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Widespread Snow Potential January 16th to January 18th


sferic
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16 minutes ago, Gorizer said:

Also representing the Eastern part of the thread here.   At about 1,500 ft elevation in western Schenectady County, I typically fall into the "Helderbergs" part of the forecast, and high enough to avoid any easterlies shadowing.   Just worried about the taint at this point that could really cut that top end of the range down. 

You usually do pretty well. Let's hope for the best 

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Model uncertainty...

The 12Z/15 NAM right now has the biggest impacts on snowfall
amounts. If it where to verify, there would be a period of mixed
precipitation for a period across parts of the CWA Sunday night.
This would lower snowfall totals from current forecasts. That said,
most all other guidance is still colder aloft. Although, the GFS and
ECMWF do get close to 0C aloft (850 hpa) when the warm conveyer belt
moves through the region. So can`t completely rule out a change over
for some locations or a mix but thinking the NAM is a bit too warm
and the outlier. As was previously said, have opted to keep it all
snow. However, wouldn`t be surprised at all if some sleet mixes in
from time to time for a brief period. Will need to closely monitored
this potenial as the event nears.

Next concern, where will the advertised strong deformation zone and
trowel actually set up. 12Z/15 Canadian-NH guidance pivots it
slightly to the west of Western NY and then across Lake Ontario.
This would focus the heaviest snowfall across northern portions of
the Niagara Frontier and along the south shore of the Lake Ontario.
The GFS/ECMWF has it focused across Western NY to Rochester in a
more of a SW to NE orientation. Only time will tell or until all
guidance gets in line.


Synopsis...

Snow will rapidly overspread the area from south to
north Sunday evening. This initial phase of heavy snow will be
driven by a powerful 80+ knot southeasterly low level jet and warm
conveyor on the front side of the system, transporting copious
amounts of Atlantic moisture into NY. Strong forcing from DPVA ahead
of the mid level wave, a coupled upper level jet structure, strongly
diffluent upper level flow, and strong isentropic upglide within the
warm conveyor will come together to produce a period of deep, strong
ascent. Forecast soundings show strong ascent through the dendritic
growth zone, which is quite high in the 10-15K foot layer, with a
deep saturated layer and ascent below supporting ongoing collection
of supercooled water for snow falling through the column.

Snow will likely continue over Western NY overnight Sunday through
the early morning hours and into early afternoon. That said, as was
previously mention above there could be some sleet. Precipitation
then pulls eastward across Central NY and the eastern Lake Ontario
region from mid afternoon through early evening as the surface low
accelerates into northern New England. The heaviest and longest
lasting snow will likely be found across a portion of Western NY
which will then likely weaken with time and have less residence time
with eastern extent.

As far as accumulations go, storm totals are forecast in the 12-20"
range across much of far Western NY, and 8-12" across the eastern
Lake Ontario region. Again, to hammer this home. Placement of the
deformation zone is key to the higher amounts. Also, if the NAM
trend shows up in other guidance the added sleet will knock down
accumulations. So don`t focus on the higher end of these ranges just
yet. Overall, confidence is still high to achieve warning criteria
across Western NY with Winter Storm Warning still in place. A Winter
Storm Watch still remain in effect east of Lake Ontario where
forecast amounts are lower due to less precipitation anticipated.

Monday night, some lake effect snow will develop following the exit
of the widespread synoptic snow. This will add several more inches
of accumulation southeast of Lake Erie for the Chautauqua Ridge,
and also areas southeast of Lake Ontario from the Monroe County
shore east to Oswego County.

Winds will be relatively light initially in this event Sunday night
through Monday morning, with 20+ mph winds limited to the south
shore of Lake Ontario. Winds will increase markedly later Monday
afternoon and Monday night as the pressure gradient tightens in the
wake of the system, with wind gusts of over 35 mph likely areawide.
This will result in blowing and drifting snow during the latter
stages of this event.
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13 minutes ago, Ottawa Blizzard said:

Have to say the 18z Canadian looks great for Toronto and Buffalo. Has the snow starting by 11PM Sunday night in Buffalo, 1 AM Monday in Toronto and pretty much continuing until Monday afternoon.

