Snowpack List: Avalanche assessments from around the U.S.: Week of January 15

The avalanche forecast for this week presents a small reprieve from last week’s alarming ratings. But even though conditions might not be extreme, dangers still lurk in the snowpack across the Western U.S. While some zones in the Rockies and Wasatch Mountains are experiencing the tail end of an avalanche hangover, the Pacific Northwest is once again ramping up with new snowfall followed by warming trends. Here is the avy report for this week.

Crested Butte Avalanche Center (CBAC)/Colorado Avalanche Information Center (CAIC)

In Colorado, the avalanche danger has generally been downgraded to moderate across the regions under the purview of the CAIC. Weak layers formed by buried facets one- to three-feet deep are the main cause for avalanche concern. The CAIC warns that the problem these facets pose is variable based on aspect and elevation, and they suggest digging pits on any new slope you may explore in the backcountry.

“These weak layers will vary with slope, aspect and elevation, so make sure you dig on every slope before you ride today,” the CAIC explained on their website on Tuesday, January 17. “As temperatures warm, the weak layers in the upper snowpack will gain strength and become less reactive in snowpack tests. If you can still trigger these weak layers in snowpack tests, you should be a bit wary of the slope.”

The forecast for Colorado brings more clear weather, so the CAIC cautions skiers and riders to keep an eye out for new surface facets forming in the days to come.

In the Crested Butte and Gunnison region, storm slabs that formed after last week’s monster snowfall are also threat. Slab thickness varies, and while it is unlikely that the weight of a human body will trigger a slide in an area of thick slab, triggering a slide where the slab is thin, near rocks and other invisible features, is possible and may propagate over a large area.

“Where these slabs are five or more feet thick, you’re unlikely to trigger an avalanche (your body weight just can’t affect the weak layers),” the CAIC continues. “However, especially in windier areas, slab thickness varies widely. There may be hidden rocks or thin spots that you can’t see. Wind-drifted slabs will also thin as you descend a slope. As there is no reliable way to ensure that you won’t hit a thinner spot, trying to use thick slabs to avoid triggering an avalanche is a dangerous game.”

To find out more about Colorado avalanche conditions, visit avalanche.state.co.us, and cbavalanchecenter.org. (Note: Since writing this, some areas have been downgraded to a low danger rating.)

Northwest Avalanche Center (NWAC)

Unlike the Rockies and Wasatch, the area of Northern Oregon and Washington is rated as having high avalanche danger as of Tuesday, January 17. Warming two weeks ago was followed by multiple storms bringing in more than 10 inches each. This new snow now sits on top of a crust layer, and with a bout of sun, wet slides are being observed throughout the area under the purview of the NWAC.

“Very wet and milder weather should substantially increase the avalanche danger late Tuesday or Tuesday night,” the NWAC reports on their website. “Natural wet snow avalanches are increasingly likely later Tuesday.”

To find out more about conditions in the Pacific Northwest, visit www.nwac.us.

Utah Avalanche Center (UAC)

Around Salt Lake, the avy conditions have taken a definitive turn for the better, with the Provo, Skyline and Salt Lake regions listed as having low avalanche danger. The northern regions are moderate currently, a welcome change from last week’s extreme conditions in that area. A round of natural avalanches in the last seven days was the primary avalanche concern after heavy snowfall last week. This week, moderate danger is limited primarily to near and above treeline where persistent slab and cornice fall avalanches are possible.

In a video from three days ago, Toby Weed from the UAC explains last week’s conditions and what to look for moving forward.

 

Toby Weed of the UAC describes why we had big avalanches and dangerous conditions when the snowpack has been generally strong and deep. It’s simple: too much snow too fast. Everything has a breaking point. In the mountains near Logan, recent storms delivered up to 10 inches of snow water equivalent which is a massive load. At times this snow came with 100 mph winds which loaded slopes even more. Now, the danger for dry snow avalanches is dropping fast.

A video posted by Utah Avalanche Center (@utavy) on Jan 14, 2017 at 3:11pm PST

To find out more about conditions in Utah, visit utahavalanchecenter.org.

Gallatin National Forest Avalanche Center (GNFAC)

Generally speaking, two layers of facets in the snowpack are responsible for the rating of moderate as of Tuesday in the GNFAC area. One layer is located at the ground and one formed around 10 days ago due to a period of cold weather. The ground instability makes steep slopes especially dangerous, and thin snowpack near rock features also poses a heightened threat.

Another concern in Montana includes windslab, and the GNFAC warns that loading has been occurring in unusual places.

“The Bridger Range has strong ridgetop and mid-mountain winds,” reports the GNFAC. “The mid-mountain winds (S) are worrisome because they are loading gullies and slopes in unusual places. There’s not much snow left to transport, but even a thin windslab can break and push you off a cliff. Weak, faceted snow is found on most slopes and with the added burden of a wind drift, avalanches are still possible.”

To find out more about conditions in Montana, visit www.mtavalanche.com.

Bridger Teton National Forest Avalanche Center (BTAC)

While deep slab avalanches remain a threat in the Bridger/Teton area, conditions have improved, and danger is generally rated as moderate for all elevations. A weak layer toward the base of the snowpack poses the primary danger on northerly aspects.

“The chance persists for backcountry travelers to trigger large, destructive deep slab avalanches that could involve the full depth of the snowpack,” the BTAC explains on their website. “The weak snow associated with this problem is deeply buried near the base of the snowpack on northwest through northeast aspects above 9000 feet. These deep slab avalanches are likely to be unsurvivable.”

Their recommendation is to stay away from steep slopes on that aspect and out of start zones. Surface slabs also pose a threat and the possibility for human-triggered avalanches remains due to this instability.

“Surface slabs could be human triggered in steep terrain features that have not already slide,” the BTAC continues. “Deep, large slab avalanches continue to be a hazard in steep north facing terrain at the upper elevations. Evaluate snow and terrain carefully and identify features of concern.”

To find out more about conditions in Wyoming, visit www.jhavalanche.org.

Sierra Avalanche Center (SAC)

For the Sierra, a period of low avalanche danger has graced the region, but the Sierra Avalanche Center cautions that spots of instability may be present, especially if windslab exists, primarily near or above treeline. They recommend following usual backcountry safety protocol to stay safe.

“Apply normal caution for backcountry travel in avalanche terrain,” encourages the SAC. “Communicate with travel partners and identify possible areas of concern. Expose one person at a time on or below steep slopes. Avoid regrouping below steep slopes or in avalanche run out zones.”

To find out more about conditions in California, visit sierraavalanchecenter.org.

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As the winter progresses, it’s important to keep an eye on snowpack trends and instabilities. This is not a complete guide to avalanche forecasts, so stay informed and educated by visiting local avalanche forecasting websites and get educated about avalanche safety through programs like Know Before You Go, the Mountain Academy hosted by Solomon and Atomic and through courses offered by the American Institute for Avalanche Research and Education (AIARE) offered nationwide.