Blog Archive for January, 2014

Avalanche Problem Web Series:
Part 7 – Loose Wet

How to Apply the Avalanche Forecast to Your Riding

 loose wet

For splitboarders venturing into the backcountry, information can be the difference between an epic day and tragedy. In an effort to increase education and avalanche awareness, Spark R&D is presenting a 7-part web series called Avalanche Problems, which will explain the nationally standardized types of slides most commonly described in advisories by avalanche forecasters.

Understanding the characteristics of each type will help to determine where avalanches are likely to occur and what kind of terrain should be avoided. In today’s final installment, we will cover Loose Wet Avalanches.

Loose wet in a nutshell

loose-wetLate in the season is often the time to go big, as the snowpack is generally more stable and predictable. But when the temperature rises during the day, the upper layer of the snowpack turns to slush and peels away from the mountain, much like a wet sluff.  Get an early start, retreat when it gets hot or the slush becomes deeper than ankle height, and be weary when nighttime temps do not dip below freezing.

What exactly is a loose wet avalanche?

• Above freezing temperatures and/or rain cause the surface to lose cohesion, and give way in a loose snow avalanche. Because of the water in the snowpack, these carry more mass, and have the potential to pack quite the punch.
• This is caused by either new spring snow, which is peeling off the underlying surface, or from frozen corn snow has thawed and turned to slush.
• This is often a springtime problem, as temperatures generally stay cold enough mid-winter.
• When temperatures cool off enough for the snowpack to re-freeze, than the problem will subside. When temperatures warm back up, the problem could come back.

Where might you find loose wet conditions, and how to avoid it

• When wet slides occur, they tend to be fairly widespread.
• The timing can vary throughout the day. Slopes facing easterly (NE, E, SE) get first sun. loose-wet-iconSoutherly slopes are late morning and mid day (SE, S, SW), and westerly slopes get the afternoon heat (S, SW, W, NW, N).  Try to follow the pattern of the sun.
• Once the snow becomes too soft, stay off of steep terrain and avoid travelling below known avalanche paths.
• Similar to “loose dry” avalanches, think not only about being buried, but also about the consequences of being carried into terrain features, like cliffs, rocks, and trees.
• Rocks can intensify the heat, so be extra cautions as wet slides can initiate around them.  In warm weather, be watchful for rock fall, too.
• If working with corn snow (frozen surface late in spring), the best riding can be had when just the top couple inches have thawed. This means the probability of wet avalanches is less likely, and the snow is not too heavy, deep and cumbersome for riding.
• Think not only of triggering slides, but naturals too. It’s very common to have natural activity with wet avalanches, so watch above on big slopes.

How to look and test for loose wet conditions

loose wet 2

Photos courtesy of Gallatin National Forest Avalanche Center (mtavalanche.com).

• Wet surface conditions can be observed without any kind of snowpack test or formal pit.
• Warning signs can start to appear:  Intense sun; above freezing temperatures; roller balls peeling away and running down slope; gloppy, wet or mushy surface conditions; and natural avalanches.
• Paying attention to the weather history and the current weather conditions provide valuable clues.  Many warm days with a very light freeze (just below 32) or no freeze at night means the snowpack is not getting time to re-strengthen, and can be especially tender when the sun comes out.
• Cold and clear nights will yield the best freeze and will give you the most time to work with during the day.

Tips: In the springtime, don’t be afraid to get pre-dawn starts to beat the heat. If you’re too early and the conditions are dangerously firm, than you can always wait for the surface to soften. Remember the conditions can change very quickly, with low hazard in the morning, and high hazard once the heat turns on.

Disclaimer: Although characteristic, these descriptions are general, so make sure to read into any specifics mentioned on your local advisory. Also, this is just one piece of the puzzle, so remember to factor in the hazard rating and any field observations.

Find your local avalanche center: www.avalanche.org

Thanks for joining us for our 7-part web series discussing the most common avalanche problems used by forecasters.  By learning about each problem, we can become familiar with the duration, terrain management and how to look for these problems.

Before heading out the door in the AM, we recommend checking the avalanche bulletin, weather forecast, and thinking about any relevant field observations. Think about where the problem may reside, and spend a little time considering what terrain might be no-go and what terrain would be attainable.

A big shout-out to the Gallatin (Bozeman), Sawtooth (Ketchum) and Colorado Avalanche centers for their collaboration and use of images! 

Presented by Clark Corey
Splitboard Guide/Avalanche Educator

Avalanche Problem Web Series:
Part 6 – Wet Slab

How to Apply the Avalanche Forecast to Your Riding

wet-slab

For splitboarders venturing into the backcountry, information can be the difference between an epic day and tragedy. In an effort to increase education and avalanche awareness, Spark R&D is presenting a 7-part web series called Avalanche Problems, which will explain the nationally standardized types of slides most commonly described in advisories by avalanche forecasters.

