Aspect: All aspects and elevations

Bottom Line: Very heavy snowfall rates are expected today, with accumulations approaching 24″ by tonight. NW winds will be whipping around the new snow, and temperatures will be warming up drastically. All the red flags are present for a large natural avalanche cycle over the next day or two.

Travel Advice: Avoid all avalanche terrain! If you head out, stick to the trees and watch out for terrain traps where even small slides could pile up to be quite deep. Stay out of avalanche runout zones along valley bottoms. 

Avalanches will be likely within the new snow, and failing on the new/old snow interface. Wind loaded areas could accumulate enough critical loading to trigger deep persistent weak layers, which could cause wide propagation and very large avalanches that run full-path.

Aspect: Mainly on wind-protected and wind loaded slopes, most likely beneath terrain features on S, SE, and E aspects

Elevation: All elevations, mainly at and above treeline.

Travel advice: Consider any possible slopes harboring buried surface hoar, or other weak snow as guilty until proven innocent. Always use safe travel techniques such as only exposing one person at a time both on the way up and down. Identify and avoid thin areas where weak layers are more likely to trigger a slide from. Group up in safe zones that are out of harms way. Have good communication, including radios and a set plan in case of an emergency. Be practiced at companion rescue..

• Surface hoar from Dec 18th may have been preserved in wind-protected areas. It is now buried by about a foot of snow.
• Recent observations from Old Faithful found a thin crust with weak snow down 60-70cm near 3,200′ and below
• This bathtub ring effect, from lower-elevations to mid-elevation, where freezing levels are more likely to cause crusts and weak layers – should be carefully evaluated.
• Weaker snow (buried facets) forming between wind slabs in the top of the pack

It is still possible that any surface avalanches could step down to deeper weak layers, the October rain crust, or even the ground in alpine areas. 

Buried surface hoar layer (thin grey line) in an opening below treeline in the Transitional zone. This layer is now about 1-3ft deep. It exists in isolated wind protected areas.