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March 12th - 13th The It's Not Coming Storm Part 2

Rjay

By Rjay,
in New York City Metro

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RU848789

RU848789

Posted
Posted
23 minutes ago, jbenedet said:

That's BS. Paved surfaces will be wet, and grassy surfaces will net near zero under those conditions. 

Disagree, as we saw on 2/17, where snow accumulated easily at night on all surfaces once the snowfall rate was about 1/4" or more per hour (and of course you need a lot more than that during the day on paved surfaces, as we saw on 3/2 and 3/7 where 1/2" or more per hour was needed to overcome the melting rate).  I'm not talking about salted surfaces either - sure those will be harder to accumulate on.  Snow will accumulate on 32F snow with minimal melting from the air as the heat transfer coefficient of air is way less than that of a solid or liquid - do you disagree with that?  And while there is some small melting rate at night from surfaces a few degrees above 32F, as long as the snowfall rate exceeds that melting rate (I'm guesstimating it at 1/4" per hour, based on decades of observing these situations - that number could be off a little - and we're likely to exceed 1/4" per hour rates), snow will accumulate and once it does, the melting rate goes way down.   Of course, if the snowfall rate is light the whole time and never exceeds the melting rate, snow will never accumulate - my assumption is we'll get rates above that at some point and then accumulations will be far easier on the snow layer.  

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allgame830

allgame830

Posted
Posted
Just now, Ericjcrash said:

The N/s has dug more than modeled, there's not doubt about that. It's just probably to late outside of suffolk.

Yea but maybe we will be able to get a couple more inches than modeled.... should continue to see some shifts west in the models.... we'll see stranger things have happened we all know that.

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jbenedet

jbenedet

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19 minutes ago, RU848789 said:

Disagree, as we saw on 2/17, where snow accumulated easily at night on all surfaces once the snowfall rate was about 1/4" or more per hour (and of course you need a lot more than that during the day on paved surfaces, as we saw on 3/2 and 3/7 where 1/2" or more per hour was needed to overcome the melting rate).  I'm not talking about salted surfaces either - sure those will be harder to accumulate on.  Snow will accumulate on 32F snow with minimal melting from the air as the heat transfer coefficient of air is way less than that of a solid or liquid - do you disagree with that?  And while there is some small melting rate at night from surfaces a few degrees above 32F, as long as the snowfall rate exceeds that melting rate (I'm guesstimating it at 1/4" per hour, based on decades of observing these situations - that number could be off a little - and we're likely to exceed 1/4" per hour rates), snow will accumulate and once it does, the melting rate goes way down.   Of course, if the snowfall rate is light the whole time and never exceeds the melting rate, snow will never accumulate - my assumption is we'll get rates above that at some point and then accumulations will be far easier on the snow layer.  

Gloucester MA got 5" of snow from Thurs. snowstorm, and it snowed for over 18 hrs there. Just sayin'

 

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allgame830

allgame830

Posted
Posted

THIS IS FROM TYPHOON TIP POSTED ON NE FORUM.................. hmmmmmmmm

I'm actually wondering (a little) about this doing an about face and coming all the way in and whacking New NJ to NYC too with ... 

Fact of the matter is, this run is a whopper correction toward more phasing, even if it only upped the QPF some and brought things more confidently to the I-95 corridor of eastern sections ... it is the 2nd trip in that regard for a trend that started last night and may yet end up on the 00z being the fuller phase this whole verkokte set up really should be heading for when based upon conventional wisdom..  

But "as is" aside... the trend in its self shows that even at 24 to 30 hours out this thing is not stable - so it's not impossible.  And should the N/stream really subsume, than all these models showing that 30+ hour escape east would be correcting pretty dramatically to a slower capture... 

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LongBeachSurfFreak

LongBeachSurfFreak

Posted
Posted
10 minutes ago, jbenedet said:

Gloucester MA got 5" of snow from Thurs. snowstorm, and it snowed for over 18 hrs there. Just sayin'

 

This is exactly why I have low expectations outside of the best banding. The western most deform that produces rates 1”/hr will have the best accumulations in our area. Right now that looks to be over central Suffolk. That’s an area that could get a surprise foot. West of there it’s mainly a few inches on the grass

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RU848789

RU848789

Posted
Posted
4 minutes ago, jbenedet said:

Gloucester MA got 5" of snow from Thurs. snowstorm, and it snowed for over 18 hrs there. Just sayin'

 

Look at the snowfall map from our area for the 3/2 storm. 4-8" SW of Philly, 2-5" SE of Philly and in Monmouth/Ocean with <1" all along I-95.  Surface temps and daytime indirect sunlight were about the same (theoretically even warmer to the S of NB to NYC, for ecample), so the only variable that mattered in that situation was snowfall rate and once it exceeded the melting rate, the snow piled up.  On that day, I watched probably 5" of snow fall at 3/8-1/2" per hour rates (never got heavy) and I got 0.5" to show for it.  That won't happen at night with surface temps close to 32F.  It simply won't.  I'm sure you know tons more about meteorology than I do, but I'm guessing you don't know more about heat transfer and kinetic rate equations (PhD in chem eng'g).  Not trying to be a jerk, just trying to provide some context for why I'm so sure about this stuff.  

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gravitylover

gravitylover

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Posted
4 hours ago, West Mtn NY said:

LOL. Dude. In Monroe I had 42" between Friday and Wednesday 

I was more making a point about how these "bust" statements can change dramatically in a rather short distance. These last two storms were devastating for so many areas on so many levels that just because someone didn't get a whopper of a snowstorm doesn't mean that it didn't happen really close to them.

