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**Snowolf** · 05-12-2008, 01:22 PM

As we enter the springtime and our resorts close, many of us hike for our spring and summer turns. In the interest of safety, I have posted the following information from the Northwest Avalanche Center regarding general information pertaining to spring slides.

Quote:

Spring Avalanche Danger

During fair spring weather the avalanche hazard is generally
lowest during the night and early morning hours when surface
snow refreezes due to heat loss to the surrounding atmosphere.
During the day, intense solar radiation and warm air
temperatures can rapidly melt and weaken surface snow layers
and produce an increasing avalanche danger during the late
morning and afternoon. Wet loose slide activity generally
starts on east and southeast facing slopes receiving morning
sunshine and progresses to west and southwest facing slopes
during the afternoon. Therefore the safest time to cross
potential avalanche terrain is during early morning hours
before the surface snow begins to warm and weaken.

This daily melt-freeze cycle is strongly affected by any cloud
cover during the night since clouds at night limit radiational
cooling and prevent freezing. This may allow melt water and
associated snowpack weakening to affect progressively deeper
layers in the snow cover. Snowpack weakening is maximized
when warm days are followed by warm overnight temperatures and
overcast skies. Backcountry travelers should exercise
particular caution under these conditions that often lead to
considerable wet loose slide activity along with possible wet
slab avalanches.

Backcountry travelers should also be aware that spring storms
might quickly produce unstable snow conditions. Although
precipitation may fall as rain at lower elevations,
substantial amounts of new snow may be deposited at higher
elevations. This new snow may form a poor bond with an old
crusted snow surface. Rapid rises in temperature following
the storm due to intense solar radiation may quickly warm and
weaken recent snow, which may need little or no disturbance to
slide. While subsequent wet loose slides may start small,
they may entrain considerable snow as they descend and may
trigger larger wet slab slides as well. Dangerous conditions
may also result from unstable cornices deposited by spring
storms, as these may be quite unstable and release during
later warm days. Also, slopes beneath glide cracks should
normally be avoided, especially during the heat of the day, as
the entire snow cover may release from melt water lubrication
and weakening.

Precipitation as rain may also create unstable snow
conditions. This is because rain falling on an already wet
snowpack causes water to quickly percolate through the
snowpack, which weakens progressively deeper snow layers. If
the water encounters a crust or an ice lens, it may flow along
this layer and lubricate it, making avalanches increasingly
likely within the snow above.

No matter what the season, backcountry travelers should avoid
slopes of questionable snow stability. Remember that many
areas, which undergo regular avalanche control during the
winter, may not be controlled in the spring.

Also remember that small avalanches may be dangerous, since
wet loose snow in motion may be soft, when it stops rapid
hardening takes place. Most avalanche victims trigger the
avalanches in which they are caught, and almost half of all
avalanche deaths occur in slides traveling less than 300 feet;
with some slide fatalities occurring with victims buried only
a few inches under the snow surface. During past springs in
the Northwest, several fatal accidents have occurred from
climbers or skiers releasing and being caught in relatively
small avalanches, which subsequently carried the victims into
or over a terrain trap. Hence, backcountry travelers should be
aware of both the terrain above and below intended routes.

Source

killclimbz · 05-19-2008, 04:15 PM

A few more rules for Spring Riding.

1. Start Early. The best time to hit slopes is 2-4 hrs after sun hit depending on the temps. The warmer the day is going to be the less time it needs to be in the sun. Pre sunrise starts are a must.

2. As mentioned, if overnight temps at the elevation you are planning on getting out in didn't freeze, watch your slopes. This is wet slide season, though slower, these slides pack a very, very powerful bunch. Heavy wet snow that just destroys what gets in it's path. It will also slide on lower angle terrain that what you experience mid winter. Slopes have been known to slide at angles of 28 degrees. Keep that in mind

3. If you are sinking in past the tops of your boots, you can squeeze water out of snowball, you see pinwheels, water on top of the snow, any one or all of these things. It's time to go. This means the snowpack is getting weak to the point that failure is imminent. It's not a matter of if it's going slide, but how quickly it's going to happen.

4. Plan your trips around the freeze thaw cycle. If you aren't off the slopes you plan to ride and on low angle terrain by 1pm (or earlier in many cases) you are doing it wrong and death could be sharpening her scythe for you.

