Hatcher Pass

Problemi valanghivi

• 

  Wind Slabs

  N

  NE

  E

  SE

  S

  SW

  W

  NW

  • Alta quota
  • Limite del bosco
  • Sotto il limite del bosco

  Probabilità

  Likely

  Dimensione

  1–2

  You are most likely to trigger a small, shallow wind slab avalanche at upper elevations in leeward and crossloaded terrain features like gullies and couloirs that are 35º and steeper. While you could find instabilities on most aspects today, the likelihood will be elevated at ridgetops on S-SW-W-NW-N terrain (clockwise) where new slabs sit on shallow, weak snow. It will be possible to find smaller slabs at mid-elevations by midday as winds remind strong to extreme. 

  It will be possible for a wind slab to step down into deeper, persistent weak layers (sugary snow) up to 2-3 feet deep in isolated or extreme terrain at upper elevations where previous wind events built up the snowpack prior to this windstorm.  These avalanches will be small to large in size. Natural avalanches will become possible as strong winds persist and overload our poorly structured snowpack. 

  Even though our overall snowpack going into the weekend is shallow, wind speed and duration will be strong enough to load features on most aspects. 

  Over the last week, Hatcher Pass received 5" of snow or about .6" of snow water equivalent above 3,500', getting the average snow depth above this elevation to just over one foot. This modest new snow overlays sugary snow throughout the forecast area. Prior wind events in November, predominantly out of the southeast, created some deeper areas on leeward aspects. So far, a theme of the season has been "Droughtember" with sporadic, small snow accumulation of just a few inches at a time.

  This wind event is just the latest change in a slow start to this season's weather. So far, winds have remained in the upper end of "strong" (26-38 miles per hour) and the lower end of "extreme" (>38mph gale) since last night and have remained steady since. With some uncertainty in how high wind speeds will gust and how long they will endure in our region, it's difficult to predict how the fresh slabs will build over our existing snowpack structure; they could be difficult to trigger ("stubborn"), they could release on their own ("naturally") or as soon as you touch them ("sensitive").  

  One thing is for sure: this setup requires a little attention, as our overall terrain selection is being influenced by the general lack of snow. The terrain in Hatcher Pass that will appear skiable /rideable is likely to have new instabilities from wind loading and will be capable of triggering deeper avalanches as they reload on top of existing poor structure. If it weren't for the lack of snow, we would have a higher avalanche hazard with deeper and wider avalanches possible this weekend. Perhaps the silver lining of the start to our season? 

  Outside of avalanches, the main hazard will be getting blown over in the wind and early-season conditions of rocks, vegetation and open water. We are likely to have a net gain of snow in some features and a net loss on exposed, windward slopes. 

  If avalanches and backcountry travel were a game of risk versus reward, consider the consequences of playing it this weekend--even a small avalanche incapable of burying you could drag you through exposed terrain.  Collapsing, shooting cracks and "whumphing" are all signs of instability related to this problem. Use caution when approaching loaded or smooth slopes, look for strong over weak snow structure using pole tests and hand pits, and consider the consequences of a slide in this overall thin snowpack.