Hatcher Pass

Avalanche problems

• 

  Loose Wet

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alpine
  • Treeline
  • Below treeline

  Likelihood

  Unlikely

  Size

  1–2

  As this active weather pattern moves through our region, cloudier conditions and easterly winds should keep wet loose activity to a minimum. Remember, now that we are in April, the strength and duration of solar input on the snowpack can be cumulative; you do not need much for snow surfaces to rapidly warm, loosen, and become unstable. Additionally, with high freezing levels also forecasted, we may experience precipitation in the form of rain today. Precip totals are expected to be trace and are unlikely to contribute to wet instabilities, but be observant as you tour. 

  At lower elevations below 2,500', there is insufficient remaining snow to significantly avalanche, and we are unlikely to have larger wet avalanches travel through this elevation band today. The remaining snowpack has become isothermal, and travel at low elevations is likely to be punchy and challenging.

  While the likelihood of wet loose instabilities is lower today, it does not mean it is impossible. Even a small break in the clouds or a strong pulse of rain with above-freezing temperatures could loosen the upper snowpack. You are most likely to encounter wet snow avalanche instabilities in the mid to late afternoon in terrain 40 degrees and steeper from west to east aspects. 

  Note that we have added east-facing terrain to the compass rose as the days become longer and the morning sun has the potential to warm these aspects rapidly, contributing to avalanche hazard (see below).

  PERSISTENT SLAB:

  We have seen some evidence of our poor snowpack structure reacting to warming with faceted weak layers failing and propagating near the ground under slabs of warm, wet snow last week (see photos). With adequate solar input and warming of the snow surface, we have seen this structure act more reactively in the afternoon. With today's weather and a more consolidated upper snowpack, you are unlikely to find and trigger a slab avalanche. However, keep this in mind for when we tilt back into spring weather after this active low pressure leaves our region. 

  CORNICES:Cornices are shrinking and drooping throughout the forecast area. We have seen signs of warming and re-freezing on shady aspects. Similar to the persistent slab problem, these are not expected to be reactive today, but are worth keeping inventory of for when we see the sun and above freezing overnight temperatures again.