Wednesday, December 18, 2013

What is surface hoar?

You may have heard us warning backcountry skiers and riders about buried surface hoar in our avalanche advisories this month.  So what is this lurking predator and how do we know where to find it? 

                Surface hoar, sometimes called “hoar frost”, is that beautiful, glimmering, feathery crystal you’ve probably admired while strolling around town.  When it gets buried on a steep slope, it can be an incredibly fragile and dangerous weak layer that can persist for weeks or months.  Surface hoar is the winter version of dew.  In order for it to form, we need 3 ingredients:  clear nighttime skies without canopy cover, calm winds, and some relative humidity in the air.  Of course, these feathery crystals aren’t a problem unless they are preserved below a slab of snow.  In Crested Butte, we frequently see strong winds prior to the arrival of the next storm, which helps destroy those fragile layers.  Sun-baked slopes can also cook the layer into submission.  The take-home point here is that there are a lot of factors at play that can make for variable and spotty distribution of buried surface hoar; some slopes may have it while others don’t.

                We had a significant surface hoar event around Thanksgiving that was buried on some slopes after our early December storms.  We’ve been finding it preserved on shaded and wind protected or leeward slopes, especially at lower elevations.  It has been the culprit for a handful of avalanches these past few weeks.  This layer has been fairly easy to identify in a snow pit: it looks like a thin grey stripe in the snow (this is not always the case). 

The obvious grey stripe in the middle of the pit is a layer of buried surface hoar found on Schuykill Ridge this week.
We are just exiting another high pressure weather pattern that is favorable for surface hoar growth.  When you’re out touring in avalanche terrain, look for surface hoar and what slopes it is forming on to give you a better idea of places to avoid if it gets buried and becomes problematic.  And don’t forget check our website for the most up-to-date avalanche conditions before you head out.

-Zach Guy

Monday, December 9, 2013

Sunday, December 8, 2013

No Niño??

For the past several years, much of the early season buzz about whether we were going to have a killer winter or a dud revolved (over. and over. and over...) about the pros and cons of an El Niño or La Niña   atmospheric and oceanic signal.  

Here is a post from one of my former meteorology professors at the University of Utah and total powder junkie himself, Jim Steenburgh.  He runs a great weather blog that discusses meteorology mostly around Utah, but a ton of his material is applicable to our locale as well.  Bookmark it and check it out! Infer what you can about how the lack of ENSO will affect our weather patterns...the overarching theme being....your guess is as good as mine.  A good perspective if nothing else.

My take is that the Arctic Oscillation is just as big of a contributing factor that is often over looked. "The positive phase of the Arctic Oscillation brings ocean storms farther north, making the weather wetter in Alaska, Scotland, and Scandinavia and drier in the western United States and the Mediterranean. In the negative phase of the Arctic Oscillation the patterns are reversed. A strongly negative phase of the Arctic Oscillation brings warm weather to high latitudes, and cold, stormy weather to the more temperate regions where people live. Over most of the past century, the Arctic Oscillation alternated between its positive and negative phase. For a period during the 1970s to mid-1990s, the Arctic Oscillation tended to stay in its positive phase. However, since then it has again alternated between positive and negative, with a record negative phase in the winter of 2009-2010"(National Snow and Ice Data Center).

What tilt are we in now you may ask??

These are very interesting (and confusing) but if you look at each graph, you have a neutral AO signal at zero, with the blue bars going up meaning positive, going down, negative. Makes you think a little what phase we have been in for extreme weather, like our early season snows, the Front Range floods in September, etc.

More info here:

I will probably steer some of my posts of this forecaster's blog to Jim's blog occasionally.  Enjoy this snowy far I like No Niño...

-Ian Havlick

Saturday, December 7, 2013

TED Talk on Avalanche Hazard and Risk

Grant Statham gave a great TED talk recently on risk in avalanche terrain that has been circulating around the avalanche community lately.  Grant has spent a lifetime climbing, skiing and guiding in extreme terrain around the world and he has spent the past 10 years or so working as a risk management specialist for Parks Canada.  Grant does a great job of explaining risk and hazard and how it relates to travel in avalanche terrain in this TED talk.

See Grant's 12 minute talk by clicking HERE or on Grant's photo below.

Grant Statham from Parks Canada

The components of avalanche risk from Bruce Tremper's (Utah Avalanche Center Director) new book Avalanche Essentials, which illustrate the points Grant makes in his talk.

-Ian Havlick
CBAC Forecaster