Fresh snow, wind and higher temperatures created extremely dangerous avalanche conditions at and above treeline in the upper Turnagain Arm region and Turnagain Pass on Friday and through the weekend, officials said.
The Chugach National Forest Avalanche Information Center advised people against traveling on slopes above 1,000 feet and steeper than 30 degrees, and in all runout zones.
Avalanche danger will remain high through Sunday as a strong storm moves through the area, said Heather Thamm, avalanche specialist with the center.
The center advised that "if anyone does go into the backcountry, that they avoid all avalanche terrain," Thamm said.
"We've had already 2 feet of snow yesterday and we're expecting another 2 to 3 feet of snow through the weekend," Thamm said.
The new snow is sitting on top of weak layers of snow, creating unstable slabs that are expected to be easy to trigger, the center said.
Strong winds, with gust up to 80 and 100 miles per hour, and a possibility of freezing rain at 1,500 feet were also forecast, Thamm said.
Below 2,000 feet, the layers are on a slick crust "and could catch you by surprise in more protected areas," the center said.
Both natural and human-triggered slabs, 1 to 3 feet deep, were likely Friday.
Over the weekend, natural avalanches were likely, and human-triggered avalanches were very likely, Thamm said.
An official avalanche warning through the National Weather Service will go out at 6 a.m. Saturday, Thamm said.
On Thursday, easterly ridgetops saw winds averaging around 30 mph and gusting to 60 mph. Temperatures increased overnight to above freezing at sea level, the center said.
Stormy weather will cause slabs to grow in size, and avalanche danger will increase through Friday, according to the center.
Below 1,000 feet, avalanche danger was considerable "where natural avalanches from above are possible in steep channeled terrain," the center said.
Areas near Portage and Whittier may be even more dangerous, as twice the amount of precipitation is expected. "Avalanche activity in these zones may run to valley bottoms," the center said.
On Saturday, the Alaska Avalanche School is hosting a free Hatcher Pass avalanche workshop at the Gold Mint Trailhead parking lot. From 11 a.m. to 1:30 p.m., avalanche professionals and experienced snowmachiners will teach participants how to perform an avalanche rescue and identify when the snowpack is unstable.