Understanding the avalanche advisory
By Scotty Savage Explorebigsky.com Avalanche Expert
“For today, it’s still possible to trigger an avalanche and the danger is rated MODERATE.”
– Gallatin National Forest Avalanche Center advisory, Valentine’s Day 2012
When you’re peering over the tips of your skis getting ready to drop into your favorite powder shot or idling your sled in the flats looking up at the pristine bowl you’re about to highmark, you’ve already made your avalanche hazard evaluation. You probably started by checking out the GNFAC website (mtavalanche.com) at home and read that the avalanche danger was rated MODERATE for the day. But what does that mean? And how do they come up with those danger ratings? Is the danger rating all you need to know, or just a piece of the puzzle?
The avalanche danger rating is a snapshot of the avalanche hazard for a given area, usually a mountain range or specific part of a range. Snow stability tends to vary considerably from slope to slope. So, while the danger for a mountain range may be MODERATE, some individual slopes will be very stable and a few others may be highly unstable.
Simply checking the danger rating before you head out to play and assuming that all slopes will behave similarly is a common mistake. The avalanche danger rating is a great starting point, but you must determine the hazard on the specific slope you choose to ride.
Avalanche centers and forecasters act as information clearinghouses, collecting weather, snowpack, and avalanche data to produce a danger rating each day. The one-word description of the avalanche hazard (LOW, MODERATE, HIGH…) gets you thinking about the expected avalanche conditions, but it’s just scratching the surface as far as the information that the advisory provides. Here are some other things included in the advisories:
• A great local mountain weather forecast. These guys usually blow away the TV weathermen and the National Weather Service forecasters because avalanche forecasters are focused on predicting the weather in the mountains, where the goods are, instead of in town.
• Bullseye data. Recent avalanche activity, collapsing and cracking in the snowpack, and whoomphing noises are red flags in the avalanche world and make stability evaluation simple—this is bullseye data. Look at the pictures and videos of recent avalanche activity.
A picture of an avalanche can be worth more than 1,000 words, especially if it’s next to a slope you planned on riding. Read the narratives and stories in the advisory that detail firsthand accounts from recent visits to specific areas—more great info that you don’t need an Avalanche PhD to interpret.
• Pearls of wisdom. The narrative style of GNFAC advisories allows the forecasters to introduce snow science and stability evaluation concepts. Take advantage of these free mini-avalanche classes. While it’s not the same as experiencing things in the field, taking 10 minutes to read and thoroughly understand the advisory every day is a great introduction to avalanche education.
Winters like this one—calling it winter seems like a stretch—challenge sledders, boarders, skiers and avalanche forecasters alike. Many slopes are stable and lull us into a false sense of security, but the facets and other persistent weak layers buried deep in the snowpack occasionally rear their ugly heads, causing MODERATE danger to linger…and linger.
Remember that advisories are merely advice. You and your partners should use them as a valuable piece of the avalanche puzzle, but only you can decide exactly when and where to play in the mountains.
Scotty Savage has spent thousands of days in the field evaluating avalanche conditions while at work and at play. Currently a Friends of the GNFAC avalanche educator, he plans on spending less time with knee surgeons and more time on skis in the coming months.