New official snow maps and a really interesting forecast discussion on this storm:

- If you haven't seen my previous post on when the next time period to watch is for a potentially big northeast snowstorm, please check it out.

- Here are the new National Weather Service snow maps as everything is on track, but there is always some uncertainty, and if you have time, please read the following, which is from the National Weather Service covering Long Island and the tri-state area:

A vigorous shortwave approaches this evening which will lead to
the first plowable snowfall for the majority of the Tri-State 
region tonight. There has been no change to winter weather 
headlines. Only minor adjustments have been made to forecast 
snowfall totals. 

Surface ridging will gradually slide to the east this evening.
A strong primary low will continue lifting towards upstate NY from 
the Ohio Valley, but will weaken and decay overnight as a secondary 
low develops off the Delmarva early Tuesday. The secondary low 
should then become the dominant low on Tuesday as it shifts south 
and east of Long Island. 

Warm advection quickly increases after 00z from west to east. 
Initial snow that moves overhead will have to saturate the lower
and middle levels, so it make take an hour or two for steadier 
snow to make it to the surface. Once the dry layer is eroded, an
impressive surge of frontogenesis will move through generally 
after 03z, shifting towards eastern portions of the region from 
around 09z- 12z. Snow is expected to become moderate as the 
frontogenesis moves through. The HREF continues to indicate 
potential for around 1 inch per hour snowfall rates to occur in 
this initial surge. After 06z, guidance has continued to hint at
some warm air aloft (around 800 mb) trying to move through 
portions of the NYC metro and southern Long Island.

One of the biggest uncertainties with this event is how long
this warmer air aloft will last and how far north and east it 
will reach. However, there are several high-resolution models 
that keep the warm advection at bay. There is a chance at some 
loss of ice nucleation for a time overnight as well, so there 
may be some sleet even if the temperatures aloft stay below 
freezing. Given the larger pattern and strong warm advection 
aloft, think some warming aloft will occur, changing the snow to
a mixture of sleet and snow near the coast. The other factor to
consider is the easterly flow and marginal surface 
temperatures. Temperatures over Long Island and NYC metro may 
never fall below freezing, and could even stay around 33-34 
degrees much of the night. Some locations closest to the coast 
could even be a degree or two higher. These factors will likely 
cut into snowfall accumulations. Across interior NE NJ, the 
Lower Hudson Valley, and southern CT snow is expected through 
day break Tuesday. 

The intensity of the precipitation will diminish by sunrise
Tuesday, but light snow is still expected inland with a mix 
down towards the coast. There will be a transition to cold rain 
across the NYC metro and Long Island. Surface temperatures 
should rise into the middle 30s the rest of the morning and then
potentially upper 30s in the afternoon. Loss of deeper 
saturation aloft will be a main factor in the precip changing 
over to a cold rain from south to north through the day.
Lift and drier air should continue to work around the low south
and east of Long Island through the day which should bring an 
end to precip from west to east. It will likely take until late 
day for light snow or a light rain/snow mix to end completely 
across southeast CT. Any additional snow accumulation during the
day Tuesday across the interior will be light and mainly in the
morning. 

Snowfall forecast of 5 to 7 inches across the warning area with
generally 3 to 5 inches in the Advisory area. Amounts across 
the southern Boroughs and southern Long Island (south of the 
LIE) will be lower, generally closer to 2 to 3 inches. If the 
warming aloft is less and surface temps end up a bit colder, 
these amounts could be slightly higher, especially closer to the
coast. At the same time, if warmer air moves in aloft and at 
the surface, then amounts could be lower near the NYC metro and 
Long Island. There is higher confidence in amounts across 
interior NE NJ, Lower Hudson Valley and southern CT. The snow
will be wet and relatively low ratio, except the interior which
likely ends up closer to 10:1.