Going-to-the-Sun Road Avalanche Forecasting Program

The Going-to-the-Sun Road (GTTSR) is one of the premier attractions in Glacier National Park (GNP), Montana. It opened in 1933 after 12 years of construction and is one of GNP’s most heavily used facilities. The two-lane, 80-kilometer road traverses the park from west to east, crossing the Continental Divide at Logan Pass at 2026m elevation. The Park closes a 56km section of the road each winter due to inclement weather, heavy snowfall, and avalanche hazards. Snow removal to re-open the GTTSR starts in April, with the mean road opening on June 9.

In 2002, GNP instituted its first formal avalanche hazard forecasting program for snow removal operations. For the 2003 season, GNP established a daily forecasting program with two full-time avalanche specialists. During the season, which typically runs from April through June, equipment operators removing snow from the upper 23km segment of the GTTSR are exposed to a variety of avalanche hazards, including loose snow avalanches, wet and dry slab avalanches, and glide avalanches. In this road section, the GTTSR lies mid-track in numerous large avalanche paths capable of destructive class 4 slides.

The avalanche paths threatening the GTTSR are predominantly sunny, windward slopes (Figure 3). The paths east of the divide face east through south; those west of the divide face southwest through west. The exceptions are in the bowl-shaped start zones of the larger west-side paths, such as Haystack Creek, Big Bend, and Triple Arches. Parts of these bowls also face west-northwest through northwest. Some west side paths are also shaded each morning by the narrow spine of the Continental Divide known as The Garden Wall, which rises 75-275m above the start zones.

This orientation towards the sun is a significant factor in springtime avalanche conditions. The start zones are subject to direct solar radiation much of the day and temperature swings can be dramatic. The site’s mid-hemisphere latitude (48o 40’ N) and the time of year magnify insolation. Although the latitude means short days and weak insolation in the winter, it makes for longer periods of ever-more intense insolation – and shorter periods of freeze – as the season progresses.

In addition to forecasting, the program also provides real-time snow safety. During the workday, the equipment operators are in avalanche tracks where stability assessment is difficult at best, and it is of utmost importance that they remain focused on the mentally-demanding task of keeping their equipment on the narrow roadbed. Our mobility affords us access to avalanche starting zones above the work area, where we can effectively monitor changing snow conditions during the day. This monitoring provides an additional margin of safety to the crew during periods of rapidly decreasing stability, or it allows them to work longer when the hazard is not increasing as expected.

The avalanche program has increased avalanche awareness among equipment operators through regular avalanche safety training. Although the plowing crew does not need to understand the intricacies of snow stability evaluation, a working knowledge of avalanche terminology and mechanics provides them with tools to make independent decisions when necessary and establishes a common language for sharing information. Further, in the event of an avalanche incident the equipment operators will likely be the first responders, so hands-on rescue training with avalanche beacons, shovels, and probes is imperative and is provided annually.

Excerpted from: Reardon, Blase and Lundy, Chris. 2004. Forecasting for natural avalanches during spring opening of the Going-to-the-Sun Road, Glacier National Park, USA. Proceedings of the International Snow Science Workshop. Jackson, Wyoming. September 19-24, 2004.

For more information contact Erich Peitzsch: epeitzsch@usgs.gov

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Going-to-the-Sun Road Avalanche Forecasting Program

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