A winter storm warning has been issued for northern Arizona from Sunday morning at 5am until Monday morning. Heavy snowfall will add stress to the snowpack and winds are expected out of the south and southwest. High accumulation may result in small avalanches on wind and rain crust that have developed in the last 24 hours. Wind loaded areas, such as the tops of gullies, ridges and cross loaded features will be particularly prone to slides.
Rapid snowfall will ring in the new year. Temperatures look to be decreasing throughout the storm, creating a right side up storm and lowering the probability of density issues within the new snow. The old snow / new snow interface will be the primary layer of concern as snow accumulates.
Large basal facets have developed at the base of the snowpack particularly on NW to E aspects. Near and above treeline this weakness is limited to isolated pockets concentrated in gullies and chutes. Additional snow will add stress to this layer, and may result in small to large slides. Be alert for obvious signs of instabiilty related to this condition such as whumpfing and collapsing.
Between 14" and 22" of snow is forecast for Saturday evening into Sunday at 10,000'. Much of this new snow will likely be transported by moderate and high winds. Numerous ridgelines are already crossloaded and this storm will add snow to existing wind loaded areas. Use caution in these areas.
Snowslide canyon 12/31/22
