Mount Washington Avalanche Center – How we generate our forecasts

Our days regularly begin at home in the pre-dawn hours, analyzing weather reports and forecasts. We’ll take this info with us to Pinkham Notch for a forecasters meeting at 6:30am. We’ll talk about the snowpack and weather forecast, and update each other if we’re coming back in after a couple days off, then head up the mountain as soon as we can.

Usually, we head into Huntington Ravine first. We’ll go as far as we safely can, in order to take a look at the gullies. We’re typically looking for evidence of avalanche activity, new wind-loaded snow, old wind-scoured snow, and anything else that will help steer us toward making an accurate assessment of the conditions. We also collect snow and weather information from a snow plot that we maintain with the caretakers at Harvard Cabin. We then take all of this information and post a forecast specific to Huntington Ravine at the Harvard Cabin.

The next stop is Tuckerman Ravine. Here we look for the same types of things we looked for in Huntington. We also maintain a snow study plot at Hermit Lake where we measure the snow depth, snow density, crystal types, temperature, etc. All of our snow and weather data is observed and recorded in accordance with the Snow Weather and Avalanche Observational Guidelines for Avalanche Programs in the United States (SWAG). Often, there is a difference between the snow and conditions reported at the summit and what is found at our snow plots. All of the information we’ve collected throughout the morning, along with recent field observations and a long history of forecasting in the Ravines, gives us a picture of how dangerous the snowpack might be.

After we post the advisories, we may hike or ski up into the ravines to get our hands into the snow. There’s no better data to collect than  firsthand observation. Unfortunately, unstable conditions or low visibility don’t allow us to do this every day. These observations are significant information for the forecast we’ll put out the following day.

Schedule of forecasts
Winter often arrives early in the mountains and we start issuing advisories or a general bulletin as soon as the snowpack has the potential to produce significant avalanches. Usually, the season will start with “Information” postings, then we usually issue a General Bulletin as snowfields begin to grow. Each General Bulletin is posted for no more than three days, after which a new one will be issued. General Bulletins are issued when instabilities are isolated throughout the entire forecast area. It’s important to realize that avalanche activity may occur within these locations before a 5-scale forecast is issued.

When the threat of instabilities exceeds isolated locations within the forecast area, we will move to issuing advisories using the 5-Scale Danger Rating System. You’ll notice on every 5-scale advisory there is an expiration date and time. This is to ensure that you know you are receiving the most accurate and up-to-date information we have. Each advisory will expire at midnight on the day it was posted.

Another tool for you is the “Weekend Update”, a blog post sometimes issued on Friday afternoons during the spring ski season. This is supplementary information designed to help people plan for their weekend. It’s important to note that the Weekend Update does not replace the posted Avalanche Advisory; it is a supplement to it containing the most recent information we have. Social media provides another format for sharing information and our Instagram, Facebook and Twitter feeds are a good way to add one more piece to your trip planning puzzle.

It is important to understand that our advisories are intended to be used as tools to help you make your own decisions in avalanche terrain. They should be used along with safe travel techniques, snow stability assessments, an understanding of weather’s effect on the snowpack, and proficiency in avalanche rescue should your assessments prove wrong. As the field of snow science grows and backcountry travellers continue to become educated in the basics of avalanche safety, we will try to stay current and provide the most accurate information that we can to help you make better decisions in the mountains.