Mill city area - Extreme winds, Reactive Wind slabs.

We traveled on a variety of aspects in exposed terrain in the Mammoth Area to look at the sensitive wind slabs forming today.

• It was easy to trigger shooting cracks and soft slab avalanches in wind-affected snow on leeward terrain features.
• The new snow was upside down, with cracks and avalanches breaking through the stiffer surface snow into lower-density snow underneath. All of the instability we observed was within the new storm snow.
• The storm lasted longer than forecast in Mammoth with snowfall and blowing snow continuing through early afternoon.

Shooting cracks and small soft wind slabs were easy to initiate on test slopes in exposed terrain.

10 to 12 inches of new snow in the Mill City area was upside-down: wind-stiffened at the top and lower density towards the bottom. In most places, the new and drifted snow was resting on settled snow from the last storm or on an inch of moist snow above a thin melt-freeze crust. All the instability we experienced was within the lower-density storm snow; nothing broke down to or below the crust. The older snow under the crust was also moist.

Wind drifts were 4 to 16 inches thick on leeward slopes. Most of them were soft with skis falling through the slab to the soft snow underneath, though some were harder with ski penetrations reduced to just 2 inches in the most exposed areas.

Windward slopes were getting stripped of new snow. There was still moderate amounts of soft snow available for continued wind transport with ski penetration up to a foot deep in 4-Finger to Fist hard snow in fetches.