[Valdez Telehead]

Another simple defintion..

"Surface hoar is winters equivalent of morning dew in summer."

Same processes at the surface.

[Gary Brill]

I ususally say, " Surface hoar is an elaborate, crystalline frost that forms on the snow surface under the same conditions as frost on your windshield. Clear skies, light winds, and some humidity."

[pjc]

Going back to the first point about snowpits... I think most of the "teachers" on this forum may have missed the original point, whereas I think skibum got it about right. Too much emphasis on snowpits, to the beginining student, may detract from the interest and ability to detect and analyze the many clues available to us above ground. Good avalanche awareness skills begin with environmental observations, and only then progress into the more technical discipline of snow science. Got to start with a firm understanding of the fundamentals.

At least that's how I saw it. My 2 cents....

[Gary Brill]

pjc:

[Missing Link]

GB, Thanks for helping me understand this.

I'm wondering though, you said 'Faceting forms in long periods of clearing, cold or not, between storms'.

So if its clear and 65f between a storm faceting will occur?

ML

[Gary Brill]

Well, I wasn't thinking 65f when I made that comment.

But the fact is, on shady or obliquely sunlit slopes with light winds and low humidity, radiational cooling and evaporation act to cool the snow surface substantially. Last year, at Blewett Pass (where I do classes most years) average temperatures were very warm, probably 30 degrees or so, but the snowpack had a good deal of faceting.

I've made this observation before, but, in our climate with light winds and low humidity, radiational cooling can cool the snow surface by 5-7 degrees C. I don't know about the effects of evaporation in absolute terms, but I believe that the evaporation of 1 cc of H2o removes 500-600 calories from the snow surface.

Another critical component is pooling of radiationally cooled air adjacent to the snow surface and katabatic effects that develop as the dense, cool air begins to run downslope (especially with light southerly winds that give it a boost to the north.

In any case a couple years ago I skied powder near Mt. Baker at 60 degrees F air temperature. That may have been the margin for keeping dry snow and faceting wasn't likely. But surface cooling may well create a gradient at air temps well above freezing. It is the snow surface temperature that is important not the air temperature under clear skies.

[snowdynamics]

To start, I respect Doug and Jill for their contributions to avalanche safety and to the recreationalists in Alaska.
after all they are the Grandmother and Grandfather of avalanche education...

However.

Snow Sense is way outdated, and not recommended reading.

For example(s):

-On page 10 the avalanche triangle is incorrect: it should read terrain, instability, people structure. The last time I checked, weather was a part of snowpack.

-On page 17 the statistics are from 1977!!!

-On page 28 they describe snow metamorphism in terms that are now officially not in use.

-On page 64 you'll find a not-so-professional (and maybe dangerous) "Banzai Test".... not just outdated, unreliable.

On page 56 you'll find a diagram using a VISA card for resistance tests. Whoa.

I prefer Bruce Jamiesons Backcountry Avalanche Awareness,,,,,it's current, perfect for US level 1 courses, and meets the AAA standards, CAA standards, and the International standards.


With all due respect.
_________________
www.snowdynamics.com
"Terrain suitable for the conditions."

[Valdez Telehead]

Negative Good Buddy,,,

The triangle is right on. Others have tried to modify it, but it's the basic triangle.

Weather is not part of the snowpack. That's very wrong.

Their discription of snow metamorphism is right on. Perhaps it is to simple. Every book is different in this regards. Some use 8 pages, Fesler uses a few paragraphs to describe the same process.

I have never seen anything hazardous in doing a Banzai Test. Perhaps you can enlighten me.

I use my Tesoro card at times. What is wrong with dragging a plastic card. Or do we need a CAA approved $75 card. I find most plastic card sufficiet to identifying weak layers when "searching out clues". A lens card work good also.

This book is great introductory guide to avalanche awareness for beginners and a great review for experts

[Valdez Telehead]

More favorite qoutes to finish of my dedication to "Feslerism"...

"Snow Sense provides a framework for evaluating avalanche hazard. It is not a substitute for field expereince. If you want to learn about dragons, you need to go to the den of dragons....but sometimes a dragon book helps."

"Avalanches do not happen by accident, they occur for particular reasons"

"Most of the avalanches catching people are triggered by people, and the same mistake are being made repeatedly."

The last quote is certainly an indication that the book is not out of date based on this years NA fatalities. A reminder that it was revised and updated in 1994, so it is not some old- time avy manual with old dated terms and such...it is quite recent. I assume another update may be in the works.


sd sayeth.."Snow Sense is way outdated, and not recommended reading."


I strongly disagree and think it should be the first primer for any newbie thinking about the BC. As you gain expereince, other books like Trempers and more advanced manuals will be easier to consume. You can read this book in two hour and it could save your life right away. Tremper's would take a week or more and is real wordy, almost too much so in my respectful opinion for introductory stuff. Just because it is the newest book by a well respected peer, it does not mean its the best. There is not much to compare it to.

I would be interested in Tremper's read on Snow Sense, but I would suspect he and the leading avalanche experts in the world would strongly disagree with sd and recommend it has a must read for any newBC skiers. Some well educated folks should review it also.