Although we are transitioning to a period of stability, there remains the wild card at the low and mid elevations (up to about 9000') with a persistent weak layer that is now buried 2-3' down. This is found on almost all aspects, and includes both buried surface hoar and near-surface facets. These weaknesses showed their cards this week producing several dangerous, human-triggered avalanches. On Wednesday, an experienced party triggered an avalanche on Mt. Aire that ran on a preserved layer of surface hoar on a northwest aspect just below 8000'. (You can read the report here.)

Yesterday, I visited the site on an intentionally-triggered avalanche from this past Tuesday on a steep southwest aspect at 7800' in Big Cottonwood Canyon. This avalanche ran on a layer of faceted snow sitting just above a crust. I found the snowpack in this area still very sensitive (observation). The photo below has arrows pointing to the small-grained faceted snow sitting just above a melt/freeze crust:

Although the concerns of these persistent weak layers are localized, triggering an avalanche that fails on one of these layers could produce a sizeable avalanche. Avalanches involving persistent weak layers can be triggered remotely (from a distance), as well as from lower-angled terrain. If you do travel in avalanche terrain at the low and mid elevations, you have to dig down with your shovel and determine if this weak layer is present, and assess the strength of the snowpack. I am especially concerned for buried surface hoar on sheltered northerly aspects at the low and mid elevations, and would avoid any slope steeper than 30 degrees if I found buried surface hoar present.

Mark White provides an excellent observation describing how he evaluated the snowpack in the Meadow Chutes on Thursday. Notice how he describes first digging down looking for surface hoar or faceted snow, and proceeding to steeper lines only after he determined the lack of weak layers and the strength of the snowpack through careful evaluation.

There are three other avalanche concerns to watch for today:

- Loose dry snow. The past few days featured several inches of classic Wasatch 3-4% fluff. This weak snow will sluff easily on steeper aspects, and will run long distances, possibly entraining large amounts of snow.

- Loose wet snow. The sun will appear for the first time in over a week, and the loose, dry snow will be reactive to any warming from the sun. Cool temperatures and light to moderate northerly winds should keep a lid on widespread wet activity, but watch for loose wet snow as the snow surface begins to warm.

- Fresh wind drifts. Winds should be light at the low and mid elevations, but may gust into the 30's mph in the upper elevations. There is an abundance of loose snow available for transport, and any bump in wind speeds will create sensitive wind drifts along upper elevation ridges. Winds are also forecasted to have a northeast component, and any time I see "east" in forecasted winds, my guard goes up for possible unusual wind loading events.

Don't let the bluebird skies and 5-star ski conditions cloud good judgement: evaluate slopes before jumping in, and watch for others below you. Ski slopes one at a time, and get out of the runout zone at the bottom of a run.