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Potential of Widespread Snow/ Mixed Precipitation 2/25


sferic
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A look at deterministic models, the 12Z NAM and 3 km NAM bring the
surface low farther northward than the 12Z GFS, ECMWF and Canadian.
If the NAM solution were to verify we would see a mix as far north
as the southern Lake Ontario shoreline. While with little support
from other 12Z models, this trend farther northward with the warm
layer have been seen times before. However the top 2 analogs from
CIPS were events (January 28th 2009 and February 5th 2014) that
featured snow totals that indeed did breech into warning criteria
across much of our forecast area. This said there is still too much
uncertainty to change headlines with this forecast package update.

The dynamics of this storm system are coming together to produce a
period of snow (with a mix towards the south). Initial snow
formation will be upon isentropic upglide motion, with a 40 to 50
knot LLJ to our south enhancing the overall lift. Aloft several jet
streaks at 300 hPa will bring pockets of deeper lift, along with a
tightening 700-850 hPa circulation that will pass over our region.
Snow will reach our Southern Tier Thursday evening and quickly
spread towards the Lake Ontario region just past midnight.

The surface low will be tracking towards western PA and possibly
into WNY by early Friday morning. This would send a warm nose aloft
northward changing the lower atmosphere to a profile that would
support sleet and eventually freezing rain. Again, the NAM is the
farthest northward with this warm layer...one that would bring a mix
up to the southern Lake Ontario shoreline. For now we will keep any
mix to our southern two rows of counties.

A secondary surface low will form off the Delmarva Peninsula early
Friday morning and rapidly deepen as it tracks northward up the
coastline. Meanwhile the initial primary low will begin to weaken
before combining with the secondary low to our east. A deformation
band of snow behind the primary low, that along with the passing of
the shortwave aloft will then be the dynamical forcing later in the
day Friday, bringing additional accumulation through the morning and
afternoon hours. This could also be the period with highest snowfall
rates...ones that could near an inch per hour.

As the cold air aloft quickly deepens behind this storm system, and
ambient moisture lingers a period of lake enhanced snow will likely
hang on along the southern shoreline of Lake Ontario as well as
southeast of Lake Erie through the afternoon hours.

Overall will have snow amounts through Friday within the advisory
range for this system south of Lake Ontario, with possible higher
amounts east of Lake Ontario where snow ratios should be higher with
the surface high to the north and a period of higher snowfall rates
through the afternoon hours under the deformation band.

Sleet and any freezing rain to the south will hold snow amounts down
across the Southern Tier.

Behind this system temperatures at 850 hPa will drop down to the mid
negative teens Celsius. This along with a northwest wind will
develop lake effect snow initially south of the Lakes Friday
afternoon, and then southeast of the Lakes Friday Night. Greater
amounts will likely be off Lake Ontario, where the waters are still
open, and where the northwest winds will have a longer residence
time over the Lake waters. Winds, backing as a surface high ridges
to our region will steer a weakening band of snow to areas east of
Lake Ontario Saturday.
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1 minute ago, TugHillMatt said:

Well, BGM has officially added the dreaded "snow, sleet, and freezing rain" into the Onondaga county forecast for Friday morning. At this point, I would think most of it stays south of the Thruway and perhaps the 20 corridor.

MMMMMMMMM.... Kissin' the taint!  I think we're both all snow.  If anything, pingers for a half hour.

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