Backpacker Magazine – February 2008

How to Avoid Sudden Thaws

Warming temps can wreak havoc on snow-packed adventures. Learn the conditions and warning signs that can cause a dangerous, sudden thaw.

by: Elisabeth Kwak-Hefferan

Subzero cold might be uncomfortable, but at least it ensures stable snow and ice conditions. Rapid warm-ups generate a new set of backcountry perils, like avalanches, thin ice, and rock fall. Follow these tips to avoid the hazards caused by seesawing mercury.

• Review the weather It may be 22°F today, but did the thermometer jump to 40°F earlier in the week? Knowing recent highs and lows can help forecast potential risks.
• Inspect beneath Warm spells can melt snow and ice from the bottom up, leaving a fragile shell over a rotten void. Tread carefully near thawing streams and large boulders (which absorb solar heat); probe the surface with trekking poles as you go.
• Look up Thaws expose bare rock and dislodge stones and icicles, making falling objects a serious menace. Avoid traveling under cliffs, especially when the slope above receives direct sunlight.
• Start early Colder night air can re-freeze mushy snow into a solid surface, making mornings the best time to travel without post-holing up to your knees.