The cold front that passed through the region last week (2/12-2/13) brought 4” to 8” of low-density, very transportable snow primarily from Mammoth Lakes north to Virginia Lakes. The storm system was accompanied by periods of moderate to strong northerly, veering to southwesterly, then swinging back toward northerly winds, which have redistributed the snow into Wind Slabs and drifts primarily treeline and above, especially near favored features on many aspects throughout the alpine. The cold temperatures post-frontal passage slowed the normal strengthening and bonding process but enough time has lapsed where tests and observations indicate they have begun to strengthen and more difficult to trigger. Use caution additional caution in steep or complex terrain above treeline where recent drifting is evident. Wind Slabs will most likely be found in the upper elevations under cornices, below ridgelines and at the top of chutes and couloirs, and on steep convexities. Hollow sounding drifts, or dense cracking snow may indicate rider triggered fail is still possible.
From treeline and below, the snow in sheltered areas remains largely undisturbed and lacks sufficient cohesion to form a well-developed slab. However, as temperatures rise above freezing during the day, sunny slopes will begin to thaw and become less stable. Rollerballs and small point releases originating from rocky outcrops or cliff bands and under trees are an indication the surface snow is loosing strength and the threat of Loose Wet avalanches is rising. Though the danger is Low for Loose Wet avalanches, isolated releases are possible on Easterly aspects during the morning, followed by South, then Westerly facing slopes by late afternoon. Hard snow surfaces (i.e. wind board, crusts, and ice) can be dangerous in the event of a fall. Ice axes and crampons are recommended in steep or complex terrain.
The patchy persistent weaknesses from early season that was confined to NE-N-NW aspects above ~9500’ is showing signs of sintering and strengthening with test results show improving cohesion. The approaching cold front is forecasted to produce trace to 2”” of low-density snow. This is unlikely enough load to stress the underlying persistent weakness enough for it to become reactive. However, near treeline where the persistent weakness exists, there is the potential that an large isolated Wind Slab failure could trigger an avalanche on these deeper weaknesses, although unlikely.
Caution – the mid to lower elevation snow coverage remains thin with plenty of hazards lurking below the snow surface, such as rocks, logs and stumps. The new snow is hiding plenty of hazards while providing little protection.
Below ~9,000’, natural and triggered releases are unlikely due to thin and well-anchored snow coverage (below threshold).
