The Science of Snow

Friday, February 18, 2011

In the last week, slight signs of spring can be found.  I try not to get sucked in.  As much as I would like to dream of goggle tans and the beer gardens on Cuzzin’s Deck, I know there is still more winter to come.  In fact, our forecaster is saying that the January weather will cycle back in March and we should see colder temps and abundant snow!

All this up and down in temperatures makes it hard to know if you are coming and going.  Especially, if your job is to keep all of our trails in shape.  A 20 degree swing in 24 hours makes it difficult to read the snow so our Grooming Department really has to know their stuff.  I went right to the source to find out the dos and don’ts of grooming in variable conditions.  Elia, who oversees our grooming department, gave me a quick lesson in the science of snow.  It went something like this.

K:  Describe ideal grooming conditions?

E:  Cold, in the teens, not windy.  A good base that is like Styrofoam with a 2” layer of fresh snow on top.

K:  What’s the worst to deal with?

E:  The classic thaw/freeze scenario.  Snow saturated with water that freezes.  Wind is also one of our worst enemies.  You can make a pass and go back and it looks like we were never there.

K:  Tonight will be a thaw/freeze scenario - how do you deal with it?

E:  First of all, we do not groom until the snow starts freezing. If we were to groom before it freezes you cause a Zamboni effect – bad!  We will send the operators out and track up the trails (called track packing.)  Track packing gives the tiller and blade something to process and also makes the freezing process occur sooner because it expands the surface area of the snow.

K:  At what point will you start grooming?  When the temp drops to 32 degrees?

E:  Because snow is colder than the air (we call this refrigeration) it will usually start freezing around 37 degrees.

K:  Do you have other tricks that help improve the snow surface in a thaw/freeze scenario?

E:  We will renovate the trails.  This is when we replace the blade on the front of the cat with an implement that can dig down deeper (10”) and it pops up chunks of snow, which the cat drives over and then the tiller (behind the cat) breaks it up even more.  Renovating allows you to aerify the snow.

Elia goes on to tell me that the difference between snow and ice is air.  He described a snowflake falling from the sky and how each crystal is intricately shaped.  If it is dry, air is held in all of its nooks and crannies (powder).  As the snow crystal breaks down and the little arms break off, it no longer holds the air and eventually it is just a ball (think spring corn.)

The most important thing to remember after a thaw/freeze event is that each day the surface gets better.  Working the snow improves it and the more people we can put on the hill, the better.  Skiers and riders create texture, which makes it easier for the snow cat to grab onto.

K:  Spring is coming Elia – how will your grooming plan change?

E:  The trails that we groom first will set up (freeze) the most overnight so we groom main face trails that are south facing first, knowing the sun will soften them earliest.

Midwinter, we groom the North Face first but in the spring we will groom it later because it gets sun later in the day.

K:  What is the hardest trail to groom?

E:  Plummet because it has two different fall lines and a nasty hole (nicknamed Johnny’s hole.)

It was good to catch up with Elia and to remind myself that our ever-changing weather creates challenges and opportunities.  As much as I would like to come in each morning and have everything perfect, patience is a virtue.  It reminded me of a very patient Vermonter who also had a love of snow, Snowflake Bentley.

Here was my day:

comments powered by Disqus