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February 12th-14 Redeveloper Nowcast/Obs


Baroclinic Zone

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3 minutes ago, dendrite said:

The cold layer below the melting layer is cold enough to produce its own small snow crystals. The problem is, there isn’t enough lift in that level to really get any decent snow growth. So you end up with sleet and snow grains. A human observer would code it -PLSG. ASOS is automated so it usually just gets called -SN. I really only see -SG from MWN.

You will like this Mike Solomonoides took this in Farmington, Dendrite examples and sleet

D7196F81-76B0-43A5-8E5B-75E42796DFBD.jpeg

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3 minutes ago, wxsniss said:

Agree

I think 2 other variables that meh-ed this event, even with H75 advance and timing of sleet changeover as it was:

1) the poor snow growth: it was baking soda just about the entire event... the lift was always significantly displaced from the DGZ... decent dendrites for the past 6 hours and we'd have a different tune in here

2) the initial thump was actually kind of meager: guidance last night was hinting at a more robust thump, ~0.5+ qpf for parts of SNE before a changeover... and then it kind of back off today. It came in like a wall but then was pretty meager the middle 3-4 hours.

I made a post last night going over typical parameters we want to see for solid warning amounts in a transition SWFE. You want a classic "cross hair" sig on the soundings...that's just a quick way of saying the omega lines up with the snow growth zone...and you typically want big omega too. Not just some 15 micro bars per second maxima. We didn't have a cross hair sig in this event so that is why it is good to stick to advisory amounts. 12/16/07 had a big cross hair sig despite it being a SWFE  it had this bullseye at like 550-600mb where the snow growth temps were.

Point two, which you mentioned, is a good one too. You want a big thump of rates on liquid equivalent. Seemed to start off that way today but then died off after the first 90 min or so. So even with crappy snowgrowth, we could have maybe tickled 5-6" if the rates stayed high...but it's usually good to see at least a tenth per hour of LE on the model guidance. 

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6 minutes ago, ORH_wxman said:

I made a post last night going over typical parameters we want to see for solid warning amounts in a transition SWFE. You want a classic "cross hair" sig on the soundings...that's just a quick way of saying the omega lines up with the snow growth zone...and you typically want big omega too. Not just some 15 micro bars per second maxima. We didn't have a cross hair sig in this event so that is why it is good to stick to advisory amounts. 12/16/07 had a big cross hair sig despite it being a SWFE  it had this bullseye at like 550-600mb where the snow growth temps were.

Point two, which you mentioned, is a good one too. You want a big thump of rates on liquid equivalent. Seemed to start off that way today but then died off after the first 90 min or so. So even with crappy snowgrowth, we could have maybe tickled 5-6" if the rates stayed high...but it's usually good to see at least a tenth per hour of LE on the model guidance. 

Cross hair sig wasn’t an option but I thought we good get a good thumpnof decent flakes which is what we had for two hours. That kind of fizzled as LLJ wasn’t ramped up yet I guess. 

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17 minutes ago, dendrite said:

The cold layer below the melting layer is cold enough to produce its own small snow crystals. The problem is, there isn’t enough lift in that level to really get any decent snow growth. So you end up with sleet and snow grains. A human observer would code it -PLSG. ASOS is automated so it usually just gets called -SN. I really only see -SG from MWN.

That's why this site is so awesome and I don't throw that word around.  You see a phenomenon you don't understand and somebody's gonna know why it is so.

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19 minutes ago, wxsniss said:

 

1) the poor snow growth: it was baking soda just about the entire event... the lift was always significantly displaced from the DGZ... decent dendrites for the past 6 hours and we'd have a different tune in here

 

Awful snow growth. There was a 5-10 minute span prior to mixing I saw some actual flakes. 

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4 minutes ago, alex said:

Really??? How is it that it's a tornado up here and you have light wind? 

 

Make the wind go away lol

Dead calm here on the eastern side of the Spine with air filled thick with flakes.... while a Wind Advisory is in effect on the west side for gusts to 50mph.

Calm on the upslope (the low level jet is rising to get over the mountains), strong winds mixing down on the downslope.  Which is why we get high winds in Stowe on NW flow.

images?q=tbn:ANd9GcQyFCBsjNQ8B8EMD32ThPH

Edit: Not sure why that graphic is so small, ha.

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5 minutes ago, Lava Rock said:

Ha. I thought u were being facetious

Sent from my Pixel 2 using Tapatalk
 

not at all, I cant imagine what it was like watching the eastern sne snowbowl up there...I did just ok down here and it drove me nuts watching them score 15 to 30 inch events like it was just another storm lol

that is why I am blown away by all the complaining from some of those folks

 

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1 minute ago, 40/70 Benchmark said:

No sleet here yet...good growth now. Really improved while I shoveled.

Must mean the warmth is nearby.  I love how that happens.  You get the mid-level warmth to cause the smaller flakes to aggregate into bigger flakes as they get slightly wet aloft.  There's probably some spring blue bomb going on at like H7-H8 at 32.1F. 

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2 minutes ago, powderfreak said:

Must mean the warmth is nearby.  I love how that happens.  You get the mid-level warmth to cause the smaller flakes to aggregate into bigger flakes as they get slightly wet aloft.  There's probably some spring blue bomb going on at like H7-H8 at 32.1F. 

I though that, too...but its snowing in Wilmington and Lowell, so...

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36 minutes ago, wxsniss said:

1) the poor snow growth: it was baking soda just about the entire event... the lift was always significantly displaced from the DGZ... decent dendrites for the past 6 hours and we'd have a different tune in here

This got me thinking how rare it is to get great snow growth in these types of events.  The mid-level warmth is also what's causing the best lift, so naturally as that level warms we lose snow growth. 

I mean you don't even have to look at soundings in these events to know its going to be baking soda or thousands of needles.  Given the size of the flakes up here it wouldn't surprise me if this came in under 10:1 even for part of this.  It's like a fog and air is thick with snow, but they are the smallest flakes you can get.

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