Snake River Range

The avalanche danger will start at Moderate and rise to Considerable today with warming temperatures, clear skies, and strong solar radiation. Wet snow avalanches will become likely in steep, sunny terrain and could be large enough to bury you. Monitor thawing crusts and watch for slushy or wet snow surfaces that indicate unstable snow. Minimize time spent under large sunny slopes or looming cornices warming in the sun, and exit the mountains early. Avalanches could be unpredictable, break wider than expected, and entrain large amounts of snow.

An abnormally warm high-pressure system continues to impact our area. Record-breaking temperatures for March are possible over the next couple of days. 

Winds helped keep snow surfaces cooler yesterday and minimized avalanche activity. With less wind today, surfaces in the sun will warm quickly, and avalanche activity will likely pick up in the afternoon. Wet slab avalanches may or may not occur today. Wet slabs are unpredictable, but the likelihood increases during extended warm-ups. Several factors contribute to the uncertainty surrounding this problem.

• Overnight freeze - temperatures did not drop below freezing anywhere below 10,000 feet (with the exception of some valleys with mild inversions). However, clear skies overnight and radiative cooling of the snow surface have led to the formation of superficial crusts in many locations. Still, much of the underlying snow remains wet on southerly slopes below 9,000 feet. Take note of when the crust starts to break down, and you start sinking into slushy snow.
• Extent of today’s heating - high temperatures are forecast to reach 45°F at 10,000 feet and 50°F at 9,000 feet. Clear skies today will allow for rapid heating of snow surfaces starting on east aspects this morning. Surface crusts will thaw quickly. Timing is critical during spring diurnal temperature swings.  Start early and take advantage of travel on supportable crusts.
• Water in the snowpack (source of uncertainty) - this is related to overnight freezing AND the extent of daytime heating, but it is hard to quantify, let alone estimate, how much meltwater it will take to become a problem and trigger avalanche activity. Water will start to flow this afternoon on sunny slopes below 9,000 feet. Keep this in mind later in the day and remember that wet slabs are unpredictable.
• Interaction with water, a bed surface, and a weak layer - melt water in the snow will eventually weaken bonds between a bed surface and the overlying slab. The tipping point for larger wet slides usually occurs after at least two nights without a freeze, but there is some uncertainty and guesswork involved. 

Regardless of how these factors affect the snowpack, we know that the avalanche hazard will rise. Don’t try to outthink this problem. Give yourself a margin of safety and stack the odds in your favor as you plan the day.

• Get into and out of the mountains early to avoid peak daytime heating and avalanche activity. Avoid sunny avalanche terrain later in the day.
• Monitor snow surfaces for thawing crusts and wet snow. If you find slushy surfaces or step out of your skis and sink above your ankles, conditions are unstable. Rollerballs and pinwheels are early clues of instability and can indicate potential for larger wet problems.
• Avoid spending time under steep warming slopes and, when possible, move to shadier aspects
• Even though many low-elevation locations lack snow, be mindful of avalanche runout areas at low elevations with start zones in middle elevations.
• Avoid terrain traps with sunny slopes above.

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