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Obi-One-Marchobi Episode III The Return of the Weenie


HoarfrostHubb

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While we wait for Euro...

Can someone comment on Matt Noyes' analysis:

" The temperature though a deep layer of the snow-producing cloud layer over New England is sub-freezing - warm enough for snow - but not cold enough for efficiently accumulating snow crystals. Rather, the temperature aloft is supportive of some of the worst kind of accumulating flakes that can develop. As a result, I've kept amounts reasonable."

Snow, but the worst kind of accumulating flakes.

What layer is this? And if it's sub-freezing throughout the column, how cold does it need to be?

I tried to find cross-sections of Oct 31 when snow flakes were flying for hours but had hard time accumulating in Boston metro.

For better ratios, typically you want to see the -12 through -18 degree Celsius column saturated in the atmosphere. It is this range where you normally have full dendrite ice crystals forming, which generally produce the best snowfall ratios. What is sounds like Matt Noyes was trying to say is that that the entire column of the atmosphere might be below freezing, but the moisture does not reach up into this "snow growth" zone where the majority of ice crystals produced are dendrites. In this case if the moisture dries up somewhere between -5 to -10 degrees Celsius, you can expect to see more needles and prisms.

morphologydiagram-thumb-500x381.jpg

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For better ratios, typically you want to see the -12 through -18 degree Celsius column saturated in the atmosphere. It is this range where you normally have full dendrite ice crystals forming, which generally produce the best snowfall ratios. What is sounds like Matt Noyes was trying to say is that that the entire column of the atmosphere might be below freezing, but the moisture does not reach up into this "snow growth" zone where the majority of ice crystals produced are dendrites. In this case if the moisture dries up somewhere between -5 to -10 degrees Celsius, you can expect to see more needles and prisms.

morphologydiagram-thumb-500x381.jpg

Thanks, and great write ups by the way the last couple day's. I have learned more since reading your thread on the main page and discussion of this storm than I have in a long time. The way you use the .gif's and label different features on the images is helpful for people like me who still have lot's to learn.

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How big is big? Accums?

Euro is def >6" for BOS conservatively...during periods of lighter precip, I'm not sure how well it would accumulate right there on the water...but they get it good overnight tomorrow night...best time to get it too avoiding March 1st sun angle.

They get over an inch of qpf as all snow, but taking into account some BL issues when its lighter, hard to say just what the final accums would be. Its got BOS hovering in the 32-34F temp range. Though it might end up a touch colder than that in reality with the high where it is.

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Euro is def >6" for BOS conservatively...during periods of lighter precip, I'm not sure how well it would accumulate right there on the water...but they get it good overnight tomorrow night...best time to get it too avoiding March 1st sun angle.

They get over an inch of qpf as all snow, but taking into account some BL issues when its lighter, hard to say just what the final accums would be. Its got BOS hovering in the 32-34F temp range. Though it might end up a touch colder than that in reality with the high where it is.

So we get at least one snow storm this year it seems? Fingers crossed!

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Wow. this has certainly turned into a Ma. storm. Does it give Ct. anything?

CT still gets their front end stuff...like a good 3-5" burst tomorrow afternoon. N CT might actually flip back to snow overnight tomorrow night when that 2nd pulse comes in as the Euro is bringing the 0C line back down to near HFD from the MA border during that time.

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Euro def caved toward the NAM...its a big storm for BOS...still not that great with the front end initial burst...much better for CT and W MA...but it goes to town overnight.

With the RGEM, UK, GGEM, NAM and SREFs all pretty much in agreement on solid QPF you kinda figured it had to cave. Really increases the confidence on going pretty boldly for something like 4-8" even for Boston and maybe even 6-12" out around ORH wouldn't you think?

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CT still gets their front end stuff...like a good 3-5" burst tomorrow afternoon. N CT might actually flip back to snow overnight tomorrow night when that 2nd pulse comes in as the Euro is bringing the 0C line back down to near HFD from the MA border during that time.

Good to hear. Definitely expecting a flip over to a mix or even plain rain, but I'm happy to hear the front burst is still there.

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For better ratios, typically you want to see the -12 through -18 degree Celsius column saturated in the atmosphere. It is this range where you normally have full dendrite ice crystals forming, which generally produce the best snowfall ratios. What is sounds like Matt Noyes was trying to say is that that the entire column of the atmosphere might be below freezing, but the moisture does not reach up into this "snow growth" zone where the majority of ice crystals produced are dendrites. In this case if the moisture dries up somewhere between -5 to -10 degrees Celsius, you can expect to see more needles and prisms.

morphologydiagram-thumb-500x381.jpg

Thanks!

I was looking between -10 to -20C, for example at 30h on the 0Z NAM... the saturation in the dgz (about 500-600mb) doesn't look all that different in BOS vs. ORH.

The differences are more pronounced on the 0Z GFS where ORH is significantly more saturated than BOS in the dgz.

In any case, this is academic. Looks like Euro has joined the party.

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