Hatcher Pass

Storm totals from 4/12 have arrived with 22″ new snow and 1.8″ SWE @IM 3550′  and 16″ new snow with 1″SWE @ Frostbite 2700′.  Prior to the majority of the precipitation, winds gusted 12 hrs SE 33-43mph on Marmot and SE 41-49mph on Hatch and ended prior to new snow at approximately 2100.  Few recent avalanches were visible on Friday due to stormy conditions and heavy snowfall throughout the entire day.

Dog triggered soft slab up Archangel trail on 4/12, approximate location NE aspect 2600′

Check observations here regularly for updates on recent avalanches.

Persistent slabs 12 to 30 inches thick will be LARGER and LIKELY to human trigger on northerly (west to north to east) aspects and SMALLER on southerly aspects, at mid and upper elevations on slopes 30º and steeper.  Triggering a slab at low elevation is less likely but still possible on all aspects.

This facet/crust sandwich known as the persistent weak layer has been the culprit weak layer in multiple avalanches  between April 1-7. This layer will continue to be problematic with the addition of 22″ of new snow from yesterday’s storm.

Shallower locations in the snowpack , on any aspect, will be possible locations to trigger the persistent slab.

Triggering this type of avalanche will be large and consequential, certainly able to bury, injure or kill a person.

The pit above shows the existing snowpack structure with 25 inches of new snow sitting over a weak sugary facet/crust layer. In this location we had propagation on isolation that failed on the persistent weak layer.

Travel protocols will be essential today. We will be choosing to travel one at a time and spacing out through avalanche terrain, paying close attention to utilizing safe zones well out of the way of the potential runout of avalanches, avoiding crowded slopes, and be digging test pits to improve the accuracy of our slope scale assessments and go-no-go decision making. Conservative choices will be key today, avoiding the largest and broadest slopes, and avoiding terrain traps.

Remotely triggered avalanches will be possible from below, above, or adjacent to slopes.

Avalanche behavior may be difficult to predict especially as slabs get thicker and weak layers get buried deeper on leeward aspects.

This type of avalanche problem often gives unreliable feedback and may not give you obvious clues and could easily surprise even the most seasoned backcountry user.  Cracking and whumping may or may not occur prior to triggering an avalanche. Pole/probe tests and formal stability tests will help you identify stiffer snow over weaker snow and where this problem exists.  Slope scale snowpack assessment will be key today for establishing safe places to recreate. Choose smaller objectives lacking terrain traps.

Loose dry avalanches (sluffs) will be likely to human trigger on all aspects, at all elevations on steep convexities and rollovers in terrain 40º and steeper. Naturals avalanches are possible.

Yesterday’s storm brought up to 22″ of new snow.  Cooler overnight temperatures will keep snow surfaces dry and loose through most of the day on true north.  On aspects where dry unconsolidated snow sits on firm bed surfaces, sluffs will be more likely to trigger and result in a larger volume of debris.  Sluffs will be capable of sweeping you off your feet or over other rocks and hazards. It will be possible to get caught and carried, injured, or tweek a knee in this terrain. Sluff management and mitigating a sluff may be challenging today due to the significant amount of new storm snow.

Yes, this is the Hatcher Pass Lodge snowstake surpassing the 6 ft mark! What an incredible April it has been!