Snow Science Thread

[mtnpull]

First off this thread was purposely placed in the General section to benefit as many snowmobilers as possible. Please don't move it.

The purpose of this thread is to provide each of us with the opportunity to discuss snow science and what different types of snow there is, how temperatures affect it, how wind affects it, how well it bonds or doesn't bond, etc etc. I believe by knowing more about the snow we are riding on the safer we can be while out there riding.

Here are the rules for this thread.

1. Each week (more often if needed) I will throw out one type of snow or factor (factors would be anything that could affect the snow pack such as winds, rain, temperature variations, etc,etc) in the snow pack for discussion. I will ask a number of questions regarding that snow type and / or factor.

2. For that week we will have open discussion answering questions about the weeks topic and giving feedback and examples.

3. Stay on topic. It will be very easy to start going into other snow types etc, but I think we can all benefit if this stays focused and on topic....kinda like a college class.

4. No bashing or thread jacking. I want this to be a resource for people. Let's keep it as an opportunity to learn and protect ourselves, our friends and our families.

Alright, here we go.

 

[mtnpull]

1st topic.

What is Graupel?

How is it formed?

Does it bond well with the snow pack?

Does it create any hazards in the snow pack?

Any characteristics of graupel in the snow pack that could cause concern?

 

[AKSNOWRIDER]

isnt gropple almost like a light hail?..maybe more like a ice fog?...I would think if it landed on the snowpack wet and warm it would bond in good...but I think any aditional snow layers on top of it would not bond to it good and would become a weak layer in the pack....

 

[mtnpull]

Yep, your pretty much on it. Graupel is typically formed similar as hail. It starts out as snow, but upper elevation winds keep picking it up and banging it against each other until they form into little balls of snow heavy enough to fall to the ground. You don't typically see it in warmer storms because those big heavy wet flakes tend to just fall to the ground.

 

[pcp911]

I would think that it would not bond well to the old snow and would become a week layer in the snow pack, Like were you would see a failure.

ps thanks, this is a great idea

 

[mtnpull]

It does not bond well and can be a weak layer. Think of two boards with a bunch a ball bearings in between. Not quite as drastic as my example, but you get the picture.

One other factor to consider with graupel. It has to do with the mechanics of the snow being round balls of snow. Any guesses?

 

[AKSNOWRIDER]

It does not bond well and can be a weak layer. Think of two boards with a bunch a ball bearings in between. Not quite as drastic as my example, but you get the picture.

One other factor to consider with groppel. It has to do with the mechanics of the snow being round balls of snow. Any guesses?

snowflakes are gusseted..thats what allows them to interlock and become stabile..a round ball has nothing to hook to..thus it will move easily.....

 

[mtnpull]

snowflakes are gusseted..thats what allows them to interlock and become stabile..a round ball has nothing to hook to..thus it will move easily.....

Great point. I am still looking for something else. Think about where avalanches usually propagate then think how graupel would apply.

 

[srx_600]

Does it allow the avalanche to break easily, then once broke be more incline to pickup speed?

 

[phatty]

Groppel is like ball bearings to an upper layer of snow. Couple more points about groppel: It usually doesn't bond well at all to existing snow. In your steepest mountain regions it will run right down off slopes that are steeper than 35 degrees leaving them free of the groppel. It is however very dangerous on slopes less than 35 degrees because it will sit on those slopes and wait for a heavy load to build on it, then release when the weight becomes too much. Very dangerous stuff...

great topic adam!

 

[mtnpull]

Groppel is like ball bearings to an upper layer of snow. Couple more points about groppel: It usually doesn't bond well at all to existing snow. In your steepest mountain regions it will run right down off slopes that are steeper than 35 degrees leaving them free of the groppel. It is however very dangerous on slopes less than 35 degrees because it will sit on those slopes and wait for a heavy load to build on it, then release when the weight becomes too much. Very dangerous stuff...

great topic adam!

That's the other factor I was looking for. One thing that can happen with groppel, as phatty stated it can roll down the slope, but if the slope has a number of roll overs or transitions in it the graupel can pile up in these areas and allow an avalanche to initiate at a lower spot on the slope than usually occurs.

 

[mtnpull]

Anybody have any pics of graupel they can post?

 

[mtnpull]

 

[mxracer328]

what temperatures would it be formed in?

what does it look like inbetween other snow layers?

 

[duffman]

Excellent topic, I am intrigued! What's the next subject?

 

[mtnpull]

what temperatures would it be formed in?

what does it look like inbetween other snow layers?

It typically forms when there is a strong convective activity in a storm.....usually with the passage of a cold front. I think that is more of the factor of graupel formation than temperature. I don't think I have actually seen much graupel in warmer storms unless it is hail and rain.

I couldn't find any pics of it in a snow pack.

Another few questions, how long does it take to stabilize?

How would you know if there is avy threat from graupel?

Where would you expect to see the problem areas (on a slope) associated with graupel?

 

[balcoboy]

It typically forms when there is a strong convective activity in a storm.....usually with the passage of a cold front. I think that is more of the factor of graupel formation than temperature. I don't think I have actually seen much graupel in warmer storms unless it is hail and rain.

I couldn't find any pics of it in a snow pack.

Another few questions, how long does it take to stabilize?

How would you know if there is avy threat from graupel?

Where would you expect to see the problem areas (on a slope) associated with graupel?

The only question that I know the answer to is, "How long does graupel take to stabilize?"

Roughly 1 or 2 days depending on the temp.

 

[mtnpull]

The only question that I know the answer to is, "How long does graupel take to stabilize?"

Roughly 1 or 2 days depending on the temp.

Right. I do want to emphasize that in some cases it could take longer considering the amount of graupel that accumulates and the snow above and below it.

 

[balcoboy]

Wouldn't the problem areas with graupel on the slopes 35 degrees? My guess is that the graupel rolls off the higher slopes onto the less severe slopes, that would be the problem areas.

Phatty pretty much said that in a couple posts prior

 

[modsledr]

if the graupel snowfall is followed by an extended cold spell with more snowfall, is it possible the graupel layer may not stabilize at all, leading to a prolonged weak layer?

In other words, if the weather patterns dont go through warm/cold cycles, would the weak layer remain?

Last season, this type of weather pattern happened...and many areas experienced an early weak layer that never fully stabilized, leading to many avy deaths later in the season. Not saying the weak layer was caused by graupel, but it is possible.

Thanks for starting this thread...if even one person learns something that will save a life, then it is a HUGE success!!