Understanding the characteristics of each type will help to determine where avalanches are likely to occur and what kind of terrain should be avoided. In today’s installment, we will cover Wet Slab Avalanches.

Wet Slabs in a nutshell

wet-slabIn the springtime, the deep winter cold begins to lose its grip and the temperatures begin to rise. On a warm spring day (or during a rain event), the snow pack can become unglued and if a slab exists, there’s a good chance it will release. If there are known slabs, there is new spring snow, or persistent weak layers are lurking in the snow pack, the best strategy is to get out early and retreat when temperatures begin to rise.  Be especially cautious if the temperatures don’t dip below freezing overnight.

What exactly is a wet slab avalanche?

• Above freezing temperatures and/or rain cause a slab of snow to become unglued to the underlying surface.  Wet slabs can be very destructive as the water in the snow pack means these slides are heavier and carry more mass.
• This is often a springtime problem, as temperatures generally stay cold enough mid-winter.
• The lifespan of wet slab avalanches completely depends on the weather. When temperatures cool off enough for the snow pack to re-freeze, than the problem will subside.
• When temperatures warm back up, the problem could come back.
• During long warm spells, the slab may entirely turn to mush and become a wet loose problem.

Where might you find wet slabs, and how to avoid them

• When wet slides occur, they tend to be fairly widespread.
wet-slab-icon• The timing can vary throughout the day.  Slopes facing easterly (NE, E, SE) get first sun; southerly slopes are late morning and mid day (SE, S, SW); and westerly slopes get the afternoon heat (SW, W, NW).
• Once the temperatures become too warm, stay off of steep terrain and avoid being caught underneath known slide paths.
• Rocks can intensify the heat, so be extra cautions as wet slides can initiate around them.
• Following the pattern of the sun works well, but once the air temperatures become too warm, it’s best to retreat all together.

How to look for and test for a wet slab

• Warning signs will start appear: Intense sun or above freezing temperatures, roller balls peeling away and running down slope, gloppy and mushy surface conditions, and natural avalanches.
wet-slab3• Often times, this can be tied to warm sunny days preceding a spring storm (especially the day after).
• Pay attention to the weather history and the current weather conditions. Many warm days with a very light freeze or no freeze at night means the snow pack is not getting time to re-strengthen, and can be especially tender when the sun comes out.

Tips: Start early! In the springtime, don’t be afraid to get pre-dawn starts to beat the heat. The avalanche hazard can change very quickly, with safe conditions in the morning, and dangerous conditions once the heat turns on.

Disclaimer: Although characteristic, these descriptions are general, so make sure to read into any specifics mentioned on your local advisory. Also, this is just one piece of the puzzle, so remember to factor in the hazard rating and any field observations.

Find your local avalanche center: www.avalanche.org

Presented by Clark Corey
Splitboard Guide/Avalanche Educator

 

Avalanche Problem Web Series:
Part 5 – Loose Dry

How to Apply the Avalanche Forecast to Your Riding

OLYMPUS DIGITAL CAMERAFor splitboarders venturing into the backcountry, information can be the difference between an epic day and tragedy. In an effort to increase education and avalanche awareness, Spark R&D is presenting a 7-part web series called Avalanche Problems, which will explain the nationally standardized types of slides most commonly described in advisories by avalanche forecasters.

Understanding the characteristics of each type will help to determine where avalanches are likely to occur and what kind of terrain should be avoided. In today’s installment, we will cover Loose Dry Avalanches.

Loose dry avalanches in a nutshell

loose-drySoft and unconsolidated surface snow means there’s potential for loose snow avalanches, otherwise known as “sluffs”. Although outrunning monster sluffs in Alaska looks doable in the movies, the reality is that not everyone has the ability and experience, nor is it the right tactic for every situation.

What exactly is a loose dry avalanche?

• Often called “sluff” slides, this is when an upper layer of cohesion-less snow starts as a small, localized slide, gains momentum, and amasses more snow as it travels down slope.
• Natural releases often have a fan like shape, originating from a single point, and gain more width as they travel down slope (also known as a point release).
• These slides tend to be on the smaller side and are less dangerous than slab avalanches. But on large, steep slopes, like in Alaska, sluffs can become quite large and lethal.
• If there is a secondary slab problem, a sluff slide could be enough weight to trigger it.
• In the event that the storm snow is forming a slab, this would be referred to as “storm slab.”
• Loose dry conditions tend to be short lived if formed by new snow (hours to days), but can stick around for longer in periods of light wind and consistent, cool temperatures.

