Recent persistent slab avalanches have been triggered on a layer of buried surface hoar or on a layer of small, faceted crystals buried 2-4 feet deep. This layer is widespread in the Ogden area mountains though there are some places where it was destroyed prior to the storm. The buried surface hoar is most dangerous where it was sheltered from the wind and buried intact. It might catch you off guard as you descend into sheltered, lower and possibly some mid-elevation slopes or gullies. Though observers near Ben Lomond noted its presence yesterday and were unable to get propagation while performing stabiity tests, this type of weak layer is deceptive and takes a while to strengthen.

Because this weak layer can be coy, your best bet for finding it is to dig about 4 feet deep, perform stabilty tests like the ECT, and make sure it doesn't exist. Buried surface hoar does not behave like a typical weak layer so a lack of cracking, collapsing, or other obvious signs of instability does not mean slopes are stable. Tracks from other people are also not a guarantee of stability. If you are not interested in digging then the easy solution is to avoid being on, connected to, or underneath slopes steeper than 30 degrees.

Left: Observed buried surface hoar near Rodeo Ridge was unreactive to stability tests yesterday. (pc:M. Henderson)

Right: One of numerous avalanches failing on buried surface hoar or small facets on Monday in the Cutler Ridge area. (pc: B. Brandt)

Though we are observing an increase in overall stability, we are also in the phase where human triggered avalanches are still very possible. The snowpack is continuing to adjust to the massive amount of snow received in the last week. The storm snow is settling and gaining strength but there are many places it has not completely stabilized. Watch for signs of instability like cracking and collapsing. Check out Brian Smith's test slope video from yesterday displaying sensitivity in the new snow at low elevations.

It might also be possible to trigger loose snow sluffs in steep terrain at all elevations. These can run far and entrain deeper snow as they descend. Inventory consequences when choosing terrain.

Cornices that built up during the storm are also suspect and should be avoided. Winds are blowing a little stronger on the ridge tops and, with lots of new snow to transport, wind slabs could build during the day. Avoid areas of freshly wind drifted snow on steep slopes.

With mostly sunny skies forecast today, you might need to keep an eye out for wet activity, specifically on southerly facing slopes. Avoid steep slopes when the snow starts to feel moist from direct sun exposure though forecast cold temperatures and the building inversion should keep warming mostly in check.