Spring riding is great, and I find it very predictable. Hard slab failures are generally not a worry. The snow has consolidated and you are playing the freeze thaw game. Watching what the weather and temps are doing is critical and timing is everything.

killclimbz · 05-19-2008, 06:38 PM

Even better than what I stated is the CAIC's advice for spring/summer riding.

Quote:

Originally Posted by CAIC

Spring Avalanche Safety

Statewide Spring Forecasts are updated Wednesday, Friday, and Sunday afternoons in the Vail Summit and North San Juan pages, and on the hotlines at 303-275-5360 and 970-668-0600.

Continue to think "avalanche " if you are planning late-spring and early summer adventures into the high-country. There is still plenty of snow for skiing, snowboarding, climbing, and snowmobiling at high elevation.
Remember that virtually all avalanches release on slopes of 30 degrees and steeper. You can effectively avoid avalanche terrain by staying off of and out from under slopes that are steeper than about 30 degrees. But if you are planning to tackle steeper terrain, here are a few safety reminders.
First, carry and know how to use avalanche rescue gear. If you are in avalanche terrain, each person in your group needs to have a beacon, shovel, and probe pole.

Second, only one person in a group should be exposed to potential avalanche danger at a time. Travel one at a time through avalanche zones.

Third, climbing, skiing, and riding down the edge of slopes is generally safer than being in the center.

Fourth, snow stability changes from day to day and hour to hour. For example a large spring storm, or a sustained period of hot weather can increase the avalanche danger. During a storm, or immediately after, new snow may not bond well to the icy old snow surface. Also, soon after a storm, several hours of bright sun can warm the surface snow enough to become unstable. Though, after a couple of days, the snow will strengthen and the danger will gradually decrease.

Fifth, watch temperatures closely and monitor the snowpack for free water. When you can wring water out of a fist full of snow or your sinking into the snow to your boot tops, it is time to move off of and out from under steep slopes. Usually it is safe to travel early in the morning when the snow surface is crusty. The danger begins to rise as the snow softens in the afternoon. If the snow is not freezing overnight, or if only the surface is frozen, the danger of wet avalanches is increasing.

And sixth, big cornices may last well into the summer. To be safe, avoid traveling under cornices when the snow turns wet or when water starts to drip from the cornices.
We would like to hear your comments on what you liked or disliked about our service and what we could do to improve our service. Please e-mail us, or drop us a note at the Colorado Avalanche Information Center; 325 Broadway, WS#1; Boulder, CO 80305.
We hope you will continue to visit our web site. We will post information summarizing this past winter in June. Through the summer we will add old accident reports and new material.
Thank you for supporting the Colorado Avalanche Information Center. We will be back in the fall to resume our mountain weather and avalanche forecasts --but first --summer!

**Snowolf** · 05-20-2008, 03:25 AM

Thanks Gary for all the good info..It is awesome to have someone of your training and experience available to all of us. I for one really appreciate your input....

Here is the updated report for the Washington Olympics and Cascades including the Mt. Hood area:

Quote:

SPECIAL AVALANCHE STATEMENT FOR THE OLYMPICS WASHINGTON CASCADES
AND MT HOOD AREA
NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON
900 AM PDT SUN MAY 18 2008

This statement applies to back country avalanche terrain below
7000 feet and does not apply to highways or operating ski areas.

&&

WAZ513-518-519-019-ORZ011-191600-

OLYMPICS-
WEST SLOPES NORTH CASCADES AND PASSES-
WEST SLOPES CENTRAL CASCADES AND PASSES-
SOUTH WASHINGTON CASCADES-
NORTH OREGON CASCADES-

... AVALANCHE WARNING TERMINATED...

Cooling and increasing northwesterly ridgetop winds as of early
Sunday has allowed for a decrease in the overall avalanche
danger. Mountain temperatures have lowered on average about 10
to 15 degrees by Sunday morning as recorded by NWAC weather
data.

The continued gradual cooling and increasing ridgetop winds
Sunday should begin to decrease surface snow melt, however a
relatively unstable snowpack should persist through Sunday and
travel in avalanche terrain should be taken with extreme
caution.

See http://www.nwac.us/products/SABSEA for current details.

This statement will be updated as conditions warrant.

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