Banner Summit

By Wednesday afternoon, heavy snowfall and strong wind will create dangerous conditions in many alpine and upper elevation locations. Both slab and loose snow avalanches will become likely. If you're out in the hills, have a safe exit plan as conditions deteriorate. Some details on what to expect for the rest of the work week:

Wind Slab Avalanches: Expect to find fresh wind slabs beneath cornices and ridgelines, on the sides of cross-loaded gullies, and lower in alpine cirques. The new slabs could overlie weak faceted snow or thin crusts that formed on Tuesday on some slopes, making avalanches wider and easier to trigger than you might expect. The new snowfall and wind slabs are burying a previous generation of wind or storm slabs on some slopes; an observer reported triggering a small avalanche near Banner Summit on Monday. Avalanches that fail on the icy surfaces below the older slabs will be thicker and more powerful. Watch for drifts, dunes, and smooth pillows of snow, signs the wind has been at work. Cracks shooting out from your boards or sled are a clear sign you've found a sensitive slab.

Dry Loose Avalanches:  On very steep slopes, the chance of natural and human-triggered loose snow avalanches (sluffs) will rise as the snow piles up. While smaller than the wind slabs, they could be big enough to knock you over and push you where you don't want to go. Also, loose snow avalanches moving downslope could trigger larger slab avalanches in wind-loaded gullies and on aprons at the bottom of chutes. 

When snowfall ends, even brief periods of sunshine could induce natural sluffs. If skies clear on Friday, expect widespread natural sluffing on sun-exposed slopes where a lot of snow fell. Friday's potential natural activity should follow the sun around the compass:  E-SE aspects in the morning, S-SW facing slopes by noon, and W-NW aspects later in the day.  Very steep, rocky, sun-drenched avalanche paths that are protected from the wind are most suspect.

Storm Slab Avalanches: Fluctuating temperatures during the storm could form touchy sliding layers or interfaces within the new snow. Subtle wind effects could form soft slabs in exposed middle elevation terrain. These avalanches are most likely on very steep slopes approaching or over about 40 degrees in steepness.

As skies clear on Thursday and Friday, the intense mid-April sun could rapidly consolidate and stiffen the powdery storm snow, producing slab avalanche issues on slopes that were safe during the storm. This scenario is most likely on very steep, wind-protected slopes that check 2 boxes:  1) around a foot or more snow fell and 2) the slope directly faces the sun. 

Recent Observations: 

• April 13th - Copper Mtn near Banner Summit: CLICK HERE
• April 12th - Williams Peak area: CLICK HERE
• April 11th - Williams Peak area: CLICK HERE
• April 10th - Williams Peak area: CLICK HERE

 

SNOWPACK AND AVALANCHE GENERAL INFORMATION

Some basic points to remember until you put the sleds and boards away for the summer:

• Spring weather can rapidly alter snow conditions and snow stability. Think minutes and hours rather than days and weeks.
• Storm slab and wind slab avalanches are most likely during and immediately following a storm. 
• Short periods of sunshine after a snowstorm can quickly create wet loose avalanche instabilities.
• Keep wet slab avalanches in mind, especially during rain events and when we go days without the temperature dropping below freezing. Many shady, upper elevation slopes have not yet gone through a "spring transition". Travel cautiously in this terrain when rain or hot, sunny spells push meltwater deeper into the snowpack. 
• Give cornices a wide berth and don’t linger beneath them. 
• Complicated, consequential terrain doesn’t get less complex or serious in the spring and summer. Respect the mountains, maintain safe travel procedures, and keep your guard up.
  
  

OBSERVATIONS

Even though we’re done issuing forecasts, we’ll continue posting observations when we get out in the mountains. We encourage you to do the same. Please let everyone know what you’re seeing out there, especially if you see or trigger any avalanches. We’re always trying to collect as much information as possible about large wet slab avalanches (where, when, etc); let us know if you come across any of these beasts in your travels. There are several ways to stay connected and to share what you see:

Submit an Observation:

• CLICK HERE for the online form
• Download the Avy App: Apple | Android
• Email us: info@sawtoothavalanche.com
• Text us at 208-481-5921

 

View Observations:

• CLICK HERE to view Observations.
• CLICK HERE for details on recent Avalanches.
• CLICK HERE to view our Photos & Video page.