Wind Slabs that formed during an unusually late season Atmospheric River storm between April 6th and 8th were reactive in some areas through Monday when natural avalanches were observed in Lundy canyon. In the Mammoth area, wind deposits from that storm were healing and were more stubborn to trigger by early in the week. But while sunny skies and warm temperatures prevailed through Wednesday night, moderate west winds still had snow to blow around on alpine ridge tops where wind slabs where most likely continuing to grow.
Meanwhile, at elevations below about 11,000’ in the southern forecast area, and below about 9,500’ in the northern zone, warm temperatures and the intense spring sun warmed up last weekend’s storm snow. Loose wet avalanches ran on many slopes up and down the east side through Wednesday when large roller balls and point releases were observed in the southern Sierra and between Rock Creek and Convict Lake.
Today will feel like spring again after a short burst of wind and light precipitation rushed through the northern area on Thursday. Winds from this quick hitter were intense at times and snowfall amounts were just enough to build large wind slabs on leeward slopes. It’s this kind of rapid loading that creates wind slabs sensitive enough for you to trigger. In areas where the most snow accumulated, north of Crowley Lake and just under ridge lines, convexities, and the side walls of gullies, you will most likely find hollow-sounding wind slabs today. Recently formed cornices and round, pillow shaped wind slabs point to where the danger has increased. Use these observations to make conservative terrain choices that keep you out of harms way. Remember that sunny weather doesn't mean no danger.
As temperatures rebound today, with highs in the upper 40s, loose wet avalanches will be another concern on solar aspects. As the sun heats the snowpack to its melting point it will become less stable. Extra heat from cliffs, rock faces, and trees can result in additional localized thawing. Large roller balls originating from exposed rocks and trees can be a good indicator that loose wet avalanches are becoming increasingly likely. Starting early and being off of rocky, solar heated slopes before they become unsupportable is the best strategy for avoiding the loose wet avalanche problem.