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What happens to snow when it gets really cold?

post #1 of 17
Thread Starter 

Can someone explain - in layman's terms - what tends to happen to snow and skiing conditions when temperatures fall into the single digits or below zero (like they did across most of NE this past weekend)?

 

Aside from the obvious challenges the low temps pose and the measures one needs to take in terms of clothing/layering and coming inside, what do the low temperatures actually do to the snow/skiing conditions?

 

Thanks.

post #2 of 17

Very cold snow tends to have a very dry, abrasive crystalline structure,  that is slooow.

post #3 of 17

Depends. If it is cold and clear following a warm or wet spell the snow will obviously be very icy and hard. Snow that falls at very cold temps will be very light and it will take a considerable amount of snow to support a skier--unless there are a couple of feet of new snow you will be skiing on the frozen crud underneath. Also--the fresh snow will not adhere to the frozen base and will sluff off of steeper slopes moguls--classic dust on crust. Around here we typically get storms that come in warm and then turn cold (rarely as cold as the East of course)--if the transition is not too abrupt the early snow adheres to the base and the late snow provides a light powder surface--ideal conditions. If the transition is abrupt then we get dust on crust. 

post #4 of 17

It depends heavily on what the snow was like before the temps dropped. If the snow was wet or warm, it'll freeze solid obviously. Upon being groomed, the snow will become sugary, as the grooming is just chewing up the ice into tiny grains of ice, rather than flakes. If the snow is dry, then the snow will stay light, as there is no moisture to cause the snow to bond together. 

 

If it snows while it is cold, then it really depends on what the temperature and humidity is when it snows. Snowflakes form differently depending on temp and humidity, so how they behave is going to change as well. Wilson "Snowflake" Bentley was a photographer from Vermont who perfected the art of photographing snowflakes. He observed that the flakes were different depending on the atmosphere. Since then, someone has put together a "snowflake thermometer" where you can determine what the general temperature is depending on the type of flakes you see. Below: 

 

As you can see, the colder it gets, the more the flakes go from having thin arms to being flat hexagons. Flat plates rubbing against each other will cause more friction than the thin armed cousins further up the thermometer. So at a microscopic level, very cold snow is slow. However, that can be offset because it is often fairly firm, which allows skis to skim more over the top of them with less drag. So very cold snow can be fast, too. 

post #5 of 17
I love nice dry, single digit snow. The right wax means it's not that slow, not like that grippy rubber mat stuff you get in warm conditions. And the temps keep'em all in the bar.

Haven't seen any of those days in a while... Grr.
post #6 of 17
Thread Starter 
That was great. Thank you.
post #7 of 17
Why does cold snow squeak when you walk on it?
post #8 of 17
Quote:
Originally Posted by slider View Post

Why does cold snow squeak when you walk on it?


Because it can't yell "Hey! get off me!"

post #9 of 17
Quote:
Originally Posted by naja View Post

Can someone explain - in layman's terms - what tends to happen to snow and skiing conditions when temperatures fall into the single digits or below zero (like they did across most of NE this past weekend)?

Aside from the obvious challenges the low temps pose and the measures one needs to take in terms of clothing/layering and coming inside, what do the low temperatures actually do to the snow/skiing conditions?

Thanks.

Depends on where it is, what kind of snow, and what the weather was like before it got cold. Our Utah snow is sometimes heavy but usually very dry, and sometimes even too dry for a snowball. After a front passes through it'll be clear and cold on the other side. Often very cold. With GS skis on corduroy you can really tell how fast it is. Fresh dry snow won't be fast. Then after a day or so of skiing and being rolled, even at 0* or single digits it'll be very nice and not the least bit slow.
post #10 of 17
Quote:
Originally Posted by Utahski View Post


Depends on where it is, what kind of snow, and what the weather was like before it got cold. Our Utah snow is sometimes heavy but usually very dry, and sometimes even too dry for a snowball. After a front passes through it'll be clear and cold on the other side. Often very cold. With GS skis on corduroy you can really tell how fast it is. Fresh dry snow won't be fast. Then after a day or so of skiing and being rolled, even at 0* or single digits it'll be very nice and not the least bit slow.



Being tilled, groomed and rolled breaks off sharp edges and causes some bonding between crystals even at low temps.  Breaking the sharp edges helps create less friction so it gets faster.

 

We get lots of lake effect where I live and when it's fresh and in the single digits it's a strange beast as it holds more moisture than one would think.  After it stops falling and it's been on the ground for a while it starts to get faster and faster.  If I'm out rolling our fatbike trail while it's still coming down I can plug the roller up even in single digit or below temps.

post #11 of 17
Quote:
Originally Posted by slider View Post

Why does cold snow squeak when you walk on it?

 

Same reason a door hinge creaks. No lubrication. When you put pressure and friction on snow, it melts in microscopic amounts, which causes the snow crystals to slide past one another. When it is really cold, the friction and pressure of walking on the snow doesn't have enough energy to overcome the cold temps, so the snow crystals are rubbing against one another. 

post #12 of 17
Quote:
Originally Posted by trailtrimmer View Post
 


  If I'm out rolling our fatbike trail while it's still coming down I can plug the roller up even in single digit or below temps.

 


What do you groom with?

 

My SOP,   I set a XC track down the middle and ski it a couple of days.   Usually,  people and animals, start to walk on it and tear it up. 

I then start to ride the fatty down the middle and I will set another XC track along the edge.

We just don't have the traffic to justify grooming, XC or Bike.

post #13 of 17
Quote:
Originally Posted by sibhusky View Post

I love nice dry, single digit snow. The right wax means it's not that slow, not like that grippy rubber mat stuff you get in warm conditions. And the temps keep'em all in the bar.

Haven't seen any of those days in a while... Grr.

 

I also like minus snow, specifically those hexagonal prisms and pyramids  shown on the 'thermometer' graph above at -20.     Powdered sugar.   It gets up into the air (like sugar at a proper beignet shop) and sparkles and glints like a proper old-time winter.     That - and the fact that most can't seem to get their skis to go at all - is just so happy, you know? 

Gratuitous Nakaya diagram:

 

post #14 of 17
Quote:
Originally Posted by naja View Post

 

Aside from the obvious challenges the low temps pose and the measures one needs to take in terms of clothing/layering and coming inside, what do the low temperatures actually do to the snow/skiing conditions?

 

 

One thing that happens that nobody has mentioned yet - avalanches get weird.    There's crust and windslab all over the place - and any given crusted pitch might have high-friction dense snow under it or might have light fluffy ready-to-slide snow under it. 

post #15 of 17
Quote:
Originally Posted by cantunamunch View Post

Quote:
Originally Posted by sibhusky View Post

I love nice dry, single digit snow. The right wax means it's not that slow, not like that grippy rubber mat stuff you get in warm conditions. And the temps keep'em all in the bar.


Haven't seen any of those days in a while... Grr.

I also like minus snow, specifically those hexagonal prisms and pyramids  shown on the 'thermometer' graph above at -20.     Powdered sugar.   It gets up into the air (like sugar at a proper beignet shop) and sparkles and glints like a proper old-time winter.     That - and the fact that most can't seem to get their skis to go at all - is just so happy, you know? 


Gratuitous Nakaya diagram:



IMG_5555.JPG
post #16 of 17
Thread Starter 

post #17 of 17

That's a pretty correct temperature shot. Today, Friday it was 6F here in town. it's currently 35F. They are saying we may get 4" over night.

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