Avalanche Forecasts, Zone by Zone

From the avalanche centre that covers the ground you are going to, and this page lists every one of them. There are 31 organisations in the national registry, 29 of them publishing forecast zones, across 13 states and 83 zones on the day of the structural snapshot. The panel at the top of this page reads their current ratings live and prints each one in the centre’s own words with its date. Every row links to the centre’s full forecast, which is the thing to plan on.

The forecast centre that covers each zone. Every rating here is the one that centre published, passed through untouched with the centre’s name, the product’s validity window and a link to the full forecast. There is one danger scale in North America, and the forecasters at each centre are the people qualified to apply it to their ground on the day.

The North American Public Avalanche Danger Scale is an ordinal five-level scale: 1 Low, 2 Moderate, 3 Considerable, 4 High, 5 Extreme, each with an official colour. It was published by Statham and colleagues in 2010, updated in 2022, and is maintained by a working group of United States and Canadian organisations rather than by any one agency. This site shows the level number, the level name and the official colour; the scale’s definitions and travel guidance are published by the National Avalanche Center and by every forecast centre, beside the forecast that applies them.

The USDA Forest Service puts it plainly: "Each winter, 25-30 people are killed by avalanches in the United States." The Colorado Avalanche Information Center’s national accident archive, which is the central record, holds 1255 deaths from 1950-51 to 2024-25 across 1016 accidents. In the last ten seasons, 2015-16 to 2024-25, there were 237, an average of 23.7 a season. The worst recent month is Feb with 74, and Feb, Jan, Mar together account for 74 percent of the total.

13 states had at least one forecast zone filed under them on the snapshot date: Alaska, Arizona, California, Colorado, Idaho, Montana, New Hampshire, New Mexico, New York, Oregon, Utah, Washington, Wyoming. That is a list of where zones are filed, not a map of where avalanches happen. Zones cross state lines, and Nevada is the case that proves it: no zone is filed under Nevada, yet the Sierra Avalanche Center’s National Weather Service zones cover Greater Lake Tahoe on both sides of the state line, and the accident archive records 15 avalanche deaths in Nevada.

It matters for what you can expect of them and for what this site is allowed to reproduce. Of the 31 organisations in the registry, 13 are USDA Forest Service programmes, 2 are state agency programmes, and 16 are nonprofits or observation exchanges. The Forest Service itself notes that "FS avalanche forecasts and education are used by millions of people each winter and have directly reduced the US avalanche fatality rate. More than half of the total funding comes from non-federal sources." That is why almost every federal centre has a "Friends of" nonprofit beside it. Two of the 31 are observation exchanges rather than forecast programmes and issue no danger rating; they are marked as exchanges wherever they appear here.

People travelling in the backcountry under their own power, mostly, with snowmobilers close behind. In the last ten seasons of the accident archive the largest group is "Backcountry Tourer" with 87 deaths, and the next four are Snowmobiler 73, Sidecountry Rider 19, Climber 13, Resident 10. The Forest Service frames the underlying point better than any statistic: "Avalanches are the only natural hazard humans can cause while moving through the landscape." Almost every fatal avalanche in the record was triggered by the person it killed or by somebody in their party.

Because most centres forecast for a defined winter season and publish nothing outside it. On the day this site’s structural snapshot was taken, in early September, every zone in the country read "no rating". That is the normal state of the system for a good part of the year. No rating means nobody has assessed the zone, not that it has been assessed and found quiet.

Yes, three of them, and they are different from a centre’s daily forecast. Avalanche Warning, Avalanche Watch and Avalanche Advisory are all live event types in the api.weather.gov alerts feed, issued by NWS forecast offices, usually in coordination with the avalanche centre. The NWS glossary describes the warning as: "Issued by the National Weather Service when avalanches are imminent or occurring in the mountains. It is usually issued for a 24 hour period." This site reads that feed live for each state and reproduces any active product word for word, because it is a US Government work in the public domain.

Live danger ratings and the centre registry come from api.avalanche.org, run by the USDA Forest Service National Avalanche Center with the American Avalanche Association. Live watches and warnings come from api.weather.gov. The accident archive comes from the Colorado Avalanche Information Center, which describes itself this way: "The CAIC is the central archive for avalanche accidents in the United States and maintains detailed records going back to 1950, and sparse records back to the 1860s." The CAIC asks to be cited as "Please cite the CAIC 2024 for all use", and it is, here and on every page that uses a number from it.