Hatcher Pass

Navigating the backcountry in springtime can be challenging.

Although March felt like April and April now feels like March, we have finally seen a gradual increase and rise in temperature this week. The danger and likelihood of persistent slabs have started to dissipate.  On Wednesday 4/17 winds at 4500′ gusted SSE 21-38 mph on Marmot and 35-53 mph on Hatch for 12-15 hours and affected ski/riding quality more than contributing to an avalanche problem. Small winds slabs are expected to be stubborn to unreactive this weekend.

Expect wet avalanches to become more active as temperatures rise, combined with multiple nights without a good refreeze.  Temperatures have remained above freezing for the past 3 nights at 2700′, 2 nights at 3500′, and hovered at freezing at 4500′ last night.  Expect wet avalanche problems on southerly aspects before they become a problem on the entire compass.

Maintaining strict habits with safe travel protocol is a good habit during ‘green light’ conditions as well as red light. The main things are exposing only one person at a time, having escape routes planned, watching your partners closely, carrying and knowing how to use your rescue equipment.

Although Spring is here, 4+ ft of snow still exists at 3000′

Springtime Avalanche Concerns

Be alert for signs of danger and monitor trends.

1. Loose Wet Avalanches-Loose wet avalanches are typically the first avalanches we see as the snowpack warms up. They can be triggered by snow heating up especially near rocks and cliffs on steep slopes.  While they are relatively small and manageable on their own, they can be dangerous if they pick up enough volume, or if they push you into terrain traps. They can also trigger larger slab avalanches as they travel downhill. They are typically preceded by rollerballs or pinwheels rolling down slopes as they heat up. This is an easily avoidable avalanche problem. Expect wet loose sluffs to be possible on all aspects in steep terrain.

2. Wet Slabs–Forecasting for Wet slab avalanches  is very difficult.  Wet snow avalanches are caused by melt water which weaken the bonds (strength) of a buried weak layer, decreasing the strength of the snowpack which can lead to wet loose avalanches on the snow surface or larger wet slab avalanches that release either on weak layers within the snowpack or on the ground.  Wet slab avalanches can be highly destructive and require careful evaluation of the snow surface conditions to minimize your exposure. The best indication of wet slab avalanche potential is to monitor how deep you are sinking into the snow surface and pay attention to any smaller wet loose avalanches that are either human triggered or naturally occurring.  A common avalanche proverb says that three nights in a row of no refreeze is an omen of major wet slab avalanches.  It is best to avoid avalanche terrain and runout zones during these periods as the ingredients for large and destructive wet slab avalanches are all in place.

3. Cornices –Cornices are very large especially on the Marmot ridgeline above Rae Wallace in addition to many upper elevation leeward aspects.  Cornices can break off naturally, especially during warm weather when they start bending downhill. Simply avoid being underneath or near the tops of large cornices as they break farther back than expected. Cornices can trigger sluff and slab avalanches and are unpredictable this time of year.

4. Glide Avalanches– A separate but related avalanche problem is Glide avalanches.  When they happen is mostly unpredictable, however, where they happen is generally predictable because there is often a huge crack in the snowpack. Glide cracks are more likely during periods of active melting of the snowpack. Common places to find glide avalanches are places with rock slabs or a smooth ground surface which are common in much of the terrain at Hatcher Pass. Avoid spending time underneath as it could release at any time and create a large and destructive avalanche.

These signs mean it’s time to head home or change to an aspect with cooler snow. Remember, even “smaller” slides can be dangerous in high-consequence terrain, such as above a terrain trap, trees, rocks, cliffs, or a long, large avalanche path. Plan your trip to have a safe exit out of the mountains.