NWS Upton noting the east shifts in their AFD. I love the very last line
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
There remains the potential for a strong winter storm to impact the
region from Friday night through Saturday night with heavy snow and
strong winds. That being said, there remains quite a bit of
uncertainty as all of the 12Z globals have shifted east with the low
track as well as their ensembles. The 12Z NAM12 was the boldest with
a farther west track and the potential for 1 to 2 ft of snow across
much of the area. However, the 18Z NAM is an eye opener as it has
shifted well east of the area with no measurable precipitation. This
scenario seems unlikely at this time. Due to the large uncertainty
and bouncing around of the guidance, we are running with a model
blend approach. Should this eastward trend continue with subsequent
runs, snowfall amounts will trend down.
There is a fair amount of complexity to the upper air pattern as
multiple pieces of energy upstream come into play with the
development and phasing within the longwave trough that is carved
out across the eastern seaboard by Friday night. Shortwave energy is
tracking down from the Northwest Territories of Canada, the PAC NW,
and even north of the Great Lakes. This interaction and where a
cutoff low develops seems to be causing the large differences in the
guidance. Once again, there is agreement overall in an eastward
shift, but due to the complexity mentioned, overall confidence
remains low with this forecast.
Liquid equivalent amounts range from one-quarter to one-half across
the western half of the forecast area (Lower Hudson Valley, NE NJ,
NYC, SW CT), to around an inch across far eastern LI and southeast
CT. This would produce warning level snows from the Hudson Valley
and NYC metro east. Once again, confidence is low and this is likely
not the final solution.
Just to show that there is a wide range in the model guidance, snow
probs at the 90th percentile have over 20 inches across eastern half
of the area, while the 10th percentile has borderline advisory
levels far easter areas. Bottom line, the goal posts are very wide
at this time.
