Avalanche Danger Update
Issued Thursday, April 12 at 11am.
General spring to early summer avalanche advisory:
Avalanches can occur year round in Southcentral Alaska, and will occur in earnest over the next couple months as the mountains undergo their annual “shed cycle.”
Significant wet avalanche activity has occurred on east, south, and west aspects due to recent warm temperatures from the lower to upper elevations with only superficial (if any) nightly re-freeze in recent days. However, significant snow remains and (given that it’s only mid-April) there’s potential for a return to more wintry conditions and additional snowfall. Generally, northerly aspects have not yet started to “shed” with significant wet avalanche activity – but there has been some wet avalanche activity even on upper elevation northerly aspects due to recent, sustained warm temperatures.
Springtime avalanche conditions will vary over the coming coming weeks; checkout the resources below to better understand spring avalanche danger assessment and conditions that might be encountered the next couple months:
Melt-Freeze Cycles: clear and cold nights freezing the snowpack into a supportable crust that gradually softens through the day (ripe corn dependent on aspect and timing), and often becomes isothermal in the afternoon. Avalanche danger increases through the day and decreases at night with darkness, cooling, and re-freezing of wet snow.
Cold & Snowy: a cold spring storm brings wintry weather. Widespread surface instabilities from new snow. Widespread wet avalanche activity when the sun comes out and affects fresh snow.
All Freeze, No Melt: unseasonably cold temperatures freeze the snowpack into a supportable crust, with limited diurnal melting (softening). Avalanche danger is reduced until significant warming and melting recommences. However, “slide for life conditions” may exist as the snow surface is very firm and icy.
All Melt, No Freeze: generally above freezing temperatures day and night with widespread wet avalanche danger that exists at all times, but increases further with daytime warming.
Check weather resources to better understand what scenario is most likely to exist at a given time.
Keep in mind that natural avalanches triggered in the upper elevations can affect lower elevation terrain (that might even be flat and snow-free). Many trails in Chugach State Park cross potentially dangerous avalanche paths.
Here are some important considerations when making plans to recreate this spring and early summer:
- Does your route cross avalanche terrain? Don’t forget to consider run-out zones (that might be even be flat and snow-free), from gullies and upper elevation slopes, especially if they could channel long-running avalanches that release in the upper elevations.
- Be on the lookout for recent (and perhaps even active) avalanche activity; this is an obvious warning to stay away from avalanche terrain and run-out zones (a.k.a. avalanche paths).
- Pay attention to the sun! The sun can heat up steep, solar aspects significantly. This can change conditions from generally safe to generally dangerous very rapidly.
- Be mindful of terrain traps that could make even a small avalanche’s debris pile up deeply enough to bury a person, cause a dangerous fall or loss of control, or cause traumatic injury. Learn from this report of a local high school teacher that died from a relatively small wet avalanche on Bird Ridge.
- The 2017-18 Chugach State Park snowpack is rife with persistent weak layers, especially a widespread basal layer of advanced facets and depth hoar. Recent natural wet slab avalanches have been observed across the park, in many cases triggered by small (and seemingly insignificant) wet loose avalanches or point releases. Persistent weak layers may continue to produce large slab avalanches throughout “shed season.”
- If you’re traveling on snow, especially in avalanche terrain (i.e. terrain steeper than 30 degrees, or in the run-out/path of terrain steeper than 30 degrees), how wet is the snow? If there’s a supportable crust from recent freezing, avalanche danger will be lower (but keep in mind that steep, solar aspects above may be significantly wetter and more dangerous). If the snowpack is soft and mushy, especially if it’s unsupportable and you’re punching through or “postholing” due to isothermal snow, steep terrain and the runout of steep terrain will be dangerous.
- Rockfall is especially rampant in the spring and early summer!
Many avalanche accidents that have happened in Anchorage’s backyard of Chugach State Park could have been prevented by basic avalanche awareness. This level of awareness can be gained through a free or low-cost class. If you missed the many offerings earlier this season, make sure you take advantage of the numerous free and low-cost courses that will be offered in the fall. You can start learning with some free online resources here. Getting avalanche education is a big part of recreating safely on your vast and wondrous public land in Alaska, and being able to enjoy the mountains during the snow season will greatly enhance your life.
Here are links to further information on fatal avalanche accidents in Chugach State Park. You can learn from others’ mistakes.
We are nearing the end of the Anchorage Avalanche Center’s sixth season of providing a grassroots snow-season backcountry snow safety program for Chugach State Park.
If you think the backcountry snow community and Chugach State Park deserves more than just a public observations platform, please consider getting involved with (or donating to) the Anchorage Avalanche Center effort. Please consider soliciting support for the Anchorage Avalanche Center from your government representatives (Municipality of Anchorage and state level), the Department of Natural Resources (Alaska State Parks and Chugach State Park), and local businesses and organizations relevant to snow-season backcountry recreation. Your help is appreciated, and imperative for the development of a sustainable avalanche information program for Chugach State Park.
*click avalanche problem icons and hyperlinks for further info