October 8th, 2009
Fall and Early Winter Avalanche Safety
The CAIC has already begun to monitor the 2009-10 snowpack. The first avalanche incident of the new season was reported from Mt Meeker in Rocky Mountain National Park on October 5th. The small slab broke loose about 6 inches deep and 40 feet across and took two climbers on a short ride, with no injuries. The slide ran on the lower, or first pitch, of the Dream Weaver alpine climb. This route is located on the east side of the prominent north aspect buttress of 13,911 foot Mt Meeker. The first pitch ramps up to 50 degrees in some places. This route can see significant cross-loading deposit any fresh snow as slab at several areas along the route, though primarily at the first and last pitches.
Across many areas of the state over a foot of new snow has fallen near and above treeline. Strong winds have already started to move this new snow into sheltered lee pockets. Temperatures have dropped into the teens at night meaning the shallow snow cover is faceting and forming future weak layers. We'll begin our daily backcountry products Friday November 20th. If conditions warrant we will start earlier. We will update this product as needed after November 1, but until daily public forecasts begin, here are a few things to think about as the winter snowpack develops.
- Fall and a taste of winter have returned to Colorado’s high country. Snow began to stick on the higher terrain by mid-September. Every season people have encounters with wintertime slab avalanches as early as August or September. Anyone traveling in the mountains, including hikers, hunters, sledders, skiers, riders and ice climbers, needs to be aware of the avalanche threat as soon as snow starts to accumulate on steep slopes.
- People are often misled when they see grass and brush sticking out of the snow surface. You should start thinking about avalanches any time you have snow resting on a steep slope. Remember, all you need is a slab resting on a weak layer of snow. The ground can easily act as a bed surface, even if it’s only a few inches below the snow surface.
- Old summer snow fields can act as the perfect bed surface too. Hard frozen old snow with new snow on top are common culprits in early season avalanche incidents.
- Early in the snow season there is not much snow on the ground. This means that rocks and stumps are near the snow surface. If you get caught in an avalanche you might get tumbled through rocks, stumps, and downed timber. These obstacles can do great bodily harm to backcountry users traveling through them at high speeds. Knee pads, helmets and full body armor may not be a solution to this problem. Even a very small slide can cause great harm if the terrain is unfriendly.Don't let an early-season injury ruin your winter!
- Wind drifts will create thicker slabs. Strong winds can take a three inch snowstorm and quickly build an 18” wind slab. Areas with shallow snow may be very close to deep drifted areas. It may be to move from a very safe area to a very dangerous area without traveling very far. The wind drifts will be denser than the new snow and thick hard snow on light fluffy snow is a great setup for avalanching.
- Once the sun returns after a storm cycle and warm temperatures cause the new snow to melt, look to see where the pockets of snow remain. The snow that lingers in sheltered areas and shady slopes could be the weak layer after the next snowfall. These areas could also become recurring problem areas throughout the winter depending on how the winter snowpack develops.
- Pockets of instability can develop quickly above early season ice climbs. Climbers should know the terrain above their route as rapid warming or heavy wind loading can quickly work to build slab or loose snow avalanches which can nudge a precariously perched climber into a bad fall.
- Hunters traveling across the high country need to exercise greater caution on steep terrain (steeper than 30 degrees with accumulated snow) when crossing ridges from one valley to another.
For more info on Avalanche Safety and to Find Resources on Avalanche Information visit Colorado Avalanche Info Center
About the CAIC
The CAIC is a cash-funded program of the Colorado Geological Survey under the directorship of the State Geologist Vince Matthews. Funding comes from donations, contributions, and the Severance Tax fund. If you would like to help support the CAIC, please visit our Supporters of the CAIC page.
The CAIC has 4 offices that issue backcountry avalanche forecasts. The main office is in Boulder, co-located with the National Weather Service. Field offices are located in Breckenridge, Aspen, and the Northern San Juan. Staff at CAIC-Boulder forecast the weather and avalanche conditions for all zones. Field office forecasters concentrate on the snowpack and avalanche conditions within their zones. The CAIC works closely with the Crested Butte Avalanche Center.