1 hour ago, RU848789 said:

Light rates will have no trouble accumulating on the 32F snow with high albedo, in general.  And for non-snow/paved surfaces, light to moderate rates will have little problem accumulating after dark, when most of this is supposed to fall, as long as the snowfall rate is probably above 1/4" per hour, which is probably the melting rate at night on 34-36F surfaces with 33-34F air temps - and once a layer of snow accumulates on non-snow/paved surfaces, further accumulation is uninhibited as the snow at 32F is now the new "surface" and melting from 33-34F air is minimal.  

Just because the surface melt rate is slower doesn't mean it's not also melting from underneath.

17 minutes ago, jbenedet said:

Gloucester MA got 5" of snow from Thurs. snowstorm, and it snowed for over 18 hrs there. Just sayin'

 

Ding ding, warm ground will do it every time. During the first storm on 3/2 at the height of the storm I had nearly a foot on the ground and by the time it stopped snowing we were down to ~8" so that's what I recorded. We lost nearly everything before the next storm and I had 16-18" at one point but before it ended was at 14" and was down to 12" a little after sunrise (3 hours after ending) when I got out to measure again so that's what got recorded. In each of these the lowest layer was pure slush with water running under the snow helping the snow to compact and melt out faster than it was replaced. The snow on the surface accumulated easily and quickly but melted out from underneath almost as quickly at the same time thereby limiting totals in a very noticeable way.

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USCG RS

USCG RS

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Posted
Ding ding, warm ground will do it every time. During the first storm on 3/2 at the height of the storm I had nearly a foot on the ground and by the time it stopped snowing we were down to ~8" so that's what I recorded. We lost nearly everything before the next storm and I had 16-18" at one point but before it ended was at 14" and was down to 12" a little after sunrise (3 hours after ending) when I got out to measure again so that's what got recorded. In each of these the lowest layer was pure slush with water running under the snow helping the snow to compact and melt out faster than it was replaced. The snow on the surface accumulated easily and quickly but melted out from underneath almost as quickly at the same time thereby limiting totals in a very noticeable way.
The only way to really compensate for this is to have the incredible rates some of long Island saw last week. This overcomes the surface and cools it down. Otherwise, it's incredibly hard to get appreciable snow on area roadways during mid March. Especially with such a marginal air mass preceeding the storm.
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gravitylover

gravitylover

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Posted
Just now, USCG RS said:
4 minutes ago, gravitylover said:
Ding ding, warm ground will do it every time. During the first storm on 3/2 at the height of the storm I had nearly a foot on the ground and by the time it stopped snowing we were down to ~8" so that's what I recorded. We lost nearly everything before the next storm and I had 16-18" at one point but before it ended was at 14" and was down to 12" a little after sunrise (3 hours after ending) when I got out to measure again so that's what got recorded. In each of these the lowest layer was pure slush with water running under the snow helping the snow to compact and melt out faster than it was replaced. The snow on the surface accumulated easily and quickly but melted out from underneath almost as quickly at the same time thereby limiting totals in a very noticeable way.

The only way to really compensate for this is to have the incredible rates some of long Island saw last week. This overcomes the surface and cools it down. Otherwise, it's incredibly hard to get appreciable snow on area roadways during mid March. Especially with such a marginal air mass preceeding the storm.

Again, I wasn't saying the surface can't accumulate when the rates are right but rather was saying that the melt rate from underneath is pretty much impossible to overcome. That 5" in Gloucester could/would have been more like 9-10 if the ground was cold and my totals for the two should have been more like 30" if not for the warm ground.

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RU848789

RU848789

Posted
Posted
4 minutes ago, gravitylover said:

I was more making a point about how these "bust" statements can change dramatically in a rather short distance. These last two storms were devastating for so many areas on so many levels that just because someone didn't get a whopper of a snowstorm doesn't mean that it didn't happen really close to them.

Just because the surface melt rate is slower doesn't mean it's not also melting from underneath.

Ding ding, warm ground will do it every time. During the first storm on 3/2 at the height of the storm I had nearly a foot on the ground and by the time it stopped snowing we were down to ~8" so that's what I recorded. We lost nearly everything before the next storm and I had 16-18" at one point but before it ended was at 14" and was down to 12" a little after sunrise (3 hours after ending) when I got out to measure again so that's what got recorded. In each of these the lowest layer was pure slush with water running under the snow helping the snow to compact and melt out faster than it was replaced. The snow on the surface accumulated easily and quickly but melted out from underneath almost as quickly at the same time thereby limiting totals in a very noticeable way.

Doubtful.  Yes, the bottom will always look slushy, since it's a mix of melted snow and snow prior to accumulations beginning, but once the ground is in equilibrium with the snow layer, it's also at 32F, unless you're talking about a city surface above a heat source (like in NYC, where that does make a big difference); by late winter, most of the ground a foot or two or more (depending on where one lives) below the first few inches (if it was warm lately) is frozen (the frost layer), so there is no heat source to melt the snow that starts accumulating.  When surface snow melts, it can form rivulets that can meander through the snowpack to the bottom of it, making it appear as if the snow at the bottom is melting.  I assure you it's not, unless you're in Manhattan with a heat source below the surface.  

By far the biggest factor in snow amounts decreasing after a storm is simple compaction, even if temps are at or below 32F, but especially if just above 32F: I measure 10-25% compaction after almost every storm within several hours after the snow stops.  The "network" of snowflakes and agglomerated snowflakes have a hard time sustaining the bulk density with which they initially layer when they fall - with some surface melting, the agglomerates break down and compact (it's like wet leaves vs. dry leaves).  

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