Banner Summit

After a wintery week with 4 to 22" of new snow (and over 3" of SWE) accumulating throughout the forecast area, our heads have refocused on winter dry snow avalanche problems. Gradual warming and the powerful spring sun will shift that perspective back towards spring wet snow concerns over the next couple of days. Although we may be craving more corn-skiing and riding, be patient for the harvest as it will take a couple of days to transition. If you're headed out into the mountains, plan to be flexible to adapt to rapidly changing conditions. Here are a few problems to look for this weekend:

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 recent snowfall buried a previous generation of wind or storm slabs on some slopes: forecasters observed a few recent natural slab avalanches just below the ridgeline of Copper Mountain on Thursday, and an observer reported triggering a small avalanche near Banner Summit on Monday. Watch for drifts, dunes, and smooth pillows of snow, signs the wind has been at work. Additionally, storm slabs may have formed due to fluctuating temperatures during the storm, especially in middle-elevation terrain. 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, there's a decent chance of natural and human-triggered loose snow avalanches (sluffs) that 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. Direct sunshine is expected to produce widespread natural sluffs on sun-exposed slopes where a lot of snow fell over the next few days. Expect the potential natural activity to 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.

As skies clear on Friday and Saturday, 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.

Wet Loose Avalanches: As the weekend warming continues, the snow surface is expected to moisten. Be aware of deteriorating conditions as the storm snow becomes wet, schmoo-ey, and challenging to ski and ride in. Look for rollerballs and pinwheels of snow moving downslope as an indicator that the surface is taking heat and that it's time to move to colder, drier slopes (or exit to the trailhead). Natural wet loose activity will follow a similar pattern as the Dry Loose avalanches described above and follow the sunshine throughout the day.

Recent Observations: 

• April 16th - Copper Mtn near Banner Summit: CLICK HERE
• April 16th - East Fork Baker Creek: CLICK HERE
• April 16th - Mushroom Ridge near Galena Lodge: CLICK HERE
• April 13th - Copper Mtn near Banner Summit: CLICK HERE
• April 12th - 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.