the city terminals.

.OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY...
.Wednesday night...VFR. Gusty WNW winds possible.
.Thursday...VFR
.Friday and Friday night...VFR on Friday, then MVFR possible in 
developing rain Friday night.
.Saturday...IFR in rain. LLWS possible.
.Sunday...Becoming VFR.

&&

.MARINE...
A weak wave of low pressure passes offshore this morning. Winds
on the waters for much of today will be below SCA levels. NW
winds start increasing late in the afternoon and will increase
above SCA levels tonight as arctic high pressure builds to the
west. Ocean seas will remain elevated through tonight as well.
Wind gusts on the ocean could come close to gale force tonight,
but should fall short. Have extended the SCA on the ocean
through tonight and issued a new SCA for the non-ocean waters
tonight. The waters east of Moriches Inlet could see seas remain
elevated into the morning, so the SCA has been extended until
15z for now. Winds weaken considerably on Thursday as high 
pressure settles over the waters. 

Low pressure approaches Friday and impacts the waters Friday
night into Saturday. Marine zones could be nearing SCA 
conditions Saturday morning through the afternoon as south winds
increase to 20-25 mph. A coastal low enters the ocean waters 
from the south and seas increase 9-11 feet by the afternoon. 
Elevated waves remain through Sunday then relax by early next 
week. 

&&

.HYDROLOGY...
No hydrologic issues are expected with mainly snow this 
Wednesday morning. 

A long duration rainfall event is possible beginning Friday night 
through late Saturday night. Total rainfall amounts range between 1-
2 inches with isolated higher amounts possible. Minor nuisance 
flooding will be possible with this event.

&&

.TIDES/COASTAL FLOODING...
There will be a chance of coastal flooding with the high tide cycle 
during Saturday morning. This will be due to onshore winds with an 
approaching storm combined with relatively high astronomical tides 
due to a nearly full moon. Minor coastal flooding will be possible 
primarily along the south shore back bays of Long Island, where even 
moderate coastal flooding is a possibility at least along the Nassau 
County bays. Minor flooding will also be possible along NY Harbor 
and parts of Western Long Island Sound. Confidence is not high at 
this point as the event is still a few days away, and shifts in 
storm's track and/or timing would change the flooding potential.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO35 (162.55 MHz) is still
operating at reduced power.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory until 11 AM EST this morning for 
     CTZ005>012.
NY...Winter Weather Advisory until 11 AM EST this morning for 
     NYZ070>075-078>081-176>179.
NJ...Winter Weather Advisory until 11 AM EST this morning for 
     NJZ006-104-106-108.
MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EST 
     Thursday for ANZ330-335-338-340-345.
     Small Craft Advisory until 6 AM EST Thursday for ANZ353-355.
     Small Craft Advisory until 10 AM EST Thursday for ANZ350.

&&

$$
SYNOPSIS...DJ/16/DS
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...DJ/16
AVIATION...BC

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