Turnagain Pass

WIND SLABS: Three inches of new snow was recorded overnight and another 3-5” is expected today. Yesterday Easterly Ridgetop winds were sustained in 30’s mph and today moderate Easterly winds will continue into early afternoon. Remember wind has a unique ability to deposit snow 10 times faster than falling snow alone, thus isolated slabs could be as thick as 1-2’ on leeward aspects or cross-loaded features. The interface where this new snow is accumulating may harbor a poor interface (weak snow grains sitting a smooth bed surface.) This combination of wind, new snow and bed surface has the potential to create reactive wind slabs that could be triggered by a person or machine. Be on the look out for active wind loading, shooting cracks or ‘wumpfing’ sounds. Should you observe any of these obvious signs today keep your slope angles below 35°.

STORM SLABS: In places protected from the wind small storm slabs have the potential to become touchy. Temperatures have warmed slightly and this new snow is falling on low-density old snow sitting on a firm bed surface. Today’s forecasted snow totals will likely make for small low consequence slabs that will be isolated to steep terrain features. However if you see snow depths exceeding 6”, storm slabs could become large enough to catch a person in the wrong place. Thus today it will be important to monitor changing snow conditions and be aware consequences of any given terrain feature. 

Active windloading was observed in Summit Lake and the Sunburst Weather Station recored mulitple gusts in the 50’s mph yesterday.

The glide crack problem continues to haunt Turnagain Pass. Yesterday a glide released on Seattle Ridge just minutes before we arrived. We didn’t talk to anyone who witnessed it in motion, but did hear some funny stories about being surprised by its sudden appearance.

Glide cracks can form and release in seconds or days later or sometimes a glide crack won’t release at all. A good example of this can be seen in the photo diagrams below documenting two glide cracks on Seattle Ridge over a 24-hour period. The glide with a small visible crack released spontaneously where the larger glide crack on a similar slope had little change.

This unpredictable avalanche problem is best to avoid. Limit your exposure time in the run-out of a glide and do not test your luck on a slope below it. Today’s visibility is likely to be poor, which can make it challenging to see existing glides. In general these cracks have been observed all along the East face Seattle Ridge in the 1500’ to 2500’ elevation band. As of yesterday morning the snow machine uptrack did not harbor any cracks, but given their spontaneous nature it is not impossible for one to form. See yesterday’s Advisory and visit our Observations Page for more pictures of existing glides in the area. 

The left hand glide released around ~10am on January 16th and the glide on the right released sometime bween January14th – 15th. East face of Seattle Ridge.

Glide release observed within a 24 hour period on Seattle Ridge.

Observed over the same amount of time as glides above, this glide had little to no movement.