This storm brings me back to December 2007, remember that here in Ottawa?  @Organizing Lowwith the play by play, it was epic!

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23 minutes ago, wolfie09 said:
Model uncertainty...

The 12Z/15 NAM right now has the biggest impacts on snowfall
amounts. If it where to verify, there would be a period of mixed
precipitation for a period across parts of the CWA Sunday night.
This would lower snowfall totals from current forecasts. That said,
most all other guidance is still colder aloft. Although, the GFS and
ECMWF do get close to 0C aloft (850 hpa) when the warm conveyer belt
moves through the region. So can`t completely rule out a change over
for some locations or a mix but thinking the NAM is a bit too warm
and the outlier. As was previously said, have opted to keep it all
snow. However, wouldn`t be surprised at all if some sleet mixes in
from time to time for a brief period. Will need to closely monitored
this potenial as the event nears.

Next concern, where will the advertised strong deformation zone and
trowel actually set up. 12Z/15 Canadian-NH guidance pivots it
slightly to the west of Western NY and then across Lake Ontario.
This would focus the heaviest snowfall across northern portions of
the Niagara Frontier and along the south shore of the Lake Ontario.
The GFS/ECMWF has it focused across Western NY to Rochester in a
more of a SW to NE orientation. Only time will tell or until all
guidance gets in line.


Synopsis...

Snow will rapidly overspread the area from south to
north Sunday evening. This initial phase of heavy snow will be
driven by a powerful 80+ knot southeasterly low level jet and warm
conveyor on the front side of the system, transporting copious
amounts of Atlantic moisture into NY. Strong forcing from DPVA ahead
of the mid level wave, a coupled upper level jet structure, strongly
diffluent upper level flow, and strong isentropic upglide within the
warm conveyor will come together to produce a period of deep, strong
ascent. Forecast soundings show strong ascent through the dendritic
growth zone, which is quite high in the 10-15K foot layer, with a
deep saturated layer and ascent below supporting ongoing collection
of supercooled water for snow falling through the column.

Snow will likely continue over Western NY overnight Sunday through
the early morning hours and into early afternoon. That said, as was
previously mention above there could be some sleet. Precipitation
then pulls eastward across Central NY and the eastern Lake Ontario
region from mid afternoon through early evening as the surface low
accelerates into northern New England. The heaviest and longest
lasting snow will likely be found across a portion of Western NY
which will then likely weaken with time and have less residence time
with eastern extent.

As far as accumulations go, storm totals are forecast in the 12-20"
range across much of far Western NY, and 8-12" across the eastern
Lake Ontario region. Again, to hammer this home. Placement of the
deformation zone is key to the higher amounts. Also, if the NAM
trend shows up in other guidance the added sleet will knock down
accumulations. So don`t focus on the higher end of these ranges just
yet. Overall, confidence is still high to achieve warning criteria
across Western NY with Winter Storm Warning still in place. A Winter
Storm Watch still remain in effect east of Lake Ontario where
forecast amounts are lower due to less precipitation anticipated.

Monday night, some lake effect snow will develop following the exit
of the widespread synoptic snow. This will add several more inches
of accumulation southeast of Lake Erie for the Chautauqua Ridge,
and also areas southeast of Lake Ontario from the Monroe County
shore east to Oswego County.

Winds will be relatively light initially in this event Sunday night
through Monday morning, with 20+ mph winds limited to the south
shore of Lake Ontario. Winds will increase markedly later Monday
afternoon and Monday night as the pressure gradient tightens in the
wake of the system, with wind gusts of over 35 mph likely areawide.
This will result in blowing and drifting snow during the latter
stages of this event.

Glad to hear they are discounting the NAM. Are we keeping both boards alive?

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9 minutes ago, PerintonMan said:

But it blows the deformation band much farther west. Verbatim, this is the difference between ROC being in the jackpot zone vs. being in the "good, but not great" zone.

Yea, we really need a SE shift. Only way that happens is a weaker wave, later phase. We shall see.

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