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Bad weather, avalanches not over yet

Posted: Monday, February 14, 2000

The last week or so I've heard many people express relief that the latest burst of bad weather is behind us. Who can blame them? The last 30 days has been characterized by horrendous snows, howling winds and a near-biblical plague of avalanches.

As the nasty-weather trend reached fruition, avalanches made an island of the Kenai Peninsula, attacked vehicles and threatened homes. Some communities had to be evacuated and others saw grocery and fuel supplies reach alarmingly low levels. Thank God that's over.

Or is it? The last time I looked, it wasn't quite mid-February. There is still plenty of time left for bad weather and worse luck. March in these parts is often characterized by monsoon-like precipitation, albeit in the form of snow.

March also is often characterized by windy weather, and the seemingly endless parade of low pressure systems that have come boiling out of the Pacific all winter to assail Alaska shows no signs of letting up. Weather service forecasters assure us that the stormy trend, under the less than benevolent influence of La Nina, will probably continue until summer.

Summer, unfortunately, may be a way off yet. The same National Weather Service forecasters assure us that La Nina episodes will be characterized by longer, colder, wetter winters. We could have another two months of the wretched weather that so recently released the peninsula from its clutches.

Even if the snow and winds don't return to dangerously load the slopes, the avalanche hazard remains high and, barring a miracle, will probably only get worse. Officials of the Chugach National Forest and others are warning the public about backcountry travel. The real avalanche season, it seems, is just beginning.

In most years, the spring that has yet to arrive, is the peak of avalanche season. As solar radiation increases, it corrodes snow pack stability and increases the danger of avalanches for backcountry travelers and even highway travelers.

According to "Snow Sense," a book about avalanches published by Jill Fredston and Doug Fesler of the Alaska Mountain Safety Center, prolonged warm spells can cause deep slab fractures in the snowpack precipitating massive slab-type avalanches down the mountain. Under the influences of rapid and prolonged warming after a long period of cold weather, slab fractures may be triggered by surface disturbances, such as a snowmachine, skier or a cornice falling from a high ridge.

Rain, such as the peninsula has experienced recently, also contributes to snowpack instability by adding weight, but no strength, to the upper layers of the snowpack, Fredston and Fesler warn. Intense solar radiation, especially with a thin layer of clouds bouncing reflected radiation back into the snow, may also trigger deep slab fractures.

While it is true that small avalanches kill more people worldwide on an annual basis, the big slab fracture slides are particularly destructive. In the spring, they tend to be heavy with water and ice.

In the spring of 1990, I was working on Atigun Pass when a big, wet heavy slab of snow and ice came ripping out of a gully, missed an Alyeska dump truck by a whisker before it tore through the guardrail. When it was all over, the slide had peeled out 200 yards of galvanized steel guard rail and stretched it out straight down the hill like a piece of string. That's power. That's what the insurance industry calls an act of God.

So, if you don't want to become an insurance industry statistic between now and June, don't travel the highways during storms and rapid warming or cooling trends, don't waste any time getting through steep country and keep your cell phone charged.

Snowmachiners, skiers and mushers would be well advised to carry functioning avalanche transceivers, probes and shovels. Snowma-chiners should refrain from high-marking on slopes above other winter recreationists. Better yet, leave the high-marking to those who think they are immortal. They might be mistaken.

Jon Holland is a reporter for the Peninsula Clarion.



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