Area Forecast Discussion


603 
FXUS61 KOKX 110554
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1254 AM EST Mon Dec 11 2017
.SYNOPSIS...
A low pressure trough will pass through late tonight, followed by
building high pressure on Monday. Low pressure will then pass
across the Great Lakes Monday night, while an associated warm
front lifts through the waters Tuesday morning, followed by a 
strong trailing cold front in the afternoon. Intensifying low 
pressure will move from the New England coast into the Canadian 
Maritimes from Tuesday night into Wednesday night, then slowly 
loosen its grip on the area on Thursday as weak high pressure 
slides across. An Alberta clipper low will pass to the south on 
Thursday, then another low will develop just off the coast late 
Friday into Friday night.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
A shortwave and upper trough axis will approach from the west
overnight, with a low pressure trough at the surface. The best 
combination of lift and moisture arrive after midnight with 
isolated to scattered snow showers. A dusting is possible. Low 
temps will be around 30 in NYC and the adjacent suburbs, with 
20s for the rest of the area.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
High pressure will briefly build in behind the departing trough
Monday morning, with a lingering snow shower still possible
mainly east of the city. Skies will start off partly to mostly
sunny, then higher level clouds will begin to increase in the
afternoon. High temperatures will be a few degrees below normal. 
Low pressure moves across the Great Lakes Monday night. An 
associated warm front approaches us with increasing chances of
precip late at night, more likely NW of the city. A digging 
upper trough and the low center then approach us during Tuesday.
Associated deeper moisture and lift bring then likelihood of 
precip across the most of the rest of the area during the 
morning. The low passes us to the north before exiting during 
the afternoon, with maybe a secondary low center moving through.
Expect precip chances to diminish in the afternoon with the 
best lift and moisture exiting. A cold front then follows 
shortly thereafter, so precip chances will continue through the
day. 
Warm advection ahead of the main portion of the storm will make this 
a mixed precip event. Primarily rain is expected for the city, 
adjacent suburbs and coastal section, although some snow can mix in 
at first. Farther inland, snow or a snow/rain mix changes over to 
rain by noon on Tuesday. Only perhaps the elevated sections of 
western Orange County could see an all snow event. Snow
accumulations expected to be 1 or 2 inches for the northern
suburbs, with perhaps 3 inches in some spots across Orange 
County. Less than an inch is expected anywhere else where snow
manages to accumulate. Highs in the 40s expected for most 
spots on Tuesday, with even some 50 degree readings for 
Long Island.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
At the start of the period, blustery and cold weather expected from 
Tuesday night into Thursday as intensifying surface low pressure 
moves from the eastern New England coast up into the Maritimes. The 
parent upper low/trough will be closing off and becoming negatively 
tilted during this time, and a strong vort max rotating around the 
upper low may help spark a few snow showers late Tue night into Wed 
morning, especially out east. Blustery conditions expected as the 
pressure gradient tightens up on the back side of the low, with 
sustained winds 25-35 mph and gusts 45-50 mph possible Wed into Wed 
night. With temps falling to the teens and lower 20s Wed night, wind 
chills should fall to 0 to 5 below well inland, and to the single 
digits in NYC metro and along the coast. High temps both Wed/Thu 
should range from the mid 20s to lower 30s.  
ECMWF has been more consistent than the GFS in the longer term 
beyond Wed night and was followed for the most part. A weak Alberta 
Clipper low should pass just south on Thu as an associated mid level 
impulse passes just south, then another low should develop close by 
late Friday as a more significant negatively-tilted upper trough 
swings through, that could bring a period of light snow Fri 
afternoon/evening.  
Upper level flow after passage of the upper trough on Friday should 
become zonal, with moderating temps, rising to the upper 30s/lower 
40s on Sat, and  into the 40s on Sunday. A surface low passing well 
to the north may manage to produce a few sprinkles/showers of snow 
or rain late Sat night into Sunday in the low level warm advection 
to its southeast.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
A cold front will pass today.
VFR through about 8Z, then ceilings drop to around 3000 ft with
snow showers in the area early this morning. Little or no 
runway accumulation, although visibility could be briefly 
reduced to MVFR or lower. Ceilings improve to VFR after 15Z, 
with VFR through the remainder of the TAF period.
Generally westerly winds through the TAF period. Direction will
be just south of west until the frontal passage, then will 
become just north of west. Occasional gusts early this morning, 
then more frequent gusts to 20 kt today. Gusts will end after 
23Z.
.OUTLOOK FOR 06Z TUESDAY THROUGH THURSDAY...
.Late Monday night-Tuesday...MVFR or lower possible with a wintry 
mix to rain at northern terminals and rain at southern terminals. 
Conditions improve to VFR Tuesday afternoon. SE-SW winds G15-25KT 
possible.
.Tuesday night-Wednesday...Mainly VFR, with a chance of MVFR in snow 
showers. W-NW winds G20-35KT probable.
.Wednesday night-Thursday night...VFR. W-SW winds G15-25KT possible.
.Friday...MVFR possible with snow. W-NW winds G15-20KT possible.
&&
.MARINE...
SCA conditions expected on the ocean waters through Monday with
winds and seas meeting criteria. Marginal SCA conditions
expected on the eastern Sound/bays. Winds and seas should fall
below criteria Monday night, then increase during Tuesday, with
SCA conds becoming likely on some of the waters. 
As intensifying low pressure pulls away, gales should develop on
the ocean Tue night, with SCA conds continuing on the remaining
waters. NW gales expected on all waters Wed night into Thu with
a tight pressure gradient and strong cold air advection. SCA 
conds may linger into Thu, then quiet conditions expected Thu 
night into Fri, though winds and seas in westerly flow after the
passage of a weak low Fri night could flirt once again with SCA
levels.
&&
.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. See our headline news on 
the web at: http:/weather.gov/nyc
The Riverhead NOAA Weather Radio Station WXM-80 (162.475 MHz) 
is currently out of service. NWS technicians are working with
Verizon to restore service. An estimated time of return to 
service is not currently known.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ350-
     353-355.
     Small Craft Advisory until 6 AM EST early this morning for 
     ANZ330-340.
&&
$$
SYNOPSIS...JC/Goodman
NEAR TERM...JMC/JC/Goodman
SHORT TERM...JC
LONG TERM...Goodman
AVIATION...BC/JMC
MARINE...JC/Goodman
HYDROLOGY...JC/Goodman
EQUIPMENT...