Where you might find loose dry conditions, and how to avoid it

• Loose avalanches tend to occur in steeper terrain, particularly approaching 40 degrees or steeper.
loose-dry-icon• Avoid steep slopes! This problem can be entirely managed by staying off of steep terrain until the new snow has settled.
• For big mountain riders, consider the consequences of being caught and what you could be pushed over (cliff bands, rocks, etc.). Avoid slopes that have these features.
• Also consider potential terrain traps, as even a small loose avalanche can pile up deep in the deposition zone.
• Plan your decent wisely, and think about areas out of the fall line to escape a sluff.
• Although an advanced technique, ski cuts can work well, as you can push off the top layer of snow and let it run out front, which may mitigate the problem.

How to look and test for loose dry conditions

• Observations about natural avalanche activity and recent weather are all useful.
OLYMPUS DIGITAL CAMERA• Fan shaped natural releases on steep slopes during or after a storm event are good indicators that a skier could trigger these slides.
• Recent new snow and loose surface conditions (from new or faceting) are signs that are easily observed, and don’t require a formal pit.
• Ski cutting short test slopes can tell us if the surface is wanting to run or not.

Tips: Although new snow is likely the cause of sluffs, long periods of cold and clear weather can facet the surface and create loose snow conditions as well.

Disclaimer: Although characteristic, these descriptions are general, so make sure to read into any specifics mentioned on your local advisory. Also, this is just one piece of the puzzle, so remember to factor in the hazard rating and any field observations.

Find your local avalanche center: www.avalanche.org

Presented by Clark Corey
Splitboard Guide/Avalanche Educator

Avalanche Problem Web Series:
Part 4 – Storm Slab

How to Apply the Avalanche Forecast to Your Riding

storm-snow

For splitboarders venturing into the backcountry, information can be the difference between an epic day and tragedy.  In an effort to increase education and avalanche awareness, Spark R&D is presenting a 7-part web series called Avalanche Problems, which will explain the nationally standardized types of slides most commonly described in advisories by avalanche forecasters.

Understanding the characteristics of each type will help to determine where avalanches are likely to occur and what kind of terrain should be avoided.  In today’s installment, we will cover Storm Slab Avalanches.

Storm slabs in a nutshell

storm-snowLet’s face it:  The best riding is often experienced during or right after a big storm. But in the backcountry, this can mean the new snow has formed a soft slab.  The new snow may not be adhered to the underlying surface, or it may have an “upside down” structure.   The best practice is to stay off of steep terrain (35 degrees and steeper) until the new snow has had time to adjust, which could take several days.

What exactly is a storm slab?

• A storm slab is new snow, which is cohesive enough to act like, or form a slab.
• Sometimes the slab is not bonding to the underlying surface. In other cases, it may form upside-down, meaning colder lighter snow on the bottom (weak layer) and heaver or wetter snow on top (slab). These tend to be smaller in size.
• If the storm snow is not a slab, than this is referred to as “loose dry” (next post). If a persistent weak layer is involved, than see the “persistent slab” problem.
• These are often short lived, and are experienced during or post storm event. The problem can last for several days, but can last longer if the temperatures remain very cold.

Where you might find a storm slab, and how to avoid them

storm-slab-icon• Storm slabs are typically widespread, but think about where the storm totals are greatest. Upper elevations, or the wet side of the range, are likely to have more of a problem.
• Higher elevations and shaded slopes are colder, which can preserve the problem for longer.
• Avalanches are more likely to occur in terrain 35 degrees or steeper.  However, play it safe and stick to terrain under 35 degrees during or after the storm.
• Always be careful around natural avalanche paths during a storm, as start zones are becoming loaded and natural slides can occur.

How to look for and test a storm slab

• Hand pits and skin track cuts are nice tests if storm totals are under 1.5 feet (about 40cm), as they are very quick, can be done many times throughout the day, and give information on how well the snow is bonding. They allow you to look for patterns throughout the day.
• Ski cuts or stomps on steep slopes are great indicators for these surface conditions.
• Compression Tests (CT) are good for testing the bonding (lower scores or sudden planer sheers), and Extended Column Tests work if the new snow isn’t too soft.

Tips: If you get out for a few days in a row, watch for settlement cones around trees and bushes. Also, look for trends in your test scores:  Higher scores, or more resistant hand sheers, mean the snow is starting to stick.

Disclaimer: Although characteristic, these descriptions are general, so make sure to read into any specifics mentioned on your local advisory. Also, this is just one piece of the puzzle, so remember to factor in the hazard rating and any field observations.

Find your local avalanche center: www.avalanche.org

Presented by Clark Corey
Splitboard Guide/Avalanche Educator