Thanks. You are trained in statistics -- another tribute to your Rutgers education -- and I doubt many other spotters are. They're probably taking only a very few samples.
My only comment on the mets' decision not to roll back their estimates is that sometimes one can be over-protective. I would rather they had said, "snow amounts are going to be lower, we think, but there's going to be a hell of a lot of sleet, which is as dangerous (maybe more so) than snow."
The thing is, they discussed all of that in their AFD, but most don't read those - they look at the map or forecasts and don't see that level of detail, but it is there. Here's their 4 am update, which is when I started getting very nervous, as I could see the sleet line moving north quickly towards 195 at that point.
What they missed on is that the sleet line didn't just make it through I-95 - it went all the way to eastern Warren through northern Morris to northern Passaic to the Tappan Zee, holding snowfall amounts down there - just look at the map above - anyone up north with less than 18" of snow had at least some sleet.
Area Forecast Discussion
National Weather Service Mount Holly NJ
406 AM EDT Tue Mar 14 2017
NEAR TERM /UNTIL 6 PM THIS EVENING/...
Major coastal storm will continue to track northeast along the mid-
Atlantic coast today. The 00Z models trended further west with the
track, and this is also verifying per WPC/MSAS analysis. Surface
observations coupled with 88D`s indicate the changeover line moving
north into the I-95 corridor, with snow changing to sleet in Philly
as of 07Z. This line is expected to straddle the NJ Turnpike/I-95
corridor through late morning, then move east into the afternoon.
This will lead to quite a variability in snowfall across our region,
with a sharp gradient in the vicinity of the NJ Turnpike/I-95. Our
latest forecast has reduced snowfall amounts south and east of here,
generally by 1-3 inches, with little change to the north and west.
As a result, we have converted the Winter Storm Warning to a Winter
Weather Advisory for portions of southern NJ/Delmarva. The Blizzard
Warning remains in effect for portions of eastern PA and northern
NJ, where a very high impact event is unfolding. Further east along
the Atlantic oceanfront, the High Wind Warning remains posted. The
snow will gradually taper down south to north late this afternoon
and